LTO: Merge -lto-no-discard-value-names with -save-temps.

[ruiu]

Summary

This patch is to remove -lto-no-discard-value-names flag and
instead to use -save-temps as we discussed in the post-commit
review thread for r267020.

[pcc]

LGTM

[mehdi_amini]

I guess the only issue is that you can't test that the linker is correctly setting up LLVM to discard names now.

[ruiu]

Right, whether the flag was set correctly or not is not visible from outside, but I think that's not a big issue.

[mehdi_amini]

It is only an issue for testability, you can't catch a regression on this aspect now, if someone removes the call to setDiscardValueNames all your tests will still be passing.
I'm just mentioning it, I understand there is a tradeoff for everything :)

lld/trunk/ELF/Config.h

struct Configuration {
   std::vector<llvm::StringRef> VersionScriptGlobals;
   bool AllowMultipleDefinition;
   bool AsNeeded = false;
   bool Bsymbolic;
   bool BsymbolicFunctions;
   bool Demangle = true;
   bool DisableVerify;
   bool DiscardAll;
-  bool DiscardValueNames;
   bool DiscardLocals;
   bool DiscardNone;
   bool EhFrameHdr;
   bool EnableNewDtags;
   bool ExportDynamic;
   bool GcSections;
   bool GnuHash = false;
   bool ICF;

lld/trunk/ELF/Driver.cpp

void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   }
 
   Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
   Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
   Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
   Config->Demangle = !Args.hasArg(OPT_no_demangle);
   Config->DisableVerify = Args.hasArg(OPT_disable_verify);
   Config->DiscardAll = Args.hasArg(OPT_discard_all);
-  Config->DiscardValueNames = !Args.hasArg(OPT_lto_no_discard_value_names);
   Config->DiscardLocals = Args.hasArg(OPT_discard_locals);
   Config->DiscardNone = Args.hasArg(OPT_discard_none);
   Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
   Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags);
   Config->ExportDynamic = Args.hasArg(OPT_export_dynamic);
   Config->GcSections = Args.hasArg(OPT_gc_sections);
   Config->ICF = Args.hasArg(OPT_icf);
   Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);

lld/trunk/ELF/LTO.cpp

static bool shouldInternalize(const SmallPtrSet<GlobalValue *, 8> &Used,
   if (Used.count(GV))
     return false;
 
   return !B.Backref->includeInDynsym();
 }
 
 BitcodeCompiler::BitcodeCompiler()
     : Combined(new llvm::Module("ld-temp.o", Context)), Mover(*Combined) {
-  Context.setDiscardValueNames(Config->DiscardValueNames);
+  // This is a flag to discard all but GlobalValue names.
+  // We want to enable it by default because it saves memory.
+  // Disable it only when a developer option (-save-temps) is given.
+  Context.setDiscardValueNames(!Config->SaveTemps);
+
   Context.enableDebugTypeODRUniquing();
 }
 
 void BitcodeCompiler::add(BitcodeFile &F) {
   std::unique_ptr<IRObjectFile> Obj =
       check(IRObjectFile::create(F.MB, Context));
   std::vector<GlobalValue *> Keep;
   unsigned BodyIndex = 0;

lld/trunk/ELF/Options.td

 def warn_execstack : Flag<["--"], "warn-execstack">;
 def warn_shared_textrel : Flag<["--"], "warn-shared-textrel">;
 def G : Separate<["-"], "G">;
 
 // Aliases for ignored options
 def alias_version_script_version_script : Joined<["--"], "version-script=">, Alias<version_script>;
 
 // LTO-related options.
-def lto_no_discard_value_names : Flag<["-"], "lto-no-discard-value-names">;
 def lto_jobs : Joined<["--"], "lto-jobs=">,
   HelpText<"Number of threads to run codegen">;
 def disable_verify : Flag<["-"], "disable-verify">;
 def mllvm : Separate<["-"], "mllvm">;
 def save_temps : Flag<["-"], "save-temps">;

lld/trunk/test/ELF/lto/discard-value-names.ll

 ; RUN: llvm-as %s -o %t.o
 
-; RUN: ld.lld -m elf_x86_64 -lto-no-discard-value-names -shared -save-temps %t.o -o %t2.o
-; RUN: llvm-dis < %t2.o.lto.bc | FileCheck %s
-
 ; RUN: ld.lld -m elf_x86_64 -shared -save-temps %t.o -o %t2.o
-; RUN: llvm-dis < %t2.o.lto.bc | FileCheck --check-prefix=NONAME %s
+; RUN: llvm-dis < %t2.o.lto.bc | FileCheck %s
 
 ; CHECK: @GlobalValueName
 ; CHECK: @foo(i32 %in)
 ; CHECK: somelabel:
 ; CHECK:  %GV = load i32, i32* @GlobalValueName
 ; CHECK:  %add = add i32 %in, %GV
 ; CHECK:  ret i32 %add
 
-; NONAME: @GlobalValueName
-; NONAME: @foo(i32)
-; NONAME-NOT: somelabel:
-; NONAME:  %2 = load i32, i32* @GlobalValueName
-; NONAME:  %3 = add i32 %0, %2
-; NONAME:  ret i32 %3
-
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @GlobalValueName = global i32 0
 
 define i32 @foo(i32 %in) {
 somelabel:
   %GV = load i32, i32* @GlobalValueName
   %add = add i32 %in, %GV
   ret i32 %add
 }

lld/trunk/test/ELF/lto/type-merge2.ll

 ; RUN: llvm-as %s -o %t.o
 ; RUN: llvm-as %p/Inputs/type-merge2.ll -o %t2.o
-; RUN: ld.lld -m elf_x86_64 %t.o %t2.o -o %t.so -shared -save-temps -lto-no-discard-value-names
+; RUN: ld.lld -m elf_x86_64 %t.o %t2.o -o %t.so -shared -save-temps
 ; RUN: llvm-dis %t.so.lto.bc -o - | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 %zed = type { i8 }
 define void @foo()  {
   call void @bar(%zed* null)