3 files changed, 32 insertions, 1 deletions
diff --git a/clang/lib/CodeGen/CGHLSLRuntime.cpp b/clang/lib/CodeGen/CGHLSLRuntime.cpp
index dbfdd0e..6d267e6 100644
--- a/clang/lib/CodeGen/CGHLSLRuntime.cpp
+++ b/clang/lib/CodeGen/CGHLSLRuntime.cpp
@@ -624,6 +624,20 @@ void CGHLSLRuntime::initializeBufferFromBinding(const HLSLBufferDecl *BufDecl,
   }
 }
 
+void CGHLSLRuntime::handleGlobalVarDefinition(const VarDecl *VD,
+                                              llvm::GlobalVariable *GV) {
+  if (auto Attr = VD->getAttr<HLSLVkExtBuiltinInputAttr>()) {
+    LLVMContext &Ctx = GV->getContext();
+    IRBuilder<> B(GV->getContext());
+    MDNode *Operands = MDNode::get(
+        Ctx, {ConstantAsMetadata::get(
+                  B.getInt32(/* Spirv::Decoration::BuiltIn */ 11)),
+              ConstantAsMetadata::get(B.getInt32(Attr->getBuiltIn()))});
+    MDNode *Decoration = MDNode::get(Ctx, {Operands});
+    GV->addMetadata("spirv.Decorations", *Decoration);
+  }
+}
+
 llvm::Instruction *CGHLSLRuntime::getConvergenceToken(BasicBlock &BB) {
   if (!CGM.shouldEmitConvergenceTokens())
     return nullptr;
diff --git a/clang/lib/CodeGen/CGHLSLRuntime.h b/clang/lib/CodeGen/CGHLSLRuntime.h
index 34c6b8d..f7ca207 100644
--- a/clang/lib/CodeGen/CGHLSLRuntime.h
+++ b/clang/lib/CodeGen/CGHLSLRuntime.h
@@ -157,6 +157,7 @@ public:
 
   void emitEntryFunction(const FunctionDecl *FD, llvm::Function *Fn);
   void setHLSLFunctionAttributes(const FunctionDecl *FD, llvm::Function *Fn);
+  void handleGlobalVarDefinition(const VarDecl *VD, llvm::GlobalVariable *Var);
 
   llvm::Instruction *getConvergenceToken(llvm::BasicBlock &BB);
 
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 9383c57..468fc6e 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -5763,7 +5763,17 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
     getCUDARuntime().handleVarRegistration(D, *GV);
   }
 
-  GV->setInitializer(Init);
+  if (LangOpts.HLSL && GetGlobalVarAddressSpace(D) == LangAS::hlsl_input) {
+    // HLSL Input variables are considered to be set by the driver/pipeline, but
+    // only visible to a single thread/wave.
+    GV->setExternallyInitialized(true);
+  } else {
+    GV->setInitializer(Init);
+  }
+
+  if (LangOpts.HLSL)
+    getHLSLRuntime().handleGlobalVarDefinition(D, GV);
+
   if (emitter)
     emitter->finalize(GV);
 
@@ -5806,6 +5816,12 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
       !D->hasAttr<ConstInitAttr>())
     Linkage = llvm::GlobalValue::InternalLinkage;
 
+  // HLSL variables in the input address space maps like memory-mapped
+  // variables. Even if they are 'static', they are externally initialized and
+  // read/write by the hardware/driver/pipeline.
+  if (LangOpts.HLSL && GetGlobalVarAddressSpace(D) == LangAS::hlsl_input)
+    Linkage = llvm::GlobalValue::ExternalLinkage;
+
   GV->setLinkage(Linkage);
   if (D->hasAttr<DLLImportAttr>())
     GV->setDLLStorageClass(llvm::GlobalVariable::DLLImportStorageClass);