[Openmp-commits] [PATCH] D62393: [OPENMP][NVPTX]Mark parallel level counter as volatile.

Tue Oct 8 07:10:20 PDT 2019

ABataev added a comment.

In D62393#1699534 <https://reviews.llvm.org/D62393#1699534>, @jlebar wrote:

> Hi, jumping in here.  I haven't read the whole bug, apologies.
>
> ptxas from CUDA 8 has *many* known bugs.  I would also strongly oppose attempting to work around them in LLVM.
>
> If you cannot upgrade from CUDA 8, you can still take a newer ptxas binary and use it in combination with the rest of CUDA 8.  We have done this at Google for years now with no problems, and with a blessing from nvidia.
>
> If you encounter bugs in the latest ptxas and can provide a reproducer, we can file bugs against nvidia if you cannot.  (Well, I guess I'm volunteering tra, I don't work on this anymore.  :)  I'm not opposed to checking in workarounds for bugs in *the latest* ptxas if we have a process to remove these workarounds soon after a newer ptxas is available (i.e. we don't say, "remove after three ptxas releases" or something).  I would strongly oppose keeping workarounds for old ptxas versions because that would greatly complicate the NVPTX backend and have little benefit.

No, I don't try to add a workaround for the bug in LLVM since there are no problems in LLVM optimizations. The same code works correctly with Cuda9.2. But I would like to add it for cuda8 since we need to fully support it unless we drop the support for cuda8. It means that, unfortunately, we need to support cuda8 in full, with all bugs and problems.
I'm not happy to add it, but we just need to do this. Later, when we drop the support for Cuda8, we can remove this workaround and just use regular code.

Repository:
  rOMP OpenMP

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https://reviews.llvm.org/D62393