diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -5302,7 +5302,9 @@
   MarshallingInfoStringInt<CodeGenOpts<"SSPBufferSize">, "8">;
 def fvisibility : Separate<["-"], "fvisibility">,
   HelpText<"Default type and symbol visibility">,
-  MarshallingInfoVisibility<LangOpts<"ValueVisibilityMode">, "DefaultVisibility">;
+  MarshallingInfoVisibility<LangOpts<"ValueVisibilityMode">, "DefaultVisibility">,
+  // Always emitting because of the relation to `-mignore-xcoff-visibility`.
+  AlwaysEmit;
 def ftype_visibility : Separate<["-"], "ftype-visibility">,
   HelpText<"Default type visibility">,
   MarshallingInfoVisibility<LangOpts<"TypeVisibilityMode">, fvisibility.KeyPath>;
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1838,6 +1838,23 @@
     }
   }
 
+  // This is the reason why '-fvisibility' needs to be always generated:
+  // its absence implies '-mignore-xcoff-visibility'.
+  //
+  // Suppose the original cc1 command line does contain '-fvisibility default':
+  // '-mignore-xcoff-visibility' should not be implied.
+  // * If '-fvisibility' is not generated (as most options with default values
+  //   don't), its absence would imply '-mignore-xcoff-visibility'. This changes
+  //   the command line semantics.
+  // * If '-fvisibility' is generated regardless of its presence and value,
+  //   '-mignore-xcoff-visibility' won't be implied and the command line
+  //   semantics are kept intact.
+  //
+  // When the original cc1 command line does **not** contain '-fvisibility',
+  // '-mignore-xcoff-visibility' is implied. The generated command line will
+  // contain both '-fvisibility default' and '-mignore-xcoff-visibility' and
+  // subsequent calls to `CreateFromArgs`/`generateCC1CommandLine` will always
+  // produce the same arguments.
   if (T.isOSAIX() && (Args.hasArg(OPT_mignore_xcoff_visibility) ||
                       !Args.hasArg(OPT_fvisibility)))
     Opts.IgnoreXCOFFVisibility = 1;