[WebGPU] Refactor MatMul algorithm selection

[Jiajia Qin (qjia7)]

Description

• Introduce explicit WebGPU MatMul algorithm enums for subgroup matrix, naive, Intel subgroup, packed, and packed Split-K implementations.
• Add a common rule-based scheduler plus Intel-specific vendor scheduling while preserving the existing selection order.
• Add the test-only ep.webgpuexecutionprovider.forceMatmulAlgorithm session option and hard-prerequisite validation.
• Dispatch ComputeMatMul directly from the selected enum and add unit/integration coverage for every algorithm.
• Support Vulkan-only Dawn builds on Windows without built DXC/HLSL generation and load Vulkan through the system component path.

Motivation and Context

MatMul currently chooses among several implementations through distributed conditionals. This makes each implementation difficult to test directly and makes vendor-specific selection rules difficult to maintain. Centralizing selection in an explicit scheduler makes the policy testable and allows vendor schedulers to extend the common rules.

Validation:

• Vulkan-only onnxruntime_provider_test build with D3D12 disabled
• MatMul scheduler and forced-algorithm tests: 16/16 passed
• Existing MatMul regression tests: 4/4 passed
• Forced FP16 subgroup-matrix execution passed on Intel Arc 140V with Vulkan cooperative-matrix support

[Copilot]

🟡 Changes recommended

Intel eligibility misses a shape constraint, and hardware-specific tests do not skip unsupported adapters.

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Pull request overview

Centralizes WebGPU MatMul algorithm selection and enables explicit path testing.

Changes:

• Adds enum-based common and Intel-specific scheduling.
• Adds forced-algorithm configuration and coverage.
• Supports Vulkan-only Dawn builds on Windows.

File summaries

File	Description
onnxruntime/test/providers/webgpu/matmul_large_test.cc	Adds forced-path integration tests.
onnxruntime/test/providers/webgpu/matmul_algorithm_scheduler_test.cc	Tests parsing, scheduling, and prerequisites.
onnxruntime/core/providers/webgpu/webgpu_provider_options.h	Declares the forcing option.
onnxruntime/core/providers/webgpu/webgpu_provider_factory.cc	Parses and validates the option.
onnxruntime/core/providers/webgpu/webgpu_execution_provider.h	Stores forced selection state.
onnxruntime/core/providers/webgpu/webgpu_execution_provider.cc	Initializes forced selection state.
onnxruntime/core/providers/webgpu/vendor/intel/math/matmul.h	Exposes Intel capability detection.
onnxruntime/core/providers/webgpu/vendor/intel/math/matmul.cc	Separates capability from heuristics.
onnxruntime/core/providers/webgpu/vendor/intel/math/matmul_algorithm_scheduler.h	Implements Intel scheduling policy.
onnxruntime/core/providers/webgpu/math/subgroup_matrix_matmul.cc	Separates applicability from execution.
onnxruntime/core/providers/webgpu/math/matmul.h	Extends implementation and scheduler caches.
onnxruntime/core/providers/webgpu/math/matmul.cc	Implements scheduling and direct dispatch.
onnxruntime/core/providers/webgpu/math/matmul_algorithm.h	Defines algorithm identities and conversion.
onnxruntime/core/providers/webgpu/math/matmul_algorithm_scheduler.h	Defines common scheduling and prerequisites.
onnxruntime/core/providers/webgpu/compute_context.h	Exposes forced selection to kernels.
docs/superpowers/specs/2026-09-16-webgpu-matmul-algorithm-scheduler-design.md	Documents the design.
docs/superpowers/plans/2026-09-16-webgpu-matmul-algorithm-scheduler.md	Records the implementation plan.
cmake/external/onnxruntime_external_deps.cmake	Configures Vulkan-only Windows Dawn builds.

Review details

• Files reviewed: 15/18 changed files
• Comments generated: 1
• Review effort level: Balanced (auto)

Note

Copilot is running an experiment and ran this review at Balanced.

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[Copilot]

🟡 Changes recommended

Forced Intel dispatch can accept small shapes that violate the subgroup kernel’s vec4-load invariant.

Get a fresh assessment by requesting another Copilot review.

Review details

• Files reviewed: 15/18 changed files
• Comments generated: 2
• Review effort level: Balanced (auto)

Note

Copilot is running an experiment and ran this review at Balanced.