Index: clang/lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -1587,12 +1587,14 @@
   // All parameters are already in place except VTT, which goes after 'this'.
   // These are Clang types, so we don't need to worry about sret yet.
 
-  // Check if we need to add a VTT parameter (which has type void **).
+  // Check if we need to add a VTT parameter (which has type global void **).
   if ((isa<CXXConstructorDecl>(GD.getDecl()) ? GD.getCtorType() == Ctor_Base
                                              : GD.getDtorType() == Dtor_Base) &&
       cast<CXXMethodDecl>(GD.getDecl())->getParent()->getNumVBases() != 0) {
+    LangAS AS = CGM.GetGlobalVarAddressSpace(nullptr);
+    QualType Q = Context.getAddrSpaceQualType(Context.VoidPtrTy, AS);
     ArgTys.insert(ArgTys.begin() + 1,
-                  Context.getPointerType(Context.VoidPtrTy));
+                  Context.getPointerType(CanQualType::CreateUnsafe(Q)));
     return AddedStructorArgCounts::prefix(1);
   }
   return AddedStructorArgCounts{};
@@ -1625,7 +1627,9 @@
     ASTContext &Context = getContext();
 
     // FIXME: avoid the fake decl
-    QualType T = Context.getPointerType(Context.VoidPtrTy);
+    LangAS AS = CGM.GetGlobalVarAddressSpace(nullptr);
+    QualType Q = Context.getAddrSpaceQualType(Context.VoidPtrTy, AS);
+    QualType T = Context.getPointerType(Q);
     auto *VTTDecl = ImplicitParamDecl::Create(
         Context, /*DC=*/nullptr, MD->getLocation(), &Context.Idents.get("vtt"),
         T, ImplicitParamDecl::CXXVTT);
@@ -1667,10 +1671,14 @@
   if (!NeedsVTTParameter(GlobalDecl(D, Type)))
     return AddedStructorArgs{};
 
-  // Insert the implicit 'vtt' argument as the second argument.
+  // Insert the implicit 'vtt' argument as the second argument. Make sure to
+  // correctly reflect its address space, which can differ from generic on
+  // some targets.
   llvm::Value *VTT =
       CGF.GetVTTParameter(GlobalDecl(D, Type), ForVirtualBase, Delegating);
-  QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
+  LangAS AS = getLangASFromTargetAS(VTT->getType()->getPointerAddressSpace());
+  QualType Q = getContext().getAddrSpaceQualType(getContext().VoidPtrTy, AS);
+  QualType VTTTy = getContext().getPointerType(Q);
   return AddedStructorArgs::prefix({{VTT, VTTTy}});
 }