Sklottie will report an error under Dawn's backend

[guodong chen]

Skia uses the Dawn backend on the Apple system. Using the Skottie module will cause the Dawn backend to report errors. But not all Lottie files result in.

I created about 5000 Lotties from the attached files,Then draw in a frame, will occasionally appear Dawn error

I Use skottie::Animation::MakeFromFile(file) this API.

It seems that attachment cannot be added here, and I also reported the problem：

https://bugs.chromium.org/p/skia/issues/detail?id=13780

GrDawnGpu: ERROR type 1, msg: Tint SPIR-V reader failure:
Parser: error: 'textureSample' must only be called from uniform control flow
note: control flow depends on non-uniform value
note: reading from module-scope private variable 'vTexIndex_S0' may result in a non-uniform value

- While validating [ShaderModuleDescriptor]
- While calling [Device].CreateShaderModule([ShaderModuleDescriptor]).
GrDawnGpu: ERROR type 1, msg: [Invalid ShaderModule] is invalid.
- While validating fragment stage (module: [Invalid ShaderModule], entryPoint: main).
- While validating fragment state.
- While calling [Device].CreateRenderPipeline([RenderPipelineDescriptor]).
GrDawnGpu: ERROR type 1, msg: [Invalid RenderPipeline] is invalid.
- While encoding [RenderPassEncoder].SetPipeline([Invalid RenderPipeline]).
GrDawnGpu: ERROR type 1, msg: [Invalid CommandBuffer] is invalid.
at ValidateObject (../../third_party/externals/dawn/src/dawn/native/Device.cpp:651)
at ValidateSubmit (../../third_party/externals/dawn/src/dawn/native/Queue.cpp:393)

[Arman Uguray]

Thank you for reporting the issue. I reproduced it and documented the root cause on the bug. This is likely a recent regression on our end that happened after uniformity analysis was enabled in Dawn.

I'll follow up on the bug tracker once I have a fix. 

[guodong chen]

I also found that the performance was much worse with Dawn than with OpengL or Metal

'Arman Uguray' via skia-discuss <skia-d...@googlegroups.com> 于 2022年10月1日周六 02:25写道：

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