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Modify the comparison optimizations in the peephole optimizer to update the

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iterator when an optimization took place. This allows us to do more insane
things with the code than just remove an instruction or two.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113640 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2010-09-10 21:55:43 +00:00
parent 51f5b67395
commit 220e240bdf
4 changed files with 22 additions and 12 deletions
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8
include/llvm/Target/TargetInstrInfo.h
View File

@ -586,9 +586,11 @@ 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) const {
/// that we can remove a "comparison with zero". Update the iterator *only*
/// if a transformation took place.
virtual bool ConvertToSetZeroFlag(MachineInstr * /*Instr*/,
MachineInstr * /*CmpInstr*/,
MachineBasicBlock::iterator &) const {
return false;
}

16
lib/CodeGen/PeepholeOptimizer.cpp
View File

@ -76,7 +76,8 @@ namespace {
}
private:
bool OptimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
bool OptimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB,
MachineBasicBlock::iterator &MII);
bool OptimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &LocalMIs);
};
@ -232,7 +233,8 @@ OptimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
/// set) the same flag as the compare, then we can remove the comparison and use
/// the flag from the previous instruction.
bool PeepholeOptimizer::OptimizeCmpInstr(MachineInstr *MI,
MachineBasicBlock *MBB) {
MachineBasicBlock *MBB,
MachineBasicBlock::iterator &NextIter){
// If this instruction is a comparison against zero and isn't comparing a
// physical register, we can try to optimize it.
unsigned SrcReg;
@ -247,7 +249,7 @@ bool PeepholeOptimizer::OptimizeCmpInstr(MachineInstr *MI,
return false;
// Attempt to convert the defining instruction to set the "zero" flag.
if (TII->ConvertToSetZeroFlag(&*DI, MI)) {
if (TII->ConvertToSetZeroFlag(&*DI, MI, NextIter)) {
++NumEliminated;
return true;
}
@ -269,12 +271,14 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
LocalMIs.clear();
for (MachineBasicBlock::iterator
MII = I->begin(), ME = I->end(); MII != ME; ) {
MII = I->begin(), MIE = I->end(); MII != MIE; ) {
MachineInstr *MI = &*MII;
if (MI->getDesc().isCompare()) {
++MII; // The iterator may become invalid if the compare is deleted.
Changed |= OptimizeCmpInstr(MI, MBB);
if (OptimizeCmpInstr(MI, MBB, MII))
Changed = true;
else
++MII;
} else {
Changed |= OptimizeExtInstr(MI, MBB, LocalMIs);
++MII;

7
lib/Target/ARM/ARMBaseInstrInfo.cpp
View File

@ -1378,9 +1378,11 @@ AnalyzeCompare(const MachineInstr *MI, unsigned &SrcReg, int &CmpValue) const {
}
/// ConvertToSetZeroFlag - Convert the instruction to set the "zero" flag so
/// that we can remove a "comparison with zero".
/// that we can remove a "comparison with zero". Update the iterator *only* if a
/// transformation took place.
bool ARMBaseInstrInfo::
ConvertToSetZeroFlag(MachineInstr *MI, MachineInstr *CmpInstr) const {
ConvertToSetZeroFlag(MachineInstr *MI, MachineInstr *CmpInstr,
MachineBasicBlock::iterator &MII) const {
// Conservatively refuse to convert an instruction which isn't in the same BB
// as the comparison.
if (MI->getParent() != CmpInstr->getParent())
@ -1414,6 +1416,7 @@ ConvertToSetZeroFlag(MachineInstr *MI, MachineInstr *CmpInstr) const {
MI->RemoveOperand(5);
MachineInstrBuilder(MI)
.addReg(ARM::CPSR, RegState::Define | RegState::Implicit);
MII = llvm::next(MachineBasicBlock::iterator(CmpInstr));
CmpInstr->eraseFromParent();
return true;
}

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

@ -347,7 +347,8 @@ 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) const;
MachineInstr *CmpInstr,
MachineBasicBlock::iterator &MII) const;
virtual unsigned getNumMicroOps(const MachineInstr *MI,
const InstrItineraryData *ItinData) const;