[clang] [HLSL] Implement D3DCOLORtoUBYTE4 intrinsic (PR #122202)

[Finn Plummer via cfe-commits]

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@@ -1857,6 +1857,23 @@ half3 cross(half3, half3);
 _HLSL_BUILTIN_ALIAS(__builtin_hlsl_cross)
 float3 cross(float3, float3);
 
+//===----------------------------------------------------------------------===//
+// D3DCOLORtoUBYTE4 builtins
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inbelic wrote:

```suggestion
// D3DCOLORtoUBYTE4 builtin
```

https://github.com/llvm/llvm-project/pull/122202