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[CK] Add FP8 per-tensor quantization support for FMHA V3 pipeline (#6051) ## Motivation The existing FMHA V3 pipeline only supports fp16/bf16 data types. This PR extends V3 to handle FP8 inputs with per-tensor descaling on gfx950, enabling higher throughput for FP8 inference workloads using the assembly-optimized V3 code path. ## Technical Details **Warp GEMM:** - Add FP8 32x32x32 warp gemm with C-transposed distribution (`WarpGemmMfma_f32_32x32x32_fp8_fp8_CTransposed`) and dispatcher entries **V3 Kernel (`fmha_fwd_v3_kernel.hpp`):** - Add per-tensor descale support for Q, K, V tensors, passing descale pointers through to pipeline kargs **V3 Pipeline (`block_fmha_fwd_v3_pipeline.hpp`):** - Add FP8 data path with dtype-aware type selection - Add asm volatile P matrix conversion from f32 to fp8 - Add FP8-aware instruction scheduling in `CoreLoopScheduler` **V3 Pipeline Policy (`block_fmha_fwd_v3_pipeline_default_policy.hpp`):** - Add FP8 QK warp gemm selection (SwizzleB variant for V tile distribution compatibility) **Codegen (`fmha_fwd.py`):** - Add gfx950 FP8BF16 V3 tile size (256x64x128x128x64x128) - Add FP8BF16 V3 pipeline variants (mask: no/causal, qscale: no/pertensor) - Extend `can_dispatch_v3` condition for fp8bf16 + pertensor **Misc:** - Add LLVM scheduler `TRANS` mask to `LLVMSchedGroupMask` enum (`arch.hpp`) - Fix `mask_info` default initialization for `no_mask` case (`mask.hpp`) V3 dispatch for FP8 is disabled by default (`F_is_v3_enabled=false`) pending further validation. ## Performance: fmha_fwd V3 FP8 (avg runs 2-6, stock ROCm 7.1.1, gfx950) | Problem | Regular (TFlops) | Varlen (TFlops) | |---|---:|---:| | batch=1 heads=6/1 seqlen=1024 causal | 48.9 | 47.6 | | batch=1 heads=6/1 seqlen=2048 causal | 119.8 | 117.4 | | batch=1 heads=6/1 seqlen=4096 causal | 263.7 | 259.2 | | batch=1 heads=6/1 seqlen=8192 causal | 548.9 | 543.6 | | batch=1 heads=6/1 seqlen=16384 causal | 1043.0 | 1063.7 | | batch=1 heads=6/1 seqlen=32768 causal | 1237.2 | 1279.6 | | batch=1 heads=6/1 seqlen=65536 causal | 1315.4 | 1382.7 | | batch=1 heads=6/1 seqlen=131072 causal | 1326.3 | 1402.2 | | batch=1 heads=16/1 seqlen=65536 causal | 1298.7 | 1388.4 | | batch=1 heads=40/40 seqlen=37200 non-causal | 1248.9 | 1326.1 | ## Test Plan Tested with aiter's `test_mha_fp8.py` test suite (176 cases) covering batch sizes (1-2), sequence lengths (113-4096), head counts (5/8/32/40), GQA ratios (1:1, 1:8), and causal/non-causal modes. Verified all cases dispatch to the V3 pipeline by enabling `F_is_v3_enabled` and confirming kernel names contain `qr_async_trload_v3`. ## Test Result 176/176 tests passed with V3 enabled. All cases correctly dispatched to V3 pipeline with `pertensor` quantization. ## Submission Checklist - [x] Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.
CK Tile Example Suite
This directory contains a comprehensive suite of examples demonstrating the CK Tile programming model for high-performance GPU kernels. Each example illustrates a key deep learning or HPC operation, implemented using tile-based parallelism, modular pipelines, and data movement policy.
What is CK Tile?
CK Tile is a composable GPU programming API that expresses kernels as a composition of "tiles"—rectangular blocks of computation and data movement. The pipeline & policy orchestrates data movement (global <-> LDS <-> registers), computation, and synchronization, enabling high efficiency and flexibility.
Example Index
| Example | Operation | Description |
|---|---|---|
| 01_fmha | Fused Multi-Head Attention | Tile-based FMHA with masking, quantization, and epilogue fusion |
| 02_layernorm2d | LayerNorm2D | Blockwise layer normalization with fusion and quantization |
| 03_gemm | GEMM | Matrix multiplication with tilewise parallelism |
| 04_img2col | im2col | Image-to-column transformation for GEMM-based convolution |
| 05_reduce | Reduction | Tilewise sum, max, mean reductions |
| 06_permute | Permute | Generic tensor permutation (up to rank-8) |
| 09_topk_softmax | TopK-Softmax | Rowwise softmax and top-k selection for MoE gating |
| 10_rmsnorm2d | RMSNorm2D | Root mean square normalization for LLMs |
| 11_add_rmsnorm2d_rdquant | Add + RMSNorm2D + RDQuant | Fused add, RMSNorm, and rowwise dynamic quantization |
| 12_smoothquant | SmoothQuant | Per-channel scaling and quantization for int8 inference |
| 13_moe_sorting | MoE Sorting | Token-to-expert rearrangement for MoE dispatch |
| 14_moe_smoothquant | MoE-SmoothQuant | Expert-dependent quantization fused with top-k selection |
| 15_fused_moe | Fused MoE | End-to-end fused MoE block: sorting, group-GEMM, activation, weighting |
| 16_batched_gemm | Batched GEMM | Parallel computation of multiple GEMMs |
| 17_grouped_gemm | Grouped GEMM | Multiple independent GEMMs with different shapes |
| 18_flatmm | FLATMM | Flattened matrix multiplication for packed layouts |
| 19_gemm_multi_d | Multi-D GEMM | GEMM with multiple side inputs (bias, residual, etc.) |
| 35_batched_transpose | Batched Transpose | NCHW <-> NHWC and other layout conversions |
| 36_copy | Copy | Minimal example for tile-based memory movement |
| 37_transpose | Block Transpose | High-performance tiled transpose for large tensors |
Technical Highlights
- Tile Distribution: See
include/ck_tile/tile_program/tile_distribution/for mapping tiles to thread blocks. - Block Tile Pipelines: See
include/ck_tile/tile_program/block_tile_pipeline/for memory/computation pipelines. - Policies and Utilities: Many examples use custom policies for tile/block size and memory access.
How to Build & Run
mkdir build && cd build
sh ../script/cmake-ck-dev.sh ../ <arch>
make -j
Each example produces its own executable in build/bin/.
Learning and Extending
- Start Simple: Try 03_gemm or 36_copy to learn tile basics.
- Explore Fusion: See 11_add_rmsnorm2d_rdquant, 15_fused_moe, or 14_moe_smoothquant for advanced fusion.
- Experiment: Modify tile sizes, layouts, or pipelines to explore performance and flexibility.