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[NVGPU] Fix nvdsl examples #156830

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[NVGPU] Fix nvdsl examples #156830

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castigli
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@castigli castigli commented Sep 4, 2025 •
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This PR aims at fixing the nvdsl examples which got a bit out of sync not being tested in the CI.

The fixed bugs were related to the following PRs:

There is one remaining bug that I think #153134 introduced. When running the Ch4 and Ch5 the nvvm.prefetch tensormap intrisic leads to the following error on sm_90a

LLVM ERROR: Cannot select: intrinsic %llvm.nvvm.prefetch.tensormap
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: mlir-opt before.mlir --gpu-module-to-binary
1.	Running pass 'Function Pass Manager' on module 'LLVMDialectModule'.
2.	Running pass 'NVPTX DAG->DAG Pattern Instruction Selection' on function '@gemm_multistage_kernel'
...

Perahps @Wolfram70 or @grypp could help me out with the last bug?
Could be the solution to revert momentarily to inline ptx?

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@castigli castigli changed the title Fix nvdsl examples [NVGPU] Fix nvdsl examples Sep 4, 2025
@Wolfram70
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Thanks for bringing this to our attention!

I looked into this a bit, and it does look like this crash is occurring in the --gpu-module-to-binary pass.
For Ch4.py, dumping the .mlir file and extracting the LLVMIR generated during --gpu-module-to-binary, we get
extracted-llvmir.txt. Running llc -mtriple=nvptx64 -mcpu=sm_90a -mattr=+ptx80 on this reproduces this crash exactly so it seems to be an issue during codegen. I am not sure why this is occurring in this specific case.

@durga4github @abhilash1910 Do you have any idea why this might be happening?

@abhilash1910
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abhilash1910 commented Sep 5, 2025 •
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Taking a look at the codegen. Thanks for highlighting. IR does not seem incorrect though at first glance.
Edit: Fix is in progress.

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@grypp grypp Awaiting requested review from grypp grypp will be requested when the pull request is marked ready for review grypp is a code owner

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@castigli @Wolfram70 @abhilash1910