Trivial fix for instruction with more than one destination in modulo peeler.

[hgreving]

Summary

When moving an instruction into a block where it was referenced by a phi when peeling,
refer to the phi's register number and assert that the instruction has it in its destinations.
This way, it also covers instructions with more than one destination.

[hgreving]

Thanks

llvm/lib/CodeGen/ModuloSchedule.cpp

void PeelingModuloScheduleExpander::moveStageBetweenBlocks(
   SmallVector<MachineInstr *, 4> PhiToDelete;
   for (MachineInstr &MI : DestBB->phis()) {
     assert(MI.getNumOperands() == 3);
     MachineInstr *Def = MRI.getVRegDef(MI.getOperand(1).getReg());
     // If the instruction referenced by the phi is moved inside the block
     // we don't need the phi anymore.
     if (getStage(Def) == Stage) {
       Register PhiReg = MI.getOperand(0).getReg();
-      MRI.replaceRegWith(MI.getOperand(0).getReg(),
-                         Def->getOperand(0).getReg());
+      assert(Def->findRegisterDefOperandIdx(MI.getOperand(1).getReg()) != -1);
+      MRI.replaceRegWith(MI.getOperand(0).getReg(), MI.getOperand(1).getReg());
       MI.getOperand(0).setReg(PhiReg);
       PhiToDelete.push_back(&MI);
     }
   }
   for (auto *P : PhiToDelete)
     P->eraseFromParent();
   InsertPt = DestBB->getFirstNonPHI();
   // Helper to clone Phi instructions into the destination block. We clone Phi