microsoft / microsoft/DirectXShaderCompiler
[HLSL] Misleading error message when using a UAV register for a raytracing acceleration structure
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Since Apr 23, 2024.
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Description
Functional impact
This bug provides a misleading error message when compiling a shader with a semantic error. This causes lots of confusion and doesn't lead the developer toward fixing the error
Minimal repro steps
- Write a shader with the HLSL code:
RaytracingAccelerationStructure opaque_as : register(u0);
Texture2D<float> depth_buffer : register(t0);
- Try to compile the shader
- Observe an error message saying that
depth_bufferandopaque_asoverlap their descriptors
Expected result
I'd expect the error message to say something like "raytracing acceleration structures must use SRV registers instead of UAV registers"
Actual result
The compiler gives an error message Shaders\Shadows\shadow.pixel.dxil.hlsl(17,1): error GDA5BD758: resource depth_buffer at register 0 overlaps with resource opaque_as at register 0, space 0
Further technical details
Brian Favela speculated that the HLSL compiler is assuming that a RT AS is always using a SRV register and ignoring the HLSL code that incorrectly says to use a UAV register
Contributor guide
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Assessment
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