Potential bug in parameter block root index (Vulkan)

[philcn]

I'm running into an issue where the rootIndex array of named parameter block seems incorrect. An simplified case is:

// MyShader.slang
cbuffer ... // Forms the default block
ParameterBlock<MaterialData> gMaterial; // From Falcor
struct MyData1 {
    StructuredBuffer<...> buffer;
};
struct MyData2 {
    StructuredBuffer<...> buffer;
};
ParameterBlock<MyData1> gMyBlock1;
ParameterBlock<MyData2> gMyBlock2;

and when I query the root index of my parameter block by

uint32_t rootIndex1 = vars->getParameterBlockRootIndices(vars->getReflection()->getParameterBlockIndex("gMyBlock1"))[0];
uint32_t rootIndex2 = vars->getParameterBlockRootIndices(vars->getReflection()->getParameterBlockIndex("gMyBlock2"))[0];

They're both 2. The consequence is that my gMyBlock2 will not have its structured buffer bound; RenderDoc shows the set index for it is 3.

I poked around and noticed in Vulkan, compareRootSets() will think my gMyBlock1 and gMyBlock2 are the same. That's probably why they're getting the same root index 2.

If I remove the #ifdef FALCOR_D3D12, the result is correct in this case.

This bug prevents me from using multiple similar parameter blocks. Can you please take a look at it? Let me know if you need more context to reproduce it.

Thanks!