[SPIR-V] Resources declared in cbuffer scope result in validation errors instead of being moved out (works with FXC)

[Dredhog]

Title

[SPIR-V] Resources declared in cbuffer scope result in validation errors instead of being moved out (works with FXC)

Functional impact

Can't declare resources inside of constant buffers which breaks backwards compatibility with FXC. The DXIL backend keeps the resources inside the CBuffer which results in a different cbuffer layout than FXC but as the types aren't opaque they at least don't fail validation so the shaders are usable. The SPIR-V backend results in a validator error about opaque types in the cbuffer.

Minimal repro steps

1. Compile repro_shader.txt (see below) with dxc.exe -T ps_6_0 -E PSMain -spirv repro_shader.txt:

cbuffer NamedCBuffer
{
    float4 testColor;
    Texture2D myTexture;
    SamplerState mySampler;
}

float4 PSMain(float2 uv : TEXCOORD) : SV_TARGET
{
	return testColor + myTexture.Sample(mySampler, uv);
}

2. Observe the output errors:

fatal error: generated SPIR-V is invalid: In Vulkan, OpTypeStruct must not contain an opaque type.
  %type_NamedCBuffer = OpTypeStruct %v4float %type_2d_image %type_sampler

note: please file a bug report on https://github.com/Microsoft/DirectXShaderCompiler/issues with source code if possible

Expected result

No validator error is printed. This could be achieved by moving the resources out of the cbuffer scope to be be declared in the global scope.

Actual result

Compiler prints the validation error seen in step 2. of the Minimlar repro steps section

Further technical details

Test output copied from shader playground (link here).

Slightly related to #2695, where resources in structs used to be placed in the global cbuffer, which was fixed.

[jaebaek]

Thank you for reporting this issue. I will take a look.