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[X86] Memory folding for commutative instructions (updated)

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This patch improves support for commutative instructions in the x86 memory folding implementation by attempting to fold a commuted version of the instruction if the original folding fails - if that folding fails as well the instruction is 're-commuted' back to its original order before returning.

Updated version of r219584 (reverted in r219595) - the commutation attempt now explicitly ensures that neither of the commuted source operands are tied to the destination operand / register, which was the source of all the regressions that occurred with the original patch attempt.

Added additional regression test case provided by Joerg Sonnenberger.

Differential Revision: http://reviews.llvm.org/D5818



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220239 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Simon Pilgrim
2014-10-20 22:14:22 +00:00
parent b9c7f60191
commit 0d1978b813
5 changed files with 202 additions and 59 deletions
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3
lib/Target/X86/X86FastISel.cpp
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@@ -3337,7 +3337,8 @@ bool X86FastISel::tryToFoldLoadIntoMI(MachineInstr *MI, unsigned OpNo,
AM.getFullAddress(AddrOps);
MachineInstr *Result =
XII.foldMemoryOperandImpl(*FuncInfo.MF, MI, OpNo, AddrOps, Size, Alignment);
XII.foldMemoryOperandImpl(*FuncInfo.MF, MI, OpNo, AddrOps,
Size, Alignment, /*AllowCommute=*/true);
if (!Result)
return false;