onnxruntime

1053327e - [WebGPU] LinearAttention: increase tile_v when subgroups are available (#28519)

[WebGPU] LinearAttention: increase tile_v when subgroups are available (#28519) ### Description - Scale tile_v by 4x when subgroup is enabled and the vectorized dimension has enough columns, improving data reuse. - Gate the tile_v expansion on seq_length >= 16, where the prefill benefit outweighs increased register pressure. - Remove redundant zero-initialization of the state tile (WGSL default- initializes vars to zero). **Intel Panther Lake (xe-3lpg)** | Model | Prefill | Baseline (TPS) | Optimized (TPS) | Change | | :----------- | ------: | -------------: | --------------: | -----: | | Qwen3.5-0.8B | 128 | 1534.30 | 1681.00 | 9.56% | | Qwen3.5-0.8B | 1024 | 3267.30 | 3917.60 | 19.90% | | Qwen3.5-0.8B | 4096 | 2864.50 | 3563.40 | 24.40% | | Qwen3.5-2B | 128 | 1295.60 | 1344.60 | 3.78% | | Qwen3.5-2B | 1024 | 2177.10 | 2344.00 | 7.67% | | Qwen3.5-2B | 4096 | 1942.60 | 2247.00 | 15.67% | | Qwen3.5-4B | 128 | 701.30 | 736.20 | 4.98% | | Qwen3.5-4B | 1024 | 946.90 | 1036.30 | 9.44% | | Qwen3.5-4B | 4096 | 824.10 | 912.00 | 10.67% | ### Motivation and Context See above.