[llvm] [InstCombine] Treat identical operands as one in pushFreezeToPreventPoisonFromPropagating (PR #145348)

[Nikita Popov via llvm-commits]

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@@ -4774,7 +4774,9 @@ InstCombinerImpl::pushFreezeToPreventPoisonFromPropagating(FreezeInst &OrigFI) {
   Use *MaybePoisonOperand = nullptr;
   for (Use &U : OrigOpInst->operands()) {
     if (isa<MetadataAsValue>(U.get()) ||
-        isGuaranteedNotToBeUndefOrPoison(U.get()))
+        isGuaranteedNotToBeUndefOrPoison(U.get()) ||
+        // Treat identical operands as a single operand.
+        (MaybePoisonOperand && MaybePoisonOperand->get() == U.get()))
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nikic wrote:

The code below is still only replacing one of the uses. We should be replacing all of them.

You kind of get away with it because we'll later try to freeze other uses in a separate transform, but this needs to be individually correct.

https://github.com/llvm/llvm-project/pull/145348