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Fix FlashAttentionDecodeSplitVx indirect dispatch input ordering #27926

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Merged
guschmue merged 1 commit into from
Apr 15, 2026
Merged

Fix FlashAttentionDecodeSplitVx indirect dispatch input ordering #27926

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12 changes: 8 additions & 4 deletions onnxruntime/contrib_ops/webgpu/bert/flash_attention.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -344,14 +344,18 @@ Status ComputeFlashAttentionDecodeSplitVxScore(onnxruntime::webgpu::ComputeConte
program.AddOutputs({{out_split_vx, ProgramTensorMetadataDependency::TypeAndRank, components}}); // [B, N, split_k, head_size]
const uint32_t batch_heads = static_cast<uint32_t>(parameters.batch_size_ * parameters.num_heads_);
if (use_indirect_dispatch) {
program.AddInput({seqlen_k, ProgramTensorMetadataDependency::None})
.SetIndirectDispatchTensor(indirect_buffer);
} else {
program.SetDispatchGroupSize(batch_heads * num_total_seq_length_tile);
program.AddInput({seqlen_k, ProgramTensorMetadataDependency::None});
}
if (has_head_sink) {
program.AddInput({head_sink, ProgramTensorMetadataDependency::Type});
}
// SetIndirectDispatchTensor must be called after all AddInput calls because it
// appends the indirect buffer as the last program input.
if (use_indirect_dispatch) {
program.SetIndirectDispatchTensor(indirect_buffer);
} else {
program.SetDispatchGroupSize(batch_heads * num_total_seq_length_tile);
}
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program.CacheHint(tile_size, head_size_vec, use_indirect_dispatch, has_head_sink)
.SetWorkgroupSize(64)
.AddUniformVariables({{static_cast<uint32_t>(parameters.total_sequence_length_)},
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