[PATCH] D125970: [amdgpu] Add amdgpu_kernel calling conv attribute to clang

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In D125970#3527685 <https://reviews.llvm.org/D125970#3527685>, @JonChesterfield wrote:

> If it was adding a calling convention, sure - caution warranted. There's no llvm change here though, an existing CC is exposed to C++. No change to the type system either.

This is adding a user-facing calling convention to Clang and it changes the type system as a result. For example, lambda function pointer conversion operators sometimes are generated for each calling convention so that you can form a function pointer of the correct type (this might not be impacted by your change here); there's a specific number of bits for representing the enumeration of calling conventions and this uses one of those bits, etc.

> I'll propose a patch with some documentation for it if you wish, but it'll just say "For ad hoc debugging of the amdgpu backend". Undocumented seems to state that more clearly.

I continue to question whether we want to support such a calling convention. This does not seem to be generally useful enough to warrant inclusion in Clang. The fact that you'd like to leave it undocumented as that's more clear for users is a pretty good indication that this calling convention doesn't meet the bar for an extension.


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