[PATCH] D119669: [NVPTX] Prefix "$L__" for branch label names

[Artem Belevich via Phabricator via llvm-commits]

tra added a comment.

In D119669#3322138 <https://reviews.llvm.org/D119669#3322138>, @slydiman wrote:

> It seems this patch requires CUDA 11.3 and PTX ISA v7.3 at least.

Can you elaborate on what exactly is failing with older versions? AFAICT, `$...` is accepted by ptxas going back as far as CUDA-9.0: https://godbolt.org/z/G5n7E9xYz

On a side note, it's apparently possible to have a global or function to start with `$`:  https://godbolt.org/z/zW41xPnPd, https://godbolt.org/z/srjdh3a46
So, prefixing with `$` does not solve the problem completely.
We may be better off using `%` or just `__` as the prefix. While it's possible to have a conflict with the latter one, at least the end users are not supposed to use it.

In D119669#3322138 <https://reviews.llvm.org/D119669#3322138>, @slydiman wrote:

> In D119669#3320786 <https://reviews.llvm.org/D119669#3320786>, @tra wrote:
>
>> @slydiman please verify that clang-generated PTX with the patch does get accepted by ptxas. I'm not quite sure what went wrong here and we can't test it in clang/llvm in-tree tests as they don't have access to CUDA SDK.
>
> It seems this patch requires CUDA 11.3 and PTX ISA v7.3 at least.




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