[clang] [llvm] [HLSL] Implement the `reflect` HLSL function (PR #122992)

[Farzon Lotfi via llvm-commits]

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@@ -51,6 +51,38 @@ bool SemaSPIRV::CheckSPIRVBuiltinFunctionCall(unsigned BuiltinID,
     TheCall->setType(RetTy);
     break;
   }
+  case SPIRV::BI__builtin_spirv_reflect: {
+    if (SemaRef.checkArgCount(TheCall, 2))
+      return true;
+
+    ExprResult A = TheCall->getArg(0);
+    QualType ArgTyA = A.get()->getType();
+    auto *VTyA = ArgTyA->getAs<VectorType>();
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farzonl wrote:

I think the helpers you are thinking about might be in SemaHLSL.cpp. SemaSPIRV.cpp is very barebones. If you think there is a helper that could be used across both files, we probably want to move it to a more generic place. 

https://github.com/llvm/llvm-project/pull/122992