[clang] [HLSL][SPIR-V] Handle SV_Postion builtin in PS (PR #141759)

[Farzon Lotfi via cfe-commits]

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@@ -384,6 +384,28 @@ static Value *buildVectorInput(IRBuilder<> &B, Function *F, llvm::Type *Ty) {
   return B.CreateCall(F, {B.getInt32(0)});
 }
 
+static void addBuiltinDecoration(llvm::GlobalVariable *GV, unsigned BuiltIn) {
+  LLVMContext &Ctx = GV->getContext();
+  IRBuilder<> B(GV->getContext());
+  MDNode *Operands =
+      MDNode::get(Ctx, {ConstantAsMetadata::get(B.getInt32(11)),
+                        ConstantAsMetadata::get(B.getInt32(BuiltIn))});
+  MDNode *Decoration = MDNode::get(Ctx, {Operands});
+  GV->addMetadata("spirv.Decorations", *Decoration);
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farzonl wrote:

hmm should this metadata be guarded with a conditional for the spirv target?

https://github.com/llvm/llvm-project/pull/141759