[Bug 59687] New: 'const' variable modifier causes null return-value in vertex shader

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59687

            Bug ID: 59687
           Summary: 'const' variable modifier causes null return-value in
                    vertex shader
           Product: Wine
           Version: 11.6
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: d3d
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 80789
  --> http://bugs.winehq.org/attachment.cgi?id=80789
trace-ok.log

Take this HLSL code which basically is a hello-triangle.

```hlsl
struct VsOut {
    float4 pos : SV_Position;
};

static const float2 VERTICES[3] = {
    float2(0.0, 0.5),
    float2(-0.5, -0.5),
    float2(0.5, -0.5)
};

static const float4 RED = float4(1.0, 0.0, 0.0, 1.0);

VsOut vs_main(uint vid : SV_VertexID)
{
    float2 position = VERTICES[min(vid, 2u)];
    VsOut output = { float4(position, 0.0, 1.0) };
    return output;
}

float4 fs_main() : SV_Target
{
    return RED;
}
```

I have this wgpu program:
https://gist.github.com/bczhc/e8d11db2280ffd20fee43fb1fed7410e to run and
render this shader. (Sorry I'm not familiar with hlsl and windows programming
so I just now only able to write the wgpu program to demonstrate it and suppose
it may not be related to wgpu anyway)

To compile and run it, do:

```bash
# ensure to put it in a cargo project first
cargo build --target x86_64-pc-windows-gnu
# run
WINEPREFIX=`pwd`/prefix WGPU_BACKEND=dx12 wine
target/x86_64-pc-windows-gnu/debug/demo.exe the-hlsl-above.hlsl vs_main
```

It will display a red triangle.

However, modify this line `VsOut output = { float4(position, 0.0, 1.0) };` to
`const VsOut output = { float4(position, 0.0, 1.0) };`, then compile the Rust
program then run it using wine again, the red triangle will not show.

Or, if that line is left as is but you add another const variable, like this:

```hlsl
VsOut vs_main(uint vid : SV_VertexID)
{
    float2 position = VERTICES[min(vid, 2u)];
    VsOut output = { float4(position, 0.0, 1.0) };
    const VsOut output1 = output;
    return output1;
}
```

The red triangle is also not able to display.

This is originally reported as a wgpu issue here:
https://github.com/gfx-rs/wgpu/issues/9056. At that time, only proton has this
issue (wine is okay). However now with wine 11.6 I tested it again, wine has
this issue either. So I suspect this is an upstream vkd3d hlsl compiler issue
then? I haven't done the bisect yet because I haven't managed how to properly
compile this project and substitute it for wine.

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