[SPIR-V] Potential regression reports VUID-StandaloneSpirv-OpTypeImage-06924

[artem-lunarg]

Here's a shader that works with DXC 1.8.2407 but ToT generates VUID-StandaloneSpirv-OpTypeImage-06924 (select DXC (trunk) in godbolt to get error message):
https://godbolt.org/z/Ph4WofKbT

fatal error: generated SPIR-V is invalid: [VUID-StandaloneSpirv-OpTypeImage-06924] Cannot store to OpTypeImage, OpTypeSampler, OpTypeSampledImage, or OpTypeAccelerationStructureKHR objects
OpStore %144 %269

The shader does not write to any of the resources mentioned in the error message. It samples image (READ) and traces ray against acceleration structure.

I found this issue by testing Vulkan SDK. DXC included in the Vulkan SDK 1.3.296 does not have this issue. But the ongoing SDK version is going to use the build based on this commit d39324e, and it generates the error.

[s-perron]

I'll look into this right now. I don't know how easy it will be to fix. I don't know if we should think of this as a regression or not.

The change that caused the "problem" is when we upgraded the submodule to include KhronosGroup/SPIRV-Tools#5368. Before we were silently generating invalid spir-v. From my perspective, this is not a regression, but something that should be fixed.

I'll try to look into why we are generating a store of a resource handle. In general, we generate lots of them, and expect optimizations to be able to remove them. No guarantees we will be able to remove them in this case. I have not yet looked at the details of the shader.

[s-perron]

This will be fixed the next time spirv-tools is updated.

[artem-lunarg]

Thank you!