[llvm-dev] cmpxchg on floats

Chris Lattner via llvm-dev llvm-dev at lists.llvm.org
Thu Aug 13 13:58:53 PDT 2020

Does the code generator support this?  If not, we should add an assertion to the verifier.  If so, we can consider relaxing langref or making it more specific about floats.


> On Aug 13, 2020, at 6:35 AM, Alex Zinenko via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> Hi LLVM-dev,
> when working on MLIR-to-LLVM-IR conversion, I noticed that it is possible to programmatically construct a cmpxchg instruction operating on floats (or actually any type since there is no assertion on pointer element type here https://github.com/llvm/llvm-project/blob/9c2e708f0dc547d386ea528450a33ef4bd2a750b/llvm/lib/IR/Instructions.cpp#L1501 <https://github.com/llvm/llvm-project/blob/9c2e708f0dc547d386ea528450a33ef4bd2a750b/llvm/lib/IR/Instructions.cpp#L1501>), but LangRef specifies that only integers and pointers are accepted (https://llvm.org/docs/LangRef.html#cmpxchg-instruction <https://llvm.org/docs/LangRef.html#cmpxchg-instruction>). Does somebody rely on other types being accepted in cmpxchg or should we add an assertion for the element type to match the LangRef?
> -- 
> Alex
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