microsoft / microsoft/DirectXShaderCompiler

[SPIRV] Invalid OpCompositeConstruct when aggregate-initializing struct with resource member

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spirv
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C++
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Description

When compiling HLSL that uses brace initialization to construct a struct containing a resource member, DXC's SPIRV backend generates invalid SPIR-V:

fatal error: generated SPIR-V is invalid: Expected Constituent type to be equal to the corresponding member type of Result Type struct %15 = OpCompositeConstruct %ResHolder_0 %Out

Repro:

RWByteAddressBuffer Out : register(u0);

struct ResHolder { RWByteAddressBuffer buf; };

[numthreads(1,1,1)] 
void main() {  
ResHolder h = {Out};
  h.buf.Store(0, 42); 
}

Command:

dxc.exe -spirv -fspv-target-env=vulkan1.3 -T cs_6_0 -Fo out.spv repro.hlsl

DXC DXIL compiles and runs this correctly. DXC version: main (built from source).

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First steps

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by building DXC from source and running the provided HLSL repro with the shown -spirv command. Inspect the SPIR-V generation and validation for aggregate initialization of a struct containing RWByteAddressBuffer. Done means the repro produces valid SPIR-V without the constituent-type error and preserves the resource member behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
48/100

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