[llvm] [AMDGPU] Detect kills in register sets when trying to form V_CMPX instructions. (PR #68293)

[Jay Foad via llvm-commits]

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@@ -599,6 +620,11 @@ bool SIOptimizeExecMasking::optimizeVCMPSaveExecSequence(
   if (Src1->isReg())
     MRI->clearKillFlags(Src1->getReg());
 
+  for (MachineOperand *MO : KillFlagCandidates) {
+    if (MO)
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jayfoad wrote:

How could MO ever be nullptr here?

https://github.com/llvm/llvm-project/pull/68293