[PATCH] D130224: [Clang][Attribute] Introduce maybe_undef attribute for function arguments which accepts undef values

Thu Jul 21 05:13:44 PDT 2022

arsenm added a comment.

In D130224#3668243 <https://reviews.llvm.org/D130224#3668243>, @aaron.ballman wrote:

> In D130224#3668240 <https://reviews.llvm.org/D130224#3668240>, @arsenm wrote:
>
>> In D130224#3668225 <https://reviews.llvm.org/D130224#3668225>, @aaron.ballman wrote:
>>
>>> It sounds like there's an extremely specific use case in mind for this attribute; is there a reason why this needs to be the user's problem instead of something the compiler can infer or handle on the backend?
>>
>> The intended user is a handful of header wrapper functions around intrinsics, not general users
>
> Great, then it sounds like we don't need to expose this as an attribute because we know which intrinsics need special behavior, so we can handle them specially at codegen time or within the backend?

The problem is the wrappers. We originally talked about specifically handling the builtins, but that falls apart given the real users come from wrapper functions which look like ordinary code

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https://reviews.llvm.org/D130224