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Factor out partial register update checks for some SSE instructions. 

Also add the AVX versions and add comments!

llvm-svn: 139854
This commit is contained in:
Bruno Cardoso Lopes 2011-09-15 21:42:23 +00:00
parent 8314c5259d
commit 6b302955b1
1 changed files with 53 additions and 32 deletions
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85
llvm/lib/Target/X86/X86InstrInfo.cpp
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@ -2558,6 +2558,49 @@ X86InstrInfo::foldMemoryOperandImpl(MachineFunction &MF,
return NULL;
}
/// hasPartialRegUpdate - Return true for all instructions that only update
/// the first 32 or 64-bits of the destination register and leave the rest
/// unmodified. This can be used to avoid folding loads if the instructions
/// only update part of the destination register, and the non-updated part is
/// not needed. e.g. cvtss2sd, sqrtss. Unfolding the load from these
/// instructions breaks the partial register dependency and it can improve
/// performance. e.g.:
///
/// movss (%rdi), %xmm0
/// cvtss2sd %xmm0, %xmm0
///
/// Instead of
/// cvtss2sd (%rdi), %xmm0
///
static bool hasPartialRegUpdate(unsigned Opcode) {
switch (Opcode) {
case X86::CVTSD2SSrr:
case X86::Int_CVTSD2SSrr:
case X86::CVTSS2SDrr:
case X86::Int_CVTSS2SDrr:
case X86::RCPSSr:
case X86::RCPSSr_Int:
case X86::ROUNDSDr:
case X86::ROUNDSSr:
case X86::RSQRTSSr:
case X86::RSQRTSSr_Int:
case X86::SQRTSSr:
case X86::SQRTSSr_Int:
// AVX encoded versions
case X86::VCVTSD2SSrr:
case X86::Int_VCVTSD2SSrr:
case X86::VCVTSS2SDrr:
case X86::Int_VCVTSS2SDrr:
case X86::VRCPSSr:
case X86::VROUNDSDr:
case X86::VROUNDSSr:
case X86::VRSQRTSSr:
case X86::VSQRTSSr:
return true;
}
return false;
}
MachineInstr* X86InstrInfo::foldMemoryOperandImpl(MachineFunction &MF,
MachineInstr *MI,
@ -2566,22 +2609,11 @@ MachineInstr* X86InstrInfo::foldMemoryOperandImpl(MachineFunction &MF,
// Check switch flag
if (NoFusing) return NULL;
if (!MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize))
switch (MI->getOpcode()) {
case X86::CVTSD2SSrr:
case X86::Int_CVTSD2SSrr:
case X86::CVTSS2SDrr:
case X86::Int_CVTSS2SDrr:
case X86::RCPSSr:
case X86::RCPSSr_Int:
case X86::ROUNDSDr:
case X86::ROUNDSSr:
case X86::RSQRTSSr:
case X86::RSQRTSSr_Int:
case X86::SQRTSSr:
case X86::SQRTSSr_Int:
return 0;
}
// Unless optimizing for size, don't fold to avoid partial
// register update stalls
if (!MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize) &&
hasPartialRegUpdate(MI->getOpcode()))
return 0;
const MachineFrameInfo *MFI = MF.getFrameInfo();
unsigned Size = MFI->getObjectSize(FrameIndex);
@ -2618,22 +2650,11 @@ MachineInstr* X86InstrInfo::foldMemoryOperandImpl(MachineFunction &MF,
// Check switch flag
if (NoFusing) return NULL;
if (!MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize))
switch (MI->getOpcode()) {
case X86::CVTSD2SSrr:
case X86::Int_CVTSD2SSrr:
case X86::CVTSS2SDrr:
case X86::Int_CVTSS2SDrr:
case X86::RCPSSr:
case X86::RCPSSr_Int:
case X86::ROUNDSDr:
case X86::ROUNDSSr:
case X86::RSQRTSSr:
case X86::RSQRTSSr_Int:
case X86::SQRTSSr:
case X86::SQRTSSr_Int:
return 0;
}
// Unless optimizing for size, don't fold to avoid partial
// register update stalls
if (!MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize) &&
hasPartialRegUpdate(MI->getOpcode()))
return 0;
// Determine the alignment of the load.
unsigned Alignment = 0;