Chandler Carruth acc068e873 Switch the lowering of CTLZ_ZERO_UNDEF from a .td pattern back to the ... X86ISelLowering C++ code. Because this is lowered via an xor wrapped around a bsr, we want the dagcombine which runs after isel lowering to have a chance to clean things up. In particular, it is very common to see code which looks like: (sizeof(x)*8 - 1) ^ __builtin_clz(x) Which is trying to compute the most significant bit of 'x'. That's actually the value computed directly by the 'bsr' instruction, but if we match it too late, we'll get completely redundant xor instructions. The more naive code for the above (subtracting rather than using an xor) still isn't handled correctly due to the dagcombine getting confused. Also, while here fix an issue spotted by inspection: we should have been expanding the zero-undef variants to the normal variants when there is an 'lzcnt' instruction. Do so, and test for this. We don't want to generate unnecessary 'bsr' instructions. These two changes fix some regressions in encoding and decoding benchmarks. However, there is still a *lot* to be improve on in this type of code. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147244 91177308-0d34-0410-b5e6-96231b3b80d8		2011-12-24 10:55:54 +00:00
..
Analysis	Make the unreachable probability much much heavier. The previous	2011-12-22 09:26:37 +00:00
Archive	Support/FileSystem: Add file_magic and move a vew clients over to it.	2011-12-13 23:17:12 +00:00
AsmParser	Removes unused field TheError from LLLexer.	2011-12-21 10:02:45 +00:00
Bitcode	The powers that be have decided that LLVM IR should now support 16-bit	2011-12-17 00:04:22 +00:00
CodeGen	drop unneeded config.h includes	2011-12-22 23:04:07 +00:00
DebugInfo	Unweaken vtables as per http://llvm.org/docs/CodingStandards.html#ll_virtual_anch	2011-12-20 02:50:00 +00:00
ExecutionEngine	Fix up the CMake build for the new files added in r146960, they're	2011-12-20 08:42:11 +00:00
Linker	When not destroying the source, the linker is not remapping the types. Added support	2011-12-23 02:18:32 +00:00
MC	Move x86 specific bits of the COFF writer to lib/Target/X86.	2011-12-24 02:14:02 +00:00
Object	Unweaken vtables as per http://llvm.org/docs/CodingStandards.html#ll_virtual_anch	2011-12-20 02:50:00 +00:00
Support	drop unneeded config.h includes	2011-12-22 23:04:07 +00:00
TableGen	TableGen: add a comment	2011-12-22 23:16:09 +00:00
Target	Switch the lowering of CTLZ_ZERO_UNDEF from a .td pattern back to the	2011-12-24 10:55:54 +00:00
Transforms	Fix typo "infinte".	2011-12-23 23:49:25 +00:00
VMCore	Give string constants generated by IRBuilder private linkage.	2011-12-22 14:22:14 +00:00
CMakeLists.txt	Move TableGen's parser and entry point into a library	2011-10-01 16:41:13 +00:00
LLVMBuild.txt	LLVMBuild: Introduce a common section which currently has a list of the	2011-12-12 22:45:54 +00:00
Makefile	Remove more of llvmc and dependencies.	2011-09-20 00:34:27 +00:00