[AutoComplete] Use stronger sort predicate for autocomplete candidate…

…s to remove non-deterministic ordering

Summary: This fixes the failure in test/Driver/autocomplete.c uncovered by D39245.

Reviewers: yamaguchi, teemperor, ruiu

Reviewed By: yamaguchi, ruiu

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D40234

llvm-svn: 318681

clang/lib/Driver/Driver.cpp

@@ -1198,7 +1198,11 @@ void Driver::handleAutocompletions(StringRef PassedFlags) const {
   // 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(),
-            [](StringRef A, StringRef B) { return A.compare_lower(B) < 0; });
+            [](StringRef A, StringRef B) {
+              if (int X = A.compare_lower(B))
+                return X < 0;
+              return A.compare(B) > 0;
+            });
 
   llvm::outs() << llvm::join(SuggestedCompletions, "\n") << '\n';
 }