Index: clang/lib/Driver/Driver.cpp
===================================================================
--- clang/lib/Driver/Driver.cpp
+++ clang/lib/Driver/Driver.cpp
@@ -1245,6 +1245,13 @@
       SuggestedCompletions = Opts->suggestValueCompletions(Option, Arg);
     }
 
+    // Sort the autocomplete candidates so that shells print them out in a
+    // 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(),
+              [](StringRef A, StringRef B) { return A.compare_lower(B) < 0; });
+
     llvm::outs() << llvm::join(SuggestedCompletions, " ") << '\n';
     return false;
   }
Index: clang/test/Driver/autocomplete.c
===================================================================
--- clang/test/Driver/autocomplete.c
+++ clang/test/Driver/autocomplete.c
@@ -11,7 +11,7 @@
 // RUN: %clang --autocomplete=-meabi,d | FileCheck %s -check-prefix=MEABI
 // MEABI: default
 // RUN: %clang --autocomplete=-meabi, | FileCheck %s -check-prefix=MEABIALL
-// MEABIALL: default 4 5 gnu
+// MEABIALL: 4 5 default gnu
 // RUN: %clang --autocomplete=-cl-std=,CL2 | FileCheck %s -check-prefix=CLSTD
 // CLSTD: CL2.0
 // RUN: %clang --autocomplete=-cl-std=, | FileCheck %s -check-prefix=CLSTDALL
@@ -19,18 +19,18 @@
 // RUN: %clang --autocomplete=-fno-sanitize-coverage=,f | FileCheck %s -check-prefix=FNOSANICOVER
 // FNOSANICOVER: func
 // RUN: %clang --autocomplete=-fno-sanitize-coverage=, | FileCheck %s -check-prefix=FNOSANICOVERALL
-// FNOSANICOVERALL: func bb edge indirect-calls trace-bb trace-cmp trace-div trace-gep 8bit-counters trace-pc trace-pc-guard no-prune inline-8bit-counters
+// FNOSANICOVERALL: 8bit-counters bb edge func indirect-calls inline-8bit-counters no-prune trace-bb trace-cmp trace-div trace-gep trace-pc trace-pc-guard
 // RUN: %clang --autocomplete=-ffp-contract=, | FileCheck %s -check-prefix=FFPALL
-// FFPALL: fast on off
+// FFPALL: fast off on
 // RUN: %clang --autocomplete=-flto=, | FileCheck %s -check-prefix=FLTOALL
-// FLTOALL: thin full
+// FLTOALL: full thin
 // RUN: %clang --autocomplete=-fveclib=, | FileCheck %s -check-prefix=FVECLIBALL
-// FVECLIBALL: Accelerate SVML none
+// FVECLIBALL: Accelerate none SVML
 // RUN: %clang --autocomplete=-fshow-overloads=, | FileCheck %s -check-prefix=FSOVERALL
-// FSOVERALL: best all
+// FSOVERALL: all best
 // RUN: %clang --autocomplete=-fvisibility=, | FileCheck %s -check-prefix=FVISIBILITYALL
-// FVISIBILITYALL: hidden default
+// FVISIBILITYALL: default hidden
 // RUN: %clang --autocomplete=-mfloat-abi=, | FileCheck %s -check-prefix=MFLOATABIALL
-// MFLOATABIALL: soft softfp hard
+// MFLOATABIALL: hard soft softfp
 // RUN: %clang --autocomplete=-mthread-model, | FileCheck %s -check-prefix=MTHREADMODELALL
 // MTHREADMODELALL: posix single