[LLVM-ML] Add standard LLVM debug flags

[epastor]

Summary

Adds support for -debug and -debug-only= flags.

[ayzhao]

Thanks!

[MaskRay]

FWIW I think the lowercase llvm-ml may be a better title as the tool is built as llvm-ml, not LLVM-ML...

llvm/tools/llvm-ml/Opts.td

 include "llvm/Option/OptParser.td"
 
 // For LLVM-specific options, we prefer a two-dash prefix, but accept one for
 // compatibility with llvm-mc. For clear separation from ML.EXE compatible
 // options, slash is not accepted.
 class LLVMFlag<string name> : Flag<["--", "-"], name>;
 class LLVMJoined<string name> : Joined<["--", "-"], name>;
 class LLVMJoinedOrSeparate<string name> : JoinedOrSeparate<["--", "-"], name>;
 class LLVMSeparate<string name> : Separate<["--", "-"], name>;
+class LLVMCommaJoined<string name> : CommaJoined<["--", "-"], name>;
 
 def ml_Group : OptionGroup<"<ml options>">,
                HelpText<"ML.EXE COMPATIBILITY OPTIONS">;
 class MLFlag<string name> : Flag<["/", "-"], name>, Group<ml_Group>;
 class MLJoined<string name> : Joined<["/", "-"], name>, Group<ml_Group>;
 class MLJoinedOrSeparate<string name> : JoinedOrSeparate<["/", "-"], name>,
                                         Group<ml_Group>;
 class MLSeparate<string name> : Separate<["/", "-"], name>, Group<ml_Group>;
 
 def unsupported_Group : OptionGroup<"unsupported">, Flags<[HelpHidden]>,
                         HelpText<"UNSUPPORTED ML.EXE COMPATIBILITY OPTIONS">;
 class UnsupportedFlag<string name> : Flag<["/", "-"], name>,
                                      Group<unsupported_Group>;
 class UnsupportedJoined<string name> : Joined<["/", "-"], name>,
                                        Group<unsupported_Group>;
 class UnsupportedJoinedOrSeparate<string name> :
         JoinedOrSeparate<["/", "-"], name>, Group<unsupported_Group>;
 class UnsupportedSeparate<string name> : Separate<["/", "-"], name>,
                                          Group<unsupported_Group>;
 
 def bitness : LLVMJoined<"m">, Values<"32,64">,
               HelpText<"Target platform (x86 or x86-64)">;
 def as_lex : LLVMFlag<"as-lex">,
              HelpText<"Lex tokens from a .asm file without assembling">;
+def debug : LLVMFlag<"debug">, Flags<[HelpHidden]>,
+            HelpText<"Enable debug output">;
+def debug_only : LLVMCommaJoined<"debug-only=">, Flags<[HelpHidden]>,
+                 HelpText<"Enable a specific type of debug output (comma "
+                          "separated list of types)">;
 def fatal_warnings : LLVMFlag<"fatal-warnings">,
                      HelpText<"Treat warnings as errors">;
 def filetype : LLVMJoined<"filetype=">, Values<"obj,s,null">,
                HelpText<"Emit a file with the given type">;
 def output_att_asm : LLVMFlag<"output-att-asm">,
                      HelpText<"Use ATT syntax for output assembly">;
 def show_encoding : LLVMFlag<"show-encoding">,
                     HelpText<"Show instruction encodings in output assembly">;

llvm/tools/llvm-ml/llvm-ml.cpp

int main(int Argc, char **Argv) {
   }
 
   for (auto *Arg : InputArgs.filtered(OPT_unsupported_Group)) {
     WithColor::warning(errs(), ProgName)
         << "ignoring unsupported '" << Arg->getOption().getName()
         << "' option\n";
   }
 
+  if (InputArgs.hasArg(OPT_debug)) {
+    DebugFlag = true;
+  }
+  for (auto *Arg : InputArgs.filtered(OPT_debug_only)) {
+    setCurrentDebugTypes(Arg->getValues().data(), Arg->getNumValues());
+  }
+
   if (InputArgs.hasArg(OPT_help)) {
     std::string Usage = llvm::formatv("{0} [ /options ] file", ProgName).str();
     T.printHelp(outs(), Usage.c_str(), "LLVM MASM Assembler",
                 /*ShowHidden=*/false);
     return 0;
   } else if (InputFilename.empty()) {
     outs() << "USAGE: " << ProgName << " [ /options ] file\n"
            << "Run \"" << ProgName << " /?\" or \"" << ProgName