[clang] [llvm] [OpenMP][clang] Register vtables on device for indirect calls runtime (PR #167011)

[Alexey Bataev via llvm-commits]

================
@@ -1762,23 +1763,137 @@ void CGOpenMPRuntime::emitDeclareTargetFunction(const FunctionDecl *FD,
   // access its value.
   llvm::GlobalValue *Addr = GV;
   if (CGM.getLangOpts().OpenMPIsTargetDevice) {
-    llvm::PointerType *FnPtrTy = llvm::PointerType::get(
-        CGM.getLLVMContext(),
-        CGM.getModule().getDataLayout().getProgramAddressSpace());
     Addr = new llvm::GlobalVariable(
-        CGM.getModule(), FnPtrTy,
+        CGM.getModule(), CGM.VoidPtrTy,
         /*isConstant=*/true, llvm::GlobalValue::ExternalLinkage, GV, Name,
         nullptr, llvm::GlobalValue::NotThreadLocal,
         CGM.getModule().getDataLayout().getDefaultGlobalsAddressSpace());
     Addr->setVisibility(llvm::GlobalValue::ProtectedVisibility);
   }
 
+  // Register the indirect Vtable:
+  // This is similar to OMPTargetGlobalVarEntryIndirect, except that the
+  // size field refers to the size of memory pointed to, not the size of
+  // the pointer symbol itself (which is implicitly the size of a pointer).
   OMPBuilder.OffloadInfoManager.registerDeviceGlobalVarEntryInfo(
       Name, Addr, CGM.GetTargetTypeStoreSize(CGM.VoidPtrTy).getQuantity(),
       llvm::OffloadEntriesInfoManager::OMPTargetGlobalVarEntryIndirect,
       llvm::GlobalValue::WeakODRLinkage);
 }
 
+void CGOpenMPRuntime::registerVTableOffloadEntry(llvm::GlobalVariable *VTable,
+                                                 const VarDecl *VD) {
+  // TODO: add logic to avoid duplicate vtable registrations per
+  // translation unit; though for external linkage, this should no
+  // longer be an issue - or at least we can avoid the issue by
+  // checking for an existing offloading entry.  But, perhaps the
+  // better approach is to defer emission of the vtables and offload
+  // entries until later (by tracking a list of items that need to be
+  // emitted).
+
+  llvm::OpenMPIRBuilder &OMPBuilder = CGM.getOpenMPRuntime().getOMPBuilder();
+
+  // Generate a new externally visible global to point to the
+  // internally visible vtable. Doing this allows us to keep the
+  // visibility and linkage of the associated vtable unchanged while
+  // allowing the runtime to access its value.  The externally
+  // visible global var needs to be emitted with a unique mangled
+  // name that won't conflict with similarly named (internal)
+  // vtables in other translation units.
+
+  // Register vtable with source location of dynamic object in map
+  // clause.
+  llvm::TargetRegionEntryInfo EntryInfo = getEntryInfoFromPresumedLoc(
+      CGM, OMPBuilder, VD->getCanonicalDecl()->getBeginLoc(),
+      VTable->getName());
+
+  llvm::GlobalVariable *Addr = VTable;
+  size_t PointerSize = CGM.getDataLayout().getPointerSize();
+  SmallString<128> AddrName;
+  OMPBuilder.OffloadInfoManager.getTargetRegionEntryFnName(AddrName, EntryInfo);
+  AddrName.append("addr");
+
+  if (CGM.getLangOpts().OpenMPIsTargetDevice) {
+    Addr = new llvm::GlobalVariable(
+        CGM.getModule(), VTable->getType(),
+        /*isConstant=*/true, llvm::GlobalValue::ExternalLinkage, VTable,
+        AddrName,
+        /*InsertBefore*/ nullptr, llvm::GlobalValue::NotThreadLocal,
----------------
alexey-bataev wrote:

```suggestion
        /*InsertBefore=*/nullptr, llvm::GlobalValue::NotThreadLocal,
```

https://github.com/llvm/llvm-project/pull/167011