James Molloy ab4e0362c7 [Thumb-1] Synthesize TBB/TBH instructions to make use of compressed jump tables ... The TBB and TBH instructions in Thumb-2 allow jump tables to be compressed into sequences of bytes or shorts respectively. These instructions do not exist in Thumb-1, however it is possible to synthesize them out of a sequence of other instructions. It turns out this sequence is so short that it's almost never a lose for performance and is ALWAYS a significant win for code size. TBB example: Before: lsls r0, r0, #2 After: add r0, pc adr r1, .LJTI0_0 ldrb r0, [r0, #6] ldr r0, [r0, r1] lsls r0, r0, #1 mov pc, r0 add pc, r0 => No change in prologue code size or dynamic instruction count. Jump table shrunk by a factor of 4. The only case that can increase dynamic instruction count is the TBH case: Before: lsls r0, r4, #2 After: lsls r4, r4, #1 adr r1, .LJTI0_0 add r4, pc ldr r0, [r0, r1] ldrh r4, [r4, #6] mov pc, r0 lsls r4, r4, #1 add pc, r4 => 1 more instruction in prologue. Jump table shrunk by a factor of 2. So there is an argument that this should be disabled when optimizing for performance (and a TBH needs to be generated). I'm not so sure about that in practice, because on small cores with Thumb-1 performance is often tied to code size. But I'm willing to turn it off when optimizing for performance if people want (also note that TBHs are fairly rare in practice!) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284580 91177308-0d34-0410-b5e6-96231b3b80d8		2016-10-19 12:06:49 +00:00
..
Analysis	[SCEV] More accurate calculation of max backedge count of some less-than loops	2016-10-18 10:10:53 +00:00
Assembler	DebugInfo: change alignment type from uint64_t to uint32_t to save space.	2016-10-18 14:31:22 +00:00
Bindings
Bitcode
BugPoint	Disable fatal errors in the Verifier instantiated by bugpoint's crash	2016-10-18 16:24:43 +00:00
CodeGen	[Thumb-1] Synthesize TBB/TBH instructions to make use of compressed jump tables	2016-10-19 12:06:49 +00:00
DebugInfo	Revert r284545 again as the regression in ppc still exists. There is bug in MBPI exposed by th patch.	2016-10-19 01:18:25 +00:00
Demangle
Examples
ExecutionEngine	Handle relocations to thumb functions when dynamic linking COFF modules	2016-10-17 18:56:18 +00:00
Feature
FileCheck
Instrumentation	[asan] Append line number to variable name if line is available and in the same file as the function.	2016-10-18 23:29:41 +00:00
Integer
JitListener
LibDriver
Linker
LTO	LTO: Use the correct mangler function in LTOCodeGenerator::applyScopeRestrictions().	2016-10-12 20:12:19 +00:00
MC	[mips][ias] Handle more complicated expressions for memory operands	2016-10-18 15:17:17 +00:00
Object	One more additional error check for invalid Mach-O files for a	2016-10-18 20:24:12 +00:00
ObjectYAML
Other
SymbolRewriter
TableGen
ThinLTO/X86	[ThinLTO] Don't link module level assembly when importing	2016-10-12 18:39:29 +00:00
tools	dwarfdump: -summarize-types: print a short summary (unqualified type name, hash, length) of type units rather than dumping contents	2016-10-18 21:09:48 +00:00
Transforms	Update the section.ll to fix non-x86 failure.	2016-10-19 03:53:41 +00:00
Unit
Verifier
YAMLParser
.clang-format
CMakeLists.txt
lit.cfg
lit.site.cfg.in
TestRunner.sh