[PATCH] D89582: clang/AMDGPU: Apply workgroup related attributes to all functions

[Stanislav Mekhanoshin via Phabricator via cfe-commits]

rampitec added a comment.

In D89582#2335704 <https://reviews.llvm.org/D89582#2335704>, @arsenm wrote:

> In D89582#2335671 <https://reviews.llvm.org/D89582#2335671>, @rampitec wrote:
>
>> In D89582#2335619 <https://reviews.llvm.org/D89582#2335619>, @arsenm wrote:
>>
>>> In D89582#2335574 <https://reviews.llvm.org/D89582#2335574>, @yaxunl wrote:
>>>
>>>> What if a device function is called by kernels with different work group sizes, will caller's work group size override callee's work group size?
>>>
>>> It's user error to call a function with a larger range than the caller
>>
>> The problem is that user can override default on a kernel with the attribute, but cannot do so on function. So a module can be compiled with a default smaller than requested on one of the kernels.
>
>
>
>> Then if default is maximum 1024 and can only be overridden with the --gpu-max-threads-per-block option it would not be problem, if not the description of the option:
>>
>>   LANGOPT(GPUMaxThreadsPerBlock, 32, 256, "default max threads per block for kernel launch bounds for HIP")
>>
>> I.e. it says about the "default", so it should be perfectly legal to set a higher limits on a specific kernel. Should the option say it restricts the maximum it would be legal to apply it to functions as well.
>
> The current backend default ends up greatly restricting the registers used in the functions, and increasing the spilling.

I know the problem, but it should be better to use AMDGPUPropagateAttributes for this. It will clone functions if needed.


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