[llvm] RegisterCoalescer: Add undef flags in removePartialRedundancy (PR #75152)

[via llvm-commits]

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@@ -1214,6 +1214,19 @@ bool RegisterCoalescer::removePartialRedundancy(const CoalescerPair &CP,
   LIS->pruneValue(*static_cast<LiveRange *>(&IntB), CopyIdx.getRegSlot(),
                   &EndPoints);
   BValNo->markUnused();
+
+  if (CopyMI.getOperand(1).isUndef()) {
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qcolombet wrote:

This check needs to be moved up because `CopyMI` is deleted a couple of lines earlier (call to `deleteInstr`).

https://github.com/llvm/llvm-project/pull/75152