mirror of
https://github.com/RPCSX/llvm.git
synced 2024-12-11 13:46:13 +00:00
f48ef5594f
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168026 91177308-0d34-0410-b5e6-96231b3b80d8
9021 lines
341 KiB
HTML
9021 lines
341 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
|
|
"http://www.w3.org/TR/html4/strict.dtd">
|
|
<html>
|
|
<head>
|
|
<title>LLVM Assembly Language Reference Manual</title>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<meta name="author" content="Chris Lattner">
|
|
<meta name="description"
|
|
content="LLVM Assembly Language Reference Manual.">
|
|
<link rel="stylesheet" href="_static/llvm.css" type="text/css">
|
|
</head>
|
|
|
|
<body>
|
|
|
|
<h1>LLVM Language Reference Manual</h1>
|
|
<ol>
|
|
<li><a href="#abstract">Abstract</a></li>
|
|
<li><a href="#introduction">Introduction</a></li>
|
|
<li><a href="#identifiers">Identifiers</a></li>
|
|
<li><a href="#highlevel">High Level Structure</a>
|
|
<ol>
|
|
<li><a href="#modulestructure">Module Structure</a></li>
|
|
<li><a href="#linkage">Linkage Types</a>
|
|
<ol>
|
|
<li><a href="#linkage_private">'<tt>private</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_linker_private">'<tt>linker_private</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_linker_private_weak">'<tt>linker_private_weak</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_internal">'<tt>internal</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_available_externally">'<tt>available_externally</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_linkonce">'<tt>linkonce</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_common">'<tt>common</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_weak">'<tt>weak</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_appending">'<tt>appending</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_externweak">'<tt>extern_weak</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_linkonce_odr">'<tt>linkonce_odr</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_linkonce_odr_auto_hide">'<tt>linkonce_odr_auto_hide</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_weak">'<tt>weak_odr</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_external">'<tt>external</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_dllimport">'<tt>dllimport</tt>' Linkage</a></li>
|
|
<li><a href="#linkage_dllexport">'<tt>dllexport</tt>' Linkage</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#callingconv">Calling Conventions</a></li>
|
|
<li><a href="#namedtypes">Named Types</a></li>
|
|
<li><a href="#globalvars">Global Variables</a></li>
|
|
<li><a href="#functionstructure">Functions</a></li>
|
|
<li><a href="#aliasstructure">Aliases</a></li>
|
|
<li><a href="#namedmetadatastructure">Named Metadata</a></li>
|
|
<li><a href="#paramattrs">Parameter Attributes</a></li>
|
|
<li><a href="#fnattrs">Function Attributes</a></li>
|
|
<li><a href="#gc">Garbage Collector Names</a></li>
|
|
<li><a href="#moduleasm">Module-Level Inline Assembly</a></li>
|
|
<li><a href="#datalayout">Data Layout</a></li>
|
|
<li><a href="#pointeraliasing">Pointer Aliasing Rules</a></li>
|
|
<li><a href="#volatile">Volatile Memory Accesses</a></li>
|
|
<li><a href="#memmodel">Memory Model for Concurrent Operations</a></li>
|
|
<li><a href="#ordering">Atomic Memory Ordering Constraints</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#typesystem">Type System</a>
|
|
<ol>
|
|
<li><a href="#t_classifications">Type Classifications</a></li>
|
|
<li><a href="#t_primitive">Primitive Types</a>
|
|
<ol>
|
|
<li><a href="#t_integer">Integer Type</a></li>
|
|
<li><a href="#t_floating">Floating Point Types</a></li>
|
|
<li><a href="#t_x86mmx">X86mmx Type</a></li>
|
|
<li><a href="#t_void">Void Type</a></li>
|
|
<li><a href="#t_label">Label Type</a></li>
|
|
<li><a href="#t_metadata">Metadata Type</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#t_derived">Derived Types</a>
|
|
<ol>
|
|
<li><a href="#t_aggregate">Aggregate Types</a>
|
|
<ol>
|
|
<li><a href="#t_array">Array Type</a></li>
|
|
<li><a href="#t_struct">Structure Type</a></li>
|
|
<li><a href="#t_opaque">Opaque Structure Types</a></li>
|
|
<li><a href="#t_vector">Vector Type</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#t_function">Function Type</a></li>
|
|
<li><a href="#t_pointer">Pointer Type</a></li>
|
|
</ol>
|
|
</li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#constants">Constants</a>
|
|
<ol>
|
|
<li><a href="#simpleconstants">Simple Constants</a></li>
|
|
<li><a href="#complexconstants">Complex Constants</a></li>
|
|
<li><a href="#globalconstants">Global Variable and Function Addresses</a></li>
|
|
<li><a href="#undefvalues">Undefined Values</a></li>
|
|
<li><a href="#poisonvalues">Poison Values</a></li>
|
|
<li><a href="#blockaddress">Addresses of Basic Blocks</a></li>
|
|
<li><a href="#constantexprs">Constant Expressions</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#othervalues">Other Values</a>
|
|
<ol>
|
|
<li><a href="#inlineasm">Inline Assembler Expressions</a></li>
|
|
<li><a href="#metadata">Metadata Nodes and Metadata Strings</a>
|
|
<ol>
|
|
<li><a href="#tbaa">'<tt>tbaa</tt>' Metadata</a></li>
|
|
<li><a href="#tbaa.struct">'<tt>tbaa.struct</tt>' Metadata</a></li>
|
|
<li><a href="#fpmath">'<tt>fpmath</tt>' Metadata</a></li>
|
|
<li><a href="#range">'<tt>range</tt>' Metadata</a></li>
|
|
</ol>
|
|
</li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#module_flags">Module Flags Metadata</a>
|
|
<ol>
|
|
<li><a href="#objc_gc_flags">Objective-C Garbage Collection Module Flags Metadata</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#intrinsic_globals">Intrinsic Global Variables</a>
|
|
<ol>
|
|
<li><a href="#intg_used">The '<tt>llvm.used</tt>' Global Variable</a></li>
|
|
<li><a href="#intg_compiler_used">The '<tt>llvm.compiler.used</tt>'
|
|
Global Variable</a></li>
|
|
<li><a href="#intg_global_ctors">The '<tt>llvm.global_ctors</tt>'
|
|
Global Variable</a></li>
|
|
<li><a href="#intg_global_dtors">The '<tt>llvm.global_dtors</tt>'
|
|
Global Variable</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#instref">Instruction Reference</a>
|
|
<ol>
|
|
<li><a href="#terminators">Terminator Instructions</a>
|
|
<ol>
|
|
<li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li>
|
|
<li><a href="#i_br">'<tt>br</tt>' Instruction</a></li>
|
|
<li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li>
|
|
<li><a href="#i_indirectbr">'<tt>indirectbr</tt>' Instruction</a></li>
|
|
<li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li>
|
|
<li><a href="#i_resume">'<tt>resume</tt>' Instruction</a></li>
|
|
<li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#binaryops">Binary Operations</a>
|
|
<ol>
|
|
<li><a href="#i_add">'<tt>add</tt>' Instruction</a></li>
|
|
<li><a href="#i_fadd">'<tt>fadd</tt>' Instruction</a></li>
|
|
<li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li>
|
|
<li><a href="#i_fsub">'<tt>fsub</tt>' Instruction</a></li>
|
|
<li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li>
|
|
<li><a href="#i_fmul">'<tt>fmul</tt>' Instruction</a></li>
|
|
<li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li>
|
|
<li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li>
|
|
<li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li>
|
|
<li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li>
|
|
<li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li>
|
|
<li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#bitwiseops">Bitwise Binary Operations</a>
|
|
<ol>
|
|
<li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li>
|
|
<li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li>
|
|
<li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li>
|
|
<li><a href="#i_and">'<tt>and</tt>' Instruction</a></li>
|
|
<li><a href="#i_or">'<tt>or</tt>' Instruction</a></li>
|
|
<li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#vectorops">Vector Operations</a>
|
|
<ol>
|
|
<li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li>
|
|
<li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li>
|
|
<li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#aggregateops">Aggregate Operations</a>
|
|
<ol>
|
|
<li><a href="#i_extractvalue">'<tt>extractvalue</tt>' Instruction</a></li>
|
|
<li><a href="#i_insertvalue">'<tt>insertvalue</tt>' Instruction</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#memoryops">Memory Access and Addressing Operations</a>
|
|
<ol>
|
|
<li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li>
|
|
<li><a href="#i_load">'<tt>load</tt>' Instruction</a></li>
|
|
<li><a href="#i_store">'<tt>store</tt>' Instruction</a></li>
|
|
<li><a href="#i_fence">'<tt>fence</tt>' Instruction</a></li>
|
|
<li><a href="#i_cmpxchg">'<tt>cmpxchg</tt>' Instruction</a></li>
|
|
<li><a href="#i_atomicrmw">'<tt>atomicrmw</tt>' Instruction</a></li>
|
|
<li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#convertops">Conversion Operations</a>
|
|
<ol>
|
|
<li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li>
|
|
<li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#otherops">Other Operations</a>
|
|
<ol>
|
|
<li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li>
|
|
<li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li>
|
|
<li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li>
|
|
<li><a href="#i_select">'<tt>select</tt>' Instruction</a></li>
|
|
<li><a href="#i_call">'<tt>call</tt>' Instruction</a></li>
|
|
<li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li>
|
|
<li><a href="#i_landingpad">'<tt>landingpad</tt>' Instruction</a></li>
|
|
</ol>
|
|
</li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#intrinsics">Intrinsic Functions</a>
|
|
<ol>
|
|
<li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_codegen">Code Generator Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_libc">Standard C Library Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_exp">'<tt>llvm.exp.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_exp2">'<tt>llvm.exp2.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_log">'<tt>llvm.log.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_log10">'<tt>llvm.log10.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_log2">'<tt>llvm.log2.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_fma">'<tt>llvm.fma.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_fabs">'<tt>llvm.fabs.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_floor">'<tt>llvm.floor.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_ceil">'<tt>llvm.ceil.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_trunc">'<tt>llvm.trunc.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_rint">'<tt>llvm.rint.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_nearbyint">'<tt>llvm.nearbyint.*</tt>' Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_manip">Bit Manipulation Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li>
|
|
<li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li>
|
|
<li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li>
|
|
<li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_overflow">Arithmetic with Overflow Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt> Intrinsics</a></li>
|
|
<li><a href="#int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt> Intrinsics</a></li>
|
|
<li><a href="#int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt> Intrinsics</a></li>
|
|
<li><a href="#int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt> Intrinsics</a></li>
|
|
<li><a href="#int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt> Intrinsics</a></li>
|
|
<li><a href="#int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt> Intrinsics</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#spec_arithmetic">Specialised Arithmetic Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#fmuladd">'<tt>llvm.fmuladd</tt> Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_fp16">Half Precision Floating Point Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_convert_to_fp16">'<tt>llvm.convert.to.fp16</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_convert_from_fp16">'<tt>llvm.convert.from.fp16</tt>' Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_debugger">Debugger intrinsics</a></li>
|
|
<li><a href="#int_eh">Exception Handling intrinsics</a></li>
|
|
<li><a href="#int_trampoline">Trampoline Intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_at">'<tt>llvm.adjust.trampoline</tt>' Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_memorymarkers">Memory Use Markers</a>
|
|
<ol>
|
|
<li><a href="#int_lifetime_start">'<tt>llvm.lifetime.start</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_lifetime_end">'<tt>llvm.lifetime.end</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_invariant_start">'<tt>llvm.invariant.start</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_invariant_end">'<tt>llvm.invariant.end</tt>' Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#int_general">General intrinsics</a>
|
|
<ol>
|
|
<li><a href="#int_var_annotation">
|
|
'<tt>llvm.var.annotation</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_annotation">
|
|
'<tt>llvm.annotation.*</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_trap">
|
|
'<tt>llvm.trap</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_debugtrap">
|
|
'<tt>llvm.debugtrap</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_stackprotector">
|
|
'<tt>llvm.stackprotector</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_objectsize">
|
|
'<tt>llvm.objectsize</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_expect">
|
|
'<tt>llvm.expect</tt>' Intrinsic</a></li>
|
|
<li><a href="#int_donothing">
|
|
'<tt>llvm.donothing</tt>' Intrinsic</a></li>
|
|
</ol>
|
|
</li>
|
|
</ol>
|
|
</li>
|
|
</ol>
|
|
|
|
<div class="doc_author">
|
|
<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
|
|
and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p>
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="abstract">Abstract</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>This document is a reference manual for the LLVM assembly language. LLVM is
|
|
a Static Single Assignment (SSA) based representation that provides type
|
|
safety, low-level operations, flexibility, and the capability of representing
|
|
'all' high-level languages cleanly. It is the common code representation
|
|
used throughout all phases of the LLVM compilation strategy.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="introduction">Introduction</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>The LLVM code representation is designed to be used in three different forms:
|
|
as an in-memory compiler IR, as an on-disk bitcode representation (suitable
|
|
for fast loading by a Just-In-Time compiler), and as a human readable
|
|
assembly language representation. This allows LLVM to provide a powerful
|
|
intermediate representation for efficient compiler transformations and
|
|
analysis, while providing a natural means to debug and visualize the
|
|
transformations. The three different forms of LLVM are all equivalent. This
|
|
document describes the human readable representation and notation.</p>
|
|
|
|
<p>The LLVM representation aims to be light-weight and low-level while being
|
|
expressive, typed, and extensible at the same time. It aims to be a
|
|
"universal IR" of sorts, by being at a low enough level that high-level ideas
|
|
may be cleanly mapped to it (similar to how microprocessors are "universal
|
|
IR's", allowing many source languages to be mapped to them). By providing
|
|
type information, LLVM can be used as the target of optimizations: for
|
|
example, through pointer analysis, it can be proven that a C automatic
|
|
variable is never accessed outside of the current function, allowing it to
|
|
be promoted to a simple SSA value instead of a memory location.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="wellformed">Well-Formedness</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<p>It is important to note that this document describes 'well formed' LLVM
|
|
assembly language. There is a difference between what the parser accepts and
|
|
what is considered 'well formed'. For example, the following instruction is
|
|
syntactically okay, but not well formed:</p>
|
|
|
|
<pre class="doc_code">
|
|
%x = <a href="#i_add">add</a> i32 1, %x
|
|
</pre>
|
|
|
|
<p>because the definition of <tt>%x</tt> does not dominate all of its uses. The
|
|
LLVM infrastructure provides a verification pass that may be used to verify
|
|
that an LLVM module is well formed. This pass is automatically run by the
|
|
parser after parsing input assembly and by the optimizer before it outputs
|
|
bitcode. The violations pointed out by the verifier pass indicate bugs in
|
|
transformation passes or input to the parser.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- Describe the typesetting conventions here. -->
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="identifiers">Identifiers</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>LLVM identifiers come in two basic types: global and local. Global
|
|
identifiers (functions, global variables) begin with the <tt>'@'</tt>
|
|
character. Local identifiers (register names, types) begin with
|
|
the <tt>'%'</tt> character. Additionally, there are three different formats
|
|
for identifiers, for different purposes:</p>
|
|
|
|
<ol>
|
|
<li>Named values are represented as a string of characters with their prefix.
|
|
For example, <tt>%foo</tt>, <tt>@DivisionByZero</tt>,
|
|
<tt>%a.really.long.identifier</tt>. The actual regular expression used is
|
|
'<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'. Identifiers which require
|
|
other characters in their names can be surrounded with quotes. Special
|
|
characters may be escaped using <tt>"\xx"</tt> where <tt>xx</tt> is the
|
|
ASCII code for the character in hexadecimal. In this way, any character
|
|
can be used in a name value, even quotes themselves.</li>
|
|
|
|
<li>Unnamed values are represented as an unsigned numeric value with their
|
|
prefix. For example, <tt>%12</tt>, <tt>@2</tt>, <tt>%44</tt>.</li>
|
|
|
|
<li>Constants, which are described in a <a href="#constants">section about
|
|
constants</a>, below.</li>
|
|
</ol>
|
|
|
|
<p>LLVM requires that values start with a prefix for two reasons: Compilers
|
|
don't need to worry about name clashes with reserved words, and the set of
|
|
reserved words may be expanded in the future without penalty. Additionally,
|
|
unnamed identifiers allow a compiler to quickly come up with a temporary
|
|
variable without having to avoid symbol table conflicts.</p>
|
|
|
|
<p>Reserved words in LLVM are very similar to reserved words in other
|
|
languages. There are keywords for different opcodes
|
|
('<tt><a href="#i_add">add</a></tt>',
|
|
'<tt><a href="#i_bitcast">bitcast</a></tt>',
|
|
'<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names
|
|
('<tt><a href="#t_void">void</a></tt>',
|
|
'<tt><a href="#t_primitive">i32</a></tt>', etc...), and others. These
|
|
reserved words cannot conflict with variable names, because none of them
|
|
start with a prefix character (<tt>'%'</tt> or <tt>'@'</tt>).</p>
|
|
|
|
<p>Here is an example of LLVM code to multiply the integer variable
|
|
'<tt>%X</tt>' by 8:</p>
|
|
|
|
<p>The easy way:</p>
|
|
|
|
<pre class="doc_code">
|
|
%result = <a href="#i_mul">mul</a> i32 %X, 8
|
|
</pre>
|
|
|
|
<p>After strength reduction:</p>
|
|
|
|
<pre class="doc_code">
|
|
%result = <a href="#i_shl">shl</a> i32 %X, i8 3
|
|
</pre>
|
|
|
|
<p>And the hard way:</p>
|
|
|
|
<pre class="doc_code">
|
|
%0 = <a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i>
|
|
%1 = <a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i>
|
|
%result = <a href="#i_add">add</a> i32 %1, %1
|
|
</pre>
|
|
|
|
<p>This last way of multiplying <tt>%X</tt> by 8 illustrates several important
|
|
lexical features of LLVM:</p>
|
|
|
|
<ol>
|
|
<li>Comments are delimited with a '<tt>;</tt>' and go until the end of
|
|
line.</li>
|
|
|
|
<li>Unnamed temporaries are created when the result of a computation is not
|
|
assigned to a named value.</li>
|
|
|
|
<li>Unnamed temporaries are numbered sequentially</li>
|
|
</ol>
|
|
|
|
<p>It also shows a convention that we follow in this document. When
|
|
demonstrating instructions, we will follow an instruction with a comment that
|
|
defines the type and name of value produced. Comments are shown in italic
|
|
text.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="highlevel">High Level Structure</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
<div>
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="modulestructure">Module Structure</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM programs are composed of <tt>Module</tt>s, each of which is a
|
|
translation unit of the input programs. Each module consists of functions,
|
|
global variables, and symbol table entries. Modules may be combined together
|
|
with the LLVM linker, which merges function (and global variable)
|
|
definitions, resolves forward declarations, and merges symbol table
|
|
entries. Here is an example of the "hello world" module:</p>
|
|
|
|
<pre class="doc_code">
|
|
<i>; Declare the string constant as a global constant.</i>
|
|
<a href="#identifiers">@.str</a> = <a href="#linkage_private">private</a> <a href="#globalvars">unnamed_addr</a> <a href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00"
|
|
|
|
<i>; External declaration of the puts function</i>
|
|
<a href="#functionstructure">declare</a> i32 @puts(i8* <a href="#nocapture">nocapture</a>) <a href="#fnattrs">nounwind</a>
|
|
|
|
<i>; Definition of main function</i>
|
|
define i32 @main() { <i>; i32()* </i>
|
|
<i>; Convert [13 x i8]* to i8 *...</i>
|
|
%cast210 = <a href="#i_getelementptr">getelementptr</a> [13 x i8]* @.str, i64 0, i64 0
|
|
|
|
<i>; Call puts function to write out the string to stdout.</i>
|
|
<a href="#i_call">call</a> i32 @puts(i8* %cast210)
|
|
<a href="#i_ret">ret</a> i32 0
|
|
}
|
|
|
|
<i>; Named metadata</i>
|
|
!1 = metadata !{i32 42}
|
|
!foo = !{!1, null}
|
|
</pre>
|
|
|
|
<p>This example is made up of a <a href="#globalvars">global variable</a> named
|
|
"<tt>.str</tt>", an external declaration of the "<tt>puts</tt>" function,
|
|
a <a href="#functionstructure">function definition</a> for
|
|
"<tt>main</tt>" and <a href="#namedmetadatastructure">named metadata</a>
|
|
"<tt>foo</tt>".</p>
|
|
|
|
<p>In general, a module is made up of a list of global values (where both
|
|
functions and global variables are global values). Global values are
|
|
represented by a pointer to a memory location (in this case, a pointer to an
|
|
array of char, and a pointer to a function), and have one of the
|
|
following <a href="#linkage">linkage types</a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="linkage">Linkage Types</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>All Global Variables and Functions have one of the following types of
|
|
linkage:</p>
|
|
|
|
<dl>
|
|
<dt><tt><b><a name="linkage_private">private</a></b></tt></dt>
|
|
<dd>Global values with "<tt>private</tt>" linkage are only directly accessible
|
|
by objects in the current module. In particular, linking code into a
|
|
module with an private global value may cause the private to be renamed as
|
|
necessary to avoid collisions. Because the symbol is private to the
|
|
module, all references can be updated. This doesn't show up in any symbol
|
|
table in the object file.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_linker_private">linker_private</a></b></tt></dt>
|
|
<dd>Similar to <tt>private</tt>, but the symbol is passed through the
|
|
assembler and evaluated by the linker. Unlike normal strong symbols, they
|
|
are removed by the linker from the final linked image (executable or
|
|
dynamic library).</dd>
|
|
|
|
<dt><tt><b><a name="linkage_linker_private_weak">linker_private_weak</a></b></tt></dt>
|
|
<dd>Similar to "<tt>linker_private</tt>", but the symbol is weak. Note that
|
|
<tt>linker_private_weak</tt> symbols are subject to coalescing by the
|
|
linker. The symbols are removed by the linker from the final linked image
|
|
(executable or dynamic library).</dd>
|
|
|
|
<dt><tt><b><a name="linkage_internal">internal</a></b></tt></dt>
|
|
<dd>Similar to private, but the value shows as a local symbol
|
|
(<tt>STB_LOCAL</tt> in the case of ELF) in the object file. This
|
|
corresponds to the notion of the '<tt>static</tt>' keyword in C.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_available_externally">available_externally</a></b></tt></dt>
|
|
<dd>Globals with "<tt>available_externally</tt>" linkage are never emitted
|
|
into the object file corresponding to the LLVM module. They exist to
|
|
allow inlining and other optimizations to take place given knowledge of
|
|
the definition of the global, which is known to be somewhere outside the
|
|
module. Globals with <tt>available_externally</tt> linkage are allowed to
|
|
be discarded at will, and are otherwise the same as <tt>linkonce_odr</tt>.
|
|
This linkage type is only allowed on definitions, not declarations.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt></dt>
|
|
<dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of
|
|
the same name when linkage occurs. This can be used to implement
|
|
some forms of inline functions, templates, or other code which must be
|
|
generated in each translation unit that uses it, but where the body may
|
|
be overridden with a more definitive definition later. Unreferenced
|
|
<tt>linkonce</tt> globals are allowed to be discarded. Note that
|
|
<tt>linkonce</tt> linkage does not actually allow the optimizer to
|
|
inline the body of this function into callers because it doesn't know if
|
|
this definition of the function is the definitive definition within the
|
|
program or whether it will be overridden by a stronger definition.
|
|
To enable inlining and other optimizations, use "<tt>linkonce_odr</tt>"
|
|
linkage.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_weak">weak</a></b></tt></dt>
|
|
<dd>"<tt>weak</tt>" linkage has the same merging semantics as
|
|
<tt>linkonce</tt> linkage, except that unreferenced globals with
|
|
<tt>weak</tt> linkage may not be discarded. This is used for globals that
|
|
are declared "weak" in C source code.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_common">common</a></b></tt></dt>
|
|
<dd>"<tt>common</tt>" linkage is most similar to "<tt>weak</tt>" linkage, but
|
|
they are used for tentative definitions in C, such as "<tt>int X;</tt>" at
|
|
global scope.
|
|
Symbols with "<tt>common</tt>" linkage are merged in the same way as
|
|
<tt>weak symbols</tt>, and they may not be deleted if unreferenced.
|
|
<tt>common</tt> symbols may not have an explicit section,
|
|
must have a zero initializer, and may not be marked '<a
|
|
href="#globalvars"><tt>constant</tt></a>'. Functions and aliases may not
|
|
have common linkage.</dd>
|
|
|
|
|
|
<dt><tt><b><a name="linkage_appending">appending</a></b></tt></dt>
|
|
<dd>"<tt>appending</tt>" linkage may only be applied to global variables of
|
|
pointer to array type. When two global variables with appending linkage
|
|
are linked together, the two global arrays are appended together. This is
|
|
the LLVM, typesafe, equivalent of having the system linker append together
|
|
"sections" with identical names when .o files are linked.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_externweak">extern_weak</a></b></tt></dt>
|
|
<dd>The semantics of this linkage follow the ELF object file model: the symbol
|
|
is weak until linked, if not linked, the symbol becomes null instead of
|
|
being an undefined reference.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_linkonce_odr">linkonce_odr</a></b></tt></dt>
|
|
<dt><tt><b><a name="linkage_weak_odr">weak_odr</a></b></tt></dt>
|
|
<dd>Some languages allow differing globals to be merged, such as two functions
|
|
with different semantics. Other languages, such as <tt>C++</tt>, ensure
|
|
that only equivalent globals are ever merged (the "one definition rule"
|
|
— "ODR"). Such languages can use the <tt>linkonce_odr</tt>
|
|
and <tt>weak_odr</tt> linkage types to indicate that the global will only
|
|
be merged with equivalent globals. These linkage types are otherwise the
|
|
same as their non-<tt>odr</tt> versions.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_linkonce_odr_auto_hide">linkonce_odr_auto_hide</a></b></tt></dt>
|
|
<dd>Similar to "<tt>linkonce_odr</tt>", but nothing in the translation unit
|
|
takes the address of this definition. For instance, functions that had an
|
|
inline definition, but the compiler decided not to inline it.
|
|
<tt>linkonce_odr_auto_hide</tt> may have only <tt>default</tt> visibility.
|
|
The symbols are removed by the linker from the final linked image
|
|
(executable or dynamic library).</dd>
|
|
|
|
<dt><tt><b><a name="linkage_external">external</a></b></tt></dt>
|
|
<dd>If none of the above identifiers are used, the global is externally
|
|
visible, meaning that it participates in linkage and can be used to
|
|
resolve external symbol references.</dd>
|
|
</dl>
|
|
|
|
<p>The next two types of linkage are targeted for Microsoft Windows platform
|
|
only. They are designed to support importing (exporting) symbols from (to)
|
|
DLLs (Dynamic Link Libraries).</p>
|
|
|
|
<dl>
|
|
<dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt></dt>
|
|
<dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function
|
|
or variable via a global pointer to a pointer that is set up by the DLL
|
|
exporting the symbol. On Microsoft Windows targets, the pointer name is
|
|
formed by combining <code>__imp_</code> and the function or variable
|
|
name.</dd>
|
|
|
|
<dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt></dt>
|
|
<dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global
|
|
pointer to a pointer in a DLL, so that it can be referenced with the
|
|
<tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer
|
|
name is formed by combining <code>__imp_</code> and the function or
|
|
variable name.</dd>
|
|
</dl>
|
|
|
|
<p>For example, since the "<tt>.LC0</tt>" variable is defined to be internal, if
|
|
another module defined a "<tt>.LC0</tt>" variable and was linked with this
|
|
one, one of the two would be renamed, preventing a collision. Since
|
|
"<tt>main</tt>" and "<tt>puts</tt>" are external (i.e., lacking any linkage
|
|
declarations), they are accessible outside of the current module.</p>
|
|
|
|
<p>It is illegal for a function <i>declaration</i> to have any linkage type
|
|
other than <tt>external</tt>, <tt>dllimport</tt>
|
|
or <tt>extern_weak</tt>.</p>
|
|
|
|
<p>Aliases can have only <tt>external</tt>, <tt>internal</tt>, <tt>weak</tt>
|
|
or <tt>weak_odr</tt> linkages.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="callingconv">Calling Conventions</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a>
|
|
and <a href="#i_invoke">invokes</a> can all have an optional calling
|
|
convention specified for the call. The calling convention of any pair of
|
|
dynamic caller/callee must match, or the behavior of the program is
|
|
undefined. The following calling conventions are supported by LLVM, and more
|
|
may be added in the future:</p>
|
|
|
|
<dl>
|
|
<dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt>
|
|
<dd>This calling convention (the default if no other calling convention is
|
|
specified) matches the target C calling conventions. This calling
|
|
convention supports varargs function calls and tolerates some mismatch in
|
|
the declared prototype and implemented declaration of the function (as
|
|
does normal C).</dd>
|
|
|
|
<dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt>
|
|
<dd>This calling convention attempts to make calls as fast as possible
|
|
(e.g. by passing things in registers). This calling convention allows the
|
|
target to use whatever tricks it wants to produce fast code for the
|
|
target, without having to conform to an externally specified ABI
|
|
(Application Binary Interface).
|
|
<a href="CodeGenerator.html#tailcallopt">Tail calls can only be optimized
|
|
when this or the GHC convention is used.</a> This calling convention
|
|
does not support varargs and requires the prototype of all callees to
|
|
exactly match the prototype of the function definition.</dd>
|
|
|
|
<dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt>
|
|
<dd>This calling convention attempts to make code in the caller as efficient
|
|
as possible under the assumption that the call is not commonly executed.
|
|
As such, these calls often preserve all registers so that the call does
|
|
not break any live ranges in the caller side. This calling convention
|
|
does not support varargs and requires the prototype of all callees to
|
|
exactly match the prototype of the function definition.</dd>
|
|
|
|
<dt><b>"<tt>cc <em>10</em></tt>" - GHC convention</b>:</dt>
|
|
<dd>This calling convention has been implemented specifically for use by the
|
|
<a href="http://www.haskell.org/ghc">Glasgow Haskell Compiler (GHC)</a>.
|
|
It passes everything in registers, going to extremes to achieve this by
|
|
disabling callee save registers. This calling convention should not be
|
|
used lightly but only for specific situations such as an alternative to
|
|
the <em>register pinning</em> performance technique often used when
|
|
implementing functional programming languages.At the moment only X86
|
|
supports this convention and it has the following limitations:
|
|
<ul>
|
|
<li>On <em>X86-32</em> only supports up to 4 bit type parameters. No
|
|
floating point types are supported.</li>
|
|
<li>On <em>X86-64</em> only supports up to 10 bit type parameters and
|
|
6 floating point parameters.</li>
|
|
</ul>
|
|
This calling convention supports
|
|
<a href="CodeGenerator.html#tailcallopt">tail call optimization</a> but
|
|
requires both the caller and callee are using it.
|
|
</dd>
|
|
|
|
<dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt>
|
|
<dd>Any calling convention may be specified by number, allowing
|
|
target-specific calling conventions to be used. Target specific calling
|
|
conventions start at 64.</dd>
|
|
</dl>
|
|
|
|
<p>More calling conventions can be added/defined on an as-needed basis, to
|
|
support Pascal conventions or any other well-known target-independent
|
|
convention.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="visibility">Visibility Styles</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>All Global Variables and Functions have one of the following visibility
|
|
styles:</p>
|
|
|
|
<dl>
|
|
<dt><b>"<tt>default</tt>" - Default style</b>:</dt>
|
|
<dd>On targets that use the ELF object file format, default visibility means
|
|
that the declaration is visible to other modules and, in shared libraries,
|
|
means that the declared entity may be overridden. On Darwin, default
|
|
visibility means that the declaration is visible to other modules. Default
|
|
visibility corresponds to "external linkage" in the language.</dd>
|
|
|
|
<dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt>
|
|
<dd>Two declarations of an object with hidden visibility refer to the same
|
|
object if they are in the same shared object. Usually, hidden visibility
|
|
indicates that the symbol will not be placed into the dynamic symbol
|
|
table, so no other module (executable or shared library) can reference it
|
|
directly.</dd>
|
|
|
|
<dt><b>"<tt>protected</tt>" - Protected style</b>:</dt>
|
|
<dd>On ELF, protected visibility indicates that the symbol will be placed in
|
|
the dynamic symbol table, but that references within the defining module
|
|
will bind to the local symbol. That is, the symbol cannot be overridden by
|
|
another module.</dd>
|
|
</dl>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="namedtypes">Named Types</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM IR allows you to specify name aliases for certain types. This can make
|
|
it easier to read the IR and make the IR more condensed (particularly when
|
|
recursive types are involved). An example of a name specification is:</p>
|
|
|
|
<pre class="doc_code">
|
|
%mytype = type { %mytype*, i32 }
|
|
</pre>
|
|
|
|
<p>You may give a name to any <a href="#typesystem">type</a> except
|
|
"<a href="#t_void">void</a>". Type name aliases may be used anywhere a type
|
|
is expected with the syntax "%mytype".</p>
|
|
|
|
<p>Note that type names are aliases for the structural type that they indicate,
|
|
and that you can therefore specify multiple names for the same type. This
|
|
often leads to confusing behavior when dumping out a .ll file. Since LLVM IR
|
|
uses structural typing, the name is not part of the type. When printing out
|
|
LLVM IR, the printer will pick <em>one name</em> to render all types of a
|
|
particular shape. This means that if you have code where two different
|
|
source types end up having the same LLVM type, that the dumper will sometimes
|
|
print the "wrong" or unexpected type. This is an important design point and
|
|
isn't going to change.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="globalvars">Global Variables</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Global variables define regions of memory allocated at compilation time
|
|
instead of run-time. Global variables may optionally be initialized, may
|
|
have an explicit section to be placed in, and may have an optional explicit
|
|
alignment specified.</p>
|
|
|
|
<p>A variable may be defined as <tt>thread_local</tt>, which
|
|
means that it will not be shared by threads (each thread will have a
|
|
separated copy of the variable). Not all targets support thread-local
|
|
variables. Optionally, a TLS model may be specified:</p>
|
|
|
|
<dl>
|
|
<dt><b><tt>localdynamic</tt></b>:</dt>
|
|
<dd>For variables that are only used within the current shared library.</dd>
|
|
|
|
<dt><b><tt>initialexec</tt></b>:</dt>
|
|
<dd>For variables in modules that will not be loaded dynamically.</dd>
|
|
|
|
<dt><b><tt>localexec</tt></b>:</dt>
|
|
<dd>For variables defined in the executable and only used within it.</dd>
|
|
</dl>
|
|
|
|
<p>The models correspond to the ELF TLS models; see
|
|
<a href="http://people.redhat.com/drepper/tls.pdf">ELF
|
|
Handling For Thread-Local Storage</a> for more information on under which
|
|
circumstances the different models may be used. The target may choose a
|
|
different TLS model if the specified model is not supported, or if a better
|
|
choice of model can be made.</p>
|
|
|
|
<p>A variable may be defined as a global
|
|
"constant," which indicates that the contents of the variable
|
|
will <b>never</b> be modified (enabling better optimization, allowing the
|
|
global data to be placed in the read-only section of an executable, etc).
|
|
Note that variables that need runtime initialization cannot be marked
|
|
"constant" as there is a store to the variable.</p>
|
|
|
|
<p>LLVM explicitly allows <em>declarations</em> of global variables to be marked
|
|
constant, even if the final definition of the global is not. This capability
|
|
can be used to enable slightly better optimization of the program, but
|
|
requires the language definition to guarantee that optimizations based on the
|
|
'constantness' are valid for the translation units that do not include the
|
|
definition.</p>
|
|
|
|
<p>As SSA values, global variables define pointer values that are in scope
|
|
(i.e. they dominate) all basic blocks in the program. Global variables
|
|
always define a pointer to their "content" type because they describe a
|
|
region of memory, and all memory objects in LLVM are accessed through
|
|
pointers.</p>
|
|
|
|
<p>Global variables can be marked with <tt>unnamed_addr</tt> which indicates
|
|
that the address is not significant, only the content. Constants marked
|
|
like this can be merged with other constants if they have the same
|
|
initializer. Note that a constant with significant address <em>can</em>
|
|
be merged with a <tt>unnamed_addr</tt> constant, the result being a
|
|
constant whose address is significant.</p>
|
|
|
|
<p>A global variable may be declared to reside in a target-specific numbered
|
|
address space. For targets that support them, address spaces may affect how
|
|
optimizations are performed and/or what target instructions are used to
|
|
access the variable. The default address space is zero. The address space
|
|
qualifier must precede any other attributes.</p>
|
|
|
|
<p>LLVM allows an explicit section to be specified for globals. If the target
|
|
supports it, it will emit globals to the section specified.</p>
|
|
|
|
<p>An explicit alignment may be specified for a global, which must be a power
|
|
of 2. If not present, or if the alignment is set to zero, the alignment of
|
|
the global is set by the target to whatever it feels convenient. If an
|
|
explicit alignment is specified, the global is forced to have exactly that
|
|
alignment. Targets and optimizers are not allowed to over-align the global
|
|
if the global has an assigned section. In this case, the extra alignment
|
|
could be observable: for example, code could assume that the globals are
|
|
densely packed in their section and try to iterate over them as an array,
|
|
alignment padding would break this iteration.</p>
|
|
|
|
<p>For example, the following defines a global in a numbered address space with
|
|
an initializer, section, and alignment:</p>
|
|
|
|
<pre class="doc_code">
|
|
@G = addrspace(5) constant float 1.0, section "foo", align 4
|
|
</pre>
|
|
|
|
<p>The following example defines a thread-local global with
|
|
the <tt>initialexec</tt> TLS model:</p>
|
|
|
|
<pre class="doc_code">
|
|
@G = thread_local(initialexec) global i32 0, align 4
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="functionstructure">Functions</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM function definitions consist of the "<tt>define</tt>" keyword, an
|
|
optional <a href="#linkage">linkage type</a>, an optional
|
|
<a href="#visibility">visibility style</a>, an optional
|
|
<a href="#callingconv">calling convention</a>,
|
|
an optional <tt>unnamed_addr</tt> attribute, a return type, an optional
|
|
<a href="#paramattrs">parameter attribute</a> for the return type, a function
|
|
name, a (possibly empty) argument list (each with optional
|
|
<a href="#paramattrs">parameter attributes</a>), optional
|
|
<a href="#fnattrs">function attributes</a>, an optional section, an optional
|
|
alignment, an optional <a href="#gc">garbage collector name</a>, an opening
|
|
curly brace, a list of basic blocks, and a closing curly brace.</p>
|
|
|
|
<p>LLVM function declarations consist of the "<tt>declare</tt>" keyword, an
|
|
optional <a href="#linkage">linkage type</a>, an optional
|
|
<a href="#visibility">visibility style</a>, an optional
|
|
<a href="#callingconv">calling convention</a>,
|
|
an optional <tt>unnamed_addr</tt> attribute, a return type, an optional
|
|
<a href="#paramattrs">parameter attribute</a> for the return type, a function
|
|
name, a possibly empty list of arguments, an optional alignment, and an
|
|
optional <a href="#gc">garbage collector name</a>.</p>
|
|
|
|
<p>A function definition contains a list of basic blocks, forming the CFG
|
|
(Control Flow Graph) for the function. Each basic block may optionally start
|
|
with a label (giving the basic block a symbol table entry), contains a list
|
|
of instructions, and ends with a <a href="#terminators">terminator</a>
|
|
instruction (such as a branch or function return).</p>
|
|
|
|
<p>The first basic block in a function is special in two ways: it is immediately
|
|
executed on entrance to the function, and it is not allowed to have
|
|
predecessor basic blocks (i.e. there can not be any branches to the entry
|
|
block of a function). Because the block can have no predecessors, it also
|
|
cannot have any <a href="#i_phi">PHI nodes</a>.</p>
|
|
|
|
<p>LLVM allows an explicit section to be specified for functions. If the target
|
|
supports it, it will emit functions to the section specified.</p>
|
|
|
|
<p>An explicit alignment may be specified for a function. If not present, or if
|
|
the alignment is set to zero, the alignment of the function is set by the
|
|
target to whatever it feels convenient. If an explicit alignment is
|
|
specified, the function is forced to have at least that much alignment. All
|
|
alignments must be a power of 2.</p>
|
|
|
|
<p>If the <tt>unnamed_addr</tt> attribute is given, the address is know to not
|
|
be significant and two identical functions can be merged.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre class="doc_code">
|
|
define [<a href="#linkage">linkage</a>] [<a href="#visibility">visibility</a>]
|
|
[<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>]
|
|
<ResultType> @<FunctionName> ([argument list])
|
|
[<a href="#fnattrs">fn Attrs</a>] [section "name"] [align N]
|
|
[<a href="#gc">gc</a>] { ... }
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="aliasstructure">Aliases</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Aliases act as "second name" for the aliasee value (which can be either
|
|
function, global variable, another alias or bitcast of global value). Aliases
|
|
may have an optional <a href="#linkage">linkage type</a>, and an
|
|
optional <a href="#visibility">visibility style</a>.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre class="doc_code">
|
|
@<Name> = alias [Linkage] [Visibility] <AliaseeTy> @<Aliasee>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="namedmetadatastructure">Named Metadata</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Named metadata is a collection of metadata. <a href="#metadata">Metadata
|
|
nodes</a> (but not metadata strings) are the only valid operands for
|
|
a named metadata.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre class="doc_code">
|
|
; Some unnamed metadata nodes, which are referenced by the named metadata.
|
|
!0 = metadata !{metadata !"zero"}
|
|
!1 = metadata !{metadata !"one"}
|
|
!2 = metadata !{metadata !"two"}
|
|
; A named metadata.
|
|
!name = !{!0, !1, !2}
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="paramattrs">Parameter Attributes</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The return type and each parameter of a function type may have a set of
|
|
<i>parameter attributes</i> associated with them. Parameter attributes are
|
|
used to communicate additional information about the result or parameters of
|
|
a function. Parameter attributes are considered to be part of the function,
|
|
not of the function type, so functions with different parameter attributes
|
|
can have the same function type.</p>
|
|
|
|
<p>Parameter attributes are simple keywords that follow the type specified. If
|
|
multiple parameter attributes are needed, they are space separated. For
|
|
example:</p>
|
|
|
|
<pre class="doc_code">
|
|
declare i32 @printf(i8* noalias nocapture, ...)
|
|
declare i32 @atoi(i8 zeroext)
|
|
declare signext i8 @returns_signed_char()
|
|
</pre>
|
|
|
|
<p>Note that any attributes for the function result (<tt>nounwind</tt>,
|
|
<tt>readonly</tt>) come immediately after the argument list.</p>
|
|
|
|
<p>Currently, only the following parameter attributes are defined:</p>
|
|
|
|
<dl>
|
|
<dt><tt><b>zeroext</b></tt></dt>
|
|
<dd>This indicates to the code generator that the parameter or return value
|
|
should be zero-extended to the extent required by the target's ABI (which
|
|
is usually 32-bits, but is 8-bits for a i1 on x86-64) by the caller (for a
|
|
parameter) or the callee (for a return value).</dd>
|
|
|
|
<dt><tt><b>signext</b></tt></dt>
|
|
<dd>This indicates to the code generator that the parameter or return value
|
|
should be sign-extended to the extent required by the target's ABI (which
|
|
is usually 32-bits) by the caller (for a parameter) or the callee (for a
|
|
return value).</dd>
|
|
|
|
<dt><tt><b>inreg</b></tt></dt>
|
|
<dd>This indicates that this parameter or return value should be treated in a
|
|
special target-dependent fashion during while emitting code for a function
|
|
call or return (usually, by putting it in a register as opposed to memory,
|
|
though some targets use it to distinguish between two different kinds of
|
|
registers). Use of this attribute is target-specific.</dd>
|
|
|
|
<dt><tt><b><a name="byval">byval</a></b></tt></dt>
|
|
<dd><p>This indicates that the pointer parameter should really be passed by
|
|
value to the function. The attribute implies that a hidden copy of the
|
|
pointee
|
|
is made between the caller and the callee, so the callee is unable to
|
|
modify the value in the caller. This attribute is only valid on LLVM
|
|
pointer arguments. It is generally used to pass structs and arrays by
|
|
value, but is also valid on pointers to scalars. The copy is considered
|
|
to belong to the caller not the callee (for example,
|
|
<tt><a href="#readonly">readonly</a></tt> functions should not write to
|
|
<tt>byval</tt> parameters). This is not a valid attribute for return
|
|
values.</p>
|
|
|
|
<p>The byval attribute also supports specifying an alignment with
|
|
the align attribute. It indicates the alignment of the stack slot to
|
|
form and the known alignment of the pointer specified to the call site. If
|
|
the alignment is not specified, then the code generator makes a
|
|
target-specific assumption.</p></dd>
|
|
|
|
<dt><tt><b><a name="sret">sret</a></b></tt></dt>
|
|
<dd>This indicates that the pointer parameter specifies the address of a
|
|
structure that is the return value of the function in the source program.
|
|
This pointer must be guaranteed by the caller to be valid: loads and
|
|
stores to the structure may be assumed by the callee to not to trap and
|
|
to be properly aligned. This may only be applied to the first parameter.
|
|
This is not a valid attribute for return values. </dd>
|
|
|
|
<dt><tt><b><a name="noalias">noalias</a></b></tt></dt>
|
|
<dd>This indicates that pointer values
|
|
<a href="#pointeraliasing"><i>based</i></a> on the argument or return
|
|
value do not alias pointer values which are not <i>based</i> on it,
|
|
ignoring certain "irrelevant" dependencies.
|
|
For a call to the parent function, dependencies between memory
|
|
references from before or after the call and from those during the call
|
|
are "irrelevant" to the <tt>noalias</tt> keyword for the arguments and
|
|
return value used in that call.
|
|
The caller shares the responsibility with the callee for ensuring that
|
|
these requirements are met.
|
|
For further details, please see the discussion of the NoAlias response in
|
|
<a href="AliasAnalysis.html#MustMayNo">alias analysis</a>.<br>
|
|
<br>
|
|
Note that this definition of <tt>noalias</tt> is intentionally
|
|
similar to the definition of <tt>restrict</tt> in C99 for function
|
|
arguments, though it is slightly weaker.
|
|
<br>
|
|
For function return values, C99's <tt>restrict</tt> is not meaningful,
|
|
while LLVM's <tt>noalias</tt> is.
|
|
</dd>
|
|
|
|
<dt><tt><b><a name="nocapture">nocapture</a></b></tt></dt>
|
|
<dd>This indicates that the callee does not make any copies of the pointer
|
|
that outlive the callee itself. This is not a valid attribute for return
|
|
values.</dd>
|
|
|
|
<dt><tt><b><a name="nest">nest</a></b></tt></dt>
|
|
<dd>This indicates that the pointer parameter can be excised using the
|
|
<a href="#int_trampoline">trampoline intrinsics</a>. This is not a valid
|
|
attribute for return values.</dd>
|
|
</dl>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="gc">Garbage Collector Names</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Each function may specify a garbage collector name, which is simply a
|
|
string:</p>
|
|
|
|
<pre class="doc_code">
|
|
define void @f() gc "name" { ... }
|
|
</pre>
|
|
|
|
<p>The compiler declares the supported values of <i>name</i>. Specifying a
|
|
collector which will cause the compiler to alter its output in order to
|
|
support the named garbage collection algorithm.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="fnattrs">Function Attributes</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Function attributes are set to communicate additional information about a
|
|
function. Function attributes are considered to be part of the function, not
|
|
of the function type, so functions with different parameter attributes can
|
|
have the same function type.</p>
|
|
|
|
<p>Function attributes are simple keywords that follow the type specified. If
|
|
multiple attributes are needed, they are space separated. For example:</p>
|
|
|
|
<pre class="doc_code">
|
|
define void @f() noinline { ... }
|
|
define void @f() alwaysinline { ... }
|
|
define void @f() alwaysinline optsize { ... }
|
|
define void @f() optsize { ... }
|
|
</pre>
|
|
|
|
<dl>
|
|
<dt><tt><b>address_safety</b></tt></dt>
|
|
<dd>This attribute indicates that the address safety analysis
|
|
is enabled for this function. </dd>
|
|
|
|
<dt><tt><b>alignstack(<<em>n</em>>)</b></tt></dt>
|
|
<dd>This attribute indicates that, when emitting the prologue and epilogue,
|
|
the backend should forcibly align the stack pointer. Specify the
|
|
desired alignment, which must be a power of two, in parentheses.
|
|
|
|
<dt><tt><b>alwaysinline</b></tt></dt>
|
|
<dd>This attribute indicates that the inliner should attempt to inline this
|
|
function into callers whenever possible, ignoring any active inlining size
|
|
threshold for this caller.</dd>
|
|
|
|
<dt><tt><b>nonlazybind</b></tt></dt>
|
|
<dd>This attribute suppresses lazy symbol binding for the function. This
|
|
may make calls to the function faster, at the cost of extra program
|
|
startup time if the function is not called during program startup.</dd>
|
|
|
|
<dt><tt><b>inlinehint</b></tt></dt>
|
|
<dd>This attribute indicates that the source code contained a hint that inlining
|
|
this function is desirable (such as the "inline" keyword in C/C++). It
|
|
is just a hint; it imposes no requirements on the inliner.</dd>
|
|
|
|
<dt><tt><b>naked</b></tt></dt>
|
|
<dd>This attribute disables prologue / epilogue emission for the function.
|
|
This can have very system-specific consequences.</dd>
|
|
|
|
<dt><tt><b>noimplicitfloat</b></tt></dt>
|
|
<dd>This attributes disables implicit floating point instructions.</dd>
|
|
|
|
<dt><tt><b>noinline</b></tt></dt>
|
|
<dd>This attribute indicates that the inliner should never inline this
|
|
function in any situation. This attribute may not be used together with
|
|
the <tt>alwaysinline</tt> attribute.</dd>
|
|
|
|
<dt><tt><b>noredzone</b></tt></dt>
|
|
<dd>This attribute indicates that the code generator should not use a red
|
|
zone, even if the target-specific ABI normally permits it.</dd>
|
|
|
|
<dt><tt><b>noreturn</b></tt></dt>
|
|
<dd>This function attribute indicates that the function never returns
|
|
normally. This produces undefined behavior at runtime if the function
|
|
ever does dynamically return.</dd>
|
|
|
|
<dt><tt><b>nounwind</b></tt></dt>
|
|
<dd>This function attribute indicates that the function never returns with an
|
|
unwind or exceptional control flow. If the function does unwind, its
|
|
runtime behavior is undefined.</dd>
|
|
|
|
<dt><tt><b>optsize</b></tt></dt>
|
|
<dd>This attribute suggests that optimization passes and code generator passes
|
|
make choices that keep the code size of this function low, and otherwise
|
|
do optimizations specifically to reduce code size.</dd>
|
|
|
|
<dt><tt><b>readnone</b></tt></dt>
|
|
<dd>This attribute indicates that the function computes its result (or decides
|
|
to unwind an exception) based strictly on its arguments, without
|
|
dereferencing any pointer arguments or otherwise accessing any mutable
|
|
state (e.g. memory, control registers, etc) visible to caller functions.
|
|
It does not write through any pointer arguments
|
|
(including <tt><a href="#byval">byval</a></tt> arguments) and never
|
|
changes any state visible to callers. This means that it cannot unwind
|
|
exceptions by calling the <tt>C++</tt> exception throwing methods.</dd>
|
|
|
|
<dt><tt><b><a name="readonly">readonly</a></b></tt></dt>
|
|
<dd>This attribute indicates that the function does not write through any
|
|
pointer arguments (including <tt><a href="#byval">byval</a></tt>
|
|
arguments) or otherwise modify any state (e.g. memory, control registers,
|
|
etc) visible to caller functions. It may dereference pointer arguments
|
|
and read state that may be set in the caller. A readonly function always
|
|
returns the same value (or unwinds an exception identically) when called
|
|
with the same set of arguments and global state. It cannot unwind an
|
|
exception by calling the <tt>C++</tt> exception throwing methods.</dd>
|
|
|
|
<dt><tt><b><a name="returns_twice">returns_twice</a></b></tt></dt>
|
|
<dd>This attribute indicates that this function can return twice. The
|
|
C <code>setjmp</code> is an example of such a function. The compiler
|
|
disables some optimizations (like tail calls) in the caller of these
|
|
functions.</dd>
|
|
|
|
<dt><tt><b><a name="ssp">ssp</a></b></tt></dt>
|
|
<dd>This attribute indicates that the function should emit a stack smashing
|
|
protector. It is in the form of a "canary"—a random value placed on
|
|
the stack before the local variables that's checked upon return from the
|
|
function to see if it has been overwritten. A heuristic is used to
|
|
determine if a function needs stack protectors or not.<br>
|
|
<br>
|
|
If a function that has an <tt>ssp</tt> attribute is inlined into a
|
|
function that doesn't have an <tt>ssp</tt> attribute, then the resulting
|
|
function will have an <tt>ssp</tt> attribute.</dd>
|
|
|
|
<dt><tt><b>sspreq</b></tt></dt>
|
|
<dd>This attribute indicates that the function should <em>always</em> emit a
|
|
stack smashing protector. This overrides
|
|
the <tt><a href="#ssp">ssp</a></tt> function attribute.<br>
|
|
<br>
|
|
If a function that has an <tt>sspreq</tt> attribute is inlined into a
|
|
function that doesn't have an <tt>sspreq</tt> attribute or which has
|
|
an <tt>ssp</tt> attribute, then the resulting function will have
|
|
an <tt>sspreq</tt> attribute.</dd>
|
|
|
|
<dt><tt><b><a name="uwtable">uwtable</a></b></tt></dt>
|
|
<dd>This attribute indicates that the ABI being targeted requires that
|
|
an unwind table entry be produce for this function even if we can
|
|
show that no exceptions passes by it. This is normally the case for
|
|
the ELF x86-64 abi, but it can be disabled for some compilation
|
|
units.</dd>
|
|
</dl>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="moduleasm">Module-Level Inline Assembly</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Modules may contain "module-level inline asm" blocks, which corresponds to
|
|
the GCC "file scope inline asm" blocks. These blocks are internally
|
|
concatenated by LLVM and treated as a single unit, but may be separated in
|
|
the <tt>.ll</tt> file if desired. The syntax is very simple:</p>
|
|
|
|
<pre class="doc_code">
|
|
module asm "inline asm code goes here"
|
|
module asm "more can go here"
|
|
</pre>
|
|
|
|
<p>The strings can contain any character by escaping non-printable characters.
|
|
The escape sequence used is simply "\xx" where "xx" is the two digit hex code
|
|
for the number.</p>
|
|
|
|
<p>The inline asm code is simply printed to the machine code .s file when
|
|
assembly code is generated.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="datalayout">Data Layout</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>A module may specify a target specific data layout string that specifies how
|
|
data is to be laid out in memory. The syntax for the data layout is
|
|
simply:</p>
|
|
|
|
<pre class="doc_code">
|
|
target datalayout = "<i>layout specification</i>"
|
|
</pre>
|
|
|
|
<p>The <i>layout specification</i> consists of a list of specifications
|
|
separated by the minus sign character ('-'). Each specification starts with
|
|
a letter and may include other information after the letter to define some
|
|
aspect of the data layout. The specifications accepted are as follows:</p>
|
|
|
|
<dl>
|
|
<dt><tt>E</tt></dt>
|
|
<dd>Specifies that the target lays out data in big-endian form. That is, the
|
|
bits with the most significance have the lowest address location.</dd>
|
|
|
|
<dt><tt>e</tt></dt>
|
|
<dd>Specifies that the target lays out data in little-endian form. That is,
|
|
the bits with the least significance have the lowest address
|
|
location.</dd>
|
|
|
|
<dt><tt>S<i>size</i></tt></dt>
|
|
<dd>Specifies the natural alignment of the stack in bits. Alignment promotion
|
|
of stack variables is limited to the natural stack alignment to avoid
|
|
dynamic stack realignment. The stack alignment must be a multiple of
|
|
8-bits. If omitted, the natural stack alignment defaults to "unspecified",
|
|
which does not prevent any alignment promotions.</dd>
|
|
|
|
<dt><tt>p[n]:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
|
|
<dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and
|
|
<i>preferred</i> alignments for address space <i>n</i>. All sizes are in
|
|
bits. Specifying the <i>pref</i> alignment is optional. If omitted, the
|
|
preceding <tt>:</tt> should be omitted too. The address space,
|
|
<i>n</i> is optional, and if not specified, denotes the default address
|
|
space 0. The value of <i>n</i> must be in the range [1,2^23).</dd>
|
|
|
|
<dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
|
|
<dd>This specifies the alignment for an integer type of a given bit
|
|
<i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd>
|
|
|
|
<dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
|
|
<dd>This specifies the alignment for a vector type of a given bit
|
|
<i>size</i>.</dd>
|
|
|
|
<dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
|
|
<dd>This specifies the alignment for a floating point type of a given bit
|
|
<i>size</i>. Only values of <i>size</i> that are supported by the target
|
|
will work. 32 (float) and 64 (double) are supported on all targets;
|
|
80 or 128 (different flavors of long double) are also supported on some
|
|
targets.
|
|
|
|
<dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
|
|
<dd>This specifies the alignment for an aggregate type of a given bit
|
|
<i>size</i>.</dd>
|
|
|
|
<dt><tt>s<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
|
|
<dd>This specifies the alignment for a stack object of a given bit
|
|
<i>size</i>.</dd>
|
|
|
|
<dt><tt>n<i>size1</i>:<i>size2</i>:<i>size3</i>...</tt></dt>
|
|
<dd>This specifies a set of native integer widths for the target CPU
|
|
in bits. For example, it might contain "n32" for 32-bit PowerPC,
|
|
"n32:64" for PowerPC 64, or "n8:16:32:64" for X86-64. Elements of
|
|
this set are considered to support most general arithmetic
|
|
operations efficiently.</dd>
|
|
</dl>
|
|
|
|
<p>When constructing the data layout for a given target, LLVM starts with a
|
|
default set of specifications which are then (possibly) overridden by the
|
|
specifications in the <tt>datalayout</tt> keyword. The default specifications
|
|
are given in this list:</p>
|
|
|
|
<ul>
|
|
<li><tt>E</tt> - big endian</li>
|
|
<li><tt>p:64:64:64</tt> - 64-bit pointers with 64-bit alignment</li>
|
|
<li><tt>p1:32:32:32</tt> - 32-bit pointers with 32-bit alignment for
|
|
address space 1</li>
|
|
<li><tt>p2:16:32:32</tt> - 16-bit pointers with 32-bit alignment for
|
|
address space 2</li>
|
|
<li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li>
|
|
<li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li>
|
|
<li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li>
|
|
<li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li>
|
|
<li><tt>i64:32:64</tt> - i64 has ABI alignment of 32-bits but preferred
|
|
alignment of 64-bits</li>
|
|
<li><tt>f32:32:32</tt> - float is 32-bit aligned</li>
|
|
<li><tt>f64:64:64</tt> - double is 64-bit aligned</li>
|
|
<li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li>
|
|
<li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li>
|
|
<li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li>
|
|
<li><tt>s0:64:64</tt> - stack objects are 64-bit aligned</li>
|
|
</ul>
|
|
|
|
<p>When LLVM is determining the alignment for a given type, it uses the
|
|
following rules:</p>
|
|
|
|
<ol>
|
|
<li>If the type sought is an exact match for one of the specifications, that
|
|
specification is used.</li>
|
|
|
|
<li>If no match is found, and the type sought is an integer type, then the
|
|
smallest integer type that is larger than the bitwidth of the sought type
|
|
is used. If none of the specifications are larger than the bitwidth then
|
|
the largest integer type is used. For example, given the default
|
|
specifications above, the i7 type will use the alignment of i8 (next
|
|
largest) while both i65 and i256 will use the alignment of i64 (largest
|
|
specified).</li>
|
|
|
|
<li>If no match is found, and the type sought is a vector type, then the
|
|
largest vector type that is smaller than the sought vector type will be
|
|
used as a fall back. This happens because <128 x double> can be
|
|
implemented in terms of 64 <2 x double>, for example.</li>
|
|
</ol>
|
|
|
|
<p>The function of the data layout string may not be what you expect. Notably,
|
|
this is not a specification from the frontend of what alignment the code
|
|
generator should use.</p>
|
|
|
|
<p>Instead, if specified, the target data layout is required to match what the
|
|
ultimate <em>code generator</em> expects. This string is used by the
|
|
mid-level optimizers to
|
|
improve code, and this only works if it matches what the ultimate code
|
|
generator uses. If you would like to generate IR that does not embed this
|
|
target-specific detail into the IR, then you don't have to specify the
|
|
string. This will disable some optimizations that require precise layout
|
|
information, but this also prevents those optimizations from introducing
|
|
target specificity into the IR.</p>
|
|
|
|
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="pointeraliasing">Pointer Aliasing Rules</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Any memory access must be done through a pointer value associated
|
|
with an address range of the memory access, otherwise the behavior
|
|
is undefined. Pointer values are associated with address ranges
|
|
according to the following rules:</p>
|
|
|
|
<ul>
|
|
<li>A pointer value is associated with the addresses associated with
|
|
any value it is <i>based</i> on.
|
|
<li>An address of a global variable is associated with the address
|
|
range of the variable's storage.</li>
|
|
<li>The result value of an allocation instruction is associated with
|
|
the address range of the allocated storage.</li>
|
|
<li>A null pointer in the default address-space is associated with
|
|
no address.</li>
|
|
<li>An integer constant other than zero or a pointer value returned
|
|
from a function not defined within LLVM may be associated with address
|
|
ranges allocated through mechanisms other than those provided by
|
|
LLVM. Such ranges shall not overlap with any ranges of addresses
|
|
allocated by mechanisms provided by LLVM.</li>
|
|
</ul>
|
|
|
|
<p>A pointer value is <i>based</i> on another pointer value according
|
|
to the following rules:</p>
|
|
|
|
<ul>
|
|
<li>A pointer value formed from a
|
|
<tt><a href="#i_getelementptr">getelementptr</a></tt> operation
|
|
is <i>based</i> on the first operand of the <tt>getelementptr</tt>.</li>
|
|
<li>The result value of a
|
|
<tt><a href="#i_bitcast">bitcast</a></tt> is <i>based</i> on the operand
|
|
of the <tt>bitcast</tt>.</li>
|
|
<li>A pointer value formed by an
|
|
<tt><a href="#i_inttoptr">inttoptr</a></tt> is <i>based</i> on all
|
|
pointer values that contribute (directly or indirectly) to the
|
|
computation of the pointer's value.</li>
|
|
<li>The "<i>based</i> on" relationship is transitive.</li>
|
|
</ul>
|
|
|
|
<p>Note that this definition of <i>"based"</i> is intentionally
|
|
similar to the definition of <i>"based"</i> in C99, though it is
|
|
slightly weaker.</p>
|
|
|
|
<p>LLVM IR does not associate types with memory. The result type of a
|
|
<tt><a href="#i_load">load</a></tt> merely indicates the size and
|
|
alignment of the memory from which to load, as well as the
|
|
interpretation of the value. The first operand type of a
|
|
<tt><a href="#i_store">store</a></tt> similarly only indicates the size
|
|
and alignment of the store.</p>
|
|
|
|
<p>Consequently, type-based alias analysis, aka TBAA, aka
|
|
<tt>-fstrict-aliasing</tt>, is not applicable to general unadorned
|
|
LLVM IR. <a href="#metadata">Metadata</a> may be used to encode
|
|
additional information which specialized optimization passes may use
|
|
to implement type-based alias analysis.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="volatile">Volatile Memory Accesses</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Certain memory accesses, such as <a href="#i_load"><tt>load</tt></a>s, <a
|
|
href="#i_store"><tt>store</tt></a>s, and <a
|
|
href="#int_memcpy"><tt>llvm.memcpy</tt></a>s may be marked <tt>volatile</tt>.
|
|
The optimizers must not change the number of volatile operations or change their
|
|
order of execution relative to other volatile operations. The optimizers
|
|
<i>may</i> change the order of volatile operations relative to non-volatile
|
|
operations. This is not Java's "volatile" and has no cross-thread
|
|
synchronization behavior.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="memmodel">Memory Model for Concurrent Operations</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The LLVM IR does not define any way to start parallel threads of execution
|
|
or to register signal handlers. Nonetheless, there are platform-specific
|
|
ways to create them, and we define LLVM IR's behavior in their presence. This
|
|
model is inspired by the C++0x memory model.</p>
|
|
|
|
<p>For a more informal introduction to this model, see the
|
|
<a href="Atomics.html">LLVM Atomic Instructions and Concurrency Guide</a>.
|
|
|
|
<p>We define a <i>happens-before</i> partial order as the least partial order
|
|
that</p>
|
|
<ul>
|
|
<li>Is a superset of single-thread program order, and</li>
|
|
<li>When a <i>synchronizes-with</i> <tt>b</tt>, includes an edge from
|
|
<tt>a</tt> to <tt>b</tt>. <i>Synchronizes-with</i> pairs are introduced
|
|
by platform-specific techniques, like pthread locks, thread
|
|
creation, thread joining, etc., and by atomic instructions.
|
|
(See also <a href="#ordering">Atomic Memory Ordering Constraints</a>).
|
|
</li>
|
|
</ul>
|
|
|
|
<p>Note that program order does not introduce <i>happens-before</i> edges
|
|
between a thread and signals executing inside that thread.</p>
|
|
|
|
<p>Every (defined) read operation (load instructions, memcpy, atomic
|
|
loads/read-modify-writes, etc.) <var>R</var> reads a series of bytes written by
|
|
(defined) write operations (store instructions, atomic
|
|
stores/read-modify-writes, memcpy, etc.). For the purposes of this section,
|
|
initialized globals are considered to have a write of the initializer which is
|
|
atomic and happens before any other read or write of the memory in question.
|
|
For each byte of a read <var>R</var>, <var>R<sub>byte</sub></var> may see
|
|
any write to the same byte, except:</p>
|
|
|
|
<ul>
|
|
<li>If <var>write<sub>1</sub></var> happens before
|
|
<var>write<sub>2</sub></var>, and <var>write<sub>2</sub></var> happens
|
|
before <var>R<sub>byte</sub></var>, then <var>R<sub>byte</sub></var>
|
|
does not see <var>write<sub>1</sub></var>.
|
|
<li>If <var>R<sub>byte</sub></var> happens before
|
|
<var>write<sub>3</sub></var>, then <var>R<sub>byte</sub></var> does not
|
|
see <var>write<sub>3</sub></var>.
|
|
</ul>
|
|
|
|
<p>Given that definition, <var>R<sub>byte</sub></var> is defined as follows:
|
|
<ul>
|
|
<li>If <var>R</var> is volatile, the result is target-dependent. (Volatile
|
|
is supposed to give guarantees which can support
|
|
<code>sig_atomic_t</code> in C/C++, and may be used for accesses to
|
|
addresses which do not behave like normal memory. It does not generally
|
|
provide cross-thread synchronization.)
|
|
<li>Otherwise, if there is no write to the same byte that happens before
|
|
<var>R<sub>byte</sub></var>, <var>R<sub>byte</sub></var> returns
|
|
<tt>undef</tt> for that byte.
|
|
<li>Otherwise, if <var>R<sub>byte</sub></var> may see exactly one write,
|
|
<var>R<sub>byte</sub></var> returns the value written by that
|
|
write.</li>
|
|
<li>Otherwise, if <var>R</var> is atomic, and all the writes
|
|
<var>R<sub>byte</sub></var> may see are atomic, it chooses one of the
|
|
values written. See the <a href="#ordering">Atomic Memory Ordering
|
|
Constraints</a> section for additional constraints on how the choice
|
|
is made.
|
|
<li>Otherwise <var>R<sub>byte</sub></var> returns <tt>undef</tt>.</li>
|
|
</ul>
|
|
|
|
<p><var>R</var> returns the value composed of the series of bytes it read.
|
|
This implies that some bytes within the value may be <tt>undef</tt>
|
|
<b>without</b> the entire value being <tt>undef</tt>. Note that this only
|
|
defines the semantics of the operation; it doesn't mean that targets will
|
|
emit more than one instruction to read the series of bytes.</p>
|
|
|
|
<p>Note that in cases where none of the atomic intrinsics are used, this model
|
|
places only one restriction on IR transformations on top of what is required
|
|
for single-threaded execution: introducing a store to a byte which might not
|
|
otherwise be stored is not allowed in general. (Specifically, in the case
|
|
where another thread might write to and read from an address, introducing a
|
|
store can change a load that may see exactly one write into a load that may
|
|
see multiple writes.)</p>
|
|
|
|
<!-- FIXME: This model assumes all targets where concurrency is relevant have
|
|
a byte-size store which doesn't affect adjacent bytes. As far as I can tell,
|
|
none of the backends currently in the tree fall into this category; however,
|
|
there might be targets which care. If there are, we want a paragraph
|
|
like the following:
|
|
|
|
Targets may specify that stores narrower than a certain width are not
|
|
available; on such a target, for the purposes of this model, treat any
|
|
non-atomic write with an alignment or width less than the minimum width
|
|
as if it writes to the relevant surrounding bytes.
|
|
-->
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="ordering">Atomic Memory Ordering Constraints</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Atomic instructions (<a href="#i_cmpxchg"><code>cmpxchg</code></a>,
|
|
<a href="#i_atomicrmw"><code>atomicrmw</code></a>,
|
|
<a href="#i_fence"><code>fence</code></a>,
|
|
<a href="#i_load"><code>atomic load</code></a>, and
|
|
<a href="#i_store"><code>atomic store</code></a>) take an ordering parameter
|
|
that determines which other atomic instructions on the same address they
|
|
<i>synchronize with</i>. These semantics are borrowed from Java and C++0x,
|
|
but are somewhat more colloquial. If these descriptions aren't precise enough,
|
|
check those specs (see spec references in the
|
|
<a href="Atomics.html#introduction">atomics guide</a>).
|
|
<a href="#i_fence"><code>fence</code></a> instructions
|
|
treat these orderings somewhat differently since they don't take an address.
|
|
See that instruction's documentation for details.</p>
|
|
|
|
<p>For a simpler introduction to the ordering constraints, see the
|
|
<a href="Atomics.html">LLVM Atomic Instructions and Concurrency Guide</a>.</p>
|
|
|
|
<dl>
|
|
<dt><code>unordered</code></dt>
|
|
<dd>The set of values that can be read is governed by the happens-before
|
|
partial order. A value cannot be read unless some operation wrote it.
|
|
This is intended to provide a guarantee strong enough to model Java's
|
|
non-volatile shared variables. This ordering cannot be specified for
|
|
read-modify-write operations; it is not strong enough to make them atomic
|
|
in any interesting way.</dd>
|
|
<dt><code>monotonic</code></dt>
|
|
<dd>In addition to the guarantees of <code>unordered</code>, there is a single
|
|
total order for modifications by <code>monotonic</code> operations on each
|
|
address. All modification orders must be compatible with the happens-before
|
|
order. There is no guarantee that the modification orders can be combined to
|
|
a global total order for the whole program (and this often will not be
|
|
possible). The read in an atomic read-modify-write operation
|
|
(<a href="#i_cmpxchg"><code>cmpxchg</code></a> and
|
|
<a href="#i_atomicrmw"><code>atomicrmw</code></a>)
|
|
reads the value in the modification order immediately before the value it
|
|
writes. If one atomic read happens before another atomic read of the same
|
|
address, the later read must see the same value or a later value in the
|
|
address's modification order. This disallows reordering of
|
|
<code>monotonic</code> (or stronger) operations on the same address. If an
|
|
address is written <code>monotonic</code>ally by one thread, and other threads
|
|
<code>monotonic</code>ally read that address repeatedly, the other threads must
|
|
eventually see the write. This corresponds to the C++0x/C1x
|
|
<code>memory_order_relaxed</code>.</dd>
|
|
<dt><code>acquire</code></dt>
|
|
<dd>In addition to the guarantees of <code>monotonic</code>,
|
|
a <i>synchronizes-with</i> edge may be formed with a <code>release</code>
|
|
operation. This is intended to model C++'s <code>memory_order_acquire</code>.</dd>
|
|
<dt><code>release</code></dt>
|
|
<dd>In addition to the guarantees of <code>monotonic</code>, if this operation
|
|
writes a value which is subsequently read by an <code>acquire</code> operation,
|
|
it <i>synchronizes-with</i> that operation. (This isn't a complete
|
|
description; see the C++0x definition of a release sequence.) This corresponds
|
|
to the C++0x/C1x <code>memory_order_release</code>.</dd>
|
|
<dt><code>acq_rel</code> (acquire+release)</dt><dd>Acts as both an
|
|
<code>acquire</code> and <code>release</code> operation on its address.
|
|
This corresponds to the C++0x/C1x <code>memory_order_acq_rel</code>.</dd>
|
|
<dt><code>seq_cst</code> (sequentially consistent)</dt><dd>
|
|
<dd>In addition to the guarantees of <code>acq_rel</code>
|
|
(<code>acquire</code> for an operation which only reads, <code>release</code>
|
|
for an operation which only writes), there is a global total order on all
|
|
sequentially-consistent operations on all addresses, which is consistent with
|
|
the <i>happens-before</i> partial order and with the modification orders of
|
|
all the affected addresses. Each sequentially-consistent read sees the last
|
|
preceding write to the same address in this global order. This corresponds
|
|
to the C++0x/C1x <code>memory_order_seq_cst</code> and Java volatile.</dd>
|
|
</dl>
|
|
|
|
<p id="singlethread">If an atomic operation is marked <code>singlethread</code>,
|
|
it only <i>synchronizes with</i> or participates in modification and seq_cst
|
|
total orderings with other operations running in the same thread (for example,
|
|
in signal handlers).</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="typesystem">Type System</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>The LLVM type system is one of the most important features of the
|
|
intermediate representation. Being typed enables a number of optimizations
|
|
to be performed on the intermediate representation directly, without having
|
|
to do extra analyses on the side before the transformation. A strong type
|
|
system makes it easier to read the generated code and enables novel analyses
|
|
and transformations that are not feasible to perform on normal three address
|
|
code representations.</p>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="t_classifications">Type Classifications</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The types fall into a few useful classifications:</p>
|
|
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr><th>Classification</th><th>Types</th></tr>
|
|
<tr>
|
|
<td><a href="#t_integer">integer</a></td>
|
|
<td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td>
|
|
</tr>
|
|
<tr>
|
|
<td><a href="#t_floating">floating point</a></td>
|
|
<td><tt>half, float, double, x86_fp80, fp128, ppc_fp128</tt></td>
|
|
</tr>
|
|
<tr>
|
|
<td><a name="t_firstclass">first class</a></td>
|
|
<td><a href="#t_integer">integer</a>,
|
|
<a href="#t_floating">floating point</a>,
|
|
<a href="#t_pointer">pointer</a>,
|
|
<a href="#t_vector">vector</a>,
|
|
<a href="#t_struct">structure</a>,
|
|
<a href="#t_array">array</a>,
|
|
<a href="#t_label">label</a>,
|
|
<a href="#t_metadata">metadata</a>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td><a href="#t_primitive">primitive</a></td>
|
|
<td><a href="#t_label">label</a>,
|
|
<a href="#t_void">void</a>,
|
|
<a href="#t_integer">integer</a>,
|
|
<a href="#t_floating">floating point</a>,
|
|
<a href="#t_x86mmx">x86mmx</a>,
|
|
<a href="#t_metadata">metadata</a>.</td>
|
|
</tr>
|
|
<tr>
|
|
<td><a href="#t_derived">derived</a></td>
|
|
<td><a href="#t_array">array</a>,
|
|
<a href="#t_function">function</a>,
|
|
<a href="#t_pointer">pointer</a>,
|
|
<a href="#t_struct">structure</a>,
|
|
<a href="#t_vector">vector</a>,
|
|
<a href="#t_opaque">opaque</a>.
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<p>The <a href="#t_firstclass">first class</a> types are perhaps the most
|
|
important. Values of these types are the only ones which can be produced by
|
|
instructions.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="t_primitive">Primitive Types</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The primitive types are the fundamental building blocks of the LLVM
|
|
system.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_integer">Integer Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The integer type is a very simple type that simply specifies an arbitrary
|
|
bit width for the integer type desired. Any bit width from 1 bit to
|
|
2<sup>23</sup>-1 (about 8 million) can be specified.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
iN
|
|
</pre>
|
|
|
|
<p>The number of bits the integer will occupy is specified by the <tt>N</tt>
|
|
value.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left"><tt>i1</tt></td>
|
|
<td class="left">a single-bit integer.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>i32</tt></td>
|
|
<td class="left">a 32-bit integer.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>i1942652</tt></td>
|
|
<td class="left">a really big integer of over 1 million bits.</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_floating">Floating Point Types</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<table>
|
|
<tbody>
|
|
<tr><th>Type</th><th>Description</th></tr>
|
|
<tr><td><tt>half</tt></td><td>16-bit floating point value</td></tr>
|
|
<tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr>
|
|
<tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr>
|
|
<tr><td><tt>fp128</tt></td><td>128-bit floating point value (112-bit mantissa)</td></tr>
|
|
<tr><td><tt>x86_fp80</tt></td><td>80-bit floating point value (X87)</td></tr>
|
|
<tr><td><tt>ppc_fp128</tt></td><td>128-bit floating point value (two 64-bits)</td></tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_x86mmx">X86mmx Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The x86mmx type represents a value held in an MMX register on an x86 machine. The operations allowed on it are quite limited: parameters and return values, load and store, and bitcast. User-specified MMX instructions are represented as intrinsic or asm calls with arguments and/or results of this type. There are no arrays, vectors or constants of this type.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
x86mmx
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_void">Void Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The void type does not represent any value and has no size.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
void
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_label">Label Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The label type represents code labels.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
label
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_metadata">Metadata Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The metadata type represents embedded metadata. No derived types may be
|
|
created from metadata except for <a href="#t_function">function</a>
|
|
arguments.
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
metadata
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="t_derived">Derived Types</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The real power in LLVM comes from the derived types in the system. This is
|
|
what allows a programmer to represent arrays, functions, pointers, and other
|
|
useful types. Each of these types contain one or more element types which
|
|
may be a primitive type, or another derived type. For example, it is
|
|
possible to have a two dimensional array, using an array as the element type
|
|
of another array.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_aggregate">Aggregate Types</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<p>Aggregate Types are a subset of derived types that can contain multiple
|
|
member types. <a href="#t_array">Arrays</a> and
|
|
<a href="#t_struct">structs</a> are aggregate types.
|
|
<a href="#t_vector">Vectors</a> are not considered to be aggregate types.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_array">Array Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The array type is a very simple derived type that arranges elements
|
|
sequentially in memory. The array type requires a size (number of elements)
|
|
and an underlying data type.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
[<# elements> x <elementtype>]
|
|
</pre>
|
|
|
|
<p>The number of elements is a constant integer value; <tt>elementtype</tt> may
|
|
be any type with a size.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left"><tt>[40 x i32]</tt></td>
|
|
<td class="left">Array of 40 32-bit integer values.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>[41 x i32]</tt></td>
|
|
<td class="left">Array of 41 32-bit integer values.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>[4 x i8]</tt></td>
|
|
<td class="left">Array of 4 8-bit integer values.</td>
|
|
</tr>
|
|
</table>
|
|
<p>Here are some examples of multidimensional arrays:</p>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left"><tt>[3 x [4 x i32]]</tt></td>
|
|
<td class="left">3x4 array of 32-bit integer values.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>[12 x [10 x float]]</tt></td>
|
|
<td class="left">12x10 array of single precision floating point values.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>[2 x [3 x [4 x i16]]]</tt></td>
|
|
<td class="left">2x3x4 array of 16-bit integer values.</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<p>There is no restriction on indexing beyond the end of the array implied by
|
|
a static type (though there are restrictions on indexing beyond the bounds
|
|
of an allocated object in some cases). This means that single-dimension
|
|
'variable sized array' addressing can be implemented in LLVM with a zero
|
|
length array type. An implementation of 'pascal style arrays' in LLVM could
|
|
use the type "<tt>{ i32, [0 x float]}</tt>", for example.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_function">Function Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The function type can be thought of as a function signature. It consists of
|
|
a return type and a list of formal parameter types. The return type of a
|
|
function type is a first class type or a void type.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<returntype> (<parameter list>)
|
|
</pre>
|
|
|
|
<p>...where '<tt><parameter list></tt>' is a comma-separated list of type
|
|
specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
|
|
which indicates that the function takes a variable number of arguments.
|
|
Variable argument functions can access their arguments with
|
|
the <a href="#int_varargs">variable argument handling intrinsic</a>
|
|
functions. '<tt><returntype></tt>' is any type except
|
|
<a href="#t_label">label</a>.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left"><tt>i32 (i32)</tt></td>
|
|
<td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt>
|
|
</td>
|
|
</tr><tr class="layout">
|
|
<td class="left"><tt>float (i16, i32 *) *
|
|
</tt></td>
|
|
<td class="left"><a href="#t_pointer">Pointer</a> to a function that takes
|
|
an <tt>i16</tt> and a <a href="#t_pointer">pointer</a> to <tt>i32</tt>,
|
|
returning <tt>float</tt>.
|
|
</td>
|
|
</tr><tr class="layout">
|
|
<td class="left"><tt>i32 (i8*, ...)</tt></td>
|
|
<td class="left">A vararg function that takes at least one
|
|
<a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C),
|
|
which returns an integer. This is the signature for <tt>printf</tt> in
|
|
LLVM.
|
|
</td>
|
|
</tr><tr class="layout">
|
|
<td class="left"><tt>{i32, i32} (i32)</tt></td>
|
|
<td class="left">A function taking an <tt>i32</tt>, returning a
|
|
<a href="#t_struct">structure</a> containing two <tt>i32</tt> values
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_struct">Structure Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The structure type is used to represent a collection of data members together
|
|
in memory. The elements of a structure may be any type that has a size.</p>
|
|
|
|
<p>Structures in memory are accessed using '<tt><a href="#i_load">load</a></tt>'
|
|
and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a field
|
|
with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.
|
|
Structures in registers are accessed using the
|
|
'<tt><a href="#i_extractvalue">extractvalue</a></tt>' and
|
|
'<tt><a href="#i_insertvalue">insertvalue</a></tt>' instructions.</p>
|
|
|
|
<p>Structures may optionally be "packed" structures, which indicate that the
|
|
alignment of the struct is one byte, and that there is no padding between
|
|
the elements. In non-packed structs, padding between field types is inserted
|
|
as defined by the DataLayout string in the module, which is required to match
|
|
what the underlying code generator expects.</p>
|
|
|
|
<p>Structures can either be "literal" or "identified". A literal structure is
|
|
defined inline with other types (e.g. <tt>{i32, i32}*</tt>) whereas identified
|
|
types are always defined at the top level with a name. Literal types are
|
|
uniqued by their contents and can never be recursive or opaque since there is
|
|
no way to write one. Identified types can be recursive, can be opaqued, and are
|
|
never uniqued.
|
|
</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
%T1 = type { <type list> } <i>; Identified normal struct type</i>
|
|
%T2 = type <{ <type list> }> <i>; Identified packed struct type</i>
|
|
</pre>
|
|
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left"><tt>{ i32, i32, i32 }</tt></td>
|
|
<td class="left">A triple of three <tt>i32</tt> values</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>{ float, i32 (i32) * }</tt></td>
|
|
<td class="left">A pair, where the first element is a <tt>float</tt> and the
|
|
second element is a <a href="#t_pointer">pointer</a> to a
|
|
<a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
|
|
an <tt>i32</tt>.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt><{ i8, i32 }></tt></td>
|
|
<td class="left">A packed struct known to be 5 bytes in size.</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_opaque">Opaque Structure Types</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>Opaque structure types are used to represent named structure types that do
|
|
not have a body specified. This corresponds (for example) to the C notion of
|
|
a forward declared structure.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
%X = type opaque
|
|
%52 = type opaque
|
|
</pre>
|
|
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left"><tt>opaque</tt></td>
|
|
<td class="left">An opaque type.</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_pointer">Pointer Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The pointer type is used to specify memory locations.
|
|
Pointers are commonly used to reference objects in memory.</p>
|
|
|
|
<p>Pointer types may have an optional address space attribute defining the
|
|
numbered address space where the pointed-to object resides. The default
|
|
address space is number zero. The semantics of non-zero address
|
|
spaces are target-specific.</p>
|
|
|
|
<p>Note that LLVM does not permit pointers to void (<tt>void*</tt>) nor does it
|
|
permit pointers to labels (<tt>label*</tt>). Use <tt>i8*</tt> instead.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<type> *
|
|
</pre>
|
|
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left"><tt>[4 x i32]*</tt></td>
|
|
<td class="left">A <a href="#t_pointer">pointer</a> to <a
|
|
href="#t_array">array</a> of four <tt>i32</tt> values.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>i32 (i32*) *</tt></td>
|
|
<td class="left"> A <a href="#t_pointer">pointer</a> to a <a
|
|
href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an
|
|
<tt>i32</tt>.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt>i32 addrspace(5)*</tt></td>
|
|
<td class="left">A <a href="#t_pointer">pointer</a> to an <tt>i32</tt> value
|
|
that resides in address space #5.</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="t_vector">Vector Type</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>A vector type is a simple derived type that represents a vector of elements.
|
|
Vector types are used when multiple primitive data are operated in parallel
|
|
using a single instruction (SIMD). A vector type requires a size (number of
|
|
elements) and an underlying primitive data type. Vector types are considered
|
|
<a href="#t_firstclass">first class</a>.</p>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
< <# elements> x <elementtype> >
|
|
</pre>
|
|
|
|
<p>The number of elements is a constant integer value larger than 0; elementtype
|
|
may be any integer or floating point type, or a pointer to these types.
|
|
Vectors of size zero are not allowed. </p>
|
|
|
|
<h5>Examples:</h5>
|
|
<table class="layout">
|
|
<tr class="layout">
|
|
<td class="left"><tt><4 x i32></tt></td>
|
|
<td class="left">Vector of 4 32-bit integer values.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt><8 x float></tt></td>
|
|
<td class="left">Vector of 8 32-bit floating-point values.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt><2 x i64></tt></td>
|
|
<td class="left">Vector of 2 64-bit integer values.</td>
|
|
</tr>
|
|
<tr class="layout">
|
|
<td class="left"><tt><4 x i64*></tt></td>
|
|
<td class="left">Vector of 4 pointers to 64-bit integer values.</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="constants">Constants</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>LLVM has several different basic types of constants. This section describes
|
|
them all and their syntax.</p>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="simpleconstants">Simple Constants</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<dl>
|
|
<dt><b>Boolean constants</b></dt>
|
|
<dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid
|
|
constants of the <tt><a href="#t_integer">i1</a></tt> type.</dd>
|
|
|
|
<dt><b>Integer constants</b></dt>
|
|
<dd>Standard integers (such as '4') are constants of
|
|
the <a href="#t_integer">integer</a> type. Negative numbers may be used
|
|
with integer types.</dd>
|
|
|
|
<dt><b>Floating point constants</b></dt>
|
|
<dd>Floating point constants use standard decimal notation (e.g. 123.421),
|
|
exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal
|
|
notation (see below). The assembler requires the exact decimal value of a
|
|
floating-point constant. For example, the assembler accepts 1.25 but
|
|
rejects 1.3 because 1.3 is a repeating decimal in binary. Floating point
|
|
constants must have a <a href="#t_floating">floating point</a> type. </dd>
|
|
|
|
<dt><b>Null pointer constants</b></dt>
|
|
<dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant
|
|
and must be of <a href="#t_pointer">pointer type</a>.</dd>
|
|
</dl>
|
|
|
|
<p>The one non-intuitive notation for constants is the hexadecimal form of
|
|
floating point constants. For example, the form '<tt>double
|
|
0x432ff973cafa8000</tt>' is equivalent to (but harder to read than)
|
|
'<tt>double 4.5e+15</tt>'. The only time hexadecimal floating point
|
|
constants are required (and the only time that they are generated by the
|
|
disassembler) is when a floating point constant must be emitted but it cannot
|
|
be represented as a decimal floating point number in a reasonable number of
|
|
digits. For example, NaN's, infinities, and other special values are
|
|
represented in their IEEE hexadecimal format so that assembly and disassembly
|
|
do not cause any bits to change in the constants.</p>
|
|
|
|
<p>When using the hexadecimal form, constants of types half, float, and double are
|
|
represented using the 16-digit form shown above (which matches the IEEE754
|
|
representation for double); half and float values must, however, be exactly
|
|
representable as IEE754 half and single precision, respectively.
|
|
Hexadecimal format is always used
|
|
for long double, and there are three forms of long double. The 80-bit format
|
|
used by x86 is represented as <tt>0xK</tt> followed by 20 hexadecimal digits.
|
|
The 128-bit format used by PowerPC (two adjacent doubles) is represented
|
|
by <tt>0xM</tt> followed by 32 hexadecimal digits. The IEEE 128-bit format
|
|
is represented by <tt>0xL</tt> followed by 32 hexadecimal digits; no
|
|
currently supported target uses this format. Long doubles will only work if
|
|
they match the long double format on your target. The IEEE 16-bit format
|
|
(half precision) is represented by <tt>0xH</tt> followed by 4 hexadecimal
|
|
digits. All hexadecimal formats are big-endian (sign bit at the left).</p>
|
|
|
|
<p>There are no constants of type x86mmx.</p>
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="aggregateconstants"></a> <!-- old anchor -->
|
|
<a name="complexconstants">Complex Constants</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Complex constants are a (potentially recursive) combination of simple
|
|
constants and smaller complex constants.</p>
|
|
|
|
<dl>
|
|
<dt><b>Structure constants</b></dt>
|
|
<dd>Structure constants are represented with notation similar to structure
|
|
type definitions (a comma separated list of elements, surrounded by braces
|
|
(<tt>{}</tt>)). For example: "<tt>{ i32 4, float 17.0, i32* @G }</tt>",
|
|
where "<tt>@G</tt>" is declared as "<tt>@G = external global i32</tt>".
|
|
Structure constants must have <a href="#t_struct">structure type</a>, and
|
|
the number and types of elements must match those specified by the
|
|
type.</dd>
|
|
|
|
<dt><b>Array constants</b></dt>
|
|
<dd>Array constants are represented with notation similar to array type
|
|
definitions (a comma separated list of elements, surrounded by square
|
|
brackets (<tt>[]</tt>)). For example: "<tt>[ i32 42, i32 11, i32 74
|
|
]</tt>". Array constants must have <a href="#t_array">array type</a>, and
|
|
the number and types of elements must match those specified by the
|
|
type.</dd>
|
|
|
|
<dt><b>Vector constants</b></dt>
|
|
<dd>Vector constants are represented with notation similar to vector type
|
|
definitions (a comma separated list of elements, surrounded by
|
|
less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32
|
|
42, i32 11, i32 74, i32 100 ></tt>". Vector constants must
|
|
have <a href="#t_vector">vector type</a>, and the number and types of
|
|
elements must match those specified by the type.</dd>
|
|
|
|
<dt><b>Zero initialization</b></dt>
|
|
<dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a
|
|
value to zero of <em>any</em> type, including scalar and
|
|
<a href="#t_aggregate">aggregate</a> types.
|
|
This is often used to avoid having to print large zero initializers
|
|
(e.g. for large arrays) and is always exactly equivalent to using explicit
|
|
zero initializers.</dd>
|
|
|
|
<dt><b>Metadata node</b></dt>
|
|
<dd>A metadata node is a structure-like constant with
|
|
<a href="#t_metadata">metadata type</a>. For example: "<tt>metadata !{
|
|
i32 0, metadata !"test" }</tt>". Unlike other constants that are meant to
|
|
be interpreted as part of the instruction stream, metadata is a place to
|
|
attach additional information such as debug info.</dd>
|
|
</dl>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="globalconstants">Global Variable and Function Addresses</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The addresses of <a href="#globalvars">global variables</a>
|
|
and <a href="#functionstructure">functions</a> are always implicitly valid
|
|
(link-time) constants. These constants are explicitly referenced when
|
|
the <a href="#identifiers">identifier for the global</a> is used and always
|
|
have <a href="#t_pointer">pointer</a> type. For example, the following is a
|
|
legal LLVM file:</p>
|
|
|
|
<pre class="doc_code">
|
|
@X = global i32 17
|
|
@Y = global i32 42
|
|
@Z = global [2 x i32*] [ i32* @X, i32* @Y ]
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="undefvalues">Undefined Values</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The string '<tt>undef</tt>' can be used anywhere a constant is expected, and
|
|
indicates that the user of the value may receive an unspecified bit-pattern.
|
|
Undefined values may be of any type (other than '<tt>label</tt>'
|
|
or '<tt>void</tt>') and be used anywhere a constant is permitted.</p>
|
|
|
|
<p>Undefined values are useful because they indicate to the compiler that the
|
|
program is well defined no matter what value is used. This gives the
|
|
compiler more freedom to optimize. Here are some examples of (potentially
|
|
surprising) transformations that are valid (in pseudo IR):</p>
|
|
|
|
|
|
<pre class="doc_code">
|
|
%A = add %X, undef
|
|
%B = sub %X, undef
|
|
%C = xor %X, undef
|
|
Safe:
|
|
%A = undef
|
|
%B = undef
|
|
%C = undef
|
|
</pre>
|
|
|
|
<p>This is safe because all of the output bits are affected by the undef bits.
|
|
Any output bit can have a zero or one depending on the input bits.</p>
|
|
|
|
<pre class="doc_code">
|
|
%A = or %X, undef
|
|
%B = and %X, undef
|
|
Safe:
|
|
%A = -1
|
|
%B = 0
|
|
Unsafe:
|
|
%A = undef
|
|
%B = undef
|
|
</pre>
|
|
|
|
<p>These logical operations have bits that are not always affected by the input.
|
|
For example, if <tt>%X</tt> has a zero bit, then the output of the
|
|
'<tt>and</tt>' operation will always be a zero for that bit, no matter what
|
|
the corresponding bit from the '<tt>undef</tt>' is. As such, it is unsafe to
|
|
optimize or assume that the result of the '<tt>and</tt>' is '<tt>undef</tt>'.
|
|
However, it is safe to assume that all bits of the '<tt>undef</tt>' could be
|
|
0, and optimize the '<tt>and</tt>' to 0. Likewise, it is safe to assume that
|
|
all the bits of the '<tt>undef</tt>' operand to the '<tt>or</tt>' could be
|
|
set, allowing the '<tt>or</tt>' to be folded to -1.</p>
|
|
|
|
<pre class="doc_code">
|
|
%A = select undef, %X, %Y
|
|
%B = select undef, 42, %Y
|
|
%C = select %X, %Y, undef
|
|
Safe:
|
|
%A = %X (or %Y)
|
|
%B = 42 (or %Y)
|
|
%C = %Y
|
|
Unsafe:
|
|
%A = undef
|
|
%B = undef
|
|
%C = undef
|
|
</pre>
|
|
|
|
<p>This set of examples shows that undefined '<tt>select</tt>' (and conditional
|
|
branch) conditions can go <em>either way</em>, but they have to come from one
|
|
of the two operands. In the <tt>%A</tt> example, if <tt>%X</tt> and
|
|
<tt>%Y</tt> were both known to have a clear low bit, then <tt>%A</tt> would
|
|
have to have a cleared low bit. However, in the <tt>%C</tt> example, the
|
|
optimizer is allowed to assume that the '<tt>undef</tt>' operand could be the
|
|
same as <tt>%Y</tt>, allowing the whole '<tt>select</tt>' to be
|
|
eliminated.</p>
|
|
|
|
<pre class="doc_code">
|
|
%A = xor undef, undef
|
|
|
|
%B = undef
|
|
%C = xor %B, %B
|
|
|
|
%D = undef
|
|
%E = icmp lt %D, 4
|
|
%F = icmp gte %D, 4
|
|
|
|
Safe:
|
|
%A = undef
|
|
%B = undef
|
|
%C = undef
|
|
%D = undef
|
|
%E = undef
|
|
%F = undef
|
|
</pre>
|
|
|
|
<p>This example points out that two '<tt>undef</tt>' operands are not
|
|
necessarily the same. This can be surprising to people (and also matches C
|
|
semantics) where they assume that "<tt>X^X</tt>" is always zero, even
|
|
if <tt>X</tt> is undefined. This isn't true for a number of reasons, but the
|
|
short answer is that an '<tt>undef</tt>' "variable" can arbitrarily change
|
|
its value over its "live range". This is true because the variable doesn't
|
|
actually <em>have a live range</em>. Instead, the value is logically read
|
|
from arbitrary registers that happen to be around when needed, so the value
|
|
is not necessarily consistent over time. In fact, <tt>%A</tt> and <tt>%C</tt>
|
|
need to have the same semantics or the core LLVM "replace all uses with"
|
|
concept would not hold.</p>
|
|
|
|
<pre class="doc_code">
|
|
%A = fdiv undef, %X
|
|
%B = fdiv %X, undef
|
|
Safe:
|
|
%A = undef
|
|
b: unreachable
|
|
</pre>
|
|
|
|
<p>These examples show the crucial difference between an <em>undefined
|
|
value</em> and <em>undefined behavior</em>. An undefined value (like
|
|
'<tt>undef</tt>') is allowed to have an arbitrary bit-pattern. This means that
|
|
the <tt>%A</tt> operation can be constant folded to '<tt>undef</tt>', because
|
|
the '<tt>undef</tt>' could be an SNaN, and <tt>fdiv</tt> is not (currently)
|
|
defined on SNaN's. However, in the second example, we can make a more
|
|
aggressive assumption: because the <tt>undef</tt> is allowed to be an
|
|
arbitrary value, we are allowed to assume that it could be zero. Since a
|
|
divide by zero has <em>undefined behavior</em>, we are allowed to assume that
|
|
the operation does not execute at all. This allows us to delete the divide and
|
|
all code after it. Because the undefined operation "can't happen", the
|
|
optimizer can assume that it occurs in dead code.</p>
|
|
|
|
<pre class="doc_code">
|
|
a: store undef -> %X
|
|
b: store %X -> undef
|
|
Safe:
|
|
a: <deleted>
|
|
b: unreachable
|
|
</pre>
|
|
|
|
<p>These examples reiterate the <tt>fdiv</tt> example: a store <em>of</em> an
|
|
undefined value can be assumed to not have any effect; we can assume that the
|
|
value is overwritten with bits that happen to match what was already there.
|
|
However, a store <em>to</em> an undefined location could clobber arbitrary
|
|
memory, therefore, it has undefined behavior.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="poisonvalues">Poison Values</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Poison values are similar to <a href="#undefvalues">undef values</a>, however
|
|
they also represent the fact that an instruction or constant expression which
|
|
cannot evoke side effects has nevertheless detected a condition which results
|
|
in undefined behavior.</p>
|
|
|
|
<p>There is currently no way of representing a poison value in the IR; they
|
|
only exist when produced by operations such as
|
|
<a href="#i_add"><tt>add</tt></a> with the <tt>nsw</tt> flag.</p>
|
|
|
|
<p>Poison value behavior is defined in terms of value <i>dependence</i>:</p>
|
|
|
|
<ul>
|
|
<li>Values other than <a href="#i_phi"><tt>phi</tt></a> nodes depend on
|
|
their operands.</li>
|
|
|
|
<li><a href="#i_phi"><tt>Phi</tt></a> nodes depend on the operand corresponding
|
|
to their dynamic predecessor basic block.</li>
|
|
|
|
<li>Function arguments depend on the corresponding actual argument values in
|
|
the dynamic callers of their functions.</li>
|
|
|
|
<li><a href="#i_call"><tt>Call</tt></a> instructions depend on the
|
|
<a href="#i_ret"><tt>ret</tt></a> instructions that dynamically transfer
|
|
control back to them.</li>
|
|
|
|
<li><a href="#i_invoke"><tt>Invoke</tt></a> instructions depend on the
|
|
<a href="#i_ret"><tt>ret</tt></a>, <a href="#i_resume"><tt>resume</tt></a>,
|
|
or exception-throwing call instructions that dynamically transfer control
|
|
back to them.</li>
|
|
|
|
<li>Non-volatile loads and stores depend on the most recent stores to all of the
|
|
referenced memory addresses, following the order in the IR
|
|
(including loads and stores implied by intrinsics such as
|
|
<a href="#int_memcpy"><tt>@llvm.memcpy</tt></a>.)</li>
|
|
|
|
<!-- TODO: In the case of multiple threads, this only applies if the store
|
|
"happens-before" the load or store. -->
|
|
|
|
<!-- TODO: floating-point exception state -->
|
|
|
|
<li>An instruction with externally visible side effects depends on the most
|
|
recent preceding instruction with externally visible side effects, following
|
|
the order in the IR. (This includes
|
|
<a href="#volatile">volatile operations</a>.)</li>
|
|
|
|
<li>An instruction <i>control-depends</i> on a
|
|
<a href="#terminators">terminator instruction</a>
|
|
if the terminator instruction has multiple successors and the instruction
|
|
is always executed when control transfers to one of the successors, and
|
|
may not be executed when control is transferred to another.</li>
|
|
|
|
<li>Additionally, an instruction also <i>control-depends</i> on a terminator
|
|
instruction if the set of instructions it otherwise depends on would be
|
|
different if the terminator had transferred control to a different
|
|
successor.</li>
|
|
|
|
<li>Dependence is transitive.</li>
|
|
|
|
</ul>
|
|
|
|
<p>Poison Values have the same behavior as <a href="#undefvalues">undef values</a>,
|
|
with the additional affect that any instruction which has a <i>dependence</i>
|
|
on a poison value has undefined behavior.</p>
|
|
|
|
<p>Here are some examples:</p>
|
|
|
|
<pre class="doc_code">
|
|
entry:
|
|
%poison = sub nuw i32 0, 1 ; Results in a poison value.
|
|
%still_poison = and i32 %poison, 0 ; 0, but also poison.
|
|
%poison_yet_again = getelementptr i32* @h, i32 %still_poison
|
|
store i32 0, i32* %poison_yet_again ; memory at @h[0] is poisoned
|
|
|
|
store i32 %poison, i32* @g ; Poison value stored to memory.
|
|
%poison2 = load i32* @g ; Poison value loaded back from memory.
|
|
|
|
store volatile i32 %poison, i32* @g ; External observation; undefined behavior.
|
|
|
|
%narrowaddr = bitcast i32* @g to i16*
|
|
%wideaddr = bitcast i32* @g to i64*
|
|
%poison3 = load i16* %narrowaddr ; Returns a poison value.
|
|
%poison4 = load i64* %wideaddr ; Returns a poison value.
|
|
|
|
%cmp = icmp slt i32 %poison, 0 ; Returns a poison value.
|
|
br i1 %cmp, label %true, label %end ; Branch to either destination.
|
|
|
|
true:
|
|
store volatile i32 0, i32* @g ; This is control-dependent on %cmp, so
|
|
; it has undefined behavior.
|
|
br label %end
|
|
|
|
end:
|
|
%p = phi i32 [ 0, %entry ], [ 1, %true ]
|
|
; Both edges into this PHI are
|
|
; control-dependent on %cmp, so this
|
|
; always results in a poison value.
|
|
|
|
store volatile i32 0, i32* @g ; This would depend on the store in %true
|
|
; if %cmp is true, or the store in %entry
|
|
; otherwise, so this is undefined behavior.
|
|
|
|
br i1 %cmp, label %second_true, label %second_end
|
|
; The same branch again, but this time the
|
|
; true block doesn't have side effects.
|
|
|
|
second_true:
|
|
; No side effects!
|
|
ret void
|
|
|
|
second_end:
|
|
store volatile i32 0, i32* @g ; This time, the instruction always depends
|
|
; on the store in %end. Also, it is
|
|
; control-equivalent to %end, so this is
|
|
; well-defined (ignoring earlier undefined
|
|
; behavior in this example).
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="blockaddress">Addresses of Basic Blocks</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p><b><tt>blockaddress(@function, %block)</tt></b></p>
|
|
|
|
<p>The '<tt>blockaddress</tt>' constant computes the address of the specified
|
|
basic block in the specified function, and always has an i8* type. Taking
|
|
the address of the entry block is illegal.</p>
|
|
|
|
<p>This value only has defined behavior when used as an operand to the
|
|
'<a href="#i_indirectbr"><tt>indirectbr</tt></a>' instruction, or for
|
|
comparisons against null. Pointer equality tests between labels addresses
|
|
results in undefined behavior — though, again, comparison against null
|
|
is ok, and no label is equal to the null pointer. This may be passed around
|
|
as an opaque pointer sized value as long as the bits are not inspected. This
|
|
allows <tt>ptrtoint</tt> and arithmetic to be performed on these values so
|
|
long as the original value is reconstituted before the <tt>indirectbr</tt>
|
|
instruction.</p>
|
|
|
|
<p>Finally, some targets may provide defined semantics when using the value as
|
|
the operand to an inline assembly, but that is target specific.</p>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="constantexprs">Constant Expressions</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Constant expressions are used to allow expressions involving other constants
|
|
to be used as constants. Constant expressions may be of
|
|
any <a href="#t_firstclass">first class</a> type and may involve any LLVM
|
|
operation that does not have side effects (e.g. load and call are not
|
|
supported). The following is the syntax for constant expressions:</p>
|
|
|
|
<dl>
|
|
<dt><b><tt>trunc (CST to TYPE)</tt></b></dt>
|
|
<dd>Truncate a constant to another type. The bit size of CST must be larger
|
|
than the bit size of TYPE. Both types must be integers.</dd>
|
|
|
|
<dt><b><tt>zext (CST to TYPE)</tt></b></dt>
|
|
<dd>Zero extend a constant to another type. The bit size of CST must be
|
|
smaller than the bit size of TYPE. Both types must be integers.</dd>
|
|
|
|
<dt><b><tt>sext (CST to TYPE)</tt></b></dt>
|
|
<dd>Sign extend a constant to another type. The bit size of CST must be
|
|
smaller than the bit size of TYPE. Both types must be integers.</dd>
|
|
|
|
<dt><b><tt>fptrunc (CST to TYPE)</tt></b></dt>
|
|
<dd>Truncate a floating point constant to another floating point type. The
|
|
size of CST must be larger than the size of TYPE. Both types must be
|
|
floating point.</dd>
|
|
|
|
<dt><b><tt>fpext (CST to TYPE)</tt></b></dt>
|
|
<dd>Floating point extend a constant to another type. The size of CST must be
|
|
smaller or equal to the size of TYPE. Both types must be floating
|
|
point.</dd>
|
|
|
|
<dt><b><tt>fptoui (CST to TYPE)</tt></b></dt>
|
|
<dd>Convert a floating point constant to the corresponding unsigned integer
|
|
constant. TYPE must be a scalar or vector integer type. CST must be of
|
|
scalar or vector floating point type. Both CST and TYPE must be scalars,
|
|
or vectors of the same number of elements. If the value won't fit in the
|
|
integer type, the results are undefined.</dd>
|
|
|
|
<dt><b><tt>fptosi (CST to TYPE)</tt></b></dt>
|
|
<dd>Convert a floating point constant to the corresponding signed integer
|
|
constant. TYPE must be a scalar or vector integer type. CST must be of
|
|
scalar or vector floating point type. Both CST and TYPE must be scalars,
|
|
or vectors of the same number of elements. If the value won't fit in the
|
|
integer type, the results are undefined.</dd>
|
|
|
|
<dt><b><tt>uitofp (CST to TYPE)</tt></b></dt>
|
|
<dd>Convert an unsigned integer constant to the corresponding floating point
|
|
constant. TYPE must be a scalar or vector floating point type. CST must be
|
|
of scalar or vector integer type. Both CST and TYPE must be scalars, or
|
|
vectors of the same number of elements. If the value won't fit in the
|
|
floating point type, the results are undefined.</dd>
|
|
|
|
<dt><b><tt>sitofp (CST to TYPE)</tt></b></dt>
|
|
<dd>Convert a signed integer constant to the corresponding floating point
|
|
constant. TYPE must be a scalar or vector floating point type. CST must be
|
|
of scalar or vector integer type. Both CST and TYPE must be scalars, or
|
|
vectors of the same number of elements. If the value won't fit in the
|
|
floating point type, the results are undefined.</dd>
|
|
|
|
<dt><b><tt>ptrtoint (CST to TYPE)</tt></b></dt>
|
|
<dd>Convert a pointer typed constant to the corresponding integer constant
|
|
<tt>TYPE</tt> must be an integer type. <tt>CST</tt> must be of pointer
|
|
type. The <tt>CST</tt> value is zero extended, truncated, or unchanged to
|
|
make it fit in <tt>TYPE</tt>.</dd>
|
|
|
|
<dt><b><tt>inttoptr (CST to TYPE)</tt></b></dt>
|
|
<dd>Convert an integer constant to a pointer constant. TYPE must be a pointer
|
|
type. CST must be of integer type. The CST value is zero extended,
|
|
truncated, or unchanged to make it fit in a pointer size. This one is
|
|
<i>really</i> dangerous!</dd>
|
|
|
|
<dt><b><tt>bitcast (CST to TYPE)</tt></b></dt>
|
|
<dd>Convert a constant, CST, to another TYPE. The constraints of the operands
|
|
are the same as those for the <a href="#i_bitcast">bitcast
|
|
instruction</a>.</dd>
|
|
|
|
<dt><b><tt>getelementptr (CSTPTR, IDX0, IDX1, ...)</tt></b></dt>
|
|
<dt><b><tt>getelementptr inbounds (CSTPTR, IDX0, IDX1, ...)</tt></b></dt>
|
|
<dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on
|
|
constants. As with the <a href="#i_getelementptr">getelementptr</a>
|
|
instruction, the index list may have zero or more indexes, which are
|
|
required to make sense for the type of "CSTPTR".</dd>
|
|
|
|
<dt><b><tt>select (COND, VAL1, VAL2)</tt></b></dt>
|
|
<dd>Perform the <a href="#i_select">select operation</a> on constants.</dd>
|
|
|
|
<dt><b><tt>icmp COND (VAL1, VAL2)</tt></b></dt>
|
|
<dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd>
|
|
|
|
<dt><b><tt>fcmp COND (VAL1, VAL2)</tt></b></dt>
|
|
<dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd>
|
|
|
|
<dt><b><tt>extractelement (VAL, IDX)</tt></b></dt>
|
|
<dd>Perform the <a href="#i_extractelement">extractelement operation</a> on
|
|
constants.</dd>
|
|
|
|
<dt><b><tt>insertelement (VAL, ELT, IDX)</tt></b></dt>
|
|
<dd>Perform the <a href="#i_insertelement">insertelement operation</a> on
|
|
constants.</dd>
|
|
|
|
<dt><b><tt>shufflevector (VEC1, VEC2, IDXMASK)</tt></b></dt>
|
|
<dd>Perform the <a href="#i_shufflevector">shufflevector operation</a> on
|
|
constants.</dd>
|
|
|
|
<dt><b><tt>extractvalue (VAL, IDX0, IDX1, ...)</tt></b></dt>
|
|
<dd>Perform the <a href="#i_extractvalue">extractvalue operation</a> on
|
|
constants. The index list is interpreted in a similar manner as indices in
|
|
a '<a href="#i_getelementptr">getelementptr</a>' operation. At least one
|
|
index value must be specified.</dd>
|
|
|
|
<dt><b><tt>insertvalue (VAL, ELT, IDX0, IDX1, ...)</tt></b></dt>
|
|
<dd>Perform the <a href="#i_insertvalue">insertvalue operation</a> on
|
|
constants. The index list is interpreted in a similar manner as indices in
|
|
a '<a href="#i_getelementptr">getelementptr</a>' operation. At least one
|
|
index value must be specified.</dd>
|
|
|
|
<dt><b><tt>OPCODE (LHS, RHS)</tt></b></dt>
|
|
<dd>Perform the specified operation of the LHS and RHS constants. OPCODE may
|
|
be any of the <a href="#binaryops">binary</a>
|
|
or <a href="#bitwiseops">bitwise binary</a> operations. The constraints
|
|
on operands are the same as those for the corresponding instruction
|
|
(e.g. no bitwise operations on floating point values are allowed).</dd>
|
|
</dl>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="othervalues">Other Values</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
<div>
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="inlineasm">Inline Assembler Expressions</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM supports inline assembler expressions (as opposed
|
|
to <a href="#moduleasm">Module-Level Inline Assembly</a>) through the use of
|
|
a special value. This value represents the inline assembler as a string
|
|
(containing the instructions to emit), a list of operand constraints (stored
|
|
as a string), a flag that indicates whether or not the inline asm
|
|
expression has side effects, and a flag indicating whether the function
|
|
containing the asm needs to align its stack conservatively. An example
|
|
inline assembler expression is:</p>
|
|
|
|
<pre class="doc_code">
|
|
i32 (i32) asm "bswap $0", "=r,r"
|
|
</pre>
|
|
|
|
<p>Inline assembler expressions may <b>only</b> be used as the callee operand of
|
|
a <a href="#i_call"><tt>call</tt></a> or an
|
|
<a href="#i_invoke"><tt>invoke</tt></a> instruction.
|
|
Thus, typically we have:</p>
|
|
|
|
<pre class="doc_code">
|
|
%X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y)
|
|
</pre>
|
|
|
|
<p>Inline asms with side effects not visible in the constraint list must be
|
|
marked as having side effects. This is done through the use of the
|
|
'<tt>sideeffect</tt>' keyword, like so:</p>
|
|
|
|
<pre class="doc_code">
|
|
call void asm sideeffect "eieio", ""()
|
|
</pre>
|
|
|
|
<p>In some cases inline asms will contain code that will not work unless the
|
|
stack is aligned in some way, such as calls or SSE instructions on x86,
|
|
yet will not contain code that does that alignment within the asm.
|
|
The compiler should make conservative assumptions about what the asm might
|
|
contain and should generate its usual stack alignment code in the prologue
|
|
if the '<tt>alignstack</tt>' keyword is present:</p>
|
|
|
|
<pre class="doc_code">
|
|
call void asm alignstack "eieio", ""()
|
|
</pre>
|
|
|
|
<p>Inline asms also support using non-standard assembly dialects. The assumed
|
|
dialect is ATT. When the '<tt>inteldialect</tt>' keyword is present, the
|
|
inline asm is using the Intel dialect. Currently, ATT and Intel are the
|
|
only supported dialects. An example is:</p>
|
|
|
|
<pre class="doc_code">
|
|
call void asm inteldialect "eieio", ""()
|
|
</pre>
|
|
|
|
<p>If multiple keywords appear the '<tt>sideeffect</tt>' keyword must come
|
|
first, the '<tt>alignstack</tt>' keyword second and the
|
|
'<tt>inteldialect</tt>' keyword last.</p>
|
|
|
|
<!--
|
|
<p>TODO: The format of the asm and constraints string still need to be
|
|
documented here. Constraints on what can be done (e.g. duplication, moving,
|
|
etc need to be documented). This is probably best done by reference to
|
|
another document that covers inline asm from a holistic perspective.</p>
|
|
-->
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="inlineasm_md">Inline Asm Metadata</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<p>The call instructions that wrap inline asm nodes may have a
|
|
"<tt>!srcloc</tt>" MDNode attached to it that contains a list of constant
|
|
integers. If present, the code generator will use the integer as the
|
|
location cookie value when report errors through the <tt>LLVMContext</tt>
|
|
error reporting mechanisms. This allows a front-end to correlate backend
|
|
errors that occur with inline asm back to the source code that produced it.
|
|
For example:</p>
|
|
|
|
<pre class="doc_code">
|
|
call void asm sideeffect "something bad", ""()<b>, !srcloc !42</b>
|
|
...
|
|
!42 = !{ i32 1234567 }
|
|
</pre>
|
|
|
|
<p>It is up to the front-end to make sense of the magic numbers it places in the
|
|
IR. If the MDNode contains multiple constants, the code generator will use
|
|
the one that corresponds to the line of the asm that the error occurs on.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="metadata">Metadata Nodes and Metadata Strings</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM IR allows metadata to be attached to instructions in the program that
|
|
can convey extra information about the code to the optimizers and code
|
|
generator. One example application of metadata is source-level debug
|
|
information. There are two metadata primitives: strings and nodes. All
|
|
metadata has the <tt>metadata</tt> type and is identified in syntax by a
|
|
preceding exclamation point ('<tt>!</tt>').</p>
|
|
|
|
<p>A metadata string is a string surrounded by double quotes. It can contain
|
|
any character by escaping non-printable characters with "<tt>\xx</tt>" where
|
|
"<tt>xx</tt>" is the two digit hex code. For example:
|
|
"<tt>!"test\00"</tt>".</p>
|
|
|
|
<p>Metadata nodes are represented with notation similar to structure constants
|
|
(a comma separated list of elements, surrounded by braces and preceded by an
|
|
exclamation point). Metadata nodes can have any values as their operand. For
|
|
example:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!{ metadata !"test\00", i32 10}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>A <a href="#namedmetadatastructure">named metadata</a> is a collection of
|
|
metadata nodes, which can be looked up in the module symbol table. For
|
|
example:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!foo = metadata !{!4, !3}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Metadata can be used as function arguments. Here <tt>llvm.dbg.value</tt>
|
|
function is using two metadata arguments:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
call void @llvm.dbg.value(metadata !24, i64 0, metadata !25)
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Metadata can be attached with an instruction. Here metadata <tt>!21</tt> is
|
|
attached to the <tt>add</tt> instruction using the <tt>!dbg</tt>
|
|
identifier:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%indvar.next = add i64 %indvar, 1, !dbg !21
|
|
</pre>
|
|
</div>
|
|
|
|
<p>More information about specific metadata nodes recognized by the optimizers
|
|
and code generator is found below.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="tbaa">'<tt>tbaa</tt>' Metadata</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<p>In LLVM IR, memory does not have types, so LLVM's own type system is not
|
|
suitable for doing TBAA. Instead, metadata is added to the IR to describe
|
|
a type system of a higher level language. This can be used to implement
|
|
typical C/C++ TBAA, but it can also be used to implement custom alias
|
|
analysis behavior for other languages.</p>
|
|
|
|
<p>The current metadata format is very simple. TBAA metadata nodes have up to
|
|
three fields, e.g.:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!0 = metadata !{ metadata !"an example type tree" }
|
|
!1 = metadata !{ metadata !"int", metadata !0 }
|
|
!2 = metadata !{ metadata !"float", metadata !0 }
|
|
!3 = metadata !{ metadata !"const float", metadata !2, i64 1 }
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The first field is an identity field. It can be any value, usually
|
|
a metadata string, which uniquely identifies the type. The most important
|
|
name in the tree is the name of the root node. Two trees with
|
|
different root node names are entirely disjoint, even if they
|
|
have leaves with common names.</p>
|
|
|
|
<p>The second field identifies the type's parent node in the tree, or
|
|
is null or omitted for a root node. A type is considered to alias
|
|
all of its descendants and all of its ancestors in the tree. Also,
|
|
a type is considered to alias all types in other trees, so that
|
|
bitcode produced from multiple front-ends is handled conservatively.</p>
|
|
|
|
<p>If the third field is present, it's an integer which if equal to 1
|
|
indicates that the type is "constant" (meaning
|
|
<tt>pointsToConstantMemory</tt> should return true; see
|
|
<a href="AliasAnalysis.html#OtherItfs">other useful
|
|
<tt>AliasAnalysis</tt> methods</a>).</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="tbaa.struct">'<tt>tbaa.struct</tt>' Metadata</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<p>The <a href="#int_memcpy"><tt>llvm.memcpy</tt></a> is often used to implement
|
|
aggregate assignment operations in C and similar languages, however it is
|
|
defined to copy a contiguous region of memory, which is more than strictly
|
|
necessary for aggregate types which contain holes due to padding. Also, it
|
|
doesn't contain any TBAA information about the fields of the aggregate.</p>
|
|
|
|
<p><tt>!tbaa.struct</tt> metadata can describe which memory subregions in a memcpy
|
|
are padding and what the TBAA tags of the struct are.</p>
|
|
|
|
<p>The current metadata format is very simple. <tt>!tbaa.struct</tt> metadata nodes
|
|
are a list of operands which are in conceptual groups of three. For each
|
|
group of three, the first operand gives the byte offset of a field in bytes,
|
|
the second gives its size in bytes, and the third gives its
|
|
tbaa tag. e.g.:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!4 = metadata !{ i64 0, i64 4, metadata !1, i64 8, i64 4, metadata !2 }
|
|
</pre>
|
|
</div>
|
|
|
|
<p>This describes a struct with two fields. The first is at offset 0 bytes
|
|
with size 4 bytes, and has tbaa tag !1. The second is at offset 8 bytes
|
|
and has size 4 bytes and has tbaa tag !2.</p>
|
|
|
|
<p>Note that the fields need not be contiguous. In this example, there is a
|
|
4 byte gap between the two fields. This gap represents padding which
|
|
does not carry useful data and need not be preserved.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="fpmath">'<tt>fpmath</tt>' Metadata</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<p><tt>fpmath</tt> metadata may be attached to any instruction of floating point
|
|
type. It can be used to express the maximum acceptable error in the result of
|
|
that instruction, in ULPs, thus potentially allowing the compiler to use a
|
|
more efficient but less accurate method of computing it. ULP is defined as
|
|
follows:</p>
|
|
|
|
<blockquote>
|
|
|
|
<p>If <tt>x</tt> is a real number that lies between two finite consecutive
|
|
floating-point numbers <tt>a</tt> and <tt>b</tt>, without being equal to one
|
|
of them, then <tt>ulp(x) = |b - a|</tt>, otherwise <tt>ulp(x)</tt> is the
|
|
distance between the two non-equal finite floating-point numbers nearest
|
|
<tt>x</tt>. Moreover, <tt>ulp(NaN)</tt> is <tt>NaN</tt>.</p>
|
|
|
|
</blockquote>
|
|
|
|
<p>The metadata node shall consist of a single positive floating point number
|
|
representing the maximum relative error, for example:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!0 = metadata !{ float 2.5 } ; maximum acceptable inaccuracy is 2.5 ULPs
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="range">'<tt>range</tt>' Metadata</a>
|
|
</h4>
|
|
|
|
<div>
|
|
<p><tt>range</tt> metadata may be attached only to loads of integer types. It
|
|
expresses the possible ranges the loaded value is in. The ranges are
|
|
represented with a flattened list of integers. The loaded value is known to
|
|
be in the union of the ranges defined by each consecutive pair. Each pair
|
|
has the following properties:</p>
|
|
<ul>
|
|
<li>The type must match the type loaded by the instruction.</li>
|
|
<li>The pair <tt>a,b</tt> represents the range <tt>[a,b)</tt>.</li>
|
|
<li>Both <tt>a</tt> and <tt>b</tt> are constants.</li>
|
|
<li>The range is allowed to wrap.</li>
|
|
<li>The range should not represent the full or empty set. That is,
|
|
<tt>a!=b</tt>. </li>
|
|
</ul>
|
|
<p> In addition, the pairs must be in signed order of the lower bound and
|
|
they must be non-contiguous.</p>
|
|
|
|
<p>Examples:</p>
|
|
<div class="doc_code">
|
|
<pre>
|
|
%a = load i8* %x, align 1, !range !0 ; Can only be 0 or 1
|
|
%b = load i8* %y, align 1, !range !1 ; Can only be 255 (-1), 0 or 1
|
|
%c = load i8* %z, align 1, !range !2 ; Can only be 0, 1, 3, 4 or 5
|
|
%d = load i8* %z, align 1, !range !3 ; Can only be -2, -1, 3, 4 or 5
|
|
...
|
|
!0 = metadata !{ i8 0, i8 2 }
|
|
!1 = metadata !{ i8 255, i8 2 }
|
|
!2 = metadata !{ i8 0, i8 2, i8 3, i8 6 }
|
|
!3 = metadata !{ i8 -2, i8 0, i8 3, i8 6 }
|
|
</pre>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2>
|
|
<a name="module_flags">Module Flags Metadata</a>
|
|
</h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>Information about the module as a whole is difficult to convey to LLVM's
|
|
subsystems. The LLVM IR isn't sufficient to transmit this
|
|
information. The <tt>llvm.module.flags</tt> named metadata exists in order to
|
|
facilitate this. These flags are in the form of key / value pairs —
|
|
much like a dictionary — making it easy for any subsystem who cares
|
|
about a flag to look it up.</p>
|
|
|
|
<p>The <tt>llvm.module.flags</tt> metadata contains a list of metadata
|
|
triplets. Each triplet has the following form:</p>
|
|
|
|
<ul>
|
|
<li>The first element is a <i>behavior</i> flag, which specifies the behavior
|
|
when two (or more) modules are merged together, and it encounters two (or
|
|
more) metadata with the same ID. The supported behaviors are described
|
|
below.</li>
|
|
|
|
<li>The second element is a metadata string that is a unique ID for the
|
|
metadata. How each ID is interpreted is documented below.</li>
|
|
|
|
<li>The third element is the value of the flag.</li>
|
|
</ul>
|
|
|
|
<p>When two (or more) modules are merged together, the resulting
|
|
<tt>llvm.module.flags</tt> metadata is the union of the
|
|
modules' <tt>llvm.module.flags</tt> metadata. The only exception being a flag
|
|
with the <i>Override</i> behavior, which may override another flag's value
|
|
(see below).</p>
|
|
|
|
<p>The following behaviors are supported:</p>
|
|
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr>
|
|
<th>Value</th>
|
|
<th>Behavior</th>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td align="left">
|
|
<dl>
|
|
<dt><b>Error</b></dt>
|
|
<dd>Emits an error if two values disagree. It is an error to have an ID
|
|
with both an Error and a Warning behavior.</dd>
|
|
</dl>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>2</td>
|
|
<td align="left">
|
|
<dl>
|
|
<dt><b>Warning</b></dt>
|
|
<dd>Emits a warning if two values disagree.</dd>
|
|
</dl>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>3</td>
|
|
<td align="left">
|
|
<dl>
|
|
<dt><b>Require</b></dt>
|
|
<dd>Emits an error when the specified value is not present or doesn't
|
|
have the specified value. It is an error for two (or more)
|
|
<tt>llvm.module.flags</tt> with the same ID to have the Require
|
|
behavior but different values. There may be multiple Require flags
|
|
per ID.</dd>
|
|
</dl>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>4</td>
|
|
<td align="left">
|
|
<dl>
|
|
<dt><b>Override</b></dt>
|
|
<dd>Uses the specified value if the two values disagree. It is an
|
|
error for two (or more) <tt>llvm.module.flags</tt> with the same
|
|
ID to have the Override behavior but different values.</dd>
|
|
</dl>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<p>An example of module flags:</p>
|
|
|
|
<pre class="doc_code">
|
|
!0 = metadata !{ i32 1, metadata !"foo", i32 1 }
|
|
!1 = metadata !{ i32 4, metadata !"bar", i32 37 }
|
|
!2 = metadata !{ i32 2, metadata !"qux", i32 42 }
|
|
!3 = metadata !{ i32 3, metadata !"qux",
|
|
metadata !{
|
|
metadata !"foo", i32 1
|
|
}
|
|
}
|
|
!llvm.module.flags = !{ !0, !1, !2, !3 }
|
|
</pre>
|
|
|
|
<ul>
|
|
<li><p>Metadata <tt>!0</tt> has the ID <tt>!"foo"</tt> and the value '1'. The
|
|
behavior if two or more <tt>!"foo"</tt> flags are seen is to emit an
|
|
error if their values are not equal.</p></li>
|
|
|
|
<li><p>Metadata <tt>!1</tt> has the ID <tt>!"bar"</tt> and the value '37'. The
|
|
behavior if two or more <tt>!"bar"</tt> flags are seen is to use the
|
|
value '37' if their values are not equal.</p></li>
|
|
|
|
<li><p>Metadata <tt>!2</tt> has the ID <tt>!"qux"</tt> and the value '42'. The
|
|
behavior if two or more <tt>!"qux"</tt> flags are seen is to emit a
|
|
warning if their values are not equal.</p></li>
|
|
|
|
<li><p>Metadata <tt>!3</tt> has the ID <tt>!"qux"</tt> and the value:</p>
|
|
|
|
<pre class="doc_code">
|
|
metadata !{ metadata !"foo", i32 1 }
|
|
</pre>
|
|
|
|
<p>The behavior is to emit an error if the <tt>llvm.module.flags</tt> does
|
|
not contain a flag with the ID <tt>!"foo"</tt> that has the value
|
|
'1'. If two or more <tt>!"qux"</tt> flags exist, then they must have
|
|
the same value or an error will be issued.</p></li>
|
|
</ul>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="objc_gc_flags">Objective-C Garbage Collection Module Flags Metadata</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>On the Mach-O platform, Objective-C stores metadata about garbage collection
|
|
in a special section called "image info". The metadata consists of a version
|
|
number and a bitmask specifying what types of garbage collection are
|
|
supported (if any) by the file. If two or more modules are linked together
|
|
their garbage collection metadata needs to be merged rather than appended
|
|
together.</p>
|
|
|
|
<p>The Objective-C garbage collection module flags metadata consists of the
|
|
following key-value pairs:</p>
|
|
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<col width="30%">
|
|
<tbody>
|
|
<tr>
|
|
<th>Key</th>
|
|
<th>Value</th>
|
|
</tr>
|
|
<tr>
|
|
<td><tt>Objective-C Version</tt></td>
|
|
<td align="left"><b>[Required]</b> — The Objective-C ABI
|
|
version. Valid values are 1 and 2.</td>
|
|
</tr>
|
|
<tr>
|
|
<td><tt>Objective-C Image Info Version</tt></td>
|
|
<td align="left"><b>[Required]</b> — The version of the image info
|
|
section. Currently always 0.</td>
|
|
</tr>
|
|
<tr>
|
|
<td><tt>Objective-C Image Info Section</tt></td>
|
|
<td align="left"><b>[Required]</b> — The section to place the
|
|
metadata. Valid values are <tt>"__OBJC, __image_info, regular"</tt> for
|
|
Objective-C ABI version 1, and <tt>"__DATA,__objc_imageinfo, regular,
|
|
no_dead_strip"</tt> for Objective-C ABI version 2.</td>
|
|
</tr>
|
|
<tr>
|
|
<td><tt>Objective-C Garbage Collection</tt></td>
|
|
<td align="left"><b>[Required]</b> — Specifies whether garbage
|
|
collection is supported or not. Valid values are 0, for no garbage
|
|
collection, and 2, for garbage collection supported.</td>
|
|
</tr>
|
|
<tr>
|
|
<td><tt>Objective-C GC Only</tt></td>
|
|
<td align="left"><b>[Optional]</b> — Specifies that only garbage
|
|
collection is supported. If present, its value must be 6. This flag
|
|
requires that the <tt>Objective-C Garbage Collection</tt> flag have the
|
|
value 2.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<p>Some important flag interactions:</p>
|
|
|
|
<ul>
|
|
<li>If a module with <tt>Objective-C Garbage Collection</tt> set to 0 is
|
|
merged with a module with <tt>Objective-C Garbage Collection</tt> set to
|
|
2, then the resulting module has the <tt>Objective-C Garbage
|
|
Collection</tt> flag set to 0.</li>
|
|
|
|
<li>A module with <tt>Objective-C Garbage Collection</tt> set to 0 cannot be
|
|
merged with a module with <tt>Objective-C GC Only</tt> set to 6.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2>
|
|
<a name="intrinsic_globals">Intrinsic Global Variables</a>
|
|
</h2>
|
|
<!-- *********************************************************************** -->
|
|
<div>
|
|
<p>LLVM has a number of "magic" global variables that contain data that affect
|
|
code generation or other IR semantics. These are documented here. All globals
|
|
of this sort should have a section specified as "<tt>llvm.metadata</tt>". This
|
|
section and all globals that start with "<tt>llvm.</tt>" are reserved for use
|
|
by LLVM.</p>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="intg_used">The '<tt>llvm.used</tt>' Global Variable</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The <tt>@llvm.used</tt> global is an array with i8* element type which has <a
|
|
href="#linkage_appending">appending linkage</a>. This array contains a list of
|
|
pointers to global variables and functions which may optionally have a pointer
|
|
cast formed of bitcast or getelementptr. For example, a legal use of it is:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
@X = global i8 4
|
|
@Y = global i32 123
|
|
|
|
@llvm.used = appending global [2 x i8*] [
|
|
i8* @X,
|
|
i8* bitcast (i32* @Y to i8*)
|
|
], section "llvm.metadata"
|
|
</pre>
|
|
</div>
|
|
|
|
<p>If a global variable appears in the <tt>@llvm.used</tt> list, then the
|
|
compiler, assembler, and linker are required to treat the symbol as if there
|
|
is a reference to the global that it cannot see. For example, if a variable
|
|
has internal linkage and no references other than that from
|
|
the <tt>@llvm.used</tt> list, it cannot be deleted. This is commonly used to
|
|
represent references from inline asms and other things the compiler cannot
|
|
"see", and corresponds to "<tt>attribute((used))</tt>" in GNU C.</p>
|
|
|
|
<p>On some targets, the code generator must emit a directive to the assembler or
|
|
object file to prevent the assembler and linker from molesting the
|
|
symbol.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="intg_compiler_used">
|
|
The '<tt>llvm.compiler.used</tt>' Global Variable
|
|
</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The <tt>@llvm.compiler.used</tt> directive is the same as the
|
|
<tt>@llvm.used</tt> directive, except that it only prevents the compiler from
|
|
touching the symbol. On targets that support it, this allows an intelligent
|
|
linker to optimize references to the symbol without being impeded as it would
|
|
be by <tt>@llvm.used</tt>.</p>
|
|
|
|
<p>This is a rare construct that should only be used in rare circumstances, and
|
|
should not be exposed to source languages.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="intg_global_ctors">The '<tt>llvm.global_ctors</tt>' Global Variable</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%0 = type { i32, void ()* }
|
|
@llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @ctor }]
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The <tt>@llvm.global_ctors</tt> array contains a list of constructor
|
|
functions and associated priorities. The functions referenced by this array
|
|
will be called in ascending order of priority (i.e. lowest first) when the
|
|
module is loaded. The order of functions with the same priority is not
|
|
defined.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="intg_global_dtors">The '<tt>llvm.global_dtors</tt>' Global Variable</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%0 = type { i32, void ()* }
|
|
@llvm.global_dtors = appending global [1 x %0] [%0 { i32 65535, void ()* @dtor }]
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The <tt>@llvm.global_dtors</tt> array contains a list of destructor functions
|
|
and associated priorities. The functions referenced by this array will be
|
|
called in descending order of priority (i.e. highest first) when the module
|
|
is loaded. The order of functions with the same priority is not defined.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="instref">Instruction Reference</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>The LLVM instruction set consists of several different classifications of
|
|
instructions: <a href="#terminators">terminator
|
|
instructions</a>, <a href="#binaryops">binary instructions</a>,
|
|
<a href="#bitwiseops">bitwise binary instructions</a>,
|
|
<a href="#memoryops">memory instructions</a>, and
|
|
<a href="#otherops">other instructions</a>.</p>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="terminators">Terminator Instructions</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>As mentioned <a href="#functionstructure">previously</a>, every basic block
|
|
in a program ends with a "Terminator" instruction, which indicates which
|
|
block should be executed after the current block is finished. These
|
|
terminator instructions typically yield a '<tt>void</tt>' value: they produce
|
|
control flow, not values (the one exception being the
|
|
'<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p>
|
|
|
|
<p>The terminator instructions are:
|
|
'<a href="#i_ret"><tt>ret</tt></a>',
|
|
'<a href="#i_br"><tt>br</tt></a>',
|
|
'<a href="#i_switch"><tt>switch</tt></a>',
|
|
'<a href="#i_indirectbr"><tt>indirectbr</tt></a>',
|
|
'<a href="#i_invoke"><tt>invoke</tt></a>',
|
|
'<a href="#i_resume"><tt>resume</tt></a>', and
|
|
'<a href="#i_unreachable"><tt>unreachable</tt></a>'.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_ret">'<tt>ret</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
ret <type> <value> <i>; Return a value from a non-void function</i>
|
|
ret void <i>; Return from void function</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>ret</tt>' instruction is used to return control flow (and optionally
|
|
a value) from a function back to the caller.</p>
|
|
|
|
<p>There are two forms of the '<tt>ret</tt>' instruction: one that returns a
|
|
value and then causes control flow, and one that just causes control flow to
|
|
occur.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>ret</tt>' instruction optionally accepts a single argument, the
|
|
return value. The type of the return value must be a
|
|
'<a href="#t_firstclass">first class</a>' type.</p>
|
|
|
|
<p>A function is not <a href="#wellformed">well formed</a> if it it has a
|
|
non-void return type and contains a '<tt>ret</tt>' instruction with no return
|
|
value or a return value with a type that does not match its type, or if it
|
|
has a void return type and contains a '<tt>ret</tt>' instruction with a
|
|
return value.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>When the '<tt>ret</tt>' instruction is executed, control flow returns back to
|
|
the calling function's context. If the caller is a
|
|
"<a href="#i_call"><tt>call</tt></a>" instruction, execution continues at the
|
|
instruction after the call. If the caller was an
|
|
"<a href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues at
|
|
the beginning of the "normal" destination block. If the instruction returns
|
|
a value, that value shall set the call or invoke instruction's return
|
|
value.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
ret i32 5 <i>; Return an integer value of 5</i>
|
|
ret void <i>; Return from a void function</i>
|
|
ret { i32, i8 } { i32 4, i8 2 } <i>; Return a struct of values 4 and 2</i>
|
|
</pre>
|
|
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_br">'<tt>br</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
br i1 <cond>, label <iftrue>, label <iffalse>
|
|
br label <dest> <i>; Unconditional branch</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>br</tt>' instruction is used to cause control flow to transfer to a
|
|
different basic block in the current function. There are two forms of this
|
|
instruction, corresponding to a conditional branch and an unconditional
|
|
branch.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The conditional branch form of the '<tt>br</tt>' instruction takes a single
|
|
'<tt>i1</tt>' value and two '<tt>label</tt>' values. The unconditional form
|
|
of the '<tt>br</tt>' instruction takes a single '<tt>label</tt>' value as a
|
|
target.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>i1</tt>'
|
|
argument is evaluated. If the value is <tt>true</tt>, control flows to the
|
|
'<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>,
|
|
control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
Test:
|
|
%cond = <a href="#i_icmp">icmp</a> eq i32 %a, %b
|
|
br i1 %cond, label %IfEqual, label %IfUnequal
|
|
IfEqual:
|
|
<a href="#i_ret">ret</a> i32 1
|
|
IfUnequal:
|
|
<a href="#i_ret">ret</a> i32 0
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_switch">'<tt>switch</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of
|
|
several different places. It is a generalization of the '<tt>br</tt>'
|
|
instruction, allowing a branch to occur to one of many possible
|
|
destinations.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>switch</tt>' instruction uses three parameters: an integer
|
|
comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination,
|
|
and an array of pairs of comparison value constants and '<tt>label</tt>'s.
|
|
The table is not allowed to contain duplicate constant entries.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The <tt>switch</tt> instruction specifies a table of values and
|
|
destinations. When the '<tt>switch</tt>' instruction is executed, this table
|
|
is searched for the given value. If the value is found, control flow is
|
|
transferred to the corresponding destination; otherwise, control flow is
|
|
transferred to the default destination.</p>
|
|
|
|
<h5>Implementation:</h5>
|
|
<p>Depending on properties of the target machine and the particular
|
|
<tt>switch</tt> instruction, this instruction may be code generated in
|
|
different ways. For example, it could be generated as a series of chained
|
|
conditional branches or with a lookup table.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<i>; Emulate a conditional br instruction</i>
|
|
%Val = <a href="#i_zext">zext</a> i1 %value to i32
|
|
switch i32 %Val, label %truedest [ i32 0, label %falsedest ]
|
|
|
|
<i>; Emulate an unconditional br instruction</i>
|
|
switch i32 0, label %dest [ ]
|
|
|
|
<i>; Implement a jump table:</i>
|
|
switch i32 %val, label %otherwise [ i32 0, label %onzero
|
|
i32 1, label %onone
|
|
i32 2, label %ontwo ]
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_indirectbr">'<tt>indirectbr</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
indirectbr <somety>* <address>, [ label <dest1>, label <dest2>, ... ]
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>The '<tt>indirectbr</tt>' instruction implements an indirect branch to a label
|
|
within the current function, whose address is specified by
|
|
"<tt>address</tt>". Address must be derived from a <a
|
|
href="#blockaddress">blockaddress</a> constant.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>The '<tt>address</tt>' argument is the address of the label to jump to. The
|
|
rest of the arguments indicate the full set of possible destinations that the
|
|
address may point to. Blocks are allowed to occur multiple times in the
|
|
destination list, though this isn't particularly useful.</p>
|
|
|
|
<p>This destination list is required so that dataflow analysis has an accurate
|
|
understanding of the CFG.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>Control transfers to the block specified in the address argument. All
|
|
possible destination blocks must be listed in the label list, otherwise this
|
|
instruction has undefined behavior. This implies that jumps to labels
|
|
defined in other functions have undefined behavior as well.</p>
|
|
|
|
<h5>Implementation:</h5>
|
|
|
|
<p>This is typically implemented with a jump through a register.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
indirectbr i8* %Addr, [ label %bb1, label %bb2, label %bb3 ]
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_invoke">'<tt>invoke</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = invoke [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ptr to function ty> <function ptr val>(<function args>) [<a href="#fnattrs">fn attrs</a>]
|
|
to label <normal label> unwind label <exception label>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified
|
|
function, with the possibility of control flow transfer to either the
|
|
'<tt>normal</tt>' label or the '<tt>exception</tt>' label. If the callee
|
|
function returns with the "<tt><a href="#i_ret">ret</a></tt>" instruction,
|
|
control flow will return to the "normal" label. If the callee (or any
|
|
indirect callees) returns via the "<a href="#i_resume"><tt>resume</tt></a>"
|
|
instruction or other exception handling mechanism, control is interrupted and
|
|
continued at the dynamically nearest "exception" label.</p>
|
|
|
|
<p>The '<tt>exception</tt>' label is a
|
|
<i><a href="ExceptionHandling.html#overview">landing pad</a></i> for the
|
|
exception. As such, '<tt>exception</tt>' label is required to have the
|
|
"<a href="#i_landingpad"><tt>landingpad</tt></a>" instruction, which contains
|
|
the information about the behavior of the program after unwinding
|
|
happens, as its first non-PHI instruction. The restrictions on the
|
|
"<tt>landingpad</tt>" instruction's tightly couples it to the
|
|
"<tt>invoke</tt>" instruction, so that the important information contained
|
|
within the "<tt>landingpad</tt>" instruction can't be lost through normal
|
|
code motion.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>This instruction requires several arguments:</p>
|
|
|
|
<ol>
|
|
<li>The optional "cconv" marker indicates which <a href="#callingconv">calling
|
|
convention</a> the call should use. If none is specified, the call
|
|
defaults to using C calling conventions.</li>
|
|
|
|
<li>The optional <a href="#paramattrs">Parameter Attributes</a> list for
|
|
return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and
|
|
'<tt>inreg</tt>' attributes are valid here.</li>
|
|
|
|
<li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to
|
|
function value being invoked. In most cases, this is a direct function
|
|
invocation, but indirect <tt>invoke</tt>s are just as possible, branching
|
|
off an arbitrary pointer to function value.</li>
|
|
|
|
<li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a
|
|
function to be invoked. </li>
|
|
|
|
<li>'<tt>function args</tt>': argument list whose types match the function
|
|
signature argument types and parameter attributes. All arguments must be
|
|
of <a href="#t_firstclass">first class</a> type. If the function
|
|
signature indicates the function accepts a variable number of arguments,
|
|
the extra arguments can be specified.</li>
|
|
|
|
<li>'<tt>normal label</tt>': the label reached when the called function
|
|
executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
|
|
|
|
<li>'<tt>exception label</tt>': the label reached when a callee returns via
|
|
the <a href="#i_resume"><tt>resume</tt></a> instruction or other exception
|
|
handling mechanism.</li>
|
|
|
|
<li>The optional <a href="#fnattrs">function attributes</a> list. Only
|
|
'<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and
|
|
'<tt>readnone</tt>' attributes are valid here.</li>
|
|
</ol>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This instruction is designed to operate as a standard
|
|
'<tt><a href="#i_call">call</a></tt>' instruction in most regards. The
|
|
primary difference is that it establishes an association with a label, which
|
|
is used by the runtime library to unwind the stack.</p>
|
|
|
|
<p>This instruction is used in languages with destructors to ensure that proper
|
|
cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown
|
|
exception. Additionally, this is important for implementation of
|
|
'<tt>catch</tt>' clauses in high-level languages that support them.</p>
|
|
|
|
<p>For the purposes of the SSA form, the definition of the value returned by the
|
|
'<tt>invoke</tt>' instruction is deemed to occur on the edge from the current
|
|
block to the "normal" label. If the callee unwinds then no return value is
|
|
available.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%retval = invoke i32 @Test(i32 15) to label %Continue
|
|
unwind label %TestCleanup <i>; {i32}:retval set</i>
|
|
%retval = invoke <a href="#callingconv">coldcc</a> i32 %Testfnptr(i32 15) to label %Continue
|
|
unwind label %TestCleanup <i>; {i32}:retval set</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
|
|
<h4>
|
|
<a name="i_resume">'<tt>resume</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
resume <type> <value>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>resume</tt>' instruction is a terminator instruction that has no
|
|
successors.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>resume</tt>' instruction requires one argument, which must have the
|
|
same type as the result of any '<tt>landingpad</tt>' instruction in the same
|
|
function.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>resume</tt>' instruction resumes propagation of an existing
|
|
(in-flight) exception whose unwinding was interrupted with
|
|
a <a href="#i_landingpad"><tt>landingpad</tt></a> instruction.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
resume { i8*, i32 } %exn
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
|
|
<h4>
|
|
<a name="i_unreachable">'<tt>unreachable</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
unreachable
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>unreachable</tt>' instruction has no defined semantics. This
|
|
instruction is used to inform the optimizer that a particular portion of the
|
|
code is not reachable. This can be used to indicate that the code after a
|
|
no-return function cannot be reached, and other facts.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="binaryops">Binary Operations</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Binary operators are used to do most of the computation in a program. They
|
|
require two operands of the same type, execute an operation on them, and
|
|
produce a single value. The operands might represent multiple data, as is
|
|
the case with the <a href="#t_vector">vector</a> data type. The result value
|
|
has the same type as its operands.</p>
|
|
|
|
<p>There are several different binary operators:</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_add">'<tt>add</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = add <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = add nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = add nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = add nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>add</tt>' instruction must
|
|
be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
|
|
integer values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the integer sum of the two operands.</p>
|
|
|
|
<p>If the sum has unsigned overflow, the result returned is the mathematical
|
|
result modulo 2<sup>n</sup>, where n is the bit width of the result.</p>
|
|
|
|
<p>Because LLVM integers use a two's complement representation, this instruction
|
|
is appropriate for both signed and unsigned integers.</p>
|
|
|
|
<p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
|
|
and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
|
|
<tt>nsw</tt> keywords are present, the result value of the <tt>add</tt>
|
|
is a <a href="#poisonvalues">poison value</a> if unsigned and/or signed overflow,
|
|
respectively, occurs.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fadd">'<tt>fadd</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fadd <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fadd</tt>' instruction returns the sum of its two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>fadd</tt>' instruction must be
|
|
<a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
|
|
floating point values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the floating point sum of the two operands.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = fadd float 4.0, %var <i>; yields {float}:result = 4.0 + %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_sub">'<tt>sub</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = sub <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = sub nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = sub nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = sub nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>sub</tt>' instruction returns the difference of its two
|
|
operands.</p>
|
|
|
|
<p>Note that the '<tt>sub</tt>' instruction is used to represent the
|
|
'<tt>neg</tt>' instruction present in most other intermediate
|
|
representations.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>sub</tt>' instruction must
|
|
be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
|
|
integer values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the integer difference of the two operands.</p>
|
|
|
|
<p>If the difference has unsigned overflow, the result returned is the
|
|
mathematical result modulo 2<sup>n</sup>, where n is the bit width of the
|
|
result.</p>
|
|
|
|
<p>Because LLVM integers use a two's complement representation, this instruction
|
|
is appropriate for both signed and unsigned integers.</p>
|
|
|
|
<p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
|
|
and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
|
|
<tt>nsw</tt> keywords are present, the result value of the <tt>sub</tt>
|
|
is a <a href="#poisonvalues">poison value</a> if unsigned and/or signed overflow,
|
|
respectively, occurs.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i>
|
|
<result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fsub">'<tt>fsub</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fsub <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fsub</tt>' instruction returns the difference of its two
|
|
operands.</p>
|
|
|
|
<p>Note that the '<tt>fsub</tt>' instruction is used to represent the
|
|
'<tt>fneg</tt>' instruction present in most other intermediate
|
|
representations.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>fsub</tt>' instruction must be
|
|
<a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
|
|
floating point values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the floating point difference of the two operands.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = fsub float 4.0, %var <i>; yields {float}:result = 4.0 - %var</i>
|
|
<result> = fsub float -0.0, %val <i>; yields {float}:result = -%var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_mul">'<tt>mul</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = mul <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = mul nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = mul nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = mul nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>mul</tt>' instruction returns the product of its two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>mul</tt>' instruction must
|
|
be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
|
|
integer values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the integer product of the two operands.</p>
|
|
|
|
<p>If the result of the multiplication has unsigned overflow, the result
|
|
returned is the mathematical result modulo 2<sup>n</sup>, where n is the bit
|
|
width of the result.</p>
|
|
|
|
<p>Because LLVM integers use a two's complement representation, and the result
|
|
is the same width as the operands, this instruction returns the correct
|
|
result for both signed and unsigned integers. If a full product
|
|
(e.g. <tt>i32</tt>x<tt>i32</tt>-><tt>i64</tt>) is needed, the operands should
|
|
be sign-extended or zero-extended as appropriate to the width of the full
|
|
product.</p>
|
|
|
|
<p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
|
|
and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
|
|
<tt>nsw</tt> keywords are present, the result value of the <tt>mul</tt>
|
|
is a <a href="#poisonvalues">poison value</a> if unsigned and/or signed overflow,
|
|
respectively, occurs.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fmul">'<tt>fmul</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fmul <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fmul</tt>' instruction returns the product of its two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>fmul</tt>' instruction must be
|
|
<a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
|
|
floating point values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the floating point product of the two operands.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = fmul float 4.0, %var <i>; yields {float}:result = 4.0 * %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_udiv">'<tt>udiv</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = udiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = udiv exact <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>udiv</tt>' instruction returns the quotient of its two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>udiv</tt>' instruction must be
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the unsigned integer quotient of the two operands.</p>
|
|
|
|
<p>Note that unsigned integer division and signed integer division are distinct
|
|
operations; for signed integer division, use '<tt>sdiv</tt>'.</p>
|
|
|
|
<p>Division by zero leads to undefined behavior.</p>
|
|
|
|
<p>If the <tt>exact</tt> keyword is present, the result value of the
|
|
<tt>udiv</tt> is a <a href="#poisonvalues">poison value</a> if %op1 is not a
|
|
multiple of %op2 (as such, "((a udiv exact b) mul b) == a").</p>
|
|
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_sdiv">'<tt>sdiv</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = sdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = sdiv exact <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>sdiv</tt>' instruction returns the quotient of its two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>sdiv</tt>' instruction must be
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the signed integer quotient of the two operands rounded
|
|
towards zero.</p>
|
|
|
|
<p>Note that signed integer division and unsigned integer division are distinct
|
|
operations; for unsigned integer division, use '<tt>udiv</tt>'.</p>
|
|
|
|
<p>Division by zero leads to undefined behavior. Overflow also leads to
|
|
undefined behavior; this is a rare case, but can occur, for example, by doing
|
|
a 32-bit division of -2147483648 by -1.</p>
|
|
|
|
<p>If the <tt>exact</tt> keyword is present, the result value of the
|
|
<tt>sdiv</tt> is a <a href="#poisonvalues">poison value</a> if the result would
|
|
be rounded.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fdiv">'<tt>fdiv</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fdiv</tt>' instruction returns the quotient of its two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>fdiv</tt>' instruction must be
|
|
<a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
|
|
floating point values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is the floating point quotient of the two operands.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_urem">'<tt>urem</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = urem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>urem</tt>' instruction returns the remainder from the unsigned
|
|
division of its two arguments.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>urem</tt>' instruction must be
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This instruction returns the unsigned integer <i>remainder</i> of a division.
|
|
This instruction always performs an unsigned division to get the
|
|
remainder.</p>
|
|
|
|
<p>Note that unsigned integer remainder and signed integer remainder are
|
|
distinct operations; for signed integer remainder, use '<tt>srem</tt>'.</p>
|
|
|
|
<p>Taking the remainder of a division by zero leads to undefined behavior.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_srem">'<tt>srem</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = srem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>srem</tt>' instruction returns the remainder from the signed
|
|
division of its two operands. This instruction can also take
|
|
<a href="#t_vector">vector</a> versions of the values in which case the
|
|
elements must be integers.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>srem</tt>' instruction must be
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This instruction returns the <i>remainder</i> of a division (where the result
|
|
is either zero or has the same sign as the dividend, <tt>op1</tt>), not the
|
|
<i>modulo</i> operator (where the result is either zero or has the same sign
|
|
as the divisor, <tt>op2</tt>) of a value.
|
|
For more information about the difference,
|
|
see <a href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The
|
|
Math Forum</a>. For a table of how this is implemented in various languages,
|
|
please see <a href="http://en.wikipedia.org/wiki/Modulo_operation">
|
|
Wikipedia: modulo operation</a>.</p>
|
|
|
|
<p>Note that signed integer remainder and unsigned integer remainder are
|
|
distinct operations; for unsigned integer remainder, use '<tt>urem</tt>'.</p>
|
|
|
|
<p>Taking the remainder of a division by zero leads to undefined behavior.
|
|
Overflow also leads to undefined behavior; this is a rare case, but can
|
|
occur, for example, by taking the remainder of a 32-bit division of
|
|
-2147483648 by -1. (The remainder doesn't actually overflow, but this rule
|
|
lets srem be implemented using instructions that return both the result of
|
|
the division and the remainder.)</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_frem">'<tt>frem</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = frem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>frem</tt>' instruction returns the remainder from the division of
|
|
its two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>frem</tt>' instruction must be
|
|
<a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
|
|
floating point values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This instruction returns the <i>remainder</i> of a division. The remainder
|
|
has the same sign as the dividend.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="bitwiseops">Bitwise Binary Operations</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Bitwise binary operators are used to do various forms of bit-twiddling in a
|
|
program. They are generally very efficient instructions and can commonly be
|
|
strength reduced from other instructions. They require two operands of the
|
|
same type, execute an operation on them, and produce a single value. The
|
|
resulting value is the same type as its operands.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_shl">'<tt>shl</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = shl <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = shl nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = shl nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = shl nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>shl</tt>' instruction returns the first operand shifted to the left
|
|
a specified number of bits.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>Both arguments to the '<tt>shl</tt>' instruction must be the
|
|
same <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
|
|
integer type. '<tt>op2</tt>' is treated as an unsigned value.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The value produced is <tt>op1</tt> * 2<sup><tt>op2</tt></sup> mod
|
|
2<sup>n</sup>, where <tt>n</tt> is the width of the result. If <tt>op2</tt>
|
|
is (statically or dynamically) negative or equal to or larger than the number
|
|
of bits in <tt>op1</tt>, the result is undefined. If the arguments are
|
|
vectors, each vector element of <tt>op1</tt> is shifted by the corresponding
|
|
shift amount in <tt>op2</tt>.</p>
|
|
|
|
<p>If the <tt>nuw</tt> keyword is present, then the shift produces a
|
|
<a href="#poisonvalues">poison value</a> if it shifts out any non-zero bits. If
|
|
the <tt>nsw</tt> keyword is present, then the shift produces a
|
|
<a href="#poisonvalues">poison value</a> if it shifts out any bits that disagree
|
|
with the resultant sign bit. As such, NUW/NSW have the same semantics as
|
|
they would if the shift were expressed as a mul instruction with the same
|
|
nsw/nuw bits in (mul %op1, (shl 1, %op2)).</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i>
|
|
<result> = shl i32 4, 2 <i>; yields {i32}: 16</i>
|
|
<result> = shl i32 1, 10 <i>; yields {i32}: 1024</i>
|
|
<result> = shl i32 1, 32 <i>; undefined</i>
|
|
<result> = shl <2 x i32> < i32 1, i32 1>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 2, i32 4></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_lshr">'<tt>lshr</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = lshr <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = lshr exact <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first
|
|
operand shifted to the right a specified number of bits with zero fill.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>Both arguments to the '<tt>lshr</tt>' instruction must be the same
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
type. '<tt>op2</tt>' is treated as an unsigned value.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This instruction always performs a logical shift right operation. The most
|
|
significant bits of the result will be filled with zero bits after the shift.
|
|
If <tt>op2</tt> is (statically or dynamically) equal to or larger than the
|
|
number of bits in <tt>op1</tt>, the result is undefined. If the arguments are
|
|
vectors, each vector element of <tt>op1</tt> is shifted by the corresponding
|
|
shift amount in <tt>op2</tt>.</p>
|
|
|
|
<p>If the <tt>exact</tt> keyword is present, the result value of the
|
|
<tt>lshr</tt> is a <a href="#poisonvalues">poison value</a> if any of the bits
|
|
shifted out are non-zero.</p>
|
|
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i>
|
|
<result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i>
|
|
<result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i>
|
|
<result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i>
|
|
<result> = lshr i32 1, 32 <i>; undefined</i>
|
|
<result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_ashr">'<tt>ashr</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = ashr <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
<result> = ashr exact <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first
|
|
operand shifted to the right a specified number of bits with sign
|
|
extension.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>Both arguments to the '<tt>ashr</tt>' instruction must be the same
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
type. '<tt>op2</tt>' is treated as an unsigned value.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This instruction always performs an arithmetic shift right operation, The
|
|
most significant bits of the result will be filled with the sign bit
|
|
of <tt>op1</tt>. If <tt>op2</tt> is (statically or dynamically) equal to or
|
|
larger than the number of bits in <tt>op1</tt>, the result is undefined. If
|
|
the arguments are vectors, each vector element of <tt>op1</tt> is shifted by
|
|
the corresponding shift amount in <tt>op2</tt>.</p>
|
|
|
|
<p>If the <tt>exact</tt> keyword is present, the result value of the
|
|
<tt>ashr</tt> is a <a href="#poisonvalues">poison value</a> if any of the bits
|
|
shifted out are non-zero.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i>
|
|
<result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i>
|
|
<result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i>
|
|
<result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i>
|
|
<result> = ashr i32 1, 32 <i>; undefined</i>
|
|
<result> = ashr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 3> <i>; yields: result=<2 x i32> < i32 -1, i32 0></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_and">'<tt>and</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = and <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>and</tt>' instruction returns the bitwise logical and of its two
|
|
operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>and</tt>' instruction must be
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The truth table used for the '<tt>and</tt>' instruction is:</p>
|
|
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr>
|
|
<th>In0</th>
|
|
<th>In1</th>
|
|
<th>Out</th>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i>
|
|
<result> = and i32 15, 40 <i>; yields {i32}:result = 8</i>
|
|
<result> = and i32 4, 8 <i>; yields {i32}:result = 0</i>
|
|
</pre>
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_or">'<tt>or</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = or <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive or of its
|
|
two operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>or</tt>' instruction must be
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The truth table used for the '<tt>or</tt>' instruction is:</p>
|
|
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr>
|
|
<th>In0</th>
|
|
<th>In1</th>
|
|
<th>Out</th>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i>
|
|
<result> = or i32 15, 40 <i>; yields {i32}:result = 47</i>
|
|
<result> = or i32 4, 8 <i>; yields {i32}:result = 12</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_xor">'<tt>xor</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = xor <ty> <op1>, <op2> <i>; yields {ty}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive or of
|
|
its two operands. The <tt>xor</tt> is used to implement the "one's
|
|
complement" operation, which is the "~" operator in C.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The two arguments to the '<tt>xor</tt>' instruction must be
|
|
<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
|
|
values. Both arguments must have identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The truth table used for the '<tt>xor</tt>' instruction is:</p>
|
|
|
|
<table border="1" cellspacing="0" cellpadding="4">
|
|
<tbody>
|
|
<tr>
|
|
<th>In0</th>
|
|
<th>In1</th>
|
|
<th>Out</th>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
<td>0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
<td>1</td>
|
|
</tr>
|
|
<tr>
|
|
<td>1</td>
|
|
<td>1</td>
|
|
<td>0</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i>
|
|
<result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i>
|
|
<result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i>
|
|
<result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="vectorops">Vector Operations</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM supports several instructions to represent vector operations in a
|
|
target-independent manner. These instructions cover the element-access and
|
|
vector-specific operations needed to process vectors effectively. While LLVM
|
|
does directly support these vector operations, many sophisticated algorithms
|
|
will want to use target-specific intrinsics to take full advantage of a
|
|
specific target.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>extractelement</tt>' instruction extracts a single scalar element
|
|
from a vector at a specified index.</p>
|
|
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first operand of an '<tt>extractelement</tt>' instruction is a value
|
|
of <a href="#t_vector">vector</a> type. The second operand is an index
|
|
indicating the position from which to extract the element. The index may be
|
|
a variable.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The result is a scalar of the same type as the element type of
|
|
<tt>val</tt>. Its value is the value at position <tt>idx</tt> of
|
|
<tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
|
|
results are undefined.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>insertelement</tt>' instruction inserts a scalar element into a
|
|
vector at a specified index.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first operand of an '<tt>insertelement</tt>' instruction is a value
|
|
of <a href="#t_vector">vector</a> type. The second operand is a scalar value
|
|
whose type must equal the element type of the first operand. The third
|
|
operand is an index indicating the position at which to insert the value.
|
|
The index may be a variable.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The result is a vector of the same type as <tt>val</tt>. Its element values
|
|
are those of <tt>val</tt> except at position <tt>idx</tt>, where it gets the
|
|
value <tt>elt</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
|
|
results are undefined.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <m x i32> <mask> <i>; yields <m x <ty>></i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>shufflevector</tt>' instruction constructs a permutation of elements
|
|
from two input vectors, returning a vector with the same element type as the
|
|
input and length that is the same as the shuffle mask.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first two operands of a '<tt>shufflevector</tt>' instruction are vectors
|
|
with the same type. The third argument is a shuffle mask whose
|
|
element type is always 'i32'. The result of the instruction is a vector
|
|
whose length is the same as the shuffle mask and whose element type is the
|
|
same as the element type of the first two operands.</p>
|
|
|
|
<p>The shuffle mask operand is required to be a constant vector with either
|
|
constant integer or undef values.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The elements of the two input vectors are numbered from left to right across
|
|
both of the vectors. The shuffle mask operand specifies, for each element of
|
|
the result vector, which element of the two input vectors the result element
|
|
gets. The element selector may be undef (meaning "don't care") and the
|
|
second operand may be undef if performing a shuffle from only one vector.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
|
|
<4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i>
|
|
<result> = shufflevector <4 x i32> %v1, <4 x i32> undef,
|
|
<4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle.
|
|
<result> = shufflevector <8 x i32> %v1, <8 x i32> undef,
|
|
<4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i>
|
|
<result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
|
|
<8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7 > <i>; yields <8 x i32></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="aggregateops">Aggregate Operations</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM supports several instructions for working with
|
|
<a href="#t_aggregate">aggregate</a> values.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_extractvalue">'<tt>extractvalue</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = extractvalue <aggregate type> <val>, <idx>{, <idx>}*
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>extractvalue</tt>' instruction extracts the value of a member field
|
|
from an <a href="#t_aggregate">aggregate</a> value.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first operand of an '<tt>extractvalue</tt>' instruction is a value
|
|
of <a href="#t_struct">struct</a> or
|
|
<a href="#t_array">array</a> type. The operands are constant indices to
|
|
specify which value to extract in a similar manner as indices in a
|
|
'<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.</p>
|
|
<p>The major differences to <tt>getelementptr</tt> indexing are:</p>
|
|
<ul>
|
|
<li>Since the value being indexed is not a pointer, the first index is
|
|
omitted and assumed to be zero.</li>
|
|
<li>At least one index must be specified.</li>
|
|
<li>Not only struct indices but also array indices must be in
|
|
bounds.</li>
|
|
</ul>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The result is the value at the position in the aggregate specified by the
|
|
index operands.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = extractvalue {i32, float} %agg, 0 <i>; yields i32</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_insertvalue">'<tt>insertvalue</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = insertvalue <aggregate type> <val>, <ty> <elt>, <idx>{, <idx>}* <i>; yields <aggregate type></i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>insertvalue</tt>' instruction inserts a value into a member field
|
|
in an <a href="#t_aggregate">aggregate</a> value.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first operand of an '<tt>insertvalue</tt>' instruction is a value
|
|
of <a href="#t_struct">struct</a> or
|
|
<a href="#t_array">array</a> type. The second operand is a first-class
|
|
value to insert. The following operands are constant indices indicating
|
|
the position at which to insert the value in a similar manner as indices in a
|
|
'<tt><a href="#i_extractvalue">extractvalue</a></tt>' instruction. The
|
|
value to insert must have the same type as the value identified by the
|
|
indices.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The result is an aggregate of the same type as <tt>val</tt>. Its value is
|
|
that of <tt>val</tt> except that the value at the position specified by the
|
|
indices is that of <tt>elt</tt>.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%agg1 = insertvalue {i32, float} undef, i32 1, 0 <i>; yields {i32 1, float undef}</i>
|
|
%agg2 = insertvalue {i32, float} %agg1, float %val, 1 <i>; yields {i32 1, float %val}</i>
|
|
%agg3 = insertvalue {i32, {float}} %agg1, float %val, 1, 0 <i>; yields {i32 1, float %val}</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="memoryops">Memory Access and Addressing Operations</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>A key design point of an SSA-based representation is how it represents
|
|
memory. In LLVM, no memory locations are in SSA form, which makes things
|
|
very simple. This section describes how to read, write, and allocate
|
|
memory in LLVM.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_alloca">'<tt>alloca</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = alloca <type>[, <ty> <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the
|
|
currently executing function, to be automatically released when this function
|
|
returns to its caller. The object is always allocated in the generic address
|
|
space (address space zero).</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>alloca</tt>' instruction
|
|
allocates <tt>sizeof(<type>)*NumElements</tt> bytes of memory on the
|
|
runtime stack, returning a pointer of the appropriate type to the program.
|
|
If "NumElements" is specified, it is the number of elements allocated,
|
|
otherwise "NumElements" is defaulted to be one. If a constant alignment is
|
|
specified, the value result of the allocation is guaranteed to be aligned to
|
|
at least that boundary. If not specified, or if zero, the target can choose
|
|
to align the allocation on any convenient boundary compatible with the
|
|
type.</p>
|
|
|
|
<p>'<tt>type</tt>' may be any sized type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>Memory is allocated; a pointer is returned. The operation is undefined if
|
|
there is insufficient stack space for the allocation. '<tt>alloca</tt>'d
|
|
memory is automatically released when the function returns. The
|
|
'<tt>alloca</tt>' instruction is commonly used to represent automatic
|
|
variables that must have an address available. When the function returns
|
|
(either with the <tt><a href="#i_ret">ret</a></tt>
|
|
or <tt><a href="#i_resume">resume</a></tt> instructions), the memory is
|
|
reclaimed. Allocating zero bytes is legal, but the result is undefined.
|
|
The order in which memory is allocated (ie., which way the stack grows) is
|
|
not specified.</p>
|
|
|
|
<p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%ptr = alloca i32 <i>; yields {i32*}:ptr</i>
|
|
%ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i>
|
|
%ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i>
|
|
%ptr = alloca i32, align 1024 <i>; yields {i32*}:ptr</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_load">'<tt>load</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = load [volatile] <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>][, !invariant.load !<index>]
|
|
<result> = load atomic [volatile] <ty>* <pointer> [singlethread] <ordering>, align <alignment>
|
|
!<index> = !{ i32 1 }
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>load</tt>' instruction is used to read from memory.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument to the '<tt>load</tt>' instruction specifies the memory address
|
|
from which to load. The pointer must point to
|
|
a <a href="#t_firstclass">first class</a> type. If the <tt>load</tt> is
|
|
marked as <tt>volatile</tt>, then the optimizer is not allowed to modify the
|
|
number or order of execution of this <tt>load</tt> with other <a
|
|
href="#volatile">volatile operations</a>.</p>
|
|
|
|
<p>If the <code>load</code> is marked as <code>atomic</code>, it takes an extra
|
|
<a href="#ordering">ordering</a> and optional <code>singlethread</code>
|
|
argument. The <code>release</code> and <code>acq_rel</code> orderings are
|
|
not valid on <code>load</code> instructions. Atomic loads produce <a
|
|
href="#memorymodel">defined</a> results when they may see multiple atomic
|
|
stores. The type of the pointee must be an integer type whose bit width
|
|
is a power of two greater than or equal to eight and less than or equal
|
|
to a target-specific size limit. <code>align</code> must be explicitly
|
|
specified on atomic loads, and the load has undefined behavior if the
|
|
alignment is not set to a value which is at least the size in bytes of
|
|
the pointee. <code>!nontemporal</code> does not have any defined semantics
|
|
for atomic loads.</p>
|
|
|
|
<p>The optional constant <tt>align</tt> argument specifies the alignment of the
|
|
operation (that is, the alignment of the memory address). A value of 0 or an
|
|
omitted <tt>align</tt> argument means that the operation has the abi
|
|
alignment for the target. It is the responsibility of the code emitter to
|
|
ensure that the alignment information is correct. Overestimating the
|
|
alignment results in undefined behavior. Underestimating the alignment may
|
|
produce less efficient code. An alignment of 1 is always safe.</p>
|
|
|
|
<p>The optional <tt>!nontemporal</tt> metadata must reference a single
|
|
metatadata name <index> corresponding to a metadata node with
|
|
one <tt>i32</tt> entry of value 1. The existence of
|
|
the <tt>!nontemporal</tt> metatadata on the instruction tells the optimizer
|
|
and code generator that this load is not expected to be reused in the cache.
|
|
The code generator may select special instructions to save cache bandwidth,
|
|
such as the <tt>MOVNT</tt> instruction on x86.</p>
|
|
|
|
<p>The optional <tt>!invariant.load</tt> metadata must reference a single
|
|
metatadata name <index> corresponding to a metadata node with no
|
|
entries. The existence of the <tt>!invariant.load</tt> metatadata on the
|
|
instruction tells the optimizer and code generator that this load address
|
|
points to memory which does not change value during program execution.
|
|
The optimizer may then move this load around, for example, by hoisting it
|
|
out of loops using loop invariant code motion.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The location of memory pointed to is loaded. If the value being loaded is of
|
|
scalar type then the number of bytes read does not exceed the minimum number
|
|
of bytes needed to hold all bits of the type. For example, loading an
|
|
<tt>i24</tt> reads at most three bytes. When loading a value of a type like
|
|
<tt>i20</tt> with a size that is not an integral number of bytes, the result
|
|
is undefined if the value was not originally written using a store of the
|
|
same type.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
|
|
<a href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i>
|
|
%val = load i32* %ptr <i>; yields {i32}:val = i32 3</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_store">'<tt>store</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
store [volatile] <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
|
|
store atomic [volatile] <ty> <value>, <ty>* <pointer> [singlethread] <ordering>, align <alignment> <i>; yields {void}</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>store</tt>' instruction is used to write to memory.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>There are two arguments to the '<tt>store</tt>' instruction: a value to store
|
|
and an address at which to store it. The type of the
|
|
'<tt><pointer></tt>' operand must be a pointer to
|
|
the <a href="#t_firstclass">first class</a> type of the
|
|
'<tt><value></tt>' operand. If the <tt>store</tt> is marked as
|
|
<tt>volatile</tt>, then the optimizer is not allowed to modify the number or
|
|
order of execution of this <tt>store</tt> with other <a
|
|
href="#volatile">volatile operations</a>.</p>
|
|
|
|
<p>If the <code>store</code> is marked as <code>atomic</code>, it takes an extra
|
|
<a href="#ordering">ordering</a> and optional <code>singlethread</code>
|
|
argument. The <code>acquire</code> and <code>acq_rel</code> orderings aren't
|
|
valid on <code>store</code> instructions. Atomic loads produce <a
|
|
href="#memorymodel">defined</a> results when they may see multiple atomic
|
|
stores. The type of the pointee must be an integer type whose bit width
|
|
is a power of two greater than or equal to eight and less than or equal
|
|
to a target-specific size limit. <code>align</code> must be explicitly
|
|
specified on atomic stores, and the store has undefined behavior if the
|
|
alignment is not set to a value which is at least the size in bytes of
|
|
the pointee. <code>!nontemporal</code> does not have any defined semantics
|
|
for atomic stores.</p>
|
|
|
|
<p>The optional constant "align" argument specifies the alignment of the
|
|
operation (that is, the alignment of the memory address). A value of 0 or an
|
|
omitted "align" argument means that the operation has the abi
|
|
alignment for the target. It is the responsibility of the code emitter to
|
|
ensure that the alignment information is correct. Overestimating the
|
|
alignment results in an undefined behavior. Underestimating the alignment may
|
|
produce less efficient code. An alignment of 1 is always safe.</p>
|
|
|
|
<p>The optional !nontemporal metadata must reference a single metatadata
|
|
name <index> corresponding to a metadata node with one i32 entry of
|
|
value 1. The existence of the !nontemporal metatadata on the
|
|
instruction tells the optimizer and code generator that this load is
|
|
not expected to be reused in the cache. The code generator may
|
|
select special instructions to save cache bandwidth, such as the
|
|
MOVNT instruction on x86.</p>
|
|
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The contents of memory are updated to contain '<tt><value></tt>' at the
|
|
location specified by the '<tt><pointer></tt>' operand. If
|
|
'<tt><value></tt>' is of scalar type then the number of bytes written
|
|
does not exceed the minimum number of bytes needed to hold all bits of the
|
|
type. For example, storing an <tt>i24</tt> writes at most three bytes. When
|
|
writing a value of a type like <tt>i20</tt> with a size that is not an
|
|
integral number of bytes, it is unspecified what happens to the extra bits
|
|
that do not belong to the type, but they will typically be overwritten.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
|
|
store i32 3, i32* %ptr <i>; yields {void}</i>
|
|
%val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fence">'<tt>fence</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
fence [singlethread] <ordering> <i>; yields {void}</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fence</tt>' instruction is used to introduce happens-before edges
|
|
between operations.</p>
|
|
|
|
<h5>Arguments:</h5> <p>'<code>fence</code>' instructions take an <a
|
|
href="#ordering">ordering</a> argument which defines what
|
|
<i>synchronizes-with</i> edges they add. They can only be given
|
|
<code>acquire</code>, <code>release</code>, <code>acq_rel</code>, and
|
|
<code>seq_cst</code> orderings.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>A fence <var>A</var> which has (at least) <code>release</code> ordering
|
|
semantics <i>synchronizes with</i> a fence <var>B</var> with (at least)
|
|
<code>acquire</code> ordering semantics if and only if there exist atomic
|
|
operations <var>X</var> and <var>Y</var>, both operating on some atomic object
|
|
<var>M</var>, such that <var>A</var> is sequenced before <var>X</var>,
|
|
<var>X</var> modifies <var>M</var> (either directly or through some side effect
|
|
of a sequence headed by <var>X</var>), <var>Y</var> is sequenced before
|
|
<var>B</var>, and <var>Y</var> observes <var>M</var>. This provides a
|
|
<i>happens-before</i> dependency between <var>A</var> and <var>B</var>. Rather
|
|
than an explicit <code>fence</code>, one (but not both) of the atomic operations
|
|
<var>X</var> or <var>Y</var> might provide a <code>release</code> or
|
|
<code>acquire</code> (resp.) ordering constraint and still
|
|
<i>synchronize-with</i> the explicit <code>fence</code> and establish the
|
|
<i>happens-before</i> edge.</p>
|
|
|
|
<p>A <code>fence</code> which has <code>seq_cst</code> ordering, in addition to
|
|
having both <code>acquire</code> and <code>release</code> semantics specified
|
|
above, participates in the global program order of other <code>seq_cst</code>
|
|
operations and/or fences.</p>
|
|
|
|
<p>The optional "<a href="#singlethread"><code>singlethread</code></a>" argument
|
|
specifies that the fence only synchronizes with other fences in the same
|
|
thread. (This is useful for interacting with signal handlers.)</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
fence acquire <i>; yields {void}</i>
|
|
fence singlethread seq_cst <i>; yields {void}</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_cmpxchg">'<tt>cmpxchg</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
cmpxchg [volatile] <ty>* <pointer>, <ty> <cmp>, <ty> <new> [singlethread] <ordering> <i>; yields {ty}</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>cmpxchg</tt>' instruction is used to atomically modify memory.
|
|
It loads a value in memory and compares it to a given value. If they are
|
|
equal, it stores a new value into the memory.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>There are three arguments to the '<code>cmpxchg</code>' instruction: an
|
|
address to operate on, a value to compare to the value currently be at that
|
|
address, and a new value to place at that address if the compared values are
|
|
equal. The type of '<var><cmp></var>' must be an integer type whose
|
|
bit width is a power of two greater than or equal to eight and less than
|
|
or equal to a target-specific size limit. '<var><cmp></var>' and
|
|
'<var><new></var>' must have the same type, and the type of
|
|
'<var><pointer></var>' must be a pointer to that type. If the
|
|
<code>cmpxchg</code> is marked as <code>volatile</code>, then the
|
|
optimizer is not allowed to modify the number or order of execution
|
|
of this <code>cmpxchg</code> with other <a href="#volatile">volatile
|
|
operations</a>.</p>
|
|
|
|
<!-- FIXME: Extend allowed types. -->
|
|
|
|
<p>The <a href="#ordering"><var>ordering</var></a> argument specifies how this
|
|
<code>cmpxchg</code> synchronizes with other atomic operations.</p>
|
|
|
|
<p>The optional "<code>singlethread</code>" argument declares that the
|
|
<code>cmpxchg</code> is only atomic with respect to code (usually signal
|
|
handlers) running in the same thread as the <code>cmpxchg</code>. Otherwise the
|
|
cmpxchg is atomic with respect to all other code in the system.</p>
|
|
|
|
<p>The pointer passed into cmpxchg must have alignment greater than or equal to
|
|
the size in memory of the operand.
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The contents of memory at the location specified by the
|
|
'<tt><pointer></tt>' operand is read and compared to
|
|
'<tt><cmp></tt>'; if the read value is the equal,
|
|
'<tt><new></tt>' is written. The original value at the location
|
|
is returned.
|
|
|
|
<p>A successful <code>cmpxchg</code> is a read-modify-write instruction for the
|
|
purpose of identifying <a href="#release_sequence">release sequences</a>. A
|
|
failed <code>cmpxchg</code> is equivalent to an atomic load with an ordering
|
|
parameter determined by dropping any <code>release</code> part of the
|
|
<code>cmpxchg</code>'s ordering.</p>
|
|
|
|
<!--
|
|
FIXME: Is compare_exchange_weak() necessary? (Consider after we've done
|
|
optimization work on ARM.)
|
|
|
|
FIXME: Is a weaker ordering constraint on failure helpful in practice?
|
|
-->
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
entry:
|
|
%orig = atomic <a href="#i_load">load</a> i32* %ptr unordered <i>; yields {i32}</i>
|
|
<a href="#i_br">br</a> label %loop
|
|
|
|
loop:
|
|
%cmp = <a href="#i_phi">phi</a> i32 [ %orig, %entry ], [%old, %loop]
|
|
%squared = <a href="#i_mul">mul</a> i32 %cmp, %cmp
|
|
%old = cmpxchg i32* %ptr, i32 %cmp, i32 %squared <i>; yields {i32}</i>
|
|
%success = <a href="#i_icmp">icmp</a> eq i32 %cmp, %old
|
|
<a href="#i_br">br</a> i1 %success, label %done, label %loop
|
|
|
|
done:
|
|
...
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_atomicrmw">'<tt>atomicrmw</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
atomicrmw [volatile] <operation> <ty>* <pointer>, <ty> <value> [singlethread] <ordering> <i>; yields {ty}</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>atomicrmw</tt>' instruction is used to atomically modify memory.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>There are three arguments to the '<code>atomicrmw</code>' instruction: an
|
|
operation to apply, an address whose value to modify, an argument to the
|
|
operation. The operation must be one of the following keywords:</p>
|
|
<ul>
|
|
<li>xchg</li>
|
|
<li>add</li>
|
|
<li>sub</li>
|
|
<li>and</li>
|
|
<li>nand</li>
|
|
<li>or</li>
|
|
<li>xor</li>
|
|
<li>max</li>
|
|
<li>min</li>
|
|
<li>umax</li>
|
|
<li>umin</li>
|
|
</ul>
|
|
|
|
<p>The type of '<var><value></var>' must be an integer type whose
|
|
bit width is a power of two greater than or equal to eight and less than
|
|
or equal to a target-specific size limit. The type of the
|
|
'<code><pointer></code>' operand must be a pointer to that type.
|
|
If the <code>atomicrmw</code> is marked as <code>volatile</code>, then the
|
|
optimizer is not allowed to modify the number or order of execution of this
|
|
<code>atomicrmw</code> with other <a href="#volatile">volatile
|
|
operations</a>.</p>
|
|
|
|
<!-- FIXME: Extend allowed types. -->
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The contents of memory at the location specified by the
|
|
'<tt><pointer></tt>' operand are atomically read, modified, and written
|
|
back. The original value at the location is returned. The modification is
|
|
specified by the <var>operation</var> argument:</p>
|
|
|
|
<ul>
|
|
<li>xchg: <code>*ptr = val</code></li>
|
|
<li>add: <code>*ptr = *ptr + val</code></li>
|
|
<li>sub: <code>*ptr = *ptr - val</code></li>
|
|
<li>and: <code>*ptr = *ptr & val</code></li>
|
|
<li>nand: <code>*ptr = ~(*ptr & val)</code></li>
|
|
<li>or: <code>*ptr = *ptr | val</code></li>
|
|
<li>xor: <code>*ptr = *ptr ^ val</code></li>
|
|
<li>max: <code>*ptr = *ptr > val ? *ptr : val</code> (using a signed comparison)</li>
|
|
<li>min: <code>*ptr = *ptr < val ? *ptr : val</code> (using a signed comparison)</li>
|
|
<li>umax: <code>*ptr = *ptr > val ? *ptr : val</code> (using an unsigned comparison)</li>
|
|
<li>umin: <code>*ptr = *ptr < val ? *ptr : val</code> (using an unsigned comparison)</li>
|
|
</ul>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%old = atomicrmw add i32* %ptr, i32 1 acquire <i>; yields {i32}</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = getelementptr <pty>* <ptrval>{, <ty> <idx>}*
|
|
<result> = getelementptr inbounds <pty>* <ptrval>{, <ty> <idx>}*
|
|
<result> = getelementptr <ptr vector> ptrval, <vector index type> idx
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>getelementptr</tt>' instruction is used to get the address of a
|
|
subelement of an <a href="#t_aggregate">aggregate</a> data structure.
|
|
It performs address calculation only and does not access memory.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is always a pointer or a vector of pointers,
|
|
and forms the basis of the
|
|
calculation. The remaining arguments are indices that indicate which of the
|
|
elements of the aggregate object are indexed. The interpretation of each
|
|
index is dependent on the type being indexed into. The first index always
|
|
indexes the pointer value given as the first argument, the second index
|
|
indexes a value of the type pointed to (not necessarily the value directly
|
|
pointed to, since the first index can be non-zero), etc. The first type
|
|
indexed into must be a pointer value, subsequent types can be arrays,
|
|
vectors, and structs. Note that subsequent types being indexed into
|
|
can never be pointers, since that would require loading the pointer before
|
|
continuing calculation.</p>
|
|
|
|
<p>The type of each index argument depends on the type it is indexing into.
|
|
When indexing into a (optionally packed) structure, only <tt>i32</tt>
|
|
integer <b>constants</b> are allowed (when using a vector of indices they
|
|
must all be the <b>same</b> <tt>i32</tt> integer constant). When indexing
|
|
into an array, pointer or vector, integers of any width are allowed, and
|
|
they are not required to be constant. These integers are treated as signed
|
|
values where relevant.</p>
|
|
|
|
<p>For example, let's consider a C code fragment and how it gets compiled to
|
|
LLVM:</p>
|
|
|
|
<pre class="doc_code">
|
|
struct RT {
|
|
char A;
|
|
int B[10][20];
|
|
char C;
|
|
};
|
|
struct ST {
|
|
int X;
|
|
double Y;
|
|
struct RT Z;
|
|
};
|
|
|
|
int *foo(struct ST *s) {
|
|
return &s[1].Z.B[5][13];
|
|
}
|
|
</pre>
|
|
|
|
<p>The LLVM code generated by Clang is:</p>
|
|
|
|
<pre class="doc_code">
|
|
%struct.RT = <a href="#namedtypes">type</a> { i8, [10 x [20 x i32]], i8 }
|
|
%struct.ST = <a href="#namedtypes">type</a> { i32, double, %struct.RT }
|
|
|
|
define i32* @foo(%struct.ST* %s) nounwind uwtable readnone optsize ssp {
|
|
entry:
|
|
%arrayidx = getelementptr inbounds %struct.ST* %s, i64 1, i32 2, i32 1, i64 5, i64 13
|
|
ret i32* %arrayidx
|
|
}
|
|
</pre>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>In the example above, the first index is indexing into the
|
|
'<tt>%struct.ST*</tt>' type, which is a pointer, yielding a
|
|
'<tt>%struct.ST</tt>' = '<tt>{ i32, double, %struct.RT }</tt>' type, a
|
|
structure. The second index indexes into the third element of the structure,
|
|
yielding a '<tt>%struct.RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]], i8 }</tt>'
|
|
type, another structure. The third index indexes into the second element of
|
|
the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an array. The
|
|
two dimensions of the array are subscripted into, yielding an '<tt>i32</tt>'
|
|
type. The '<tt>getelementptr</tt>' instruction returns a pointer to this
|
|
element, thus computing a value of '<tt>i32*</tt>' type.</p>
|
|
|
|
<p>Note that it is perfectly legal to index partially through a structure,
|
|
returning a pointer to an inner element. Because of this, the LLVM code for
|
|
the given testcase is equivalent to:</p>
|
|
|
|
<pre class="doc_code">
|
|
define i32* @foo(%struct.ST* %s) {
|
|
%t1 = getelementptr %struct.ST* %s, i32 1 <i>; yields %struct.ST*:%t1</i>
|
|
%t2 = getelementptr %struct.ST* %t1, i32 0, i32 2 <i>; yields %struct.RT*:%t2</i>
|
|
%t3 = getelementptr %struct.RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i>
|
|
%t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i>
|
|
%t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i>
|
|
ret i32* %t5
|
|
}
|
|
</pre>
|
|
|
|
<p>If the <tt>inbounds</tt> keyword is present, the result value of the
|
|
<tt>getelementptr</tt> is a <a href="#poisonvalues">poison value</a> if the
|
|
base pointer is not an <i>in bounds</i> address of an allocated object,
|
|
or if any of the addresses that would be formed by successive addition of
|
|
the offsets implied by the indices to the base address with infinitely
|
|
precise signed arithmetic are not an <i>in bounds</i> address of that
|
|
allocated object. The <i>in bounds</i> addresses for an allocated object
|
|
are all the addresses that point into the object, plus the address one
|
|
byte past the end.
|
|
In cases where the base is a vector of pointers the <tt>inbounds</tt> keyword
|
|
applies to each of the computations element-wise. </p>
|
|
|
|
<p>If the <tt>inbounds</tt> keyword is not present, the offsets are added to
|
|
the base address with silently-wrapping two's complement arithmetic. If the
|
|
offsets have a different width from the pointer, they are sign-extended or
|
|
truncated to the width of the pointer. The result value of the
|
|
<tt>getelementptr</tt> may be outside the object pointed to by the base
|
|
pointer. The result value may not necessarily be used to access memory
|
|
though, even if it happens to point into allocated storage. See the
|
|
<a href="#pointeraliasing">Pointer Aliasing Rules</a> section for more
|
|
information.</p>
|
|
|
|
<p>The getelementptr instruction is often confusing. For some more insight into
|
|
how it works, see <a href="GetElementPtr.html">the getelementptr FAQ</a>.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<i>; yields [12 x i8]*:aptr</i>
|
|
%aptr = getelementptr {i32, [12 x i8]}* %saptr, i64 0, i32 1
|
|
<i>; yields i8*:vptr</i>
|
|
%vptr = getelementptr {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1
|
|
<i>; yields i8*:eptr</i>
|
|
%eptr = getelementptr [12 x i8]* %aptr, i64 0, i32 1
|
|
<i>; yields i32*:iptr</i>
|
|
%iptr = getelementptr [10 x i32]* @arr, i16 0, i16 0
|
|
</pre>
|
|
|
|
<p>In cases where the pointer argument is a vector of pointers, each index must
|
|
be a vector with the same number of elements. For example: </p>
|
|
<pre class="doc_code">
|
|
%A = getelementptr <4 x i8*> %ptrs, <4 x i64> %offsets,
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="convertops">Conversion Operations</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The instructions in this category are the conversion instructions (casting)
|
|
which all take a single operand and a type. They perform various bit
|
|
conversions on the operand.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>trunc</tt>' instruction truncates its operand to the
|
|
type <tt>ty2</tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>trunc</tt>' instruction takes a value to trunc, and a type to trunc it to.
|
|
Both types must be of <a href="#t_integer">integer</a> types, or vectors
|
|
of the same number of integers.
|
|
The bit size of the <tt>value</tt> must be larger than
|
|
the bit size of the destination type, <tt>ty2</tt>.
|
|
Equal sized types are not allowed.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>trunc</tt>' instruction truncates the high order bits
|
|
in <tt>value</tt> and converts the remaining bits to <tt>ty2</tt>. Since the
|
|
source size must be larger than the destination size, <tt>trunc</tt> cannot
|
|
be a <i>no-op cast</i>. It will always truncate bits.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = trunc i32 257 to i8 <i>; yields i8:1</i>
|
|
%Y = trunc i32 123 to i1 <i>; yields i1:true</i>
|
|
%Z = trunc i32 122 to i1 <i>; yields i1:false</i>
|
|
%W = trunc <2 x i16> <i16 8, i16 7> to <2 x i8> <i>; yields <i8 8, i8 7></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_zext">'<tt>zext .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = zext <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>zext</tt>' instruction zero extends its operand to type
|
|
<tt>ty2</tt>.</p>
|
|
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>zext</tt>' instruction takes a value to cast, and a type to cast it to.
|
|
Both types must be of <a href="#t_integer">integer</a> types, or vectors
|
|
of the same number of integers.
|
|
The bit size of the <tt>value</tt> must be smaller than
|
|
the bit size of the destination type,
|
|
<tt>ty2</tt>.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero
|
|
bits until it reaches the size of the destination type, <tt>ty2</tt>.</p>
|
|
|
|
<p>When zero extending from i1, the result will always be either 0 or 1.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = zext i32 257 to i64 <i>; yields i64:257</i>
|
|
%Y = zext i1 true to i32 <i>; yields i32:1</i>
|
|
%Z = zext <2 x i16> <i16 8, i16 7> to <2 x i32> <i>; yields <i32 8, i32 7></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_sext">'<tt>sext .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = sext <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>sext</tt>' instruction takes a value to cast, and a type to cast it to.
|
|
Both types must be of <a href="#t_integer">integer</a> types, or vectors
|
|
of the same number of integers.
|
|
The bit size of the <tt>value</tt> must be smaller than
|
|
the bit size of the destination type,
|
|
<tt>ty2</tt>.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>sext</tt>' instruction performs a sign extension by copying the sign
|
|
bit (highest order bit) of the <tt>value</tt> until it reaches the bit size
|
|
of the type <tt>ty2</tt>.</p>
|
|
|
|
<p>When sign extending from i1, the extension always results in -1 or 0.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = sext i8 -1 to i16 <i>; yields i16 :65535</i>
|
|
%Y = sext i1 true to i32 <i>; yields i32:-1</i>
|
|
%Z = sext <2 x i16> <i16 8, i16 7> to <2 x i32> <i>; yields <i32 8, i32 7></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type
|
|
<tt>ty2</tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating
|
|
point</a> value to cast and a <a href="#t_floating">floating point</a> type
|
|
to cast it to. The size of <tt>value</tt> must be larger than the size of
|
|
<tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a
|
|
<i>no-op cast</i>.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger
|
|
<a href="#t_floating">floating point</a> type to a smaller
|
|
<a href="#t_floating">floating point</a> type. If the value cannot fit
|
|
within the destination type, <tt>ty2</tt>, then the results are
|
|
undefined.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = fptrunc double 123.0 to float <i>; yields float:123.0</i>
|
|
%Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger
|
|
floating point value.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>fpext</tt>' instruction takes a
|
|
<a href="#t_floating">floating point</a> <tt>value</tt> to cast, and
|
|
a <a href="#t_floating">floating point</a> type to cast it to. The source
|
|
type must be smaller than the destination type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller
|
|
<a href="#t_floating">floating point</a> type to a larger
|
|
<a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be
|
|
used to make a <i>no-op cast</i> because it always changes bits. Use
|
|
<tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = fpext float 3.125 to double <i>; yields double:3.125000e+00</i>
|
|
%Y = fpext double %X to fp128 <i>; yields fp128:0xL00000000000000004000900000000000</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its
|
|
unsigned integer equivalent of type <tt>ty2</tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a
|
|
scalar or vector <a href="#t_floating">floating point</a> value, and a type
|
|
to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
|
|
type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
|
|
vector integer type with the same number of elements as <tt>ty</tt></p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>fptoui</tt>' instruction converts its
|
|
<a href="#t_floating">floating point</a> operand into the nearest (rounding
|
|
towards zero) unsigned integer value. If the value cannot fit
|
|
in <tt>ty2</tt>, the results are undefined.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = fptoui double 123.0 to i32 <i>; yields i32:123</i>
|
|
%Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i>
|
|
%Z = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fptosi</tt>' instruction converts
|
|
<a href="#t_floating">floating point</a> <tt>value</tt> to
|
|
type <tt>ty2</tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a
|
|
scalar or vector <a href="#t_floating">floating point</a> value, and a type
|
|
to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
|
|
type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
|
|
vector integer type with the same number of elements as <tt>ty</tt></p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>fptosi</tt>' instruction converts its
|
|
<a href="#t_floating">floating point</a> operand into the nearest (rounding
|
|
towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>,
|
|
the results are undefined.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = fptosi double -123.0 to i32 <i>; yields i32:-123</i>
|
|
%Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i>
|
|
%Z = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned
|
|
integer and converts that value to the <tt>ty2</tt> type.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be a
|
|
scalar or vector <a href="#t_integer">integer</a> value, and a type to cast
|
|
it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
|
|
type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
|
|
floating point type with the same number of elements as <tt>ty</tt></p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned
|
|
integer quantity and converts it to the corresponding floating point
|
|
value. If the value cannot fit in the floating point value, the results are
|
|
undefined.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = uitofp i32 257 to float <i>; yields float:257.0</i>
|
|
%Y = uitofp i8 -1 to double <i>; yields double:255.0</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed integer
|
|
and converts that value to the <tt>ty2</tt> type.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be a
|
|
scalar or vector <a href="#t_integer">integer</a> value, and a type to cast
|
|
it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
|
|
type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
|
|
floating point type with the same number of elements as <tt>ty</tt></p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed integer
|
|
quantity and converts it to the corresponding floating point value. If the
|
|
value cannot fit in the floating point value, the results are undefined.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = sitofp i32 257 to float <i>; yields float:257.0</i>
|
|
%Y = sitofp i8 -1 to double <i>; yields double:-1.0</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>ptrtoint</tt>' instruction converts the pointer or a vector of
|
|
pointers <tt>value</tt> to
|
|
the integer (or vector of integers) type <tt>ty2</tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which
|
|
must be a a value of type <a href="#t_pointer">pointer</a> or a vector of
|
|
pointers, and a type to cast it to
|
|
<tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> or a vector
|
|
of integers type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type
|
|
<tt>ty2</tt> by interpreting the pointer value as an integer and either
|
|
truncating or zero extending that value to the size of the integer type. If
|
|
<tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If
|
|
<tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they
|
|
are the same size, then nothing is done (<i>no-op cast</i>) other than a type
|
|
change.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = ptrtoint i32* %P to i8 <i>; yields truncation on 32-bit architecture</i>
|
|
%Y = ptrtoint i32* %P to i64 <i>; yields zero extension on 32-bit architecture</i>
|
|
%Z = ptrtoint <4 x i32*> %P to <4 x i64><i>; yields vector zero extension for a vector of addresses on 32-bit architecture</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to a
|
|
pointer type, <tt>ty2</tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a>
|
|
value to cast, and a type to cast it to, which must be a
|
|
<a href="#t_pointer">pointer</a> type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type
|
|
<tt>ty2</tt> by applying either a zero extension or a truncation depending on
|
|
the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the
|
|
size of a pointer then a truncation is done. If <tt>value</tt> is smaller
|
|
than the size of a pointer then a zero extension is done. If they are the
|
|
same size, nothing is done (<i>no-op cast</i>).</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i>
|
|
%Y = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i>
|
|
%Z = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i>
|
|
%Z = inttoptr <4 x i32> %G to <4 x i8*><i>; yields truncation of vector G to four pointers</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
|
|
<tt>ty2</tt> without changing any bits.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be a
|
|
non-aggregate first class value, and a type to cast it to, which must also be
|
|
a non-aggregate <a href="#t_firstclass">first class</a> type. The bit sizes
|
|
of <tt>value</tt> and the destination type, <tt>ty2</tt>, must be
|
|
identical. If the source type is a pointer, the destination type must also be
|
|
a pointer. This instruction supports bitwise conversion of vectors to
|
|
integers and to vectors of other types (as long as they have the same
|
|
size).</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
|
|
<tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with
|
|
this conversion. The conversion is done as if the <tt>value</tt> had been
|
|
stored to memory and read back as type <tt>ty2</tt>.
|
|
Pointer (or vector of pointers) types may only be converted to other pointer
|
|
(or vector of pointers) types with this instruction. To convert
|
|
pointers to other types, use the <a href="#i_inttoptr">inttoptr</a> or
|
|
<a href="#i_ptrtoint">ptrtoint</a> instructions first.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = bitcast i8 255 to i8 <i>; yields i8 :-1</i>
|
|
%Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i>
|
|
%Z = bitcast <2 x int> %V to i64; <i>; yields i64: %V</i>
|
|
%Z = bitcast <2 x i32*> %V to <2 x i64*> <i>; yields <2 x i64*></i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="otherops">Other Operations</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The instructions in this category are the "miscellaneous" instructions, which
|
|
defy better classification.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_icmp">'<tt>icmp</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = icmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>icmp</tt>' instruction returns a boolean value or a vector of
|
|
boolean values based on comparison of its two integer, integer vector,
|
|
pointer, or pointer vector operands.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is
|
|
the condition code indicating the kind of comparison to perform. It is not a
|
|
value, just a keyword. The possible condition code are:</p>
|
|
|
|
<ol>
|
|
<li><tt>eq</tt>: equal</li>
|
|
<li><tt>ne</tt>: not equal </li>
|
|
<li><tt>ugt</tt>: unsigned greater than</li>
|
|
<li><tt>uge</tt>: unsigned greater or equal</li>
|
|
<li><tt>ult</tt>: unsigned less than</li>
|
|
<li><tt>ule</tt>: unsigned less or equal</li>
|
|
<li><tt>sgt</tt>: signed greater than</li>
|
|
<li><tt>sge</tt>: signed greater or equal</li>
|
|
<li><tt>slt</tt>: signed less than</li>
|
|
<li><tt>sle</tt>: signed less or equal</li>
|
|
</ol>
|
|
|
|
<p>The remaining two arguments must be <a href="#t_integer">integer</a> or
|
|
<a href="#t_pointer">pointer</a> or integer <a href="#t_vector">vector</a>
|
|
typed. They must also be identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>icmp</tt>' compares <tt>op1</tt> and <tt>op2</tt> according to the
|
|
condition code given as <tt>cond</tt>. The comparison performed always yields
|
|
either an <a href="#t_integer"><tt>i1</tt></a> or vector of <tt>i1</tt>
|
|
result, as follows:</p>
|
|
|
|
<ol>
|
|
<li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal,
|
|
<tt>false</tt> otherwise. No sign interpretation is necessary or
|
|
performed.</li>
|
|
|
|
<li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal,
|
|
<tt>false</tt> otherwise. No sign interpretation is necessary or
|
|
performed.</li>
|
|
|
|
<li><tt>ugt</tt>: interprets the operands as unsigned values and yields
|
|
<tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li>
|
|
|
|
<li><tt>uge</tt>: interprets the operands as unsigned values and yields
|
|
<tt>true</tt> if <tt>op1</tt> is greater than or equal
|
|
to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>ult</tt>: interprets the operands as unsigned values and yields
|
|
<tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li>
|
|
|
|
<li><tt>ule</tt>: interprets the operands as unsigned values and yields
|
|
<tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>sgt</tt>: interprets the operands as signed values and yields
|
|
<tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li>
|
|
|
|
<li><tt>sge</tt>: interprets the operands as signed values and yields
|
|
<tt>true</tt> if <tt>op1</tt> is greater than or equal
|
|
to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>slt</tt>: interprets the operands as signed values and yields
|
|
<tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li>
|
|
|
|
<li><tt>sle</tt>: interprets the operands as signed values and yields
|
|
<tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
|
|
</ol>
|
|
|
|
<p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer
|
|
values are compared as if they were integers.</p>
|
|
|
|
<p>If the operands are integer vectors, then they are compared element by
|
|
element. The result is an <tt>i1</tt> vector with the same number of elements
|
|
as the values being compared. Otherwise, the result is an <tt>i1</tt>.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = icmp eq i32 4, 5 <i>; yields: result=false</i>
|
|
<result> = icmp ne float* %X, %X <i>; yields: result=false</i>
|
|
<result> = icmp ult i16 4, 5 <i>; yields: result=true</i>
|
|
<result> = icmp sgt i16 4, 5 <i>; yields: result=false</i>
|
|
<result> = icmp ule i16 -4, 5 <i>; yields: result=false</i>
|
|
<result> = icmp sge i16 4, 5 <i>; yields: result=false</i>
|
|
</pre>
|
|
|
|
<p>Note that the code generator does not yet support vector types with
|
|
the <tt>icmp</tt> instruction.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = fcmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>fcmp</tt>' instruction returns a boolean value or vector of boolean
|
|
values based on comparison of its operands.</p>
|
|
|
|
<p>If the operands are floating point scalars, then the result type is a boolean
|
|
(<a href="#t_integer"><tt>i1</tt></a>).</p>
|
|
|
|
<p>If the operands are floating point vectors, then the result type is a vector
|
|
of boolean with the same number of elements as the operands being
|
|
compared.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is
|
|
the condition code indicating the kind of comparison to perform. It is not a
|
|
value, just a keyword. The possible condition code are:</p>
|
|
|
|
<ol>
|
|
<li><tt>false</tt>: no comparison, always returns false</li>
|
|
<li><tt>oeq</tt>: ordered and equal</li>
|
|
<li><tt>ogt</tt>: ordered and greater than </li>
|
|
<li><tt>oge</tt>: ordered and greater than or equal</li>
|
|
<li><tt>olt</tt>: ordered and less than </li>
|
|
<li><tt>ole</tt>: ordered and less than or equal</li>
|
|
<li><tt>one</tt>: ordered and not equal</li>
|
|
<li><tt>ord</tt>: ordered (no nans)</li>
|
|
<li><tt>ueq</tt>: unordered or equal</li>
|
|
<li><tt>ugt</tt>: unordered or greater than </li>
|
|
<li><tt>uge</tt>: unordered or greater than or equal</li>
|
|
<li><tt>ult</tt>: unordered or less than </li>
|
|
<li><tt>ule</tt>: unordered or less than or equal</li>
|
|
<li><tt>une</tt>: unordered or not equal</li>
|
|
<li><tt>uno</tt>: unordered (either nans)</li>
|
|
<li><tt>true</tt>: no comparison, always returns true</li>
|
|
</ol>
|
|
|
|
<p><i>Ordered</i> means that neither operand is a QNAN while
|
|
<i>unordered</i> means that either operand may be a QNAN.</p>
|
|
|
|
<p>Each of <tt>val1</tt> and <tt>val2</tt> arguments must be either
|
|
a <a href="#t_floating">floating point</a> type or
|
|
a <a href="#t_vector">vector</a> of floating point type. They must have
|
|
identical types.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>fcmp</tt>' instruction compares <tt>op1</tt> and <tt>op2</tt>
|
|
according to the condition code given as <tt>cond</tt>. If the operands are
|
|
vectors, then the vectors are compared element by element. Each comparison
|
|
performed always yields an <a href="#t_integer">i1</a> result, as
|
|
follows:</p>
|
|
|
|
<ol>
|
|
<li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li>
|
|
|
|
<li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and
|
|
<tt>op1</tt> is equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
|
|
<tt>op1</tt> is greater than <tt>op2</tt>.</li>
|
|
|
|
<li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and
|
|
<tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
|
|
<tt>op1</tt> is less than <tt>op2</tt>.</li>
|
|
|
|
<li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and
|
|
<tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and
|
|
<tt>op1</tt> is not equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li>
|
|
|
|
<li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or
|
|
<tt>op1</tt> is equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or
|
|
<tt>op1</tt> is greater than <tt>op2</tt>.</li>
|
|
|
|
<li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or
|
|
<tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or
|
|
<tt>op1</tt> is less than <tt>op2</tt>.</li>
|
|
|
|
<li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or
|
|
<tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or
|
|
<tt>op1</tt> is not equal to <tt>op2</tt>.</li>
|
|
|
|
<li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li>
|
|
|
|
<li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li>
|
|
</ol>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
<result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i>
|
|
<result> = fcmp one float 4.0, 5.0 <i>; yields: result=true</i>
|
|
<result> = fcmp olt float 4.0, 5.0 <i>; yields: result=true</i>
|
|
<result> = fcmp ueq double 1.0, 2.0 <i>; yields: result=false</i>
|
|
</pre>
|
|
|
|
<p>Note that the code generator does not yet support vector types with
|
|
the <tt>fcmp</tt> instruction.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_phi">'<tt>phi</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = phi <ty> [ <val0>, <label0>], ...
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>phi</tt>' instruction is used to implement the φ node in the
|
|
SSA graph representing the function.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The type of the incoming values is specified with the first type field. After
|
|
this, the '<tt>phi</tt>' instruction takes a list of pairs as arguments, with
|
|
one pair for each predecessor basic block of the current block. Only values
|
|
of <a href="#t_firstclass">first class</a> type may be used as the value
|
|
arguments to the PHI node. Only labels may be used as the label
|
|
arguments.</p>
|
|
|
|
<p>There must be no non-phi instructions between the start of a basic block and
|
|
the PHI instructions: i.e. PHI instructions must be first in a basic
|
|
block.</p>
|
|
|
|
<p>For the purposes of the SSA form, the use of each incoming value is deemed to
|
|
occur on the edge from the corresponding predecessor block to the current
|
|
block (but after any definition of an '<tt>invoke</tt>' instruction's return
|
|
value on the same edge).</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value
|
|
specified by the pair corresponding to the predecessor basic block that
|
|
executed just prior to the current block.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
Loop: ; Infinite loop that counts from 0 on up...
|
|
%indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
|
|
%nextindvar = add i32 %indvar, 1
|
|
br label %Loop
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_select">'<tt>select</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = select <i>selty</i> <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
|
|
|
|
<i>selty</i> is either i1 or {<N x i1>}
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>select</tt>' instruction is used to choose one value based on a
|
|
condition, without branching.</p>
|
|
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>select</tt>' instruction requires an 'i1' value or a vector of 'i1'
|
|
values indicating the condition, and two values of the
|
|
same <a href="#t_firstclass">first class</a> type. If the val1/val2 are
|
|
vectors and the condition is a scalar, then entire vectors are selected, not
|
|
individual elements.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>If the condition is an i1 and it evaluates to 1, the instruction returns the
|
|
first value argument; otherwise, it returns the second value argument.</p>
|
|
|
|
<p>If the condition is a vector of i1, then the value arguments must be vectors
|
|
of the same size, and the selection is done element by element.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i>
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_call">'<tt>call</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<result> = [tail] call [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ty> [<fnty>*] <fnptrval>(<function args>) [<a href="#fnattrs">fn attrs</a>]
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>call</tt>' instruction represents a simple function call.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>This instruction requires several arguments:</p>
|
|
|
|
<ol>
|
|
<li>The optional "tail" marker indicates that the callee function does not
|
|
access any allocas or varargs in the caller. Note that calls may be
|
|
marked "tail" even if they do not occur before
|
|
a <a href="#i_ret"><tt>ret</tt></a> instruction. If the "tail" marker is
|
|
present, the function call is eligible for tail call optimization,
|
|
but <a href="CodeGenerator.html#tailcallopt">might not in fact be
|
|
optimized into a jump</a>. The code generator may optimize calls marked
|
|
"tail" with either 1) automatic <a href="CodeGenerator.html#sibcallopt">
|
|
sibling call optimization</a> when the caller and callee have
|
|
matching signatures, or 2) forced tail call optimization when the
|
|
following extra requirements are met:
|
|
<ul>
|
|
<li>Caller and callee both have the calling
|
|
convention <tt>fastcc</tt>.</li>
|
|
<li>The call is in tail position (ret immediately follows call and ret
|
|
uses value of call or is void).</li>
|
|
<li>Option <tt>-tailcallopt</tt> is enabled,
|
|
or <code>llvm::GuaranteedTailCallOpt</code> is <code>true</code>.</li>
|
|
<li><a href="CodeGenerator.html#tailcallopt">Platform specific
|
|
constraints are met.</a></li>
|
|
</ul>
|
|
</li>
|
|
|
|
<li>The optional "cconv" marker indicates which <a href="#callingconv">calling
|
|
convention</a> the call should use. If none is specified, the call
|
|
defaults to using C calling conventions. The calling convention of the
|
|
call must match the calling convention of the target function, or else the
|
|
behavior is undefined.</li>
|
|
|
|
<li>The optional <a href="#paramattrs">Parameter Attributes</a> list for
|
|
return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and
|
|
'<tt>inreg</tt>' attributes are valid here.</li>
|
|
|
|
<li>'<tt>ty</tt>': the type of the call instruction itself which is also the
|
|
type of the return value. Functions that return no value are marked
|
|
<tt><a href="#t_void">void</a></tt>.</li>
|
|
|
|
<li>'<tt>fnty</tt>': shall be the signature of the pointer to function value
|
|
being invoked. The argument types must match the types implied by this
|
|
signature. This type can be omitted if the function is not varargs and if
|
|
the function type does not return a pointer to a function.</li>
|
|
|
|
<li>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to
|
|
be invoked. In most cases, this is a direct function invocation, but
|
|
indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer
|
|
to function value.</li>
|
|
|
|
<li>'<tt>function args</tt>': argument list whose types match the function
|
|
signature argument types and parameter attributes. All arguments must be
|
|
of <a href="#t_firstclass">first class</a> type. If the function
|
|
signature indicates the function accepts a variable number of arguments,
|
|
the extra arguments can be specified.</li>
|
|
|
|
<li>The optional <a href="#fnattrs">function attributes</a> list. Only
|
|
'<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and
|
|
'<tt>readnone</tt>' attributes are valid here.</li>
|
|
</ol>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>call</tt>' instruction is used to cause control flow to transfer to
|
|
a specified function, with its incoming arguments bound to the specified
|
|
values. Upon a '<tt><a href="#i_ret">ret</a></tt>' instruction in the called
|
|
function, control flow continues with the instruction after the function
|
|
call, and the return value of the function is bound to the result
|
|
argument.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
%retval = call i32 @test(i32 %argc)
|
|
call i32 (i8*, ...)* @printf(i8* %msg, i32 12, i8 42) <i>; yields i32</i>
|
|
%X = tail call i32 @foo() <i>; yields i32</i>
|
|
%Y = tail call <a href="#callingconv">fastcc</a> i32 @foo() <i>; yields i32</i>
|
|
call void %foo(i8 97 signext)
|
|
|
|
%struct.A = type { i32, i8 }
|
|
%r = call %struct.A @foo() <i>; yields { 32, i8 }</i>
|
|
%gr = extractvalue %struct.A %r, 0 <i>; yields i32</i>
|
|
%gr1 = extractvalue %struct.A %r, 1 <i>; yields i8</i>
|
|
%Z = call void @foo() noreturn <i>; indicates that %foo never returns normally</i>
|
|
%ZZ = call zeroext i32 @bar() <i>; Return value is %zero extended</i>
|
|
</pre>
|
|
|
|
<p>llvm treats calls to some functions with names and arguments that match the
|
|
standard C99 library as being the C99 library functions, and may perform
|
|
optimizations or generate code for them under that assumption. This is
|
|
something we'd like to change in the future to provide better support for
|
|
freestanding environments and non-C-based languages.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_va_arg">'<tt>va_arg</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<resultval> = va_arg <va_list*> <arglist>, <argty>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through
|
|
the "variable argument" area of a function call. It is used to implement the
|
|
<tt>va_arg</tt> macro in C.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>This instruction takes a <tt>va_list*</tt> value and the type of the
|
|
argument. It returns a value of the specified argument type and increments
|
|
the <tt>va_list</tt> to point to the next argument. The actual type
|
|
of <tt>va_list</tt> is target specific.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>va_arg</tt>' instruction loads an argument of the specified type
|
|
from the specified <tt>va_list</tt> and causes the <tt>va_list</tt> to point
|
|
to the next argument. For more information, see the variable argument
|
|
handling <a href="#int_varargs">Intrinsic Functions</a>.</p>
|
|
|
|
<p>It is legal for this instruction to be called in a function which does not
|
|
take a variable number of arguments, for example, the <tt>vfprintf</tt>
|
|
function.</p>
|
|
|
|
<p><tt>va_arg</tt> is an LLVM instruction instead of
|
|
an <a href="#intrinsics">intrinsic function</a> because it takes a type as an
|
|
argument.</p>
|
|
|
|
<h5>Example:</h5>
|
|
<p>See the <a href="#int_varargs">variable argument processing</a> section.</p>
|
|
|
|
<p>Note that the code generator does not yet fully support va_arg on many
|
|
targets. Also, it does not currently support va_arg with aggregate types on
|
|
any target.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="i_landingpad">'<tt>landingpad</tt>' Instruction</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
<resultval> = landingpad <resultty> personality <type> <pers_fn> <clause>+
|
|
<resultval> = landingpad <resultty> personality <type> <pers_fn> cleanup <clause>*
|
|
|
|
<clause> := catch <type> <value>
|
|
<clause> := filter <array constant type> <array constant>
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>landingpad</tt>' instruction is used by
|
|
<a href="ExceptionHandling.html#overview">LLVM's exception handling
|
|
system</a> to specify that a basic block is a landing pad — one where
|
|
the exception lands, and corresponds to the code found in the
|
|
<i><tt>catch</tt></i> portion of a <i><tt>try/catch</tt></i> sequence. It
|
|
defines values supplied by the personality function (<tt>pers_fn</tt>) upon
|
|
re-entry to the function. The <tt>resultval</tt> has the
|
|
type <tt>resultty</tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>This instruction takes a <tt>pers_fn</tt> value. This is the personality
|
|
function associated with the unwinding mechanism. The optional
|
|
<tt>cleanup</tt> flag indicates that the landing pad block is a cleanup.</p>
|
|
|
|
<p>A <tt>clause</tt> begins with the clause type — <tt>catch</tt>
|
|
or <tt>filter</tt> — and contains the global variable representing the
|
|
"type" that may be caught or filtered respectively. Unlike the
|
|
<tt>catch</tt> clause, the <tt>filter</tt> clause takes an array constant as
|
|
its argument. Use "<tt>[0 x i8**] undef</tt>" for a filter which cannot
|
|
throw. The '<tt>landingpad</tt>' instruction must contain <em>at least</em>
|
|
one <tt>clause</tt> or the <tt>cleanup</tt> flag.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>landingpad</tt>' instruction defines the values which are set by the
|
|
personality function (<tt>pers_fn</tt>) upon re-entry to the function, and
|
|
therefore the "result type" of the <tt>landingpad</tt> instruction. As with
|
|
calling conventions, how the personality function results are represented in
|
|
LLVM IR is target specific.</p>
|
|
|
|
<p>The clauses are applied in order from top to bottom. If two
|
|
<tt>landingpad</tt> instructions are merged together through inlining, the
|
|
clauses from the calling function are appended to the list of clauses.
|
|
When the call stack is being unwound due to an exception being thrown, the
|
|
exception is compared against each <tt>clause</tt> in turn. If it doesn't
|
|
match any of the clauses, and the <tt>cleanup</tt> flag is not set, then
|
|
unwinding continues further up the call stack.</p>
|
|
|
|
<p>The <tt>landingpad</tt> instruction has several restrictions:</p>
|
|
|
|
<ul>
|
|
<li>A landing pad block is a basic block which is the unwind destination of an
|
|
'<tt>invoke</tt>' instruction.</li>
|
|
<li>A landing pad block must have a '<tt>landingpad</tt>' instruction as its
|
|
first non-PHI instruction.</li>
|
|
<li>There can be only one '<tt>landingpad</tt>' instruction within the landing
|
|
pad block.</li>
|
|
<li>A basic block that is not a landing pad block may not include a
|
|
'<tt>landingpad</tt>' instruction.</li>
|
|
<li>All '<tt>landingpad</tt>' instructions in a function must have the same
|
|
personality function.</li>
|
|
</ul>
|
|
|
|
<h5>Example:</h5>
|
|
<pre>
|
|
;; A landing pad which can catch an integer.
|
|
%res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
|
|
catch i8** @_ZTIi
|
|
;; A landing pad that is a cleanup.
|
|
%res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
|
|
cleanup
|
|
;; A landing pad which can catch an integer and can only throw a double.
|
|
%res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
|
|
catch i8** @_ZTIi
|
|
filter [1 x i8**] [@_ZTId]
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2><a name="intrinsics">Intrinsic Functions</a></h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>LLVM supports the notion of an "intrinsic function". These functions have
|
|
well known names and semantics and are required to follow certain
|
|
restrictions. Overall, these intrinsics represent an extension mechanism for
|
|
the LLVM language that does not require changing all of the transformations
|
|
in LLVM when adding to the language (or the bitcode reader/writer, the
|
|
parser, etc...).</p>
|
|
|
|
<p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This
|
|
prefix is reserved in LLVM for intrinsic names; thus, function names may not
|
|
begin with this prefix. Intrinsic functions must always be external
|
|
functions: you cannot define the body of intrinsic functions. Intrinsic
|
|
functions may only be used in call or invoke instructions: it is illegal to
|
|
take the address of an intrinsic function. Additionally, because intrinsic
|
|
functions are part of the LLVM language, it is required if any are added that
|
|
they be documented here.</p>
|
|
|
|
<p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents a
|
|
family of functions that perform the same operation but on different data
|
|
types. Because LLVM can represent over 8 million different integer types,
|
|
overloading is used commonly to allow an intrinsic function to operate on any
|
|
integer type. One or more of the argument types or the result type can be
|
|
overloaded to accept any integer type. Argument types may also be defined as
|
|
exactly matching a previous argument's type or the result type. This allows
|
|
an intrinsic function which accepts multiple arguments, but needs all of them
|
|
to be of the same type, to only be overloaded with respect to a single
|
|
argument or the result.</p>
|
|
|
|
<p>Overloaded intrinsics will have the names of its overloaded argument types
|
|
encoded into its function name, each preceded by a period. Only those types
|
|
which are overloaded result in a name suffix. Arguments whose type is matched
|
|
against another type do not. For example, the <tt>llvm.ctpop</tt> function
|
|
can take an integer of any width and returns an integer of exactly the same
|
|
integer width. This leads to a family of functions such as
|
|
<tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29
|
|
%val)</tt>. Only one type, the return type, is overloaded, and only one type
|
|
suffix is required. Because the argument's type is matched against the return
|
|
type, it does not require its own name suffix.</p>
|
|
|
|
<p>To learn how to add an intrinsic function, please see the
|
|
<a href="ExtendingLLVM.html">Extending LLVM Guide</a>.</p>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_varargs">Variable Argument Handling Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Variable argument support is defined in LLVM with
|
|
the <a href="#i_va_arg"><tt>va_arg</tt></a> instruction and these three
|
|
intrinsic functions. These functions are related to the similarly named
|
|
macros defined in the <tt><stdarg.h></tt> header file.</p>
|
|
|
|
<p>All of these functions operate on arguments that use a target-specific value
|
|
type "<tt>va_list</tt>". The LLVM assembly language reference manual does
|
|
not define what this type is, so all transformations should be prepared to
|
|
handle these functions regardless of the type used.</p>
|
|
|
|
<p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a>
|
|
instruction and the variable argument handling intrinsic functions are
|
|
used.</p>
|
|
|
|
<pre class="doc_code">
|
|
define i32 @test(i32 %X, ...) {
|
|
; Initialize variable argument processing
|
|
%ap = alloca i8*
|
|
%ap2 = bitcast i8** %ap to i8*
|
|
call void @llvm.va_start(i8* %ap2)
|
|
|
|
; Read a single integer argument
|
|
%tmp = va_arg i8** %ap, i32
|
|
|
|
; Demonstrate usage of llvm.va_copy and llvm.va_end
|
|
%aq = alloca i8*
|
|
%aq2 = bitcast i8** %aq to i8*
|
|
call void @llvm.va_copy(i8* %aq2, i8* %ap2)
|
|
call void @llvm.va_end(i8* %aq2)
|
|
|
|
; Stop processing of arguments.
|
|
call void @llvm.va_end(i8* %ap2)
|
|
ret i32 %tmp
|
|
}
|
|
|
|
declare void @llvm.va_start(i8*)
|
|
declare void @llvm.va_copy(i8*, i8*)
|
|
declare void @llvm.va_end(i8*)
|
|
</pre>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void %llvm.va_start(i8* <arglist>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.va_start</tt>' intrinsic initializes <tt>*<arglist></tt>
|
|
for subsequent use by <tt><a href="#i_va_arg">va_arg</a></tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt>
|
|
macro available in C. In a target-dependent way, it initializes
|
|
the <tt>va_list</tt> element to which the argument points, so that the next
|
|
call to <tt>va_arg</tt> will produce the first variable argument passed to
|
|
the function. Unlike the C <tt>va_start</tt> macro, this intrinsic does not
|
|
need to know the last argument of the function as the compiler can figure
|
|
that out.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.va_end(i8* <arglist>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt>*<arglist></tt>,
|
|
which has been initialized previously
|
|
with <tt><a href="#int_va_start">llvm.va_start</a></tt>
|
|
or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument is a pointer to a <tt>va_list</tt> to destroy.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt>
|
|
macro available in C. In a target-dependent way, it destroys
|
|
the <tt>va_list</tt> element to which the argument points. Calls
|
|
to <a href="#int_va_start"><tt>llvm.va_start</tt></a>
|
|
and <a href="#int_va_copy"> <tt>llvm.va_copy</tt></a> must be matched exactly
|
|
with calls to <tt>llvm.va_end</tt>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position
|
|
from the source argument list to the destination argument list.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is a pointer to a <tt>va_list</tt> element to initialize.
|
|
The second argument is a pointer to a <tt>va_list</tt> element to copy
|
|
from.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt>
|
|
macro available in C. In a target-dependent way, it copies the
|
|
source <tt>va_list</tt> element into the destination <tt>va_list</tt>
|
|
element. This intrinsic is necessary because
|
|
the <tt><a href="#int_va_start"> llvm.va_start</a></tt> intrinsic may be
|
|
arbitrarily complex and require, for example, memory allocation.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_gc">Accurate Garbage Collection Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM support for <a href="GarbageCollection.html">Accurate Garbage
|
|
Collection</a> (GC) requires the implementation and generation of these
|
|
intrinsics. These intrinsics allow identification of <a href="#int_gcroot">GC
|
|
roots on the stack</a>, as well as garbage collector implementations that
|
|
require <a href="#int_gcread">read</a> and <a href="#int_gcwrite">write</a>
|
|
barriers. Front-ends for type-safe garbage collected languages should generate
|
|
these intrinsics to make use of the LLVM garbage collectors. For more details,
|
|
see <a href="GarbageCollection.html">Accurate Garbage Collection with
|
|
LLVM</a>.</p>
|
|
|
|
<p>The garbage collection intrinsics only operate on objects in the generic
|
|
address space (address space zero).</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to
|
|
the code generator, and allows some metadata to be associated with it.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument specifies the address of a stack object that contains the
|
|
root pointer. The second pointer (which must be either a constant or a
|
|
global value address) contains the meta-data to be associated with the
|
|
root.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>At runtime, a call to this intrinsic stores a null pointer into the "ptrloc"
|
|
location. At compile-time, the code generator generates information to allow
|
|
the runtime to find the pointer at GC safe points. The '<tt>llvm.gcroot</tt>'
|
|
intrinsic may only be used in a function which <a href="#gc">specifies a GC
|
|
algorithm</a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap
|
|
locations, allowing garbage collector implementations that require read
|
|
barriers.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The second argument is the address to read from, which should be an address
|
|
allocated from the garbage collector. The first object is a pointer to the
|
|
start of the referenced object, if needed by the language runtime (otherwise
|
|
null).</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load
|
|
instruction, but may be replaced with substantially more complex code by the
|
|
garbage collector runtime, as needed. The '<tt>llvm.gcread</tt>' intrinsic
|
|
may only be used in a function which <a href="#gc">specifies a GC
|
|
algorithm</a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap
|
|
locations, allowing garbage collector implementations that require write
|
|
barriers (such as generational or reference counting collectors).</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is the reference to store, the second is the start of the
|
|
object to store it to, and the third is the address of the field of Obj to
|
|
store to. If the runtime does not require a pointer to the object, Obj may
|
|
be null.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store
|
|
instruction, but may be replaced with substantially more complex code by the
|
|
garbage collector runtime, as needed. The '<tt>llvm.gcwrite</tt>' intrinsic
|
|
may only be used in a function which <a href="#gc">specifies a GC
|
|
algorithm</a>.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_codegen">Code Generator Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>These intrinsics are provided by LLVM to expose special features that may
|
|
only be implemented with code generator support.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i8 *@llvm.returnaddress(i32 <level>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute a
|
|
target-specific value indicating the return address of the current function
|
|
or one of its callers.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument to this intrinsic indicates which function to return the address
|
|
for. Zero indicates the calling function, one indicates its caller, etc.
|
|
The argument is <b>required</b> to be a constant integer value.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer
|
|
indicating the return address of the specified call frame, or zero if it
|
|
cannot be identified. The value returned by this intrinsic is likely to be
|
|
incorrect or 0 for arguments other than zero, so it should only be used for
|
|
debugging purposes.</p>
|
|
|
|
<p>Note that calling this intrinsic does not prevent function inlining or other
|
|
aggressive transformations, so the value returned may not be that of the
|
|
obvious source-language caller.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i8* @llvm.frameaddress(i32 <level>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return the
|
|
target-specific frame pointer value for the specified stack frame.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument to this intrinsic indicates which function to return the frame
|
|
pointer for. Zero indicates the calling function, one indicates its caller,
|
|
etc. The argument is <b>required</b> to be a constant integer value.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer
|
|
indicating the frame address of the specified call frame, or zero if it
|
|
cannot be identified. The value returned by this intrinsic is likely to be
|
|
incorrect or 0 for arguments other than zero, so it should only be used for
|
|
debugging purposes.</p>
|
|
|
|
<p>Note that calling this intrinsic does not prevent function inlining or other
|
|
aggressive transformations, so the value returned may not be that of the
|
|
obvious source-language caller.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i8* @llvm.stacksave()
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state
|
|
of the function stack, for use
|
|
with <a href="#int_stackrestore"> <tt>llvm.stackrestore</tt></a>. This is
|
|
useful for implementing language features like scoped automatic variable
|
|
sized arrays in C99.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic returns a opaque pointer value that can be passed
|
|
to <a href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When
|
|
an <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved
|
|
from <tt>llvm.stacksave</tt>, it effectively restores the state of the stack
|
|
to the state it was in when the <tt>llvm.stacksave</tt> intrinsic executed.
|
|
In practice, this pops any <a href="#i_alloca">alloca</a> blocks from the
|
|
stack that were allocated after the <tt>llvm.stacksave</tt> was executed.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.stackrestore(i8* %ptr)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of
|
|
the function stack to the state it was in when the
|
|
corresponding <a href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic
|
|
executed. This is useful for implementing language features like scoped
|
|
automatic variable sized arrays in C99.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>See the description
|
|
for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>, i32 <cache type>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to
|
|
insert a prefetch instruction if supported; otherwise, it is a noop.
|
|
Prefetches have no effect on the behavior of the program but can change its
|
|
performance characteristics.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p><tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the
|
|
specifier determining if the fetch should be for a read (0) or write (1),
|
|
and <tt>locality</tt> is a temporal locality specifier ranging from (0) - no
|
|
locality, to (3) - extremely local keep in cache. The <tt>cache type</tt>
|
|
specifies whether the prefetch is performed on the data (1) or instruction (0)
|
|
cache. The <tt>rw</tt>, <tt>locality</tt> and <tt>cache type</tt> arguments
|
|
must be constant integers.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic does not modify the behavior of the program. In particular,
|
|
prefetches cannot trap and do not produce a value. On targets that support
|
|
this intrinsic, the prefetch can provide hints to the processor cache for
|
|
better performance.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.pcmarker(i32 <id>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program
|
|
Counter (PC) in a region of code to simulators and other tools. The method
|
|
is target specific, but it is expected that the marker will use exported
|
|
symbols to transmit the PC of the marker. The marker makes no guarantees
|
|
that it will remain with any specific instruction after optimizations. It is
|
|
possible that the presence of a marker will inhibit optimizations. The
|
|
intended use is to be inserted after optimizations to allow correlations of
|
|
simulation runs.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p><tt>id</tt> is a numerical id identifying the marker.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic does not modify the behavior of the program. Backends that do
|
|
not support this intrinsic may ignore it.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i64 @llvm.readcyclecounter()
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle
|
|
counter register (or similar low latency, high accuracy clocks) on those
|
|
targets that support it. On X86, it should map to RDTSC. On Alpha, it
|
|
should map to RPCC. As the backing counters overflow quickly (on the order
|
|
of 9 seconds on alpha), this should only be used for small timings.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>When directly supported, reading the cycle counter should not modify any
|
|
memory. Implementations are allowed to either return a application specific
|
|
value or a system wide value. On backends without support, this is lowered
|
|
to a constant 0.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_libc">Standard C Library Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM provides intrinsics for a few important standard C library functions.
|
|
These intrinsics allow source-language front-ends to pass information about
|
|
the alignment of the pointer arguments to the code generator, providing
|
|
opportunity for more efficient code generation.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.memcpy</tt> on any
|
|
integer bit width and for different address spaces. Not all targets support
|
|
all bit widths however.</p>
|
|
|
|
<pre>
|
|
declare void @llvm.memcpy.p0i8.p0i8.i32(i8* <dest>, i8* <src>,
|
|
i32 <len>, i32 <align>, i1 <isvolatile>)
|
|
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* <dest>, i8* <src>,
|
|
i64 <len>, i32 <align>, i1 <isvolatile>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the
|
|
source location to the destination location.</p>
|
|
|
|
<p>Note that, unlike the standard libc function, the <tt>llvm.memcpy.*</tt>
|
|
intrinsics do not return a value, takes extra alignment/isvolatile arguments
|
|
and the pointers can be in specified address spaces.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>The first argument is a pointer to the destination, the second is a pointer
|
|
to the source. The third argument is an integer argument specifying the
|
|
number of bytes to copy, the fourth argument is the alignment of the
|
|
source and destination locations, and the fifth is a boolean indicating a
|
|
volatile access.</p>
|
|
|
|
<p>If the call to this intrinsic has an alignment value that is not 0 or 1,
|
|
then the caller guarantees that both the source and destination pointers are
|
|
aligned to that boundary.</p>
|
|
|
|
<p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
|
|
<tt>llvm.memcpy</tt> call is a <a href="#volatile">volatile operation</a>.
|
|
The detailed access behavior is not very cleanly specified and it is unwise
|
|
to depend on it.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the
|
|
source location to the destination location, which are not allowed to
|
|
overlap. It copies "len" bytes of memory over. If the argument is known to
|
|
be aligned to some boundary, this can be specified as the fourth argument,
|
|
otherwise it should be set to 0 or 1.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use llvm.memmove on any integer bit
|
|
width and for different address space. Not all targets support all bit
|
|
widths however.</p>
|
|
|
|
<pre>
|
|
declare void @llvm.memmove.p0i8.p0i8.i32(i8* <dest>, i8* <src>,
|
|
i32 <len>, i32 <align>, i1 <isvolatile>)
|
|
declare void @llvm.memmove.p0i8.p0i8.i64(i8* <dest>, i8* <src>,
|
|
i64 <len>, i32 <align>, i1 <isvolatile>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the
|
|
source location to the destination location. It is similar to the
|
|
'<tt>llvm.memcpy</tt>' intrinsic but allows the two memory locations to
|
|
overlap.</p>
|
|
|
|
<p>Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt>
|
|
intrinsics do not return a value, takes extra alignment/isvolatile arguments
|
|
and the pointers can be in specified address spaces.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
|
|
<p>The first argument is a pointer to the destination, the second is a pointer
|
|
to the source. The third argument is an integer argument specifying the
|
|
number of bytes to copy, the fourth argument is the alignment of the
|
|
source and destination locations, and the fifth is a boolean indicating a
|
|
volatile access.</p>
|
|
|
|
<p>If the call to this intrinsic has an alignment value that is not 0 or 1,
|
|
then the caller guarantees that the source and destination pointers are
|
|
aligned to that boundary.</p>
|
|
|
|
<p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
|
|
<tt>llvm.memmove</tt> call is a <a href="#volatile">volatile operation</a>.
|
|
The detailed access behavior is not very cleanly specified and it is unwise
|
|
to depend on it.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
|
|
<p>The '<tt>llvm.memmove.*</tt>' intrinsics copy a block of memory from the
|
|
source location to the destination location, which may overlap. It copies
|
|
"len" bytes of memory over. If the argument is known to be aligned to some
|
|
boundary, this can be specified as the fourth argument, otherwise it should
|
|
be set to 0 or 1.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use llvm.memset on any integer bit
|
|
width and for different address spaces. However, not all targets support all
|
|
bit widths.</p>
|
|
|
|
<pre>
|
|
declare void @llvm.memset.p0i8.i32(i8* <dest>, i8 <val>,
|
|
i32 <len>, i32 <align>, i1 <isvolatile>)
|
|
declare void @llvm.memset.p0i8.i64(i8* <dest>, i8 <val>,
|
|
i64 <len>, i32 <align>, i1 <isvolatile>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.memset.*</tt>' intrinsics fill a block of memory with a
|
|
particular byte value.</p>
|
|
|
|
<p>Note that, unlike the standard libc function, the <tt>llvm.memset</tt>
|
|
intrinsic does not return a value and takes extra alignment/volatile
|
|
arguments. Also, the destination can be in an arbitrary address space.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is a pointer to the destination to fill, the second is the
|
|
byte value with which to fill it, the third argument is an integer argument
|
|
specifying the number of bytes to fill, and the fourth argument is the known
|
|
alignment of the destination location.</p>
|
|
|
|
<p>If the call to this intrinsic has an alignment value that is not 0 or 1,
|
|
then the caller guarantees that the destination pointer is aligned to that
|
|
boundary.</p>
|
|
|
|
<p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
|
|
<tt>llvm.memset</tt> call is a <a href="#volatile">volatile operation</a>.
|
|
The detailed access behavior is not very cleanly specified and it is unwise
|
|
to depend on it.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.memset.*</tt>' intrinsics fill "len" bytes of memory starting
|
|
at the destination location. If the argument is known to be aligned to some
|
|
boundary, this can be specified as the fourth argument, otherwise it should
|
|
be set to 0 or 1.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.sqrt.f32(float %Val)
|
|
declare double @llvm.sqrt.f64(double %Val)
|
|
declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.sqrt.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand,
|
|
returning the same value as the libm '<tt>sqrt</tt>' functions would.
|
|
Unlike <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined
|
|
behavior for negative numbers other than -0.0 (which allows for better
|
|
optimization, because there is no need to worry about errno being
|
|
set). <tt>llvm.sqrt(-0.0)</tt> is defined to return -0.0 like IEEE sqrt.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the sqrt of the specified operand if it is a
|
|
nonnegative floating point number.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.powi.f32(float %Val, i32 %power)
|
|
declare double @llvm.powi.f64(double %Val, i32 %power)
|
|
declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power)
|
|
declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power)
|
|
declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the
|
|
specified (positive or negative) power. The order of evaluation of
|
|
multiplications is not defined. When a vector of floating point type is
|
|
used, the second argument remains a scalar integer value.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The second argument is an integer power, and the first is a value to raise to
|
|
that power.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the first value raised to the second power with an
|
|
unspecified sequence of rounding operations.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.sin.f32(float %Val)
|
|
declare double @llvm.sin.f64(double %Val)
|
|
declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.sin.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the sine of the specified operand, returning the same
|
|
values as the libm <tt>sin</tt> functions would, and handles error conditions
|
|
in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.cos.f32(float %Val)
|
|
declare double @llvm.cos.f64(double %Val)
|
|
declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.cos.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the cosine of the specified operand, returning the same
|
|
values as the libm <tt>cos</tt> functions would, and handles error conditions
|
|
in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.pow.f32(float %Val, float %Power)
|
|
declare double @llvm.pow.f64(double %Val, double %Power)
|
|
declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power)
|
|
declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power)
|
|
declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the
|
|
specified (positive or negative) power.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The second argument is a floating point power, and the first is a value to
|
|
raise to that power.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the first value raised to the second power, returning
|
|
the same values as the libm <tt>pow</tt> functions would, and handles error
|
|
conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_exp">'<tt>llvm.exp.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.exp</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.exp.f32(float %Val)
|
|
declare double @llvm.exp.f64(double %Val)
|
|
declare x86_fp80 @llvm.exp.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.exp.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.exp.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.exp.*</tt>' intrinsics perform the exp function.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>exp</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_exp2">'<tt>llvm.exp2.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.exp2</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.exp2.f32(float %Val)
|
|
declare double @llvm.exp2.f64(double %Val)
|
|
declare x86_fp80 @llvm.exp2.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.exp2.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.exp2.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.exp2.*</tt>' intrinsics perform the exp2 function.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>exp2</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_log">'<tt>llvm.log.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.log</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.log.f32(float %Val)
|
|
declare double @llvm.log.f64(double %Val)
|
|
declare x86_fp80 @llvm.log.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.log.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.log.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.log.*</tt>' intrinsics perform the log function.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>log</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_log10">'<tt>llvm.log10.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.log10</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.log10.f32(float %Val)
|
|
declare double @llvm.log10.f64(double %Val)
|
|
declare x86_fp80 @llvm.log10.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.log10.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.log10.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.log10.*</tt>' intrinsics perform the log10 function.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>log10</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_log2">'<tt>llvm.log2.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.log2</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.log2.f32(float %Val)
|
|
declare double @llvm.log2.f64(double %Val)
|
|
declare x86_fp80 @llvm.log2.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.log2.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.log2.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.log2.*</tt>' intrinsics perform the log2 function.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>log2</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_fma">'<tt>llvm.fma.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.fma</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.fma.f32(float %a, float %b, float %c)
|
|
declare double @llvm.fma.f64(double %a, double %b, double %c)
|
|
declare x86_fp80 @llvm.fma.f80(x86_fp80 %a, x86_fp80 %b, x86_fp80 %c)
|
|
declare fp128 @llvm.fma.f128(fp128 %a, fp128 %b, fp128 %c)
|
|
declare ppc_fp128 @llvm.fma.ppcf128(ppc_fp128 %a, ppc_fp128 %b, ppc_fp128 %c)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.fma.*</tt>' intrinsics perform the fused multiply-add
|
|
operation.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>fma</tt> functions
|
|
would.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_fabs">'<tt>llvm.fabs.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.fabs</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.fabs.f32(float %Val)
|
|
declare double @llvm.fabs.f64(double %Val)
|
|
declare x86_fp80 @llvm.fabs.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.fabs.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.fabs.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.fabs.*</tt>' intrinsics return the absolute value of
|
|
the operand.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>fabs</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_floor">'<tt>llvm.floor.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.floor</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.floor.f32(float %Val)
|
|
declare double @llvm.floor.f64(double %Val)
|
|
declare x86_fp80 @llvm.floor.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.floor.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.floor.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.floor.*</tt>' intrinsics return the floor of
|
|
the operand.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>floor</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_ceil">'<tt>llvm.ceil.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.ceil</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.ceil.f32(float %Val)
|
|
declare double @llvm.ceil.f64(double %Val)
|
|
declare x86_fp80 @llvm.ceil.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.ceil.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.ceil.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.ceil.*</tt>' intrinsics return the ceiling of
|
|
the operand.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>ceil</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_trunc">'<tt>llvm.trunc.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.trunc</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.trunc.f32(float %Val)
|
|
declare double @llvm.trunc.f64(double %Val)
|
|
declare x86_fp80 @llvm.trunc.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.trunc.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.trunc.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.trunc.*</tt>' intrinsics returns the operand rounded to the
|
|
nearest integer not larger in magnitude than the operand.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>trunc</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_rint">'<tt>llvm.rint.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.rint</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.rint.f32(float %Val)
|
|
declare double @llvm.rint.f64(double %Val)
|
|
declare x86_fp80 @llvm.rint.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.rint.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.rint.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.rint.*</tt>' intrinsics returns the operand rounded to the
|
|
nearest integer. It may raise an inexact floating-point exception if the
|
|
operand isn't an integer.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>rint</tt> functions
|
|
would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_nearbyint">'<tt>llvm.nearbyint.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.nearbyint</tt> on any
|
|
floating point or vector of floating point type. Not all targets support all
|
|
types however.</p>
|
|
|
|
<pre>
|
|
declare float @llvm.nearbyint.f32(float %Val)
|
|
declare double @llvm.nearbyint.f64(double %Val)
|
|
declare x86_fp80 @llvm.nearbyint.f80(x86_fp80 %Val)
|
|
declare fp128 @llvm.nearbyint.f128(fp128 %Val)
|
|
declare ppc_fp128 @llvm.nearbyint.ppcf128(ppc_fp128 %Val)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.nearbyint.*</tt>' intrinsics returns the operand rounded to the
|
|
nearest integer.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The argument and return value are floating point numbers of the same
|
|
type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This function returns the same values as the libm <tt>nearbyint</tt>
|
|
functions would, and handles error conditions in the same way.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_manip">Bit Manipulation Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM provides intrinsics for a few important bit manipulation operations.
|
|
These allow efficient code generation for some algorithms.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic function. You can use bswap on any integer
|
|
type that is an even number of bytes (i.e. BitWidth % 16 == 0).</p>
|
|
|
|
<pre>
|
|
declare i16 @llvm.bswap.i16(i16 <id>)
|
|
declare i32 @llvm.bswap.i32(i32 <id>)
|
|
declare i64 @llvm.bswap.i64(i64 <id>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer
|
|
values with an even number of bytes (positive multiple of 16 bits). These
|
|
are useful for performing operations on data that is not in the target's
|
|
native byte order.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high
|
|
and low byte of the input i16 swapped. Similarly,
|
|
the <tt>llvm.bswap.i32</tt> intrinsic returns an i32 value that has the four
|
|
bytes of the input i32 swapped, so that if the input bytes are numbered 0, 1,
|
|
2, 3 then the returned i32 will have its bytes in 3, 2, 1, 0 order.
|
|
The <tt>llvm.bswap.i48</tt>, <tt>llvm.bswap.i64</tt> and other intrinsics
|
|
extend this concept to additional even-byte lengths (6 bytes, 8 bytes and
|
|
more, respectively).</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit
|
|
width, or on any vector with integer elements. Not all targets support all
|
|
bit widths or vector types, however.</p>
|
|
|
|
<pre>
|
|
declare i8 @llvm.ctpop.i8(i8 <src>)
|
|
declare i16 @llvm.ctpop.i16(i16 <src>)
|
|
declare i32 @llvm.ctpop.i32(i32 <src>)
|
|
declare i64 @llvm.ctpop.i64(i64 <src>)
|
|
declare i256 @llvm.ctpop.i256(i256 <src>)
|
|
declare <2 x i32> @llvm.ctpop.v2i32(<2 x i32> <src>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set
|
|
in a value.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The only argument is the value to be counted. The argument may be of any
|
|
integer type, or a vector with integer elements.
|
|
The return type must match the argument type.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable, or within each
|
|
element of a vector.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any
|
|
integer bit width, or any vector whose elements are integers. Not all
|
|
targets support all bit widths or vector types, however.</p>
|
|
|
|
<pre>
|
|
declare i8 @llvm.ctlz.i8 (i8 <src>, i1 <is_zero_undef>)
|
|
declare i16 @llvm.ctlz.i16 (i16 <src>, i1 <is_zero_undef>)
|
|
declare i32 @llvm.ctlz.i32 (i32 <src>, i1 <is_zero_undef>)
|
|
declare i64 @llvm.ctlz.i64 (i64 <src>, i1 <is_zero_undef>)
|
|
declare i256 @llvm.ctlz.i256(i256 <src>, i1 <is_zero_undef>)
|
|
declase <2 x i32> @llvm.ctlz.v2i32(<2 x i32> <src>, i1 <is_zero_undef>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.ctlz</tt>' family of intrinsic functions counts the number of
|
|
leading zeros in a variable.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is the value to be counted. This argument may be of any
|
|
integer type, or a vectory with integer element type. The return type
|
|
must match the first argument type.</p>
|
|
|
|
<p>The second argument must be a constant and is a flag to indicate whether the
|
|
intrinsic should ensure that a zero as the first argument produces a defined
|
|
result. Historically some architectures did not provide a defined result for
|
|
zero values as efficiently, and many algorithms are now predicated on
|
|
avoiding zero-value inputs.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant)
|
|
zeros in a variable, or within each element of the vector.
|
|
If <tt>src == 0</tt> then the result is the size in bits of the type of
|
|
<tt>src</tt> if <tt>is_zero_undef == 0</tt> and <tt>undef</tt> otherwise.
|
|
For example, <tt>llvm.ctlz(i32 2) = 30</tt>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any
|
|
integer bit width, or any vector of integer elements. Not all targets
|
|
support all bit widths or vector types, however.</p>
|
|
|
|
<pre>
|
|
declare i8 @llvm.cttz.i8 (i8 <src>, i1 <is_zero_undef>)
|
|
declare i16 @llvm.cttz.i16 (i16 <src>, i1 <is_zero_undef>)
|
|
declare i32 @llvm.cttz.i32 (i32 <src>, i1 <is_zero_undef>)
|
|
declare i64 @llvm.cttz.i64 (i64 <src>, i1 <is_zero_undef>)
|
|
declare i256 @llvm.cttz.i256(i256 <src>, i1 <is_zero_undef>)
|
|
declase <2 x i32> @llvm.cttz.v2i32(<2 x i32> <src>, i1 <is_zero_undef>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.cttz</tt>' family of intrinsic functions counts the number of
|
|
trailing zeros.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is the value to be counted. This argument may be of any
|
|
integer type, or a vectory with integer element type. The return type
|
|
must match the first argument type.</p>
|
|
|
|
<p>The second argument must be a constant and is a flag to indicate whether the
|
|
intrinsic should ensure that a zero as the first argument produces a defined
|
|
result. Historically some architectures did not provide a defined result for
|
|
zero values as efficiently, and many algorithms are now predicated on
|
|
avoiding zero-value inputs.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant)
|
|
zeros in a variable, or within each element of a vector.
|
|
If <tt>src == 0</tt> then the result is the size in bits of the type of
|
|
<tt>src</tt> if <tt>is_zero_undef == 0</tt> and <tt>undef</tt> otherwise.
|
|
For example, <tt>llvm.cttz(2) = 1</tt>.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_overflow">Arithmetic with Overflow Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>LLVM provides intrinsics for some arithmetic with overflow operations.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_sadd_overflow">
|
|
'<tt>llvm.sadd.with.overflow.*</tt>' Intrinsics
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.sadd.with.overflow</tt>
|
|
on any integer bit width.</p>
|
|
|
|
<pre>
|
|
declare {i16, i1} @llvm.sadd.with.overflow.i16(i16 %a, i16 %b)
|
|
declare {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
|
|
declare {i64, i1} @llvm.sadd.with.overflow.i64(i64 %a, i64 %b)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform
|
|
a signed addition of the two arguments, and indicate whether an overflow
|
|
occurred during the signed summation.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The arguments (%a and %b) and the first element of the result structure may
|
|
be of integer types of any bit width, but they must have the same bit
|
|
width. The second element of the result structure must be of
|
|
type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
|
|
undergo signed addition.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform
|
|
a signed addition of the two variables. They return a structure — the
|
|
first element of which is the signed summation, and the second element of
|
|
which is a bit specifying if the signed summation resulted in an
|
|
overflow.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
|
|
%sum = extractvalue {i32, i1} %res, 0
|
|
%obit = extractvalue {i32, i1} %res, 1
|
|
br i1 %obit, label %overflow, label %normal
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_uadd_overflow">
|
|
'<tt>llvm.uadd.with.overflow.*</tt>' Intrinsics
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.uadd.with.overflow</tt>
|
|
on any integer bit width.</p>
|
|
|
|
<pre>
|
|
declare {i16, i1} @llvm.uadd.with.overflow.i16(i16 %a, i16 %b)
|
|
declare {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
|
|
declare {i64, i1} @llvm.uadd.with.overflow.i64(i64 %a, i64 %b)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform
|
|
an unsigned addition of the two arguments, and indicate whether a carry
|
|
occurred during the unsigned summation.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The arguments (%a and %b) and the first element of the result structure may
|
|
be of integer types of any bit width, but they must have the same bit
|
|
width. The second element of the result structure must be of
|
|
type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
|
|
undergo unsigned addition.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform
|
|
an unsigned addition of the two arguments. They return a structure —
|
|
the first element of which is the sum, and the second element of which is a
|
|
bit specifying if the unsigned summation resulted in a carry.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%res = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
|
|
%sum = extractvalue {i32, i1} %res, 0
|
|
%obit = extractvalue {i32, i1} %res, 1
|
|
br i1 %obit, label %carry, label %normal
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_ssub_overflow">
|
|
'<tt>llvm.ssub.with.overflow.*</tt>' Intrinsics
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.ssub.with.overflow</tt>
|
|
on any integer bit width.</p>
|
|
|
|
<pre>
|
|
declare {i16, i1} @llvm.ssub.with.overflow.i16(i16 %a, i16 %b)
|
|
declare {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
|
|
declare {i64, i1} @llvm.ssub.with.overflow.i64(i64 %a, i64 %b)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform
|
|
a signed subtraction of the two arguments, and indicate whether an overflow
|
|
occurred during the signed subtraction.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The arguments (%a and %b) and the first element of the result structure may
|
|
be of integer types of any bit width, but they must have the same bit
|
|
width. The second element of the result structure must be of
|
|
type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
|
|
undergo signed subtraction.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform
|
|
a signed subtraction of the two arguments. They return a structure —
|
|
the first element of which is the subtraction, and the second element of
|
|
which is a bit specifying if the signed subtraction resulted in an
|
|
overflow.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%res = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
|
|
%sum = extractvalue {i32, i1} %res, 0
|
|
%obit = extractvalue {i32, i1} %res, 1
|
|
br i1 %obit, label %overflow, label %normal
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_usub_overflow">
|
|
'<tt>llvm.usub.with.overflow.*</tt>' Intrinsics
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.usub.with.overflow</tt>
|
|
on any integer bit width.</p>
|
|
|
|
<pre>
|
|
declare {i16, i1} @llvm.usub.with.overflow.i16(i16 %a, i16 %b)
|
|
declare {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
|
|
declare {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %b)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform
|
|
an unsigned subtraction of the two arguments, and indicate whether an
|
|
overflow occurred during the unsigned subtraction.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The arguments (%a and %b) and the first element of the result structure may
|
|
be of integer types of any bit width, but they must have the same bit
|
|
width. The second element of the result structure must be of
|
|
type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
|
|
undergo unsigned subtraction.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform
|
|
an unsigned subtraction of the two arguments. They return a structure —
|
|
the first element of which is the subtraction, and the second element of
|
|
which is a bit specifying if the unsigned subtraction resulted in an
|
|
overflow.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%res = call {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
|
|
%sum = extractvalue {i32, i1} %res, 0
|
|
%obit = extractvalue {i32, i1} %res, 1
|
|
br i1 %obit, label %overflow, label %normal
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_smul_overflow">
|
|
'<tt>llvm.smul.with.overflow.*</tt>' Intrinsics
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.smul.with.overflow</tt>
|
|
on any integer bit width.</p>
|
|
|
|
<pre>
|
|
declare {i16, i1} @llvm.smul.with.overflow.i16(i16 %a, i16 %b)
|
|
declare {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
|
|
declare {i64, i1} @llvm.smul.with.overflow.i64(i64 %a, i64 %b)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
|
|
<p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform
|
|
a signed multiplication of the two arguments, and indicate whether an
|
|
overflow occurred during the signed multiplication.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The arguments (%a and %b) and the first element of the result structure may
|
|
be of integer types of any bit width, but they must have the same bit
|
|
width. The second element of the result structure must be of
|
|
type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
|
|
undergo signed multiplication.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform
|
|
a signed multiplication of the two arguments. They return a structure —
|
|
the first element of which is the multiplication, and the second element of
|
|
which is a bit specifying if the signed multiplication resulted in an
|
|
overflow.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%res = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
|
|
%sum = extractvalue {i32, i1} %res, 0
|
|
%obit = extractvalue {i32, i1} %res, 1
|
|
br i1 %obit, label %overflow, label %normal
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_umul_overflow">
|
|
'<tt>llvm.umul.with.overflow.*</tt>' Intrinsics
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use <tt>llvm.umul.with.overflow</tt>
|
|
on any integer bit width.</p>
|
|
|
|
<pre>
|
|
declare {i16, i1} @llvm.umul.with.overflow.i16(i16 %a, i16 %b)
|
|
declare {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
|
|
declare {i64, i1} @llvm.umul.with.overflow.i64(i64 %a, i64 %b)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform
|
|
a unsigned multiplication of the two arguments, and indicate whether an
|
|
overflow occurred during the unsigned multiplication.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The arguments (%a and %b) and the first element of the result structure may
|
|
be of integer types of any bit width, but they must have the same bit
|
|
width. The second element of the result structure must be of
|
|
type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
|
|
undergo unsigned multiplication.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform
|
|
an unsigned multiplication of the two arguments. They return a structure
|
|
— the first element of which is the multiplication, and the second
|
|
element of which is a bit specifying if the unsigned multiplication resulted
|
|
in an overflow.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%res = call {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
|
|
%sum = extractvalue {i32, i1} %res, 0
|
|
%obit = extractvalue {i32, i1} %res, 1
|
|
br i1 %obit, label %overflow, label %normal
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="spec_arithmetic">Specialised Arithmetic Intrinsics</a>
|
|
</h3>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
|
|
<h4>
|
|
<a name="fmuladd">'<tt>llvm.fmuladd.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare float @llvm.fmuladd.f32(float %a, float %b, float %c)
|
|
declare double @llvm.fmuladd.f64(double %a, double %b, double %c)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.fmuladd.*</tt>' intrinsic functions represent multiply-add
|
|
expressions that can be fused if the code generator determines that the fused
|
|
expression would be legal and efficient.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The '<tt>llvm.fmuladd.*</tt>' intrinsics each take three arguments: two
|
|
multiplicands, a and b, and an addend c.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The expression:</p>
|
|
<pre>
|
|
%0 = call float @llvm.fmuladd.f32(%a, %b, %c)
|
|
</pre>
|
|
<p>is equivalent to the expression a * b + c, except that rounding will not be
|
|
performed between the multiplication and addition steps if the code generator
|
|
fuses the operations. Fusion is not guaranteed, even if the target platform
|
|
supports it. If a fused multiply-add is required the corresponding llvm.fma.*
|
|
intrinsic function should be used instead.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%r2 = call float @llvm.fmuladd.f32(float %a, float %b, float %c) ; yields {float}:r2 = (a * b) + c
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_fp16">Half Precision Floating Point Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>For most target platforms, half precision floating point is a storage-only
|
|
format. This means that it is
|
|
a dense encoding (in memory) but does not support computation in the
|
|
format.</p>
|
|
|
|
<p>This means that code must first load the half-precision floating point
|
|
value as an i16, then convert it to float with <a
|
|
href="#int_convert_from_fp16"><tt>llvm.convert.from.fp16</tt></a>.
|
|
Computation can then be performed on the float value (including extending to
|
|
double etc). To store the value back to memory, it is first converted to
|
|
float if needed, then converted to i16 with
|
|
<a href="#int_convert_to_fp16"><tt>llvm.convert.to.fp16</tt></a>, then
|
|
storing as an i16 value.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_convert_to_fp16">
|
|
'<tt>llvm.convert.to.fp16</tt>' Intrinsic
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i16 @llvm.convert.to.fp16(f32 %a)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.convert.to.fp16</tt>' intrinsic function performs
|
|
a conversion from single precision floating point format to half precision
|
|
floating point format.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The intrinsic function contains single argument - the value to be
|
|
converted.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.convert.to.fp16</tt>' intrinsic function performs
|
|
a conversion from single precision floating point format to half precision
|
|
floating point format. The return value is an <tt>i16</tt> which
|
|
contains the converted number.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%res = call i16 @llvm.convert.to.fp16(f32 %a)
|
|
store i16 %res, i16* @x, align 2
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_convert_from_fp16">
|
|
'<tt>llvm.convert.from.fp16</tt>' Intrinsic
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare f32 @llvm.convert.from.fp16(i16 %a)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.convert.from.fp16</tt>' intrinsic function performs
|
|
a conversion from half precision floating point format to single precision
|
|
floating point format.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The intrinsic function contains single argument - the value to be
|
|
converted.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The '<tt>llvm.convert.from.fp16</tt>' intrinsic function performs a
|
|
conversion from half single precision floating point format to single
|
|
precision floating point format. The input half-float value is represented by
|
|
an <tt>i16</tt> value.</p>
|
|
|
|
<h5>Examples:</h5>
|
|
<pre>
|
|
%a = load i16* @x, align 2
|
|
%res = call f32 @llvm.convert.from.fp16(i16 %a)
|
|
</pre>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_debugger">Debugger Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt>
|
|
prefix), are described in
|
|
the <a href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source
|
|
Level Debugging</a> document.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_eh">Exception Handling Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>The LLVM exception handling intrinsics (which all start with
|
|
<tt>llvm.eh.</tt> prefix), are described in
|
|
the <a href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception
|
|
Handling</a> document.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_trampoline">Trampoline Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>These intrinsics make it possible to excise one parameter, marked with
|
|
the <a href="#nest"><tt>nest</tt></a> attribute, from a function.
|
|
The result is a callable
|
|
function pointer lacking the nest parameter - the caller does not need to
|
|
provide a value for it. Instead, the value to use is stored in advance in a
|
|
"trampoline", a block of memory usually allocated on the stack, which also
|
|
contains code to splice the nest value into the argument list. This is used
|
|
to implement the GCC nested function address extension.</p>
|
|
|
|
<p>For example, if the function is
|
|
<tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function
|
|
pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as
|
|
follows:</p>
|
|
|
|
<pre class="doc_code">
|
|
%tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
|
|
%tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
|
|
call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8*, i32, i32)* @f to i8*), i8* %nval)
|
|
%p = call i8* @llvm.adjust.trampoline(i8* %tramp1)
|
|
%fp = bitcast i8* %p to i32 (i32, i32)*
|
|
</pre>
|
|
|
|
<p>The call <tt>%val = call i32 %fp(i32 %x, i32 %y)</tt> is then equivalent
|
|
to <tt>%val = call i32 %f(i8* %nval, i32 %x, i32 %y)</tt>.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_it">
|
|
'<tt>llvm.init.trampoline</tt>' Intrinsic
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>This fills the memory pointed to by <tt>tramp</tt> with executable code,
|
|
turning it into a trampoline.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all
|
|
pointers. The <tt>tramp</tt> argument must point to a sufficiently large and
|
|
sufficiently aligned block of memory; this memory is written to by the
|
|
intrinsic. Note that the size and the alignment are target-specific - LLVM
|
|
currently provides no portable way of determining them, so a front-end that
|
|
generates this intrinsic needs to have some target-specific knowledge.
|
|
The <tt>func</tt> argument must hold a function bitcast to
|
|
an <tt>i8*</tt>.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The block of memory pointed to by <tt>tramp</tt> is filled with target
|
|
dependent code, turning it into a function. Then <tt>tramp</tt> needs to be
|
|
passed to <a href="#int_at">llvm.adjust.trampoline</a> to get a pointer
|
|
which can be <a href="#int_trampoline">bitcast (to a new function) and
|
|
called</a>. The new function's signature is the same as that of
|
|
<tt>func</tt> with any arguments marked with the <tt>nest</tt> attribute
|
|
removed. At most one such <tt>nest</tt> argument is allowed, and it must be of
|
|
pointer type. Calling the new function is equivalent to calling <tt>func</tt>
|
|
with the same argument list, but with <tt>nval</tt> used for the missing
|
|
<tt>nest</tt> argument. If, after calling <tt>llvm.init.trampoline</tt>, the
|
|
memory pointed to by <tt>tramp</tt> is modified, then the effect of any later call
|
|
to the returned function pointer is undefined.</p>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_at">
|
|
'<tt>llvm.adjust.trampoline</tt>' Intrinsic
|
|
</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i8* @llvm.adjust.trampoline(i8* <tramp>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>This performs any required machine-specific adjustment to the address of a
|
|
trampoline (passed as <tt>tramp</tt>).</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p><tt>tramp</tt> must point to a block of memory which already has trampoline code
|
|
filled in by a previous call to <a href="#int_it"><tt>llvm.init.trampoline</tt>
|
|
</a>.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>On some architectures the address of the code to be executed needs to be
|
|
different to the address where the trampoline is actually stored. This
|
|
intrinsic returns the executable address corresponding to <tt>tramp</tt>
|
|
after performing the required machine specific adjustments.
|
|
The pointer returned can then be <a href="#int_trampoline"> bitcast and
|
|
executed</a>.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_memorymarkers">Memory Use Markers</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>This class of intrinsics exists to information about the lifetime of memory
|
|
objects and ranges where variables are immutable.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_lifetime_start">'<tt>llvm.lifetime.start</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.lifetime.start(i64 <size>, i8* nocapture <ptr>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.lifetime.start</tt>' intrinsic specifies the start of a memory
|
|
object's lifetime.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is a constant integer representing the size of the
|
|
object, or -1 if it is variable sized. The second argument is a pointer to
|
|
the object.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic indicates that before this point in the code, the value of the
|
|
memory pointed to by <tt>ptr</tt> is dead. This means that it is known to
|
|
never be used and has an undefined value. A load from the pointer that
|
|
precedes this intrinsic can be replaced with
|
|
<tt>'<a href="#undefvalues">undef</a>'</tt>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_lifetime_end">'<tt>llvm.lifetime.end</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.lifetime.end(i64 <size>, i8* nocapture <ptr>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.lifetime.end</tt>' intrinsic specifies the end of a memory
|
|
object's lifetime.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is a constant integer representing the size of the
|
|
object, or -1 if it is variable sized. The second argument is a pointer to
|
|
the object.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic indicates that after this point in the code, the value of the
|
|
memory pointed to by <tt>ptr</tt> is dead. This means that it is known to
|
|
never be used and has an undefined value. Any stores into the memory object
|
|
following this intrinsic may be removed as dead.
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_invariant_start">'<tt>llvm.invariant.start</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare {}* @llvm.invariant.start(i64 <size>, i8* nocapture <ptr>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.invariant.start</tt>' intrinsic specifies that the contents of
|
|
a memory object will not change.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is a constant integer representing the size of the
|
|
object, or -1 if it is variable sized. The second argument is a pointer to
|
|
the object.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic indicates that until an <tt>llvm.invariant.end</tt> that uses
|
|
the return value, the referenced memory location is constant and
|
|
unchanging.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_invariant_end">'<tt>llvm.invariant.end</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.invariant.end({}* <start>, i64 <size>, i8* nocapture <ptr>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.invariant.end</tt>' intrinsic specifies that the contents of
|
|
a memory object are mutable.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is the matching <tt>llvm.invariant.start</tt> intrinsic.
|
|
The second argument is a constant integer representing the size of the
|
|
object, or -1 if it is variable sized and the third argument is a pointer
|
|
to the object.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic indicates that the memory is mutable again.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h3>
|
|
<a name="int_general">General Intrinsics</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>This class of intrinsics is designed to be generic and has no specific
|
|
purpose.</p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.var.annotation</tt>' intrinsic.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is a pointer to a value, the second is a pointer to a
|
|
global string, the third is a pointer to a global string which is the source
|
|
file name, and the last argument is the line number.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic allows annotation of local variables with arbitrary strings.
|
|
This can be useful for special purpose optimizations that want to look for
|
|
these annotations. These have no other defined use; they are ignored by code
|
|
generation and optimization.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on
|
|
any integer bit width.</p>
|
|
|
|
<pre>
|
|
declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int>)
|
|
declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int>)
|
|
declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int>)
|
|
declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int>)
|
|
declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.annotation</tt>' intrinsic.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The first argument is an integer value (result of some expression), the
|
|
second is a pointer to a global string, the third is a pointer to a global
|
|
string which is the source file name, and the last argument is the line
|
|
number. It returns the value of the first argument.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic allows annotations to be put on arbitrary expressions with
|
|
arbitrary strings. This can be useful for special purpose optimizations that
|
|
want to look for these annotations. These have no other defined use; they
|
|
are ignored by code generation and optimization.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_trap">'<tt>llvm.trap</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.trap() noreturn nounwind
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.trap</tt>' intrinsic.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>None.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic is lowered to the target dependent trap instruction. If the
|
|
target does not have a trap instruction, this intrinsic will be lowered to
|
|
a call of the <tt>abort()</tt> function.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_debugtrap">'<tt>llvm.debugtrap</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.debugtrap() nounwind
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The '<tt>llvm.debugtrap</tt>' intrinsic.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>None.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic is lowered to code which is intended to cause an execution
|
|
trap with the intention of requesting the attention of a debugger.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_stackprotector">'<tt>llvm.stackprotector</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.stackprotector(i8* <guard>, i8** <slot>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The <tt>llvm.stackprotector</tt> intrinsic takes the <tt>guard</tt> and
|
|
stores it onto the stack at <tt>slot</tt>. The stack slot is adjusted to
|
|
ensure that it is placed on the stack before local variables.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The <tt>llvm.stackprotector</tt> intrinsic requires two pointer
|
|
arguments. The first argument is the value loaded from the stack
|
|
guard <tt>@__stack_chk_guard</tt>. The second variable is an <tt>alloca</tt>
|
|
that has enough space to hold the value of the guard.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic causes the prologue/epilogue inserter to force the position of
|
|
the <tt>AllocaInst</tt> stack slot to be before local variables on the
|
|
stack. This is to ensure that if a local variable on the stack is
|
|
overwritten, it will destroy the value of the guard. When the function exits,
|
|
the guard on the stack is checked against the original guard. If they are
|
|
different, then the program aborts by calling the <tt>__stack_chk_fail()</tt>
|
|
function.</p>
|
|
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_objectsize">'<tt>llvm.objectsize</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i32 @llvm.objectsize.i32(i8* <object>, i1 <min>)
|
|
declare i64 @llvm.objectsize.i64(i8* <object>, i1 <min>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The <tt>llvm.objectsize</tt> intrinsic is designed to provide information to
|
|
the optimizers to determine at compile time whether a) an operation (like
|
|
memcpy) will overflow a buffer that corresponds to an object, or b) that a
|
|
runtime check for overflow isn't necessary. An object in this context means
|
|
an allocation of a specific class, structure, array, or other object.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The <tt>llvm.objectsize</tt> intrinsic takes two arguments. The first
|
|
argument is a pointer to or into the <tt>object</tt>. The second argument
|
|
is a boolean and determines whether <tt>llvm.objectsize</tt> returns 0 (if
|
|
true) or -1 (if false) when the object size is unknown.
|
|
The second argument only accepts constants.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>The <tt>llvm.objectsize</tt> intrinsic is lowered to a constant representing
|
|
the size of the object concerned. If the size cannot be determined at compile
|
|
time, <tt>llvm.objectsize</tt> returns <tt>i32/i64 -1 or 0</tt>
|
|
(depending on the <tt>min</tt> argument).</p>
|
|
|
|
</div>
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_expect">'<tt>llvm.expect</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare i32 @llvm.expect.i32(i32 <val>, i32 <expected_val>)
|
|
declare i64 @llvm.expect.i64(i64 <val>, i64 <expected_val>)
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The <tt>llvm.expect</tt> intrinsic provides information about expected (the
|
|
most probable) value of <tt>val</tt>, which can be used by optimizers.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>The <tt>llvm.expect</tt> intrinsic takes two arguments. The first
|
|
argument is a value. The second argument is an expected value, this needs to
|
|
be a constant value, variables are not allowed.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic is lowered to the <tt>val</tt>.</p>
|
|
</div>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
<h4>
|
|
<a name="int_donothing">'<tt>llvm.donothing</tt>' Intrinsic</a>
|
|
</h4>
|
|
|
|
<div>
|
|
|
|
<h5>Syntax:</h5>
|
|
<pre>
|
|
declare void @llvm.donothing() nounwind readnone
|
|
</pre>
|
|
|
|
<h5>Overview:</h5>
|
|
<p>The <tt>llvm.donothing</tt> intrinsic doesn't perform any operation. It's the
|
|
only intrinsic that can be called with an invoke instruction.</p>
|
|
|
|
<h5>Arguments:</h5>
|
|
<p>None.</p>
|
|
|
|
<h5>Semantics:</h5>
|
|
<p>This intrinsic does nothing, and it's removed by optimizers and ignored by
|
|
codegen.</p>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
<hr>
|
|
<address>
|
|
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
|
|
src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
|
|
<a href="http://validator.w3.org/check/referer"><img
|
|
src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
|
|
|
|
<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
|
|
<a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
|
|
Last modified: $Date$
|
|
</address>
|
|
|
|
</body>
|
|
</html>
|