Reflection gets confused by DXC's debug outputs

[Jakub Okoński]

Hi, I saw your announcement on /r/rust_gamedev and tried out your library to replace spirv_reflect. I love the API and Debug instances, the types in spirq::ty are also idiomatic to work with!

I have a problem where enabling -Zi and/or -fspv-reflect affects the reflection (negatively in both cases). I don't need these for now so I'm good, but it would be a good idea to look into why these annotations break things. From what I could gather, -fspv-reflect only added a couple OpDecorateString entries which caused spirq to not see any inputs for that entrypoint.

I'm attaching my shader, dxc compile options and Debug output from spirq:

struct PushConstants {
  float2 scale;
  float2 translate;
};

[[vk::push_constant]] PushConstants pushConstants;

float4 main(in float2 pos : POSITION,
            in float2 uv : TEXCOORD,
            in float4 col : COLOR,
            out float4 outColor : COLOR,
            out float2 outUv : TEXCOORD): SV_POSITION {
  outColor = col;
  outUv = uv;
  float4 outPos = float4(pos * pushConstants.scale + pushConstants.translate, 0, 1);
  outPos.y *= -1.0;
  return outPos;
}

$ dxc -spirv -T vs_6_0 -E main -fspv-target-env=vulkan1.1 -Fo whatever.spv

Debug output:

    main {
        push_const: Some(
            { scale: vec2<f32>, translate: vec2<f32> },
        ),
        inputs: {
            (loc=0, comp=0): vec2<f32>,
            (loc=1, comp=0): vec2<f32>,
            (loc=2, comp=0): vec4<f32>,
        },
        outputs: {
            (loc=0, comp=0): vec4<f32>,
            (loc=1, comp=0): vec2<f32>,
        },
        descriptors: {},
        spec_consts: {},
    },

Perfect!

Now adding -fspv-reflect as an option to dxc, SPIR-V diff is now:

diff --git a/a.spv b/b.spv
index a3e8063..f22924c 100644
--- a/bare.spv
+++ b/test.spv
@@ -4,6 +4,7 @@
 ; Bound: 42
 ; Schema: 0
                OpCapability Shader
+               OpExtension "SPV_GOOGLE_hlsl_functionality1"
                OpMemoryModel Logical GLSL450
                OpEntryPoint Vertex %main "main" %in_var_POSITION %in_var_TEXCOORD %in_var_COLOR %gl_Position %out_var_COLOR %out_var_TEXCOORD
                OpSource HLSL 600
@@ -17,7 +18,13 @@
                OpName %out_var_COLOR "out.var.COLOR"
                OpName %out_var_TEXCOORD "out.var.TEXCOORD"
                OpName %main "main"
+               OpDecorateString %in_var_POSITION UserSemantic "POSITION"
+               OpDecorateString %in_var_TEXCOORD UserSemantic "TEXCOORD"
+               OpDecorateString %in_var_COLOR UserSemantic "COLOR"
                OpDecorate %gl_Position BuiltIn Position
+               OpDecorateString %gl_Position UserSemantic "SV_POSITION"
+               OpDecorateString %out_var_COLOR UserSemantic "COLOR"
+               OpDecorateString %out_var_TEXCOORD UserSemantic "TEXCOORD"
                OpDecorate %in_var_POSITION Location 0
                OpDecorate %in_var_TEXCOORD Location 1
                OpDecorate %in_var_COLOR Location 2

But the output is:

    main {
        push_const: None,
        inputs: {},
        outputs: {},
        descriptors: {},
        spec_consts: {},
    },

It gets similarly confused by the -Zi flag, but not to such a great extent. It would be nice to support these flags as they're seemingly becoming standard for HLSL on Vulkan debugging and other tools.

[PENGUINLIONG]

Glad you like it. :)
It seems spirq is currently not recognizing
OpDecorateStrings. Will fix soon.

[PENGUINLIONG]

Thanks for the reproduction details! They made things easy.