[llvm] [InstCombine] Push freeze through non-recurrence PHIs (PR #157678)

[Cullen Rhodes via llvm-commits]

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@@ -5070,7 +5078,10 @@ InstCombinerImpl::pushFreezeToPreventPoisonFromPropagating(FreezeInst &OrigFI) {
         return nullptr;
 
       auto *UserI = cast<Instruction>(U->getUser());
-      Builder.SetInsertPoint(UserI);
+      if (auto *PN = dyn_cast<PHINode>(UserI))
+        Builder.SetInsertPoint(PN->getIncomingBlock(*U)->getTerminator());
+      else
+        Builder.SetInsertPoint(UserI);
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c-rhodes wrote:

> Can you please add a test where the phi input is an invoke result? It won't work in that case.
> 
> Also similar to the other PR, we need to be careful about multi-edges here.

Added test cases for both of these where it was crashing, now fixed.

https://github.com/llvm/llvm-project/pull/157678