[ELF] - Support -plugin-opt=-debugger-tune=xxx option.

[grimar]

Summary

This is part of PR36035, currently LLD is unable to recongize
following LTO option:

-plugin-opt=-debugger-tune=XXX, where XXX is one of: gdb, lldb, sce.

It is incompatible with gold LTO plugin.
Patch teaches LLD about the option.

[grimar]

Abandoning. D42733 was landed instead. Will post patch with testcase for -plugin-opt=-debugger-tune separatelly.

ELF/Config.h

 
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/Support/CachePruning.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Endian.h"
+#include "llvm/Target/TargetOptions.h"
 
 #include <vector>
 
 namespace lld {
 namespace elf {
 
 class InputFile;
 
struct Configuration {
   uint16_t EMachine = llvm::ELF::EM_NONE;
   llvm::Optional<uint64_t> ImageBase;
   uint64_t MaxPageSize;
   uint64_t ZStackSize;
   unsigned LTOPartitions;
   unsigned LTOO;
   unsigned Optimize;
   unsigned ThinLTOJobs;
+  llvm::DebuggerKind LTODebuggerTune = llvm::DebuggerKind::Default;
 
   // The following config options do not directly correspond to any
   // particualr command line options.
 
   // True if we need to pass through relocations in input files to the
   // output file. Usually false because we consume relocations.
   bool CopyRelocs;
 

ELF/Driver.cpp

 static int parseInt(StringRef S, opt::Arg *Arg) {
   int V = 0;
   if (!to_integer(S, V, 10))
     error(Arg->getSpelling() + "=" + Arg->getValue() +
           ": number expected, but got '" + S + "'");
   return V;
 }
 
+static DebuggerKind parseLTODebuggerTune(StringRef S, opt::Arg *Arg) {
+  if (S == "gdb")
+    return DebuggerKind::GDB;
+  if (S == "lldb")
+    return DebuggerKind::LLDB;
+  if (S == "sce")
+    return DebuggerKind::SCE;
+  error(Arg->getSpelling() + "=" + Arg->getValue() + ": unknown tune '" + S +
+        "'");
+  return DebuggerKind::Default;
+}
+
 // Initializes Config members by the command line options.
 void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->AllowMultipleDefinition =
       Args.hasArg(OPT_allow_multiple_definition) || hasZOption(Args, "muldefs");
   Config->AuxiliaryList = args::getStrings(Args, OPT_auxiliary);
   Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
   Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
   Config->Chroot = Args.getLastArgValue(OPT_chroot);
for (auto *Arg : Args.filtered(OPT_plugin_opt)) {
     else if (S == "save-temps")
       Config->SaveTemps = true;
     else if (S.startswith("O"))
       Config->LTOO = parseInt(S.substr(1), Arg);
     else if (S.startswith("lto-partitions="))
       Config->LTOPartitions = parseInt(S.substr(15), Arg);
     else if (S.startswith("jobs="))
       Config->ThinLTOJobs = parseInt(S.substr(5), Arg);
+    else if (S.startswith("-debugger-tune="))
+      Config->LTODebuggerTune = parseLTODebuggerTune(S.substr(15), Arg);
     else if (!S.startswith("/") && !S.startswith("-fresolution=") &&
              !S.startswith("-pass-through=") && !S.startswith("mcpu=") &&
              !S.startswith("thinlto") && S != "-function-sections" &&
              S != "-data-sections")
       error(Arg->getSpelling() + ": unknown option: " + S);
   }
 
   if (Config->LTOO > 3)

ELF/LTO.cpp

static std::unique_ptr<lto::LTO> createLTO() {
   // LLD supports the new relocations.
   Conf.Options = InitTargetOptionsFromCodeGenFlags();
   Conf.Options.RelaxELFRelocations = true;
 
   // Always emit a section per function/datum with LTO.
   Conf.Options.FunctionSections = true;
   Conf.Options.DataSections = true;
 
+  Conf.Options.DebuggerTuning = Config->LTODebuggerTune;
+
   if (Config->Relocatable)
     Conf.RelocModel = None;
   else if (Config->Pic)
     Conf.RelocModel = Reloc::PIC_;
   else
     Conf.RelocModel = Reloc::Static;
   Conf.CodeModel = GetCodeModelFromCMModel();
   Conf.DisableVerify = Config->DisableVerify;

test/ELF/lto/debugger-tune.s

+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: ld.lld %t -plugin-opt=-debugger-tune=gdb -o /dev/null
+# RUN: ld.lld %t -plugin-opt=-debugger-tune=lldb -o /dev/null
+# RUN: ld.lld %t -plugin-opt=-debugger-tune=sce -o /dev/null
+
+# RUN: not ld.lld %t -plugin-opt=-debugger-tune=xxx -o /dev/null 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=ERR
+# ERR: error: --plugin-opt=-debugger-tune=xxx: unknown tune 'xxx'