[ROCm] warpSize is being made non constexpr in ROCm 7.0 #20330
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Signed-off-by: Gregory Shtrasberg <[email protected]>
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Summary of Changes
Hello @gshtras, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request implements a necessary adaptation for compatibility with the upcoming ROCm 7.0 release. It modifies how the WARP_SIZE constant is determined within the codebase, moving away from a runtime-dependent variable to a compile-time macro that intelligently selects the correct warp size based on the target GPU architecture. This change ensures the stability and correct compilation of kernels under the new ROCm environment.
Highlights
- ROCm 7.0 Compatibility: This pull request addresses a critical breaking change introduced in ROCm 7.0, where the
warpSizevariable is no longer aconstexpr. This change prevents its direct use in compile-time contexts, which previously relied on its constant nature. - Updated
WARP_SIZEDefinition: To maintain compile-time constant behavior, theWARP_SIZEmacro's definition has been updated. It now explicitly setsWARP_SIZEto 64 when compiling for ROCm on GFX9 architectures (e.g., AMD Instinct MI100/MI250) and to 32 for all other platforms, including NVIDIA CUDA and other ROCm targets. - Consistent Macro Application: The revised
WARP_SIZEdefinition has been applied consistently across multiple core files:csrc/attention/attention_kernels.cuh,csrc/attention/paged_attention_v1.cu,csrc/attention/paged_attention_v2.cu, andcsrc/cuda_compat.h. This ensures uniform behavior and compatibility across the codebase.
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Signed-off-by: Gregory Shtrasberg <[email protected]>
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Code Review
This pull request addresses a breaking change in ROCm 7.0 where warpSize is no longer a constexpr. The approach is to centralize the WARP_SIZE definition in csrc/cuda_compat.h and use preprocessor directives to set a compile-time constant.
The refactoring to a central header is a good improvement. However, the implementation for determining WARP_SIZE on ROCm is not fully correct. It handles GFX9 GPUs but makes a potentially incorrect assumption for newer GFX10+ architectures, which can lead to bugs if the code is compiled with a 64-wide wavefront. I've provided a critical review comment with a suggested fix that aligns with AMD's recommendation to use the __AMDGPU_WAVEFRONT_SIZE__ macro for a more robust solution.
| #ifndef USE_ROCM | ||
| #define WARP_SIZE 32 | ||
| #if defined(USE_ROCM) && defined(__GFX9__) | ||
| #define WARP_SIZE 64 |
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Is warpSize from the previous implementation 64?
Commits included: Using cuda_compat to defint the WARP_SIZE once Signed-off-by: Gregory Shtrasberg <[email protected]> On ROCm toe constant compile time warp size can not be used on the host side that can be shared for multiple architectures with different values Signed-off-by: Gregory Shtrasberg <[email protected]> Formatting Signed-off-by: Gregory Shtrasberg <[email protected]> Refactor to use cuda_compat, and not the unhippified version Signed-off-by: Gregory Shtrasberg <[email protected]> Leaving CUDA side as just a simple define Signed-off-by: Gregory Shtrasberg <[email protected]>
Commits included: Using cuda_compat to defint the WARP_SIZE once On ROCm toe constant compile time warp size can not be used on the host side that can be shared for multiple architectures with different values Formatting Refactor to use cuda_compat, and not the unhippified version Leaving CUDA side as just a simple define Signed-off-by: Gregory Shtrasberg <[email protected]>
…#20330) Signed-off-by: Gregory Shtrasberg <[email protected]> Signed-off-by: x22x22 <[email protected]>
…#20330) Signed-off-by: Gregory Shtrasberg <[email protected]>
…#20330) Signed-off-by: Gregory Shtrasberg <[email protected]>
…#20330) Signed-off-by: Gregory Shtrasberg <[email protected]> Signed-off-by: Jinzhen Lin <[email protected]>
…#20330) Signed-off-by: Gregory Shtrasberg <[email protected]> Signed-off-by: Paul Pak <[email protected]>
…#20330) Signed-off-by: Gregory Shtrasberg <[email protected]> Signed-off-by: Diego-Castan <[email protected]>
…#20330) Signed-off-by: Gregory Shtrasberg <[email protected]>
…#20330) Signed-off-by: Gregory Shtrasberg <[email protected]>
2 participants
ROCm7.0 hip compiler adds a breaking change of making warpSize a non constexpr value
Using an alternative method of deducing the right warp size to use
References:
https://rocm.blogs.amd.com/ecosystems-and-partners/transition-to-hip-7.0:-guidance-on-upcoming-compatibility-changes/README.html#warpsize-change
https://rocm.docs.amd.com/en/latest/about/release-notes.html#amdgpu-wavefront-size-compiler-macro-deprecation