[PATCH] D92270: [ConstantFold] Fold more operations to poison

[Neil Dhar via Phabricator via llvm-commits]

neildhar added inline comments.


================
Comment at: llvm/lib/IR/ConstantFold.cpp:633
         // the input constant.
-        return UndefValue::get(DestTy);
+        return PoisonValue::get(DestTy);
       }
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spatel wrote:
> MatzeB wrote:
> > I believe this is causing some of our clients trouble, especially since we somehow have a `-fno-strict-float-cast-overflow` flag in clang that says float->int overflows are not UB... (CC @spatel )
> I can guess at what the example looks like, but it would be great to have a reduced test.
> There should be a function attribute in IR corresponding to that clang flag, so we could alter the behavior here based on checking that? Not sure if there's precedence for that kind of transform though.
Here's a minimal repro for the issue we ran into: https://godbolt.org/z/Wdr7q1a9M


Repository:
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  https://reviews.llvm.org/D92270/new/

https://reviews.llvm.org/D92270