Incorrect semantic labels for stage inputs and outputs

[ds5678]

Summary

Semantic labels for stage inputs and outputs appear to be incorrect. For example, a POSITION input was incorrectly labeled as TEXCOORD0.

Erroneous Output

cbuffer _25_27 : register(b0)
{
    float4 _27_m0[4] : packoffset(c0);
    float4 _27_m1[4] : packoffset(c4);
    float4 _27_m2 : packoffset(c8);
};


static float4 gl_Position;
static float4 _9;
static float2 vs_TEXCOORD0;
static float3 _18;
static float3 _41;

struct SPIRV_Cross_Input
{
    float3 _41 : TEXCOORD0;
    float3 _18 : TEXCOORD1;
};

struct SPIRV_Cross_Output
{
    float2 vs_TEXCOORD0 : TEXCOORD0;
    float4 _9 : TEXCOORD1;
    float4 gl_Position : SV_Position;
};

static float4 _40;
static float4 _68;

void vert_main()
{
    _9 = float4(0.0f, 0.0f, 0.0f, 1.0f);
    vs_TEXCOORD0 = (_18.xy * _27_m2.xy) + _27_m2.zw;
    _40 = _41.yyyy * _27_m0[1];
    _40 = (_27_m0[0] * _41.xxxx) + _40;
    _40 = (_27_m0[2] * _41.zzzz) + _40;
    _40 += _27_m0[3];
    _68 = _40.yyyy * _27_m1[1];
    _68 = (_27_m1[0] * _40.xxxx) + _68;
    _68 = (_27_m1[2] * _40.zzzz) + _68;
    gl_Position = (_27_m1[3] * _40.wwww) + _68;
    gl_Position.y = -gl_Position.y;
}

SPIRV_Cross_Output main(SPIRV_Cross_Input stage_input)
{
    _18 = stage_input._18;
    _41 = stage_input._41;
    vert_main();
    SPIRV_Cross_Output stage_output;
    stage_output.gl_Position = gl_Position;
    stage_output._9 = _9;
    stage_output.vs_TEXCOORD0 = vs_TEXCOORD0;
    return stage_output;
}

Expected Output

cbuffer _25_27 : register(b0)
{
    float4 _27_m0[4] : packoffset(c0); // object to world matrix
    float4 _27_m1[4] : packoffset(c4); // view projection matrix
    float4 _27_m2 : packoffset(c8); // _MainTex_ST
};


static float4 gl_Position;
static float4 _9;
static float2 vs_TEXCOORD0;
static float3 _18;
static float3 _41;

struct SPIRV_Cross_Input
{
    float3 _41 : POSITION; // Not TEXCOORD0
    float3 _18 : TEXCOORD0; // Not TEXCOORD1
};

struct SPIRV_Cross_Output
{
    float2 vs_TEXCOORD0 : TEXCOORD0;
    float4 _9 : COLOR0; // Not TEXCOORD1
    float4 gl_Position : SV_Position;
};

static float4 _40;
static float4 _68;

void vert_main()
{
    _9 = float4(0.0f, 0.0f, 0.0f, 1.0f);
    vs_TEXCOORD0 = (_18.xy * _27_m2.xy) + _27_m2.zw;
    _40 = _41.yyyy * _27_m0[1];
    _40 = (_27_m0[0] * _41.xxxx) + _40;
    _40 = (_27_m0[2] * _41.zzzz) + _40;
    _40 += _27_m0[3];
    _68 = _40.yyyy * _27_m1[1];
    _68 = (_27_m1[0] * _40.xxxx) + _68;
    _68 = (_27_m1[2] * _40.zzzz) + _68;
    gl_Position = (_27_m1[3] * _40.wwww) + _68;
    gl_Position.y = -gl_Position.y;
}

SPIRV_Cross_Output main(SPIRV_Cross_Input stage_input)
{
    _18 = stage_input._18;
    _41 = stage_input._41;
    vert_main();
    SPIRV_Cross_Output stage_output;
    stage_output.gl_Position = gl_Position;
    stage_output._9 = _9;
    stage_output.vs_TEXCOORD0 = vs_TEXCOORD0;
    return stage_output;
}

Reproduction

With the current latest commit (cb71abe):

./spirv-cross.exe Blob_1_Data_0_Snippet_0.spv --hlsl --shader-model 40

Blob_1_Data_0_Snippet_0.zip

Additional Context

I'm investigating the issue and am willing to submit a pull request. However, I'm brand new to working in this codebase and would appreciate any and all guidance.

Related

• [Discussion] HLSL vertex shader input semantics from attribute names #163
• HLSL Vertex Attribute remap #320
• Add support for new HLSL semantic/counter buffer decorations. #509
• Getting the HLSL Semantic Name using the Reflection API #1687
• How to Relection Hlsl semantic name #1713
• HLSL: Add option to bind vertex input smemantics by name. #2045
• Cannot get hlsl stage input semantic string #2202

After reading these, I feel like my issue might be caused by a lack of information in the Spir-V file about semantics. With some additional investigation, I discovered HLSLVertexAttributeRemap and CompilerHLSL::add_vertex_attribute_remap, which allows setting semantics for inputs. I have some questions:

• CompilerHLSL::add_vertex_attribute_remap lets me set the semantics for stage inputs. Is there any way to set stage outputs?
• Setting the UserSemantic or HlslSemanticGoogle seems to do nothing. Should they affect the program output?

[HansKristian-Work]

Using TEXCOORD for stage IO (except vertex input, which has attribute_remap) is working as intended since SPIR-V matches by location, not semantic. Maybe it's possible to add an option to try and respect UserSemantic instead, but IIRC that's not implemented right now.

[ds5678]

Maybe it's possible to add an option to try and respect UserSemantic instead, but IIRC that's not implemented right now.

If I made a pull request, is that something you would be receptive to? Is there anything I should keep in mind when making the pr?

[HansKristian-Work]

I don't mind making it an option. It should just be if option and has_decoration(Semantic), use that, otherwise use TEXCOORD#locn.