[llvm] [Inline][Cloning] Drop incompatible attributes from `NewFunc` before `instSimplify` (PR #90489)

[Nikita Popov via llvm-commits]

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@@ -700,6 +697,16 @@ void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
     }
   }
 
+  // Drop all incompatible return attributes that cannot be applied to NewFunc
+  // during cloning, so as to allow instruction simplification later to reason
+  // on the old state of the function. The original attributes are restored
+  // before returning.
+  AttributeMask IncompatibleAttrs =
+      AttributeFuncs::typeIncompatible(OldFunc->getReturnType());
+  AttrBuilder RetAttrs(NewFunc->getContext(),
+                       NewFunc->getAttributes().getRetAttrs());
+  NewFunc->removeRetAttrs(IncompatibleAttrs);
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nikic wrote:

Maybe move this directly before the code doing the actual simplification?

https://github.com/llvm/llvm-project/pull/90489