[llvm] [InstCombine] Don't sink if it would require dropping deref assumptions. (PR #166945)

[Florian Hahn via llvm-commits]

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@@ -5413,6 +5413,18 @@ bool InstCombinerImpl::tryToSinkInstruction(Instruction *I,
         return false;
   }
 
+  // Do not sink if there are dereferenceable assumes that would be removed.
+  for (User *User : I->users()) {
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fhahn wrote:

Yep thanks, we can do better in `getOptionalSinkBlockForInst`, by just not skipping such assumes there we can still sink up to the deref assume. Also added some extra tests.

https://github.com/llvm/llvm-project/pull/166945