Index: lib/CodeGen/AtomicExpandPass.cpp
===================================================================
--- lib/CodeGen/AtomicExpandPass.cpp
+++ lib/CodeGen/AtomicExpandPass.cpp
@@ -1691,8 +1691,13 @@
   }
 
   // 'ptr' argument.
-  Value *PtrVal =
-      Builder.CreateBitCast(PointerOperand, Type::getInt8PtrTy(Ctx));
+  // note: This assumes all address spaces share a common libfunc
+  // implementation and that addresses are convertable.  For systems without
+  // that property, we'd need to extend this mechanism to support As-specific
+  // families of atomic intrinsics.
+  auto *PtrTypeAS0 = PointerOperand->getType()->getPointerTo(0);
+  Value *PtrVal = Builder.CreateAddrSpaceCast(PointerOperand, PtrTypeAS0);
+  PtrVal = Builder.CreateBitCast(PtrVal, Type::getInt8PtrTy(Ctx));
   Args.push_back(PtrVal);
 
   // 'expected' argument, if present.