[PATCH] D99233: [HIP] Add option --gpu-inline-threshold

[Artem Belevich via Phabricator via cfe-commits]

tra added a comment.

I'm concerned that if we make it a top-level option, it's likely to be cargo-culted and (mis)used as a sledgehammer in cases where it's not needed. I think the option should remain hidden.

While thresholds do need to be tweaked,  in my experience it happens very rarely. 
When it does, most of the time it's sufficient to apply `__attribute__((always_inline))` to a few functions where it matters.
If AMDGPU bumps into the limit too often, perhaps it's the default threshold value that needs to be changed.

If we do add an option to control inlining threshold, then we should also consider doing the same for other thresholds. 
For instance, loop unrolling thresholds in my experience need bumping up about as often as the inlining ones. 
Similarly, most of the time the issue can be dealt with at the source code level with `#pragma unroll`.

Perhaps we should generalize this patch to deal with wider range of threshold. 
E.g. we could have something like `--gpu-threshold threshold-kind=x` which would expand to appropriate cc1 options for GPU sub-compilations.
It would also be nice to handle it in a way that can be used by both CUDA and HIP w/o having to copy/paste code.

Also, this patch would not be necessary if we had the generalized way to specify options for particular offload targets. Alas, we don't have it yet.


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  https://reviews.llvm.org/D99233/new/

https://reviews.llvm.org/D99233