[clang] [HLSL] Implement output parameter (PR #101083)

[Damyan Pepper via cfe-commits]

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@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.0-compute -finclude-default-header -verify -Wdouble-promotion -Wconversion %s
+
+void OutVecFn(out float3) {}
+void InOutVecFn(inout float3) {}
+
+// Case 1: Calling out and inout parameters with types that cannot be
+// back-converted. In HLSL 2021 and earlier this only occurs when passing scalar
+// arguments to vector parameters because scalar->vector converison is implicit,
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damyanp wrote:

```suggestion
// arguments to vector parameters because scalar->vector conversion is implicit,
```

https://github.com/llvm/llvm-project/pull/101083