[SPIR-V] Allow zero outputcontrolpoints #6190
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It is valid HLSL for a Hull shader to have zero outputcontrolpoints or have the outputcontrolpoints attribute unset, based on the tests added here passing when compiling for DXIL. This change removes the checks in the SPIR-V backend that required a strictly positive number of control points and adds tests to verify the result. Fixes microsoft#3733
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This is awkward. Vulkan does not allow a zero for the number of output vertices. See https://docs.vulkan.org/spec/latest/chapters/pipelines.html#VUID-VkPipelineShaderStageCreateInfo-stage-00713. I can't tell of the code generated when there is no output vertices is correct. GLSL does not generate anything https://shader-playground.timjones.io/7f6252b21a9b099056aaccd511ec7046. |
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Hm... upon closer review of the D3D documentation for Hull shaders it seems like it also shouldn't be allowed there: "The shader output is between 1 and 32 control points". I'll look into whether disallowing it on the frontend is a reasonable option. |
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It is valid HLSL for a Hull shader to have zero outputcontrolpoints or have the outputcontrolpoints attribute unset, based on the tests added here passing when compiling for DXIL. This change removes the checks in the SPIR-V backend that required a strictly positive number of control points and adds tests to verify the result.
Fixes #3733