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

[Yaxun Liu via cfe-commits]

https://github.com/yxsamliu created https://github.com/llvm/llvm-project/pull/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.

>From 11d10a8ac561b77e7f69ba39c1b49f2f7a7afad6 Mon Sep 17 00:00:00 2001
From: "Yaxun (Sam) Liu" <yaxun.liu at amd.com>
Date: Wed, 20 Mar 2024 13:34:29 -0400
Subject: [PATCH] [HIP][NFC] Refactor managed var codegen

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.
---
 clang/lib/CodeGen/CGCUDANV.cpp | 27 +++++++++------------------
 1 file changed, 9 insertions(+), 18 deletions(-)

diff --git a/clang/lib/CodeGen/CGCUDANV.cpp b/clang/lib/CodeGen/CGCUDANV.cpp
index d3f2573fd5e38a..b756318c46a900 100644
--- a/clang/lib/CodeGen/CGCUDANV.cpp
+++ b/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