[clang][driver] Add -foperator-names

[zero9178]

Summary

This patch adds the command line option -foperator-names which acts as the opposite of -fno-operator-names. With this command line option it is possible to reenable C++ operator keywords on the command line if -fno-operator-names had previously been passed.

clang/include/clang/Driver/Options.td

def fno_module_file_deps : Flag <["-"], "fno-module-file-deps">, Group<f_Group>,
   Flags<[NoXarchOption]>;
 def fno_ms_extensions : Flag<["-"], "fno-ms-extensions">, Group<f_Group>,
   Flags<[CoreOption]>;
 def fno_ms_compatibility : Flag<["-"], "fno-ms-compatibility">, Group<f_Group>,
   Flags<[CoreOption]>;
 def fno_objc_legacy_dispatch : Flag<["-"], "fno-objc-legacy-dispatch">, Group<f_Group>;
 def fno_objc_weak : Flag<["-"], "fno-objc-weak">, Group<f_Group>, Flags<[CC1Option]>;
 def fno_omit_frame_pointer : Flag<["-"], "fno-omit-frame-pointer">, Group<f_Group>;
-def fno_operator_names : Flag<["-"], "fno-operator-names">, Group<f_Group>,
-  HelpText<"Do not treat C++ operator name keywords as synonyms for operators">,
-  Flags<[CC1Option]>, MarshallingInfoNegativeFlag<LangOpts<"CXXOperatorNames">, cplusplus.KeyPath>;
+defm operator_names : BoolFOption<"operator-names",
+  LangOpts<"CXXOperatorNames">, Default<cplusplus.KeyPath>,
+  NegFlag<SetFalse, [CC1Option], "Do not treat C++ operator name keywords as synonyms for operators">,
+  PosFlag<SetTrue>>;
 def fdiagnostics_absolute_paths : Flag<["-"], "fdiagnostics-absolute-paths">, Group<f_Group>,
   Flags<[CC1Option, CoreOption]>, HelpText<"Print absolute paths in diagnostics">,
   MarshallingInfoFlag<DiagnosticOpts<"AbsolutePath">>;
 def fno_stack_protector : Flag<["-"], "fno-stack-protector">, Group<f_Group>,
   HelpText<"Disable the use of stack protectors">;
 def fno_strict_aliasing : Flag<["-"], "fno-strict-aliasing">, Group<f_Group>,
   Flags<[NoXarchOption, CoreOption]>;
 def fstruct_path_tbaa : Flag<["-"], "fstruct-path-tbaa">, Group<f_Group>;

clang/lib/Driver/ToolChains/Clang.cpp

if (Args.hasFlag(options::OPT_fvisibility_inlines_hidden,
     CmdArgs.push_back("-fvisibility-inlines-hidden");
 
   Args.AddLastArg(CmdArgs, options::OPT_fvisibility_inlines_hidden_static_local_var,
                            options::OPT_fno_visibility_inlines_hidden_static_local_var);
   Args.AddLastArg(CmdArgs, options::OPT_fvisibility_global_new_delete_hidden);
 
   Args.AddLastArg(CmdArgs, options::OPT_ftlsmodel_EQ);
 
+  if (Args.hasFlag(options::OPT_fno_operator_names,
+                   options::OPT_foperator_names, false))
+    CmdArgs.push_back("-fno-operator-names");
+
   // Forward -f (flag) options which we can pass directly.
   Args.AddLastArg(CmdArgs, options::OPT_femit_all_decls);
   Args.AddLastArg(CmdArgs, options::OPT_fheinous_gnu_extensions);
   Args.AddLastArg(CmdArgs, options::OPT_fdigraphs, options::OPT_fno_digraphs);
-  Args.AddLastArg(CmdArgs, options::OPT_fno_operator_names);
   Args.AddLastArg(CmdArgs, options::OPT_femulated_tls,
                   options::OPT_fno_emulated_tls);
 
   // AltiVec-like language extensions aren't relevant for assembling.
   if (!isa<PreprocessJobAction>(JA) || Output.getType() != types::TY_PP_Asm)
     Args.AddLastArg(CmdArgs, options::OPT_fzvector);
 
   Args.AddLastArg(CmdArgs, options::OPT_fdiagnostics_show_template_tree);

clang/test/Driver/cxx-operator-names.cpp

+// RUN: %clang -### -S -foperator-names -fno-operator-names %s 2>&1 | \
+// RUN:   FileCheck -check-prefix=CHECK-1 %s
+// CHECK-1: "-fno-operator-names"
+
+// RUN: %clang -### -S -fno-operator-names -foperator-names %s 2>&1 | \
+// RUN:   FileCheck -check-prefix=CHECK-2 %s
+// CHECK-2-NOT: "-fno-operator-names"