[llvm] TwoAddressInstruction: Fix assert on undef operand with -early-live-intervals (PR #125518)

[Sander de Smalen via llvm-commits]

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@@ -489,6 +489,9 @@ MachineInstr *TwoAddressInstructionImpl::findOnlyInterestingUse(
     bool &IsDstPhys) const {
   MachineOperand *UseOp = nullptr;
   for (MachineOperand &MO : MRI->use_nodbg_operands(Reg)) {
+    if (MO.isUndef())
+      continue;
+
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sdesmalen-arm wrote:

Unrelated to your patch, but should there be a break after line 499?

https://github.com/llvm/llvm-project/pull/125518