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Move some of the decision logic for converting an instruction into one that sets

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the 'zero' bit down into the back-end. There are other cases where this logic
isn't sufficient, so they should be handled separately.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113665 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2010-09-10 23:34:19 +00:00
parent d10cd7b314
commit 92ad57f066
4 changed files with 24 additions and 18 deletions
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9
include/llvm/Target/TargetInstrInfo.h
View File

@ -585,11 +585,10 @@ public:
return false;
}
/// ConvertToSetZeroFlag - Convert the instruction to set the zero flag so
/// that we can remove a "comparison with zero". Update the iterator *only*
/// if a transformation took place.
virtual bool ConvertToSetZeroFlag(MachineInstr * /*Instr*/,
MachineInstr * /*CmpInstr*/,
/// ConvertToSetZeroFlag - Convert the instruction supplying the argument to
/// the comparison into one that sets the zero bit in the flags
/// register. Update the iterator *only* if a transformation took place.
virtual bool ConvertToSetZeroFlag(MachineInstr * /*CmpInstr*/,
MachineBasicBlock::iterator &) const {
return false;
}

9
lib/CodeGen/PeepholeOptimizer.cpp
View File

@ -240,16 +240,11 @@ bool PeepholeOptimizer::OptimizeCmpInstr(MachineInstr *MI,
unsigned SrcReg;
int CmpValue;
if (!TII->AnalyzeCompare(MI, SrcReg, CmpValue) ||
TargetRegisterInfo::isPhysicalRegister(SrcReg) || CmpValue != 0)
return false;
MachineRegisterInfo::def_iterator DI = MRI->def_begin(SrcReg);
if (llvm::next(DI) != MRI->def_end())
// Only support one definition.
TargetRegisterInfo::isPhysicalRegister(SrcReg))
return false;
// Attempt to convert the defining instruction to set the "zero" flag.
if (TII->ConvertToSetZeroFlag(&*DI, MI, NextIter)) {
if (TII->ConvertToSetZeroFlag(MI, NextIter)) {
++NumEliminated;
return true;
}

21
lib/Target/ARM/ARMBaseInstrInfo.cpp
View File

@ -1377,12 +1377,25 @@ AnalyzeCompare(const MachineInstr *MI, unsigned &SrcReg, int &CmpValue) const {
return false;
}
/// ConvertToSetZeroFlag - Convert the instruction to set the "zero" flag so
/// that we can remove a "comparison with zero". Update the iterator *only* if a
/// transformation took place.
/// ConvertToSetZeroFlag - Convert the instruction supplying the argument to the
/// comparison into one that sets the zero bit in the flags register. Update the
/// iterator *only* if a transformation took place.
bool ARMBaseInstrInfo::
ConvertToSetZeroFlag(MachineInstr *MI, MachineInstr *CmpInstr,
ConvertToSetZeroFlag(MachineInstr *CmpInstr,
MachineBasicBlock::iterator &MII) const {
unsigned SrcReg;
int CmpValue;
if (!AnalyzeCompare(CmpInstr, SrcReg, CmpValue) || CmpValue != 0)
return false;
MachineRegisterInfo &MRI = CmpInstr->getParent()->getParent()->getRegInfo();
MachineRegisterInfo::def_iterator DI = MRI.def_begin(SrcReg);
if (llvm::next(DI) != MRI.def_end())
// Only support one definition.
return false;
MachineInstr *MI = &*DI;
// Conservatively refuse to convert an instruction which isn't in the same BB
// as the comparison.
if (MI->getParent() != CmpInstr->getParent())

3
lib/Target/ARM/ARMBaseInstrInfo.h
View File

@ -346,8 +346,7 @@ public:
/// ConvertToSetZeroFlag - Convert the instruction to set the zero flag so
/// that we can remove a "comparison with zero".
virtual bool ConvertToSetZeroFlag(MachineInstr *Instr,
MachineInstr *CmpInstr,
virtual bool ConvertToSetZeroFlag(MachineInstr *CmpInstr,
MachineBasicBlock::iterator &MII) const;
virtual unsigned getNumMicroOps(const MachineInstr *MI,