[clang][flang] Moke the definition of `-module-dir` restricted to Flang

[awarzynski]

Summary

-module-dir is a Flang specific option and should not be visible in
Clang. This patch adds FlangOnlyOption flag to its definition. This
way Clang will know that it should reject it and skip it when generating
output for clang -help.

The definition of -module-dir is moved next to other Flang options.
As -J is an alias for -module-dir, it has to be moved as well (the
alias cannot be defined before the original option). As gfortran mode
is effectively no longer supported (*), -J is claimed as Flang only
option.

This is a follow-up of a post-commit review for
https://reviews.llvm.org/D95448.

• https://reviews.llvm.org/rG6a75496836ea14bcfd2f4b59d35a1cad4ac58cee

[MaskRay]

Thanks. I do not know why FlangOption and FC1 Options needs be in clang/include/clang/Driver/Options.td but perhaps that is how things work:)

[awarzynski]

Thank you for reviewing!

In D99018#2639680, @MaskRay wrote:

Thanks. I do not know why FlangOption and FC1 Options needs be in clang/include/clang/Driver/Options.td but perhaps that is how things work:)

Options.td is where all options for clangDriver (the library) are defined. Since flang is implemented in terms of clangDriver, all options end up here. AFAIK, there is no mechanism to have separate Options.td files for Flang and Clang. But since there is meant to be only one driver library in llvm-project, I think that this is fine. Instead, IMHO, we should aim for producing separate files for e.g. clang -cc1 and flang -fc1 (to have a clearer separation from the compiler and frontend drivers).

The extra flags: FlangOption, FC1Option and FlangOnlyOption, were added to enable _some_ filtering of the options. In particular, for making sure that clang -help doesn't contain any Flang-only options.

Btw, here's an RFC in which I discussed some of these issues.

CC @protze.joachim - this is somewhat related to what you brought up here: https://reviews.llvm.org/D95460.

clang/include/clang/Driver/Options.td

def dependency_file : Separate<["-"], "dependency-file">, Flags<[CC1Option]>,
   HelpText<"Filename (or -) to write dependency output to">,
   MarshallingInfoString<DependencyOutputOpts<"OutputFile">>;
 def dependency_dot : Separate<["-"], "dependency-dot">, Flags<[CC1Option]>,
   HelpText<"Filename to write DOT-formatted header dependencies to">,
   MarshallingInfoString<DependencyOutputOpts<"DOTOutputFile">>;
 def module_dependency_dir : Separate<["-"], "module-dependency-dir">,
   Flags<[CC1Option]>, HelpText<"Directory to dump module dependencies to">,
   MarshallingInfoString<DependencyOutputOpts<"ModuleDependencyOutputDir">>;
-def module_dir : Separate<["-"], "module-dir">, Flags<[FlangOption,FC1Option]>, MetaVarName<"<dir>">,
-  HelpText<"Put MODULE files in <dir>">,
-  DocBrief<[{This option specifies where to put .mod files for compiled modules.
-It is also added to the list of directories to be searched by an USE statement.
-The default is the current directory.}]>;
 def dsym_dir : JoinedOrSeparate<["-"], "dsym-dir">,
   Flags<[NoXarchOption, RenderAsInput]>,
   HelpText<"Directory to output dSYM's (if any) to">, MetaVarName<"<dir>">;
 def dumpmachine : Flag<["-"], "dumpmachine">;
 def dumpspecs : Flag<["-"], "dumpspecs">, Flags<[Unsupported]>;
 def dumpversion : Flag<["-"], "dumpversion">;
 def dylib__file : Separate<["-"], "dylib_file">;
 def dylinker__install__name : JoinedOrSeparate<["-"], "dylinker_install_name">;

 defm web : BooleanFFlag<"web">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm whole_program : BooleanFFlag<"whole-program">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm devirtualize : BooleanFFlag<"devirtualize">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm devirtualize_speculatively : BooleanFFlag<"devirtualize-speculatively">,
     Group<clang_ignored_gcc_optimization_f_Group>;
 
 // Generic gfortran options.
 def A_DASH : Joined<["-"], "A-">, Group<gfortran_Group>;
-def J : JoinedOrSeparate<["-"], "J">, Flags<[RenderJoined,FlangOption,FC1Option]>, Group<gfortran_Group>, Alias<module_dir>;
 def cpp : Flag<["-"], "cpp">, Group<gfortran_Group>;
 def nocpp : Flag<["-"], "nocpp">, Group<gfortran_Group>;
 def static_libgfortran : Flag<["-"], "static-libgfortran">, Group<gfortran_Group>;
 
 // "f" options with values for gfortran.
 def fblas_matmul_limit_EQ : Joined<["-"], "fblas-matmul-limit=">, Group<gfortran_Group>;
 def fcheck_EQ : Joined<["-"], "fcheck=">, Group<gfortran_Group>;
 def fcoarray_EQ : Joined<["-"], "fcoarray=">, Group<gfortran_Group>;
def Xflang : Separate<["-"], "Xflang">,
   Flags<[NoXarchOption, CoreOption]>, Group<CompileOnly_Group>;
 }
 
 //===----------------------------------------------------------------------===//
 // FlangOption and FC1 Options
 //===----------------------------------------------------------------------===//
 let Flags = [FC1Option, FlangOption, FlangOnlyOption] in {
 
+def module_dir : Separate<["-"], "module-dir">, MetaVarName<"<dir>">,
+  HelpText<"Put MODULE files in <dir>">,
+  DocBrief<[{This option specifies where to put .mod files for compiled modules.
+It is also added to the list of directories to be searched by an USE statement.
+The default is the current directory.}]>;
+
 def ffixed_form : Flag<["-"], "ffixed-form">, Group<f_Group>,
   HelpText<"Process source files in fixed form">;
 def ffree_form : Flag<["-"], "ffree-form">, Group<f_Group>,
   HelpText<"Process source files in free form">;
 def ffixed_line_length_EQ : Joined<["-"], "ffixed-line-length=">, Group<f_Group>,
   HelpText<"Use <value> as character line width in fixed mode">,
   DocBrief<[{Set column after which characters are ignored in typical fixed-form lines in the source
 file}]>;

 def fno_logical_abbreviations : Flag<["-"], "fno-logical-abbreviations">, Group<f_Group>;
 def fimplicit_none : Flag<["-"], "fimplicit-none">, Group<f_Group>,
   HelpText<"No implicit typing allowed unless overridden by IMPLICIT statements">;
 def fno_implicit_none : Flag<["-"], "fno-implicit-none">, Group<f_Group>;
 def falternative_parameter_statement : Flag<["-"], "falternative-parameter-statement">, Group<f_Group>,
   HelpText<"Enable the old style PARAMETER statement">;
 }
 
+def J : JoinedOrSeparate<["-"], "J">,
+  Flags<[RenderJoined, FlangOption, FC1Option, FlangOnlyOption]>,
+  Group<gfortran_Group>,
+  Alias<module_dir>;
+
 //===----------------------------------------------------------------------===//
 // FC1 Options
 //===----------------------------------------------------------------------===//
 let Flags = [FC1Option, FlangOnlyOption] in {
 
 def test_io : Flag<["-"], "test-io">, Group<Action_Group>,
   HelpText<"Run the InputOuputTest action. Use for development and testing only.">;
 def fdebug_unparse : Flag<["-"], "fdebug-unparse">, Group<Action_Group>,