+/// replacePHIInstrs - Completely replace PHI instructions with selects.
+/// This is possible when the only Tail predecessors are the if-converted
+/// blocks.
+void SSAIfConv::replacePHIInstrs() {
+ assert(Tail->pred_size() == 2 && "Cannot replace PHIs");
+ MachineBasicBlock::iterator FirstTerm = Head->getFirstTerminator();
+ assert(FirstTerm != Head->end() && "No terminators");
+ DebugLoc HeadDL = FirstTerm->getDebugLoc();
+
+ // Convert all PHIs to select instructions inserted before FirstTerm.
+ for (unsigned i = 0, e = PHIs.size(); i != e; ++i) {
+ PHIInfo &PI = PHIs[i];
+ DEBUG(dbgs() << "If-converting " << *PI.PHI);
+ unsigned DstReg = PI.PHI->getOperand(0).getReg();
+ TII->insertSelect(*Head, FirstTerm, HeadDL, DstReg, Cond, PI.TReg, PI.FReg);
+ DEBUG(dbgs() << " --> " << *llvm::prior(FirstTerm));
+ PI.PHI->eraseFromParent();
+ PI.PHI = 0;
+ }
+}
+
+/// rewritePHIOperands - When there are additional Tail predecessors, insert
+/// select instructions in Head and rewrite PHI operands to use the selects.
+/// Keep the PHI instructions in Tail to handle the other predecessors.
+void SSAIfConv::rewritePHIOperands() {
+ MachineBasicBlock::iterator FirstTerm = Head->getFirstTerminator();
+ assert(FirstTerm != Head->end() && "No terminators");
+ DebugLoc HeadDL = FirstTerm->getDebugLoc();
+
+ // Convert all PHIs to select instructions inserted before FirstTerm.
+ for (unsigned i = 0, e = PHIs.size(); i != e; ++i) {
+ PHIInfo &PI = PHIs[i];
+ 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() << " --> " << *llvm::prior(FirstTerm));
+
+ // Rewrite PHI operands TPred -> (DstReg, Head), remove FPred.
+ for (unsigned i = PI.PHI->getNumOperands(); i != 1; i -= 2) {
+ MachineBasicBlock *MBB = PI.PHI->getOperand(i-1).getMBB();
+ if (MBB == getTPred()) {
+ PI.PHI->getOperand(i-1).setMBB(Head);
+ PI.PHI->getOperand(i-2).setReg(DstReg);
+ } else if (MBB == getFPred()) {
+ PI.PHI->RemoveOperand(i-1);
+ PI.PHI->RemoveOperand(i-2);
+ }
+ }
+ DEBUG(dbgs() << " --> " << *PI.PHI);
+ }
+}