Fix WebGPU EP crash on exit

[fs-eire]

Description

Fixes crash on exit in some scenario.

• When onnxruntime::webgpu::WebGpuContextFactory::Cleanup() is called:

  • This is when:

    • OrtEnv::~OrtEnv() is called (for embedded WebGPU EP), or
    • ReleaseEpFactory() is called (for WebGPU plugin EP)

  • This will cause:

    • destructor of onnxruntime::webgpu::WebGpuContextFactory will be called, so that:
      • default WGPU instance will be released
      • each of the active instance of WebGpuContext will be destructed
    • the destruction may call into TLS of DXC threads, hosted in dxcompiler.dll
    • dxcompiler.dll may be unloaded already (if it's called from _at_exit)

  • Solution

    • explicitly load the dxc DLLs and keep a reference to them
    • explicit implementation of destructor of onnxruntime::webgpu::WebGpuContextFactory to ensure resources release in the expected order

• When onnxruntime::webgpu::WebGpuContextFactory::Cleanup() is NOT called:

  • This is when the process is being killed
  • This will cause:
    • unexpected order of DLL unload
  • Solution
    • intentionally leak static members in onnxruntime::webgpu::WebGpuContextFactory

[Copilot]

Pull request overview

This PR fixes a crash-on-exit issue in the WebGPU execution provider caused by DLL unload ordering. When WebGpuContextFactory::Cleanup() runs, dependent DLLs like dxcompiler.dll may have already been unloaded, leading to crashes during resource destruction.

Changes:

• Explicitly loads and holds references to dxil.dll and dxcompiler.dll to prevent premature unloading.
• Changes default_instance_ from wgpu::Instance (C++ RAII wrapper) to raw WGPUInstance for explicit lifetime control.
• Reorders cleanup in WebGpuContextFactory::Cleanup() to ensure resources are released before DLL handles.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
onnxruntime/core/providers/webgpu/webgpu_context.h	Reorders static members, changes default_instance_ to raw WGPUInstance, adds modules_ and modules_dxc_loaded_ fields.
onnxruntime/core/providers/webgpu/webgpu_context.cc	Moves context map allocation inside instance creation block, adds DXC DLL loading logic, implements explicit cleanup with correct ordering.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

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