[HIP][NFC] Refactor managed var codegen (#85976)

Refactor managed variable handling in codegen so that the transformation
is done separately from registration.

This will allow the new driver to register the managed var in the linker
wrapper.

Author: yxsamliu

clang/lib/CodeGen/CGCUDANV.cpp

@@ -605,20 +605,10 @@ llvm::Function *CGNVCUDARuntime::makeRegisterGlobalsFn() {
       uint64_t VarSize =
           CGM.getDataLayout().getTypeAllocSize(Var->getValueType());
       if (Info.Flags.isManaged()) {
-        auto *ManagedVar = new llvm::GlobalVariable(
-            CGM.getModule(), Var->getType(),
-            /*isConstant=*/false, Var->getLinkage(),
-            /*Init=*/Var->isDeclaration()
-                ? nullptr
-                : llvm::ConstantPointerNull::get(Var->getType()),
-            /*Name=*/"", /*InsertBefore=*/nullptr,
-            llvm::GlobalVariable::NotThreadLocal);
-        ManagedVar->setDSOLocal(Var->isDSOLocal());
-        ManagedVar->setVisibility(Var->getVisibility());
-        ManagedVar->setExternallyInitialized(true);
-        ManagedVar->takeName(Var);
-        Var->setName(Twine(ManagedVar->getName() + ".managed"));
-        replaceManagedVar(Var, ManagedVar);
+        assert(Var->getName().ends_with(".managed") &&
+               "HIP managed variables not transformed");
+        auto *ManagedVar = CGM.getModule().getNamedGlobal(
+            Var->getName().drop_back(StringRef(".managed").size()));
         llvm::Value *Args[] = {
             &GpuBinaryHandlePtr,
             ManagedVar,
@@ -1093,7 +1083,9 @@ void CGNVCUDARuntime::transformManagedVars() {
               : llvm::ConstantPointerNull::get(Var->getType()),
           /*Name=*/"", /*InsertBefore=*/nullptr,
           llvm::GlobalVariable::NotThreadLocal,
-          CGM.getContext().getTargetAddressSpace(LangAS::cuda_device));
+          CGM.getContext().getTargetAddressSpace(CGM.getLangOpts().CUDAIsDevice
+                                                     ? LangAS::cuda_device
+                                                     : LangAS::Default));
       ManagedVar->setDSOLocal(Var->isDSOLocal());
       ManagedVar->setVisibility(Var->getVisibility());
       ManagedVar->setExternallyInitialized(true);
@@ -1102,7 +1094,7 @@ void CGNVCUDARuntime::transformManagedVars() {
       Var->setName(Twine(ManagedVar->getName()) + ".managed");
       // Keep managed variables even if they are not used in device code since
       // they need to be allocated by the runtime.
-      if (!Var->isDeclaration()) {
+      if (CGM.getLangOpts().CUDAIsDevice && !Var->isDeclaration()) {
         assert(!ManagedVar->isDeclaration());
         CGM.addCompilerUsedGlobal(Var);
         CGM.addCompilerUsedGlobal(ManagedVar);
@@ -1160,9 +1152,8 @@ void CGNVCUDARuntime::createOffloadingEntries() {
 
 // Returns module constructor to be added.
 llvm::Function *CGNVCUDARuntime::finalizeModule() {
+  transformManagedVars();
   if (CGM.getLangOpts().CUDAIsDevice) {
-    transformManagedVars();
-
     // Mark ODR-used device variables as compiler used to prevent it from being
     // eliminated by optimization. This is necessary for device variables
     // ODR-used by host functions. Sema correctly marks them as ODR-used no