[clang] fcf75ae - [clang][cli] Fix generation of '-fvisibility' with regards to '-mignore-xcoff-visibility'

[Jan Svoboda via cfe-commits]

Author: Jan Svoboda
Date: 2021-03-05T10:57:06+01:00
New Revision: fcf75ae6ce20e3575b1464ce724619f38c43edd2

URL: https://github.com/llvm/llvm-project/commit/fcf75ae6ce20e3575b1464ce724619f38c43edd2
DIFF: https://github.com/llvm/llvm-project/commit/fcf75ae6ce20e3575b1464ce724619f38c43edd2.diff

LOG: [clang][cli] Fix generation of '-fvisibility' with regards to '-mignore-xcoff-visibility'

This patch fixes failure of the `CodeGen/aix-ignore-xcoff-visibility.cpp` test with command line round-trip.

The absence of '-fvisibility' implies '-mignore-xcoff-visibility'.

The problem is that when '-fvisibility default' is passed to -cc1, it isn't being generated. (This adheres to the principle that generation doesn't produce arguments with default values.)

However, that caused '-mignore-xcoff-visibility' to be implied in the generated command line (without '-fvisibility'), while it wasn't implied in the original command line (with '-fvisibility').

This patch fixes that by always generating '-fvisibility' and explains the situation in comment.

(The '-mginore-xcoff-visibility' option was added in D87451).

Reviewed By: Bigcheese

Differential Revision: https://reviews.llvm.org/D97552

Added: 
    

Modified: 
    clang/include/clang/Driver/Options.td
    clang/lib/Frontend/CompilerInvocation.cpp

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index d4d48deb649f..299d4619c7e1 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -5321,7 +5321,9 @@ def stack_protector_buffer_size : Separate<["-"], "stack-protector-buffer-size">
   MarshallingInfoInt<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
index b0654f9d706e..89e485a29384 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1831,6 +1831,23 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
     }
   }
 
+  // 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;