mirror of
https://github.com/RPCSX/llvm.git
synced 2024-11-26 21:20:37 +00:00
b3b28275da
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12690 91177308-0d34-0410-b5e6-96231b3b80d8
216 lines
7.2 KiB
HTML
216 lines
7.2 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
|
|
"http://www.w3.org/TR/html4/strict.dtd">
|
|
<html>
|
|
<head>
|
|
<title>Extending LLVM: Adding instructions, intrinsics, types, etc.</title>
|
|
<link rel="stylesheet" href="llvm.css" type="text/css">
|
|
</head>
|
|
|
|
<body>
|
|
|
|
<div class="doc_title">
|
|
Extending LLVM: Adding instructions, intrinsics, types, etc.
|
|
</div>
|
|
|
|
<ol>
|
|
<li><a href="#introduction">Introduction and Warning</a></li>
|
|
<li><a href="#instruction">Adding a new instruction</a></li>
|
|
<li><a href="#intrinsic">Adding a new intrinsic function</a></li>
|
|
<li><a href="#type">Adding a new type</a>
|
|
<ol>
|
|
<li><a href="#fund_type">Adding a new fundamental type</a></li>
|
|
<li><a href="#derived_type">Adding a new derived type</a></li>
|
|
</ol></li>
|
|
</ol>
|
|
|
|
<div class="doc_text">
|
|
<p><b>Written by <a href="http://misha.brukman.net">Misha Brukman</a></b></p>
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="introduction">Introduction and Warning</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>During the course of using LLVM, you may wish to customize it for your
|
|
research project or for experimentation. At this point, you may realize that
|
|
you need to add something to LLVM, whether it be a new fundamental type, a new
|
|
intrinsic function, or a whole new instruction.</p>
|
|
|
|
<p>When you come to this realization, stop and think. Do you really need to
|
|
extend LLVM? Is it a new fundamental capability that LLVM does not support at
|
|
its current incarnation or can it be synthesized from already pre-existing LLVM
|
|
elements? If you are not sure, ask on the <a
|
|
href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM-dev</a> list. The
|
|
reason is that extending LLVM will get involved as you need to update all the
|
|
different passes that you intend to use with your extension, and there are
|
|
<em>many</em> LLVM analyses and transformations, so it may be quite a bit of
|
|
work.</p>
|
|
|
|
<p>Adding an <a href="#intrinsic">intrinsic function</a> is easier than adding
|
|
an instruction, and is transparent to optimization passes which treat it as an
|
|
unanalyzable function. If your added functionality can be expressed as a
|
|
function call, an intrinsic function is the method of choice for LLVM
|
|
extension.</p>
|
|
|
|
<p>Before you invest a significant amount of effort into a non-trivial
|
|
extension, <span class="doc_warning">ask on the list</span> if what you are
|
|
looking to do can be done with already-existing infrastructure, or if maybe
|
|
someone else is already working on it. You will save yourself a lot of time and
|
|
effort by doing so.</p>
|
|
|
|
<p>Finally, these are my notes, and since my extensions are not complete, I may
|
|
be missing steps. If you find some omissions, please let me know <a
|
|
href="http://misha.brukman.net/contact.html">directly</a> or post on <a
|
|
href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM-dev</a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="instruction">Adding a new instruction</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p><span class="doc_warning">WARNING: adding instructions changes the bytecode
|
|
format, and it will take some effort to maintain compatibility with
|
|
the previous version.</span> Only add an instruction if it is absolutely
|
|
necessary.</p>
|
|
|
|
<ol>
|
|
|
|
<li><tt>llvm/include/llvm/Instruction.def</tt>:
|
|
add a number for your instruction and an enum name</li>
|
|
|
|
<li><tt>llvm/include/llvm/i*.h</tt>:
|
|
add a definition for the class that will represent your instruction</li>
|
|
|
|
<li><tt>llvm/include/llvm/Support/InstVisitor.h</tt>:
|
|
add a prototype for a visitor to your new instruction type</li>
|
|
|
|
<li><tt>llvm/lib/AsmParser/Lexer.l</tt>:
|
|
add a new token to parse your instruction from assembly text file</li>
|
|
|
|
<li><tt>llvm/lib/AsmParser/llvmAsmParser.y</tt>:
|
|
add the grammar on how your instruction can be read and what it will
|
|
construct as a result</li>
|
|
|
|
<li><tt>llvm/lib/Bytecode/Reader/InstructionReader.cpp</tt>:
|
|
add a case for your instruction and how it will be parsed from bytecode</li>
|
|
|
|
<li><tt>llvm/lib/VMCore/Instruction.cpp</tt>:
|
|
add a case for how your instruction will be printed out to assembly</li>
|
|
|
|
<li><tt>llvm/lib/VMCore/i*.cpp</tt>:
|
|
implement the class you defined in <tt>llvm/include/llvm/i*.h</tt></li>
|
|
|
|
</ol>
|
|
|
|
<p>Also, you need to implement (or modify) any analyses or passes that you want
|
|
to understand this new instruction.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="intrinsic">Adding a new intrinsic function</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<ol>
|
|
|
|
<li><tt>llvm/include/llvm/Intrinsics.h</tt>:
|
|
add an enum in the <tt>llvm::Intrinsic</tt> namespace</li>
|
|
|
|
<li><tt>llvm/lib/VMCore/IntrinsicLowering.cpp</tt>:
|
|
implement the lowering for this intrinsic</li>
|
|
|
|
<li><tt>llvm/lib/VMCore/Verifier.cpp</tt>:
|
|
handle the new intrinsic</li>
|
|
|
|
<li><tt>llvm/lib/VMCore/Function.cpp</tt>:
|
|
handle the new intrinsic</li>
|
|
|
|
</ol>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="type">Adding a new type</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p><span class="doc_warning">WARNING: adding new types changes the bytecode
|
|
format, and will break compatibility with currently-existing LLVM
|
|
installations.</span> Only add new types if it is absolutely necessary.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="fund_type">Adding a fundamental type</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ol>
|
|
|
|
<li><tt>llvm/include/llvm/Type.def</tt>:
|
|
add enum for the type</li>
|
|
|
|
<li><tt>llvm/include/llvm/Type.h</tt>:
|
|
add ID number for the new type; add static <tt>Type*</tt> for this type</li>
|
|
|
|
<li><tt>llvm/lib/VMCore/Type.cpp</tt>:
|
|
add mapping from <tt>TypeID</tt> => <tt>Type*</tt>;
|
|
initialize the static <tt>Type*</tt></li>
|
|
|
|
<li><tt>llvm/lib/AsmReader/Lexer.l</tt>:
|
|
add ability to parse in the type from text assembly</li>
|
|
|
|
<li><tt>llvm/lib/AsmReader/llvmAsmParser.y</tt>:
|
|
add a token for that type</li>
|
|
|
|
</ol>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="derived_type">Adding a derived type</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>TODO</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
<hr>
|
|
<address>
|
|
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
|
|
src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
|
|
<a href="http://validator.w3.org/check/referer"><img
|
|
src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
|
|
|
|
<a href="http://misha.brukman.net">Misha Brukman</a><br>
|
|
<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
|
|
<br>
|
|
Last modified: $Date$
|
|
</address>
|
|
|
|
</body>
|
|
</html>
|