[PATCH] D90409: [HIP] Math Headers to use type promotion

[Yaxun Liu via Phabricator via cfe-commits]

yaxunl added a comment.

In D90409#2372023 <https://reviews.llvm.org/D90409#2372023>, @yaxunl wrote:

> In D90409#2371987 <https://reviews.llvm.org/D90409#2371987>, @tra wrote:
>
>> In D90409#2371969 <https://reviews.llvm.org/D90409#2371969>, @yaxunl wrote:
>>
>>> nvcc does not support fma(float,float,char)
>>
>> It does, it just needs an explicit flag to match clang's treatment of `constexpr` functions as HD.
>
>
>
> In D90409#2371972 <https://reviews.llvm.org/D90409#2371972>, @tra wrote:
>
>> In D90409#2371679 <https://reviews.llvm.org/D90409#2371679>, @jlebar wrote:
>>
>>>> LGTM. I think the change would make sense for CUDA, too. @jlebar - WDYT?
>>>
>>> I agree that the C and C++ standard libraries should behave the same in CUDA mode and host mode!
>>>
>>> But if doing so would make our behavior different than nvcc's, maybe we could emit a warning or something?  Like, "this code you wrote maybe for nvcc is going to do something different with clang."
>>
>> Interestingly enough CUDA 10.1+ already promotes integer `fma()` arguments to double:
>> https://godbolt.org/z/crbqTe
>>
>> I wonder what makes HIP different to require this change.
>
> Practically the behavior is the same since they all promote integer types to double. This matches the C++ behavior. However the HIP change will make it conform to C++ for a target supporting long double whereas the previous header did not.

Sorry I mean the change can make the header extendable to `long double` easily although it does not yet. Another thing is that it allows resolution of mixed argument types with _Float16.


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