Don't emit .gnu_pubnames when tuning for LLDB

[aprantl]

Summary

LLDB reads the various .apple* accelerator tables which should make .gnu_pubnames redundant. This changes the Clang driver to no longer pass -ggnu-pubnames when tuning for LLDB.

Thanks to @dblaikie for pointing this out (a few months back; my backlog is real).

rdar://problem/50142073

[dblaikie]

Have you got a link to the original thread where this was discussed/I mentioned it? Want to page in some context to double-check if I had any ideas that might've let this simplify things.

[aprantl]

In D67373#1663924, @dblaikie wrote:

Have you got a link to the original thread where this was discussed/I mentioned it? Want to page in some context to double-check if I had any ideas that might've let this simplify things.

Sure! http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190422/thread.html#646062

[JDevlieghere]

clang/lib/Driver/ToolChains/Clang.cpp

3400

Is this codepath Darwin only? Even if it's not this should be fine because we should emit debug_names if debugger tuning is lldb.

[dblaikie]

Seems good to me - thanks!

clang/lib/Driver/ToolChains/Clang.cpp

if (checkDebugInfoOption(Args.getLastArg(options::OPT_fdebug_macro), Args,
                              D, TC))
       CmdArgs.push_back("-debug-info-macro");
 
   // -ggnu-pubnames turns on gnu style pubnames in the backend.
   const auto *PubnamesArg =
       Args.getLastArg(options::OPT_ggnu_pubnames, options::OPT_gno_gnu_pubnames,
                       options::OPT_gpubnames, options::OPT_gno_pubnames);
   if (DwarfFission != DwarfFissionKind::None ||
-      DebuggerTuning == llvm::DebuggerKind::LLDB ||
       (PubnamesArg && checkDebugInfoOption(PubnamesArg, Args, D, TC)))
     if (!PubnamesArg ||
         (!PubnamesArg->getOption().matches(options::OPT_gno_gnu_pubnames) &&
          !PubnamesArg->getOption().matches(options::OPT_gno_pubnames)))
       CmdArgs.push_back(PubnamesArg && PubnamesArg->getOption().matches(
                                            options::OPT_gpubnames)
                             ? "-gpubnames"
                             : "-ggnu-pubnames");

clang/test/Driver/debug-options.c

 //
 // RUN: %clang -### -c -gsplit-dwarf %s 2>&1 | FileCheck -check-prefix=GPUB %s
 // RUN: %clang -### -c -gsplit-dwarf -gno-pubnames %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 //
 // RUN: %clang -### -c -fdebug-ranges-base-address %s 2>&1 | FileCheck -check-prefix=RNGBSE %s
 // RUN: %clang -### -c %s 2>&1 | FileCheck -check-prefix=NORNGBSE %s
 // RUN: %clang -### -c -fdebug-ranges-base-address -fno-debug-ranges-base-address %s 2>&1 | FileCheck -check-prefix=NORNGBSE %s
 //
-// RUN: %clang -### -c -glldb %s 2>&1 | FileCheck -check-prefix=GPUB %s
+// RUN: %clang -### -c -glldb %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 // RUN: %clang -### -c -glldb -gno-pubnames %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 //
 // RUN: %clang -### -c -gdwarf-aranges %s 2>&1 | FileCheck -check-prefix=GARANGE %s
 //
 // RUN: %clang -### -fdebug-types-section -target x86_64-unknown-linux %s 2>&1 \
 // RUN:        | FileCheck -check-prefix=FDTS %s
 //
 // RUN: %clang -### -fdebug-types-section -fno-debug-types-section -target x86_64-unknown-linux %s 2>&1 \