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[CK_TILE][FMHA] Fix sink un-mask under right-window and emit fp8bf16 batch_prefill sink kernels (#6914) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit ## Summary Two related fixes to `ck_tile` FMHA so that StreamLLM-sink + sliding-window batch-prefill works correctly for fp8 KV / bf16 compute. Review the commits in this order: 1. `fmha: emit sink kernels for fp8bf16 batch_prefill` Extends `example/ck_tile/01_fmha/codegen/ops/fmha_batch_prefill.py` so the fp8(KV) / bf16(QO) batch-prefill codegen also emits the `mask=mask_enum::generic_with_sink` variant. Without this the runtime could not dispatch to a sink-aware kernel for the fp8bf16 path. 2. `fmha: respect right-window in IsOutOfSinkBound` The sink un-mask in `GenericAttentionMask::IsOutOfSinkBound` (local-mask branch) used `(i_y + x) > 1` as the gate, which conditioned on the row index instead of the column index. As a result, queries `1..sink-1` could attend to *future* sink positions (violating causal / right-window), while query `0` fell back to the plain causal mask. The fix replaces the guard with `i_x < i_y + x` so every query only sees sink columns up to its own right-window boundary. 3. `fmha: clarify IsOutOfSinkBound predicate comment` Doc-only follow-up that rewrites the comment above the predicate as a clause-by-clause explanation (`i_x < sink`, `i_x < i_y + x`, `y < y_total`, `i_y < x_total`). ## Test plan - [x] Repro on aiter `op_tests/test_batch_prefill.py` (fp8 + bf16_dequant modes with `sink=4`, `win_left=1023`, `softcap=0.0`, `sal=True`) now passes for all parametrized shapes. - [x] Existing fp16/bf16 batch-prefill paths (no sink) unchanged — codegen diff only adds the `generic_with_sink` variant for fp8bf16; existing kernel object lists unaffected. ## 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.