Index: lib/Driver/Driver.cpp
===================================================================
--- lib/Driver/Driver.cpp
+++ lib/Driver/Driver.cpp
@@ -1199,7 +1199,7 @@
   // deterministic order. We could sort in any way, but we chose
   // case-insensitive sorting for consistency with the -help option
   // which prints out options in the case-insensitive alphabetical order.
-  std::sort(SuggestedCompletions.begin(), SuggestedCompletions.end(),
+  std::stable_sort(SuggestedCompletions.begin(), SuggestedCompletions.end(),
             [](StringRef A, StringRef B) { return A.compare_lower(B) < 0; });
 
   llvm::outs() << llvm::join(SuggestedCompletions, "\n") << '\n';