Remove time-trace message as it is inconsistent style

[russell.gallop]

Summary

https://reviews.llvm.org/D68260 removed some of the message that -ftime-trace prints out. Running large builds still prints out a lot of "Time trace json-file dumped to " messages which are not the normal style for clang and are not necessary for locating the trace file.

There are other options which create files but don't tell you where they've written them. For example, this command generates a time trace, an yaml optimization record and a dependency file but only tells you about the time trace file:

$ clang -c foo.cpp -ftime-trace -fsave-optimisation-record -MD
Time trace json-file dumped to foo.json
$ ls
foo.cpp foo.d foo.json foo.o foo.opt.yaml

Supplemented the command line reference to help users locate this file and updated Options.td which is used to generate ClangCommandLineReference and clang --help.

[sylvestre.ledru]

clang/include/clang/Driver/Options.td

1797

I am not a big fan of adding products in the in-product help.
If Chrome removes the feature or Speedscope goes done, we will still list that in the old version of clang.
Deprecated doc is more common and accepted.

I would remove this line and the next line and keep the doc.

[sylvestre.ledru]

besides that, I think we should do it; thanks :)

[russell.gallop]

Update so --help helps user find trace file.
Documentation has the further details on how to view it.

[russell.gallop]

clang/include/clang/Driver/Options.td

1797

I would remove this line and the next line and keep the doc.

I agree. Updated to do that via the tablegen file. Removed the changes to the rst file which is generated from tablegen.

[anton-afanasyev]

Yes, I agree. LGTM.

clang/docs/ClangCommandLineReference.rst

 Perform ThinLTO importing using provided function summary index
 
 .. option:: -fthreadsafe-statics, -fno-threadsafe-statics
 
 .. option:: -ftime-report
 
 .. option:: -ftime-trace
 
-Turn on time profiler. Results can be analyzed with chrome://tracing or
-`Speedscope App <https://www.speedscope.app>`_ for flamegraph visualization
+Turn on time profiler. Generates JSON file based on output filename.  Results
+can be analyzed with chrome://tracing or `Speedscope App
+<https://www.speedscope.app>`_ for flamegraph visualization
 
 .. option:: -ftime-trace-granularity=<arg>
 
 Minimum time granularity (in microseconds) traced by time profiler
 
 .. option:: -ftls-model=<arg>
 
 .. option:: -ftrap-function=<arg>

clang/include/clang/Driver/Options.td

 def Wlarger_than_EQ : Joined<["-"], "Wlarger-than=">, Group<clang_ignored_f_Group>;
 def Wlarger_than_ : Joined<["-"], "Wlarger-than-">, Alias<Wlarger_than_EQ>;
 def Wframe_larger_than_EQ : Joined<["-"], "Wframe-larger-than=">, Group<f_Group>, Flags<[DriverOption]>;
 
 def : Flag<["-"], "fterminated-vtables">, Alias<fapple_kext>;
 def fthreadsafe_statics : Flag<["-"], "fthreadsafe-statics">, Group<f_Group>;
 def ftime_report : Flag<["-"], "ftime-report">, Group<f_Group>, Flags<[CC1Option]>;
 def ftime_trace : Flag<["-"], "ftime-trace">, Group<f_Group>,
-  HelpText<"Turn on time profiler">, Flags<[CC1Option, CoreOption]>;
+  HelpText<"Turn on time profiler. Generates JSON file based on output filename. "
+           "Results can be analyzed with chrome://tracing or `Speedscope App "
+           "<https://www.speedscope.app>`_ for flamegraph visualization." >,
+  Flags<[CC1Option, CoreOption]>;
 def ftime_trace_granularity_EQ : Joined<["-"], "ftime-trace-granularity=">, Group<f_Group>,
   HelpText<"Minimum time granularity (in microseconds) traced by time profiler">,
   Flags<[CC1Option, CoreOption]>;
 def ftlsmodel_EQ : Joined<["-"], "ftls-model=">, Group<f_Group>, Flags<[CC1Option]>;
 def ftrapv : Flag<["-"], "ftrapv">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Trap on integer overflow">;
 def ftrapv_handler_EQ : Joined<["-"], "ftrapv-handler=">, Group<f_Group>,
   MetaVarName<"<function name>">,

clang/tools/driver/cc1_main.cpp

if (auto profilerOutput =
                                     /*RemoveFileOnSignal=*/false, "",
                                     /*Extension=*/"json",
                                     /*useTemporary=*/false)) {
 
       llvm::timeTraceProfilerWrite(*profilerOutput);
       // FIXME(ibiryukov): make profilerOutput flush in destructor instead.
       profilerOutput->flush();
       llvm::timeTraceProfilerCleanup();
-
-      llvm::errs() << "Time trace json-file dumped to " << Path.str() << "\n";
     }
   }
 
   // Our error handler depends on the Diagnostics object, which we're
   // potentially about to delete. Uninstall the handler now so that any
   // later errors use the default handling behavior instead.
   llvm::remove_fatal_error_handler();
 
   // When running with -disable-free, don't do any destruction or shutdown.
   if (Clang->getFrontendOpts().DisableFree) {
     llvm::BuryPointer(std::move(Clang));
     return !Success;
   }
 
   return !Success;
 }