Index: llvm/lib/Support/Windows/Path.inc
===================================================================
--- llvm/lib/Support/Windows/Path.inc
+++ llvm/lib/Support/Windows/Path.inc
@@ -734,8 +734,8 @@
 
   HANDLE FileMappingHandle =
       ::CreateFileMappingW(FileHandle, 0, flprotect,
-                           (Offset + Size) >> 32,
-                           (Offset + Size) & 0xffffffff,
+                           Size >> 32,
+                           Size & 0xffffffff,
                            0);
   if (FileMappingHandle == NULL) {
     std::error_code ec = mapWindowsError(GetLastError());