// Convert all PHIs to select instructions inserted before FirstTerm.
for (unsigned i = 0, e = PHIs.size(); i != e; ++i) {
PHIInfo &PI = PHIs[i];
+ unsigned DstReg = 0;
+
DEBUG(dbgs() << "If-converting " << *PI.PHI);
- unsigned PHIDst = PI.PHI->getOperand(0).getReg();
- unsigned DstReg = MRI->createVirtualRegister(MRI->getRegClass(PHIDst));
- TII->insertSelect(*Head, FirstTerm, HeadDL, DstReg, Cond, PI.TReg, PI.FReg);
- DEBUG(dbgs() << " --> " << *std::prev(FirstTerm));
+ if (PI.TReg == PI.FReg) {
+ // We do not need the select instruction if both incoming values are
+ // equal.
+ DstReg = PI.TReg;
+ } else {
+ unsigned PHIDst = PI.PHI->getOperand(0).getReg();
+ DstReg = MRI->createVirtualRegister(MRI->getRegClass(PHIDst));
+ TII->insertSelect(*Head, FirstTerm, HeadDL,
+ DstReg, Cond, PI.TReg, PI.FReg);
+ DEBUG(dbgs() << " --> " << *std::prev(FirstTerm));
+ }
// Rewrite PHI operands TPred -> (DstReg, Head), remove FPred.
for (unsigned i = PI.PHI->getNumOperands(); i != 1; i -= 2) {