diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index c5f1a2b..b162e72 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -710,11 +710,15 @@
                                      SourceLocation Loc = SourceLocation(),
                                      bool TLS = false);
 
-  /// Return the address space of the underlying global variable for D, as
+  /// Return the AST address space of the underlying global variable for D, as
   /// determined by its declaration. Normally this is the same as the address
   /// space of D's type, but in CUDA, address spaces are associated with
-  /// declarations, not types.
-  unsigned GetGlobalVarAddressSpace(const VarDecl *D, unsigned AddrSpace);
+  /// declarations, not types. If D is nullptr, return the default address
+  /// space for global variable.
+  ///
+  /// For languages without explicit address spaces, if D has default address
+  /// space, target-specific global or constant address space may be returned.
+  unsigned GetGlobalVarAddressSpace(const VarDecl *D);
 
   /// Return the llvm::Constant for the address of the given global variable.
   /// If Ty is non-null and if the global doesn't exist, then it will be created