[GlobalISel] Fix GIM_CheckIsSameOperandIgnoreCopies

[Pierre-vh]

Summary

If the MI had more than one def it incorrectly returrned true.

[arsenm]

Test would be nice

[Pierre-vh]

In D156119#4528025, @arsenm wrote:

Test would be nice

We don't have one for this I think, I only caught it while working on MIR patterns

llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h

case GIM_CheckIsSameOperandIgnoreCopies: {
       assert(State.MIs[InsnID] != nullptr && "Used insn before defined");
       assert(State.MIs[OtherInsnID] != nullptr && "Used insn before defined");
 
       MachineOperand &Op = State.MIs[InsnID]->getOperand(OpIdx);
       MachineOperand &OtherOp = State.MIs[OtherInsnID]->getOperand(OtherOpIdx);
 
       if (MatcherOpcode == GIM_CheckIsSameOperandIgnoreCopies) {
         if (Op.isReg() && OtherOp.isReg()) {
-          MachineInstr *MI = getDefIgnoringCopies(Op.getReg(), MRI);
-          MachineInstr *OtherMI = getDefIgnoringCopies(OtherOp.getReg(), MRI);
-          if (MI && MI == OtherMI)
+          if (getSrcRegIgnoringCopies(Op.getReg(), MRI) ==
+              getSrcRegIgnoringCopies(OtherOp.getReg(), MRI))
             break;
         }
       }
 
       if (!Op.isIdenticalTo(OtherOp)) {
         if (handleReject() == RejectAndGiveUp)
           return false;
       }