[WebGPU] QKV and MLP fusions for Qwen3

[hariharans29]

Description

Summary

Adds two WebGPU-only graph fusions and the contrib ops they target, plus a small
refactor of the existing MatMulNBits dispatch logic so the new fused kernels
can share its predicates.

Component	Files	Purpose
MatMulNBitsMlp op + kernel	contrib_ops/webgpu/quantization/matmul_nbits_mlp.{cc,h}, *.wgsl.template (3)	Fuses the SwiGLU MLP block: optional (Skip)SimplifiedLayerNormalization + two MatMulNBits projections (gate, up) + optional biases + Sigmoid/Mul (SiLU) + element-wise Mul. Single dispatch instead of 5–7.
MatMulNBitsQkv op + kernel	contrib_ops/webgpu/quantization/matmul_nbits_qkv.{cc,h}, *.wgsl.template	Fuses (Skip)SimplifiedLayerNormalization + three MatMulNBits projections (Q, K, V) sharing the same input. Single dispatch instead of 4.
Op schemas	core/graph/contrib_ops/contrib_defs.cc	MatMulNBitsMlp and MatMulNBitsQkv contrib op schemas (kMSDomain, opset 1).
Graph transformers	core/optimizer/matmul_nbits_{mlp,qkv}_fusion.{cc,h}	Pattern-match the source subgraphs and emit the fused ops. EP-gated to WebGPU only — no impact on other EPs. Registered in graph_transformer_utils.cc.
Dispatch helpers	contrib_ops/webgpu/quantization/matmul_nbits_common.{cc,h} + matmul_nbits.cc	Extracts the "would this dispatch use Subgroup-Matrix / DP4A / WideTile?" predicates into pure functions reusable by the fused kernels. No behavior change in the unfused MatMulNBits path.
Tests	test/optimizer/matmul_nbits_{mlp,qkv}_fusion_test.cc, graph_transform_utils_test.cc	Unit tests for the new transformers (positive + negative cases).

Motivation and Context

~25-30% decode TPS throughput improvement on WebGPU + D3D backend on Windows. GPU used: RTX 5060Ti for Qwe3-1.7B.

BEFORE (95 decode TPS): main branch

AFTER (120+ decode TPS): PR branch

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Pull request overview

This PR adds WebGPU-focused fused operators and optimizer passes for decoder-style MatMulNBits patterns (MLP gate/up and QKV projections), along with tests and a microbenchmark to evaluate decode performance/correctness.

Changes:

• Introduces new contrib ops MatMulNBitsMlp and MatMulNBitsQkv (schemas + WebGPU kernels + WGSL templates).
• Adds graph transformers MatMulNBitsMlpFusion / MatMulNBitsQkvFusion and corresponding optimizer tests.
• Improves WebGPU runtime support (graph-capture buffer manager activation, queue-idle wait helper, better shader compilation diagnostics) and adds a decode microbenchmark.

Reviewed changes

Copilot reviewed 33 out of 33 changed files in this pull request and generated 4 comments.

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File	Description
onnxruntime/test/optimizer/matmul_nbits_qkv_fusion_test.cc	New unit tests validating QKV fusion and output contracts on WebGPU.
onnxruntime/test/optimizer/matmul_nbits_mlp_fusion_test.cc	New unit tests validating MLP fusion (simplified/skip + passthrough) on WebGPU.
onnxruntime/test/optimizer/graph_transform_utils_test.cc	Minor formatting-only tweak (blank line).
onnxruntime/test/onnx/microbenchmark/webgpu_matmul_nbits_decode.cc	New benchmark harness for fused/unfused decode paths on WebGPU.
onnxruntime/test/onnx/microbenchmark/main.cc	Adjusts benchmark env logging severity.
onnxruntime/core/session/ort_version_check.h	Makes version parsing consteval-friendly with a macro fallback.
onnxruntime/core/providers/webgpu/webgpu_execution_provider.h	Tracks when graph-capture buffer manager is active.
onnxruntime/core/providers/webgpu/webgpu_execution_provider.cc	Lazily creates/activates graph buffer manager for capture; allocator uses dynamic buffer manager getter.
onnxruntime/core/providers/webgpu/webgpu_context.h	Adds WaitForQueueIdle() declaration.
onnxruntime/core/providers/webgpu/webgpu_context.cc	Implements WaitForQueueIdle() using OnSubmittedWorkDone.
onnxruntime/core/providers/webgpu/program_manager.cc	Enhances pipeline build failures with shader compilation diagnostics.
onnxruntime/core/providers/webgpu/compute_context.h	Adds FlushAndWait() convenience for flushing + waiting on queue idle.
onnxruntime/core/providers/webgpu/allocator.h	Adds allocator ctor that accepts a buffer-manager getter function.
onnxruntime/core/providers/webgpu/allocator.cc	Implements getter-based allocator to support switching buffer managers.
onnxruntime/core/optimizer/matmul_nbits_qkv_fusion.h	New transformer declaration for QKV fusion.
onnxruntime/core/optimizer/matmul_nbits_qkv_fusion.cc	New transformer implementation for QKV fusion.
onnxruntime/core/optimizer/matmul_nbits_mlp_fusion.h	New transformer declaration for MLP fusion.
onnxruntime/core/optimizer/matmul_nbits_mlp_fusion.cc	New transformer implementation for MLP fusion.
onnxruntime/core/optimizer/graph_transformer_utils.cc	Registers the new fusion transformers.
onnxruntime/core/graph/contrib_ops/contrib_defs.cc	Adds contrib operator schemas/docs for MatMulNBitsMlp and MatMulNBitsQkv.
onnxruntime/contrib_ops/webgpu/webgpu_contrib_kernels.cc	Registers WebGPU kernels for the new fused ops.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_qkv.wgsl.template	New WGSL template implementing fused QKV decode kernel.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_qkv.h	New WebGPU kernel wrapper for MatMulNBitsQkv.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_qkv.cc	New WebGPU kernel implementation for MatMulNBitsQkv.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_mlp_wide_tile_m1.wgsl.template	New WGSL template for an MLP wide-tile variant.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_mlp.wgsl.template	New WGSL template implementing fused MLP (optionally with norm/skip/passthrough).
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_mlp.h	New WebGPU kernel wrapper for MatMulNBitsMlp.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_mlp.cc	New WebGPU kernel implementation for MatMulNBitsMlp.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_common.h	Adds declarations for “would apply” dispatch-selection helpers and shared constants.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits_common.cc	Implements the new dispatch-selection helpers.
onnxruntime/contrib_ops/webgpu/quantization/matmul_nbits.cc	Refactors path selection to use the new “would apply” helpers.
onnxruntime/contrib_ops/webgpu/quantization/dp4a_matmul_mlp.wgsl.template	Adds WGSL template for DP4A MLP path.
cmake/onnxruntime_unittests.cmake	Wires the new WebGPU decode benchmark into the benchmark target sources.

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Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated 5 comments.

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