Modify the comparison optimizations in the peephole optimizer to update the
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
diff --git a/lib/CodeGen/PeepholeOptimizer.cpp b/lib/CodeGen/PeepholeOptimizer.cpp
index ea14d27..a4ff04b 100644
--- a/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/lib/CodeGen/PeepholeOptimizer.cpp
@@ -76,7 +76,8 @@
}
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 @@
/// 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 @@
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 @@
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;
diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index e7024d6..142633c 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -1378,9 +1378,11 @@
}
/// 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 @@
MI->RemoveOperand(5);
MachineInstrBuilder(MI)
.addReg(ARM::CPSR, RegState::Define | RegState::Implicit);
+ MII = llvm::next(MachineBasicBlock::iterator(CmpInstr));
CmpInstr->eraseFromParent();
return true;
}
diff --git a/lib/Target/ARM/ARMBaseInstrInfo.h b/lib/Target/ARM/ARMBaseInstrInfo.h
index f471b67..622402e 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.h
+++ b/lib/Target/ARM/ARMBaseInstrInfo.h
@@ -347,7 +347,8 @@
/// 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;