Re: [PATCH v3 0/1] MR239: vkd3d-shader/codegen: Skip register allocation for unused object variables.

[Francisco Casas (＠fcasas)]

Approving. However, we still may want a better criteria for a variable begin used that `var->last_read`, probably something regset-wise.

This compiles in native (ps_5_0), yet we would be detecting overlaps:

```hlsl
struct {
    Texture2D tex;
    sampler sam;
} a : register(s0);

sampler sam_alone : register(s0);

float4 main() : sv_target
{
    return a.tex.Sample(sam_alone, float2(0, 0));
}
```

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https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/239#note_36378