test_shader_io_mismatch seems to use xfb incorrectly

vkd3dopen

HansKristian-Work/vkd3d-proton#1938 · opened 2024-03-12 by hakzsam · updated 2026-09-15 · 6 comments · github

Hhakzsam 2024-03-12 github

d3d12: ======== test_shader_io_mismatch begin ========
d3d12: ../src/compiler/nir/nir_gather_xfb_info.c:104: add_var_xfb_outputs: Assertion `xfb->buffer_to_stream[buffer] == var->data.stream' failed.
Aborted (core dumped)

#version 450
layout(triangles) in;
layout(max_vertices = 3, points) out;

layout(xfb_buffer = 0, xfb_stride = 64, stream = 1) out gl_PerVertex
{
    layout(xfb_offset = 0) vec4 gl_Position;
};

invariant gl_Position;

layout(location = 1) in vec3 ARG[3];
layout(location = 2) in vec2 ARG_1[3];
layout(location = 3) in uvec4 ARG_2[3];
layout(location = 1, xfb_buffer = 0, xfb_stride = 64, xfb_offset = 16) out vec3 ARG_3;
layout(location = 2, xfb_buffer = 0, xfb_stride = 64, xfb_offset = 28) flat out uvec4 ARG_2_1;
layout(location = 4, xfb_buffer = 1, xfb_stride = 64, xfb_offset = 0, stream = 1) out vec2 ARG_1_1;

void main()
{
    uint _44;
    _44 = 0u;
    for (;;)
    {
        gl_Position.x = gl_in[_44].gl_Position.x;
        gl_Position.y = gl_in[_44].gl_Position.y;
        gl_Position.z = gl_in[_44].gl_Position.z;
        gl_Position.w = gl_in[_44].gl_Position.w;
        ARG_3.x = ARG[_44].x;
        ARG_3.y = ARG[_44].y;
        ARG_3.z = ARG[_44].z;
        ARG_2_1.x = ARG_2[_44].x;
        ARG_2_1.y = ARG_2[_44].y;
        ARG_2_1.z = ARG_2[_44].z;
        ARG_2_1.w = ARG_2[_44].w;
        EmitStreamVertex(int(0u));
        uint _45 = _44 + 1u;
        if (_45 == 3u)
        {
            break;
        }
        else
        {
            _44 = _45;
        }
    }
    gl_Position.x = gl_in[0u].gl_Position.x;
    gl_Position.y = gl_in[0u].gl_Position.y;
    gl_Position.z = gl_in[0u].gl_Position.z;
    gl_Position.w = gl_in[0u].gl_Position.w;
    ARG_1_1.x = ARG_1[0u].x;
    ARG_1_1.y = ARG_1[0u].y;
    EmitStreamVertex(int(1u));
}

The Vulkan spec says:

"VUID-StandaloneSpirv-Stream-04694
If any variables or block members in the output interface of the entry point being compiled are decorated with Stream, then all variables belonging to the same XfbBuffer must specify the same Stream value"

I think it's a test bug.

Ddoitsujin maintainer 2024-03-12 github

The test should be correct, this looks more like an actual xfb bug since the test deliberately declares multiple variables in different streams as SV_Position and our shader compilers don't seem to handle that. This is perfectly legal in D3D12.

Hhakzsam 2024-03-12 github

But it doesn't seem legal in VK.

Ddoitsujin maintainer 2024-03-12 github

Again, the problem is that we have multiple SV_Position variables that our compilers map to a single one. The correct fix here is to only map the one for the rasterized stream to gl_Position and keep the other ones separate, same for all other potential system values.

Hhakzsam 2026-09-15 github

This seems fixed now with the following patch:

diff --git i/tests/d3d12_pso.c w/tests/d3d12_pso.c
index e8bcd612..19678043 100644
--- i/tests/d3d12_pso.c
+++ w/tests/d3d12_pso.c
@@ -4717,7 +4717,7 @@ void test_shader_io_mismatch(void)
 
     /* TODO Fix DXBC/DXIL translation bugs that currently lead to
      * mesa asserts with these tests */
-#if 0
+#if 1
     for (i = 0; i < ARRAY_SIZE(so_tests); i++)
     {
         vkd3d_test_set_context("Test %u", i);

Hhakzsam 2026-09-15 github

Actually, I spoke too soon and it still asserts on NAVI21

$ VKD3D_TEST_FILTER=test_shader_io_mismatch ./build/tests/d3d12
d3d12:748: Driver name: radv, driver info: Mesa 26.3.0-devel (git-7dd952f52a).
d3d12: ======== test_shader_io_mismatch begin ========
Validation Error: [ VUID-StandaloneSpirv-OpEntryPoint-09659 ] | MessageID = 0x9ddb94d7
vkCreateShaderModule(): pCreateInfo->pCode (spirv-val produced an error):
OpEntryPoint contains duplicate output variables with Position builtin
  %SV_Position_1 = OpVariable %_ptr_Output_v4float Output

Command to reproduce:
	spirv-val <input.spv> --relax-block-layout --uniform-buffer-standard-layout --scalar-block-layout --allow-localsizeid --allow-offset-texture-operand --allow-vulkan-32-bit-bitwise --target-env vulkan1.3

The Vulkan spec states: For a given OpEntryPoint, any BuiltIn decoration must not be used more than once by the Output interface (https://docs.vulkan.org/spec/latest/appendices/spirvenv.html#VUID-StandaloneSpirv-OpEntryPoint-09659)

d3d12: ../src/compiler/nir/nir_gather_xfb_info.c:105: add_var_xfb_outputs: Assertion `xfb->buffer_to_stream[buffer] == var->data.stream' failed.
Aborted                    (core dumped) VKD3D_TEST_FILTER=test_shader_io_mismatch ./build/tests/d3d12

Ddoitsujin maintainer 2026-09-15 github

Yes, this would need to be addressed in dxil-spirv, but is not exactly trivial and nobody actually uses multi-stream xfb in the wild.

Launch options

VKD3D_TEST_FILTER=test_shader_io_mismatchx1 2026-09