STATISTIC(NumCmps, "Number of compares eliminated");
STATISTIC(NumImmFold, "Number of move immediate folded");
STATISTIC(NumLoadFold, "Number of loads folded");
+STATISTIC(NumSelects, "Number of selects optimized");
namespace {
class PeepholeOptimizer : public MachineFunctionPass {
bool optimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &LocalMIs);
+ bool optimizeSelect(MachineInstr *MI);
bool isMoveImmediate(MachineInstr *MI,
SmallSet<unsigned, 4> &ImmDefRegs,
DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
return false;
}
+/// Optimize a select instruction.
+bool PeepholeOptimizer::optimizeSelect(MachineInstr *MI) {
+ unsigned TrueOp = 0;
+ unsigned FalseOp = 0;
+ bool Optimizable = false;
+ SmallVector<MachineOperand, 4> Cond;
+ if (TII->analyzeSelect(MI, Cond, TrueOp, FalseOp, Optimizable))
+ return false;
+ if (!Optimizable)
+ return false;
+ if (!TII->optimizeSelect(MI))
+ return false;
+ MI->eraseFromParent();
+ ++NumSelects;
+ return true;
+}
+
/// isLoadFoldable - Check whether MI is a candidate for folding into a later
/// instruction. We only fold loads to virtual registers and the virtual
/// register defined has a single use.
bool PeepholeOptimizer::isLoadFoldable(MachineInstr *MI,
unsigned &FoldAsLoadDefReg) {
- if (MI->canFoldAsLoad()) {
- const MCInstrDesc &MCID = MI->getDesc();
- if (MCID.getNumDefs() == 1) {
- unsigned Reg = MI->getOperand(0).getReg();
- // To reduce compilation time, we check MRI->hasOneUse when inserting
- // loads. It should be checked when processing uses of the load, since
- // uses can be removed during peephole.
- if (!MI->getOperand(0).getSubReg() &&
- TargetRegisterInfo::isVirtualRegister(Reg) &&
- MRI->hasOneUse(Reg)) {
- FoldAsLoadDefReg = Reg;
- return true;
- }
- }
+ if (!MI->canFoldAsLoad() || !MI->mayLoad())
+ return false;
+ const MCInstrDesc &MCID = MI->getDesc();
+ if (MCID.getNumDefs() != 1)
+ return false;
+
+ unsigned Reg = MI->getOperand(0).getReg();
+ // To reduce compilation time, we check MRI->hasOneUse when inserting
+ // loads. It should be checked when processing uses of the load, since
+ // uses can be removed during peephole.
+ if (!MI->getOperand(0).getSubReg() &&
+ TargetRegisterInfo::isVirtualRegister(Reg) &&
+ MRI->hasOneUse(Reg)) {
+ FoldAsLoadDefReg = Reg;
+ return true;
}
return false;
}
ImmDefMIs.clear();
FoldAsLoadDefReg = 0;
- bool First = true;
- MachineBasicBlock::iterator PMII;
for (MachineBasicBlock::iterator
MII = I->begin(), MIE = I->end(); MII != MIE; ) {
MachineInstr *MI = &*MII;
+ // We may be erasing MI below, increment MII now.
+ ++MII;
LocalMIs.insert(MI);
// If there exists an instruction which belongs to the following
MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
MI->hasUnmodeledSideEffects()) {
FoldAsLoadDefReg = 0;
- ++MII;
continue;
}
if (MI->mayStore() || MI->isCall())
FoldAsLoadDefReg = 0;
- if (MI->isBitcast()) {
- if (optimizeBitcastInstr(MI, MBB)) {
- // MI is deleted.
- LocalMIs.erase(MI);
- Changed = true;
- MII = First ? I->begin() : llvm::next(PMII);
- continue;
- }
- } else if (MI->isCompare()) {
- if (optimizeCmpInstr(MI, MBB)) {
- // MI is deleted.
- LocalMIs.erase(MI);
- Changed = true;
- MII = First ? I->begin() : llvm::next(PMII);
- continue;
- }
+ if ((MI->isBitcast() && optimizeBitcastInstr(MI, MBB)) ||
+ (MI->isCompare() && optimizeCmpInstr(MI, MBB)) ||
+ (MI->isSelect() && optimizeSelect(MI))) {
+ // MI is deleted.
+ LocalMIs.erase(MI);
+ Changed = true;
+ continue;
}
if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) {
SeenMoveImm = true;
} else {
Changed |= optimizeExtInstr(MI, MBB, LocalMIs);
+ // optimizeExtInstr might have created new instructions after MI
+ // and before the already incremented MII. Adjust MII so that the
+ // next iteration sees the new instructions.
+ MII = MI;
+ ++MII;
if (SeenMoveImm)
Changed |= foldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
}
// MI is replaced with FoldMI.
Changed = true;
- PMII = FoldMI;
- MII = llvm::next(PMII);
continue;
}
}
- First = false;
- PMII = MII;
- ++MII;
}
}