Index: lib/Support/Path.cpp
===================================================================
--- lib/Support/Path.cpp
+++ lib/Support/Path.cpp
@@ -1150,8 +1150,16 @@
   // If we can't cancel the delete don't rename.
   auto H = reinterpret_cast<HANDLE>(_get_osfhandle(FD));
   std::error_code RenameEC = setDeleteDisposition(H, false);
-  if (!RenameEC)
+  if (!RenameEC) {
     RenameEC = rename_fd(FD, Name);
+    // If rename failed because it's cross-device, copy instead
+    if (RenameEC ==
+      std::error_code(ERROR_NOT_SAME_DEVICE, std::system_category())) {
+      RenameEC = copy_file(TmpName, Name);
+      setDeleteDisposition(H, true);
+    }
+  }
+
   // If we can't rename, discard the temporary file.
   if (RenameEC)
     setDeleteDisposition(H, true);
Index: lib/Support/Windows/Path.inc
===================================================================
--- lib/Support/Windows/Path.inc
+++ lib/Support/Windows/Path.inc
@@ -450,7 +450,7 @@
       if (std::error_code EC2 = realPathFromHandle(FromHandle, WideFrom))
         return EC2;
       if (::MoveFileExW(WideFrom.begin(), WideTo.begin(),
-                        MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED))
+                        MOVEFILE_REPLACE_EXISTING))
         return std::error_code();
       return mapWindowsError(GetLastError());
     }