Description
When compiling any Domain/TessellationEvaluation shader, the %gl_TessCoord variable that's generated from the SV_DomainLocation semantic is decorated with the Patch decoration. According to the SPIR-V spec this is invalid.

This causes Vulkan graphics pipeline creation to fail for some pipelines with complex tessellation shaders on current NVIDIA drivers after updating from Vulkan SDK 1.3.296.0 to 1.4.304.1, since the generated SPIR-V code changed in some other way:

(Left is the result of the generated code from the new SDK, right it old. Please ignore the SPIR-V ids since those are the result of manual patching).

The issue is still there in commit 0a1143572d107c8b6980df092b84a79190ec1fbd of the main branch from Feb 28 2025`.

I suppose the check in DeclResultIdMapper.cpp line 3519 may not be sufficient, though I don't have enough knowlege to come up with a fix myself that I'd feel comfortable with:

 // TODO: the following may not be correct? if (stageVarData.sigPoint->GetSignatureKind() == hlsl::DXIL::SignatureKind::PatchConstOrPrim) { if (stageVarData.sigPoint->GetKind() == hlsl::SigPoint::Kind::MSPOut) { // Decorate with PerPrimitiveNV for per-primitive out variables. spvBuilder.decoratePerPrimitiveNV(varInstr, varInstr->getSourceLocation()); } else { spvBuilder.decoratePatch(varInstr, varInstr->getSourceLocation()); } } 

Steps to Reproduce
Compile the attached HLSL file (please replace the extension) with the following dxc command line:

-nologo -spirv -E tes_main -Fc test.s -Fo test.spv -HV 202x -Wconversion -Wdouble-promotion -T ds_6_2 -Wx -fspv-target-env="vulkan1.1" test.hlsl 

or have a look at godbolt: https://godbolt.org/z/TqTnK7GYj

Actual Behavior
%gl_TessCoord has the Patch decoration, which is not valid SPIR-V.

OpDecorate %gl_TessCoord Patch 

Environment

• DXC version: dxcompiler.dll: 1.8 - 1.8.0.4775 (d39324e06) and commit 0a1143572d107c8b6980df092b84a79190ec1fbd compiled from source
• Host Operating System: Windows 10