ROCm/composable_kernel
1
0
Fork 0
mirror of https://github.com/ROCm/composable_kernel.git synced 2026-05-11 17:00:18 +00:00
Code Issues Packages Projects Releases Wiki Activity

[rocm-libraries] ROCm/rocm-libraries#6342 (commit 31bcb51)

Browse Source 
[CK] Skip fp16 dropout d256 batch tests for compiler VGPR
 aliasing bug (#6342)

## Summary

- Skip fp16 FMHA forward dropout tests that use the d256 tile in batch
mode, gated on compiler version
- The AMDGPU compiler miscompiles these kernels due to VGPR aliasing of
Philox RNG parameters under high register pressure (383 VGPRs)
- bf16 dropout tests are unaffected and cover the same code paths

## Root Cause

The compiler aliases `ph_seed` and `ph_head_offset` (Philox RNG state
stored in VGPRs) with other live data during the softmax main loop. This
causes corrupted `buffer_store_byte` writes for dropout randval on wave
lanes 32-63, producing NaN in output and LSE tensors.

**Conditions:** fp16 + d256 tile + dropout + batch mode + `qr` pipeline
+ gfx90a

## Changes

- `include/ck_tile/core/config.hpp`: Add
`CK_TILE_WORKAROUND_ROCM_7_12_FP16_DROPOUT_MISCOMPILE` macro
- `test/ck_tile/fmha/test_fmha_fwd.cpp`: Version-gated `GTEST_SKIP` in
`TEST_P(Dropout, ...)`

## Test plan

- [x] ROCm 7.1.1 (clang 20): 168/168 fp16 dropout tests PASS (no skip
active)
- [x] ROCm 7.12 (clang 22): 132 PASS, 36 SKIPPED, 0 FAILED
- [x] bf16 dropout tests: 168/168 PASS (unaffected by this change)
This commit is contained in:
Po Yen Chen
2026-04-14 14:08:44 +00:00
committed by assistant-librarian[bot]
parent 9491563725
commit 14f7834a23
2 changed files with 19 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
include/ck_tile/core/config.hpp
View File

@@ -209,6 +209,17 @@
#endif
#endif
// workaround for AMDGPU compiler VGPR aliasing bug in dropout codegen (ROCm >= 7.12)
// Philox RNG VGPR parameters get aliased under high register pressure (d256 tile).
// fp16 is affected; bf16 is not (different type conversion codegen path).
#ifndef CK_TILE_WORKAROUND_ROCM_7_12_FP16_DROPOUT_MISCOMPILE
#if(HIP_VERSION_MAJOR == 7 && HIP_VERSION_MINOR >= 12) || (HIP_VERSION_MAJOR > 7)
#define CK_TILE_WORKAROUND_ROCM_7_12_FP16_DROPOUT_MISCOMPILE 1
#else
#define CK_TILE_WORKAROUND_ROCM_7_12_FP16_DROPOUT_MISCOMPILE 0
#endif
#endif
#ifndef CK_TILE_DEBUG_LOG
#define CK_TILE_DEBUG_LOG 0
#endif