Add Intel WebGPU subgroup-matrix MatMul implementation

[jchen10]

• Add an Intel-specific F16 MatMul path built on the 8x16x16 subgroup-matrix config (Xe2/Xe3). A and B are loaded directly from global memory with no prepacking, and results are written through workgroup scratch with bounds-checked stores, so M and N may be any size while only K must be a multiple of 16. The impl is created in MatMul::PrePackInternal and dispatched from Compute when the device reports the required config.
• The tile shape and split-K factor are chosen per call rather than fixed: TileM in {8,16,32,64}, TileN in {16,32,64}, and split-K to top up occupancy, sized to the device's resident subgroups. The WGSL kernel is parameterized by sg_mat_count_m/n and split_k, emitting the needed subgroup-matrix accumulators via generation-time guards.
• An optional offline-tuned config table (generated from an autotuner sweep) can override the heuristic; selection precedence is tuned table > heuristic.
• Adds MatMul subgroup-matrix unit tests covering tile selections and partial/large non-aligned dims.

[jchen10]

@qjia7 PTAL

[jchen10]

Done!

[Copilot]

Pull request overview

This PR adds an Intel-specific WebGPU MatMul fast-path that uses the Chromium experimental subgroup-matrix feature (8x16x16 F16 config) for Xe2/Xe3 GPUs, with adaptive tile/split-K selection and optional baked-in tuned configs.

Changes:

• Introduces an Intel subgroup-matrix MatMul implementation (WGSL template + C++ dispatch/config selection) and wires it into WebGPU MatMul via a vendor opt-impl hook.
• Adds Intel device-info helpers for architecture-based occupancy heuristics and subgroup-matrix capability detection.
• Adds new MatMul tests intended to exercise the subgroup-matrix path across representative tile/split-K/edge cases.

Reviewed changes

Copilot reviewed 4 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
onnxruntime/test/providers/cpu/math/matmul_test.cc	Adds a new fp16 MatMul test suite aimed at covering subgroup-matrix tile/split-K behavior.
onnxruntime/core/providers/webgpu/vendor/intel/math/subgroup_matrix_matmul.wgsl.template	Adds the parameterized WGSL subgroup-matrix MatMul kernel template with optional split-K reduction.
onnxruntime/core/providers/webgpu/vendor/intel/math/subgroup_matrix_matmul.h	Declares the Intel subgroup-matrix MatMul program/impl factory and related constants.
onnxruntime/core/providers/webgpu/vendor/intel/math/subgroup_matrix_matmul.cc	Implements config selection (tuned table + heuristic) and the WebGPU dispatch path for subgroup-matrix MatMul.
onnxruntime/core/providers/webgpu/vendor/intel/intel_device_info.h	Declares Intel adapter helpers for subgroup occupancy estimation and subgroup-matrix config support checks.
onnxruntime/core/providers/webgpu/vendor/intel/intel_device_info.cc	Implements Intel architecture-to-occupancy mapping and config enumeration checks.
onnxruntime/core/providers/webgpu/math/matmul.h	Adds a MatMul optimized-implementation abstraction and cached implementation pointer.
onnxruntime/core/providers/webgpu/math/matmul.cc	Dispatches to the vendor optimized impl when present and instantiates it during PrePackInternal.
onnxruntime/contrib_ops/webgpu/quantization/subgroup_matrix_matmul_nbits.cc	Refactors Intel occupancy logic to use the new HwSubgroups helper.