[lld] r272812 - Internalize symbols in comdats.

[Sean Silva via llvm-commits]

Is this fixing a regression or did we never get this right? Just wondering
which time window of performance measurements may be affected.

-- Sean Silva

On Wed, Jun 15, 2016 at 10:56 AM, Rafael Espindola via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: rafael
> Date: Wed Jun 15 12:56:10 2016
> New Revision: 272812
>
> URL: http://llvm.org/viewvc/llvm-project?rev=272812&view=rev
> Log:
> Internalize symbols in comdats.
>
> We were dropping the CanOmitFromDynSym bit when creating undefined
> symbols because of comdat.
>
> Added:
>     lld/trunk/test/ELF/lto/unnamed-addr-comdat.ll
> Modified:
>     lld/trunk/ELF/InputFiles.cpp
>     lld/trunk/ELF/SymbolTable.cpp
>     lld/trunk/ELF/SymbolTable.h
>
> Modified: lld/trunk/ELF/InputFiles.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=272812&r1=272811&r2=272812&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/InputFiles.cpp (original)
> +++ lld/trunk/ELF/InputFiles.cpp Wed Jun 15 12:56:10 2016
> @@ -351,7 +351,8 @@ SymbolBody *elf::ObjectFile<ELFT>::creat
>    switch (Sym->st_shndx) {
>    case SHN_UNDEF:
>      return elf::Symtab<ELFT>::X
> -        ->addUndefined(Name, Binding, Sym->st_other, Sym->getType(), this)
> +        ->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
> +                       /*CanOmitFromDynSym*/ false, this)
>          ->body();
>    case SHN_COMMON:
>      return elf::Symtab<ELFT>::X
> @@ -368,7 +369,8 @@ SymbolBody *elf::ObjectFile<ELFT>::creat
>    case STB_GNU_UNIQUE:
>      if (Sec == &InputSection<ELFT>::Discarded)
>        return elf::Symtab<ELFT>::X
> -          ->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
> this)
> +          ->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
> +                         /*CanOmitFromDynSym*/ false, this)
>            ->body();
>      return elf::Symtab<ELFT>::X->addRegular(Name, *Sym, Sec)->body();
>    }
> @@ -589,12 +591,12 @@ Symbol *BitcodeFile::createSymbol(const
>      if (const Comdat *C = GV->getComdat())
>        if (!KeptComdats.count(C))
>          return Symtab<ELFT>::X->addUndefined(NameRef, Binding,
> Visibility, Type,
> -                                             this);
> +                                             CanOmitFromDynSym, this);
>
>    const Module &M = Obj.getModule();
>    if (Flags & BasicSymbolRef::SF_Undefined)
>      return Symtab<ELFT>::X->addUndefined(NameRef, Binding, Visibility,
> Type,
> -                                         this);
> +                                         CanOmitFromDynSym, this);
>    if (Flags & BasicSymbolRef::SF_Common) {
>      // FIXME: Set SF_Common flag correctly for module asm symbols, and
> expose
>      // size and alignment.
>
> Modified: lld/trunk/ELF/SymbolTable.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SymbolTable.cpp?rev=272812&r1=272811&r2=272812&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/SymbolTable.cpp (original)
> +++ lld/trunk/ELF/SymbolTable.cpp Wed Jun 15 12:56:10 2016
> @@ -220,17 +220,18 @@ std::string SymbolTable<ELFT>::conflictM
>
>  template <class ELFT> Symbol *SymbolTable<ELFT>::addUndefined(StringRef
> Name) {
>    return addUndefined(Name, STB_GLOBAL, STV_DEFAULT, /*Type*/ 0,
> -                      /*File*/ nullptr);
> +                      /*CanOmitFromDynSym*/ false, /*File*/ nullptr);
>  }
>
>  template <class ELFT>
>  Symbol *SymbolTable<ELFT>::addUndefined(StringRef Name, uint8_t Binding,
>                                          uint8_t StOther, uint8_t Type,
> +                                        bool CanOmitFromDynSym,
>                                          InputFile *File) {
>    Symbol *S;
>    bool WasInserted;
>    std::tie(S, WasInserted) =
> -      insert(Name, Type, StOther & 3, /*CanOmitFromDynSym*/ false,
> +      insert(Name, Type, StOther & 3, CanOmitFromDynSym,
>               /*IsUsedInRegularObj*/ !File || !isa<BitcodeFile>(File),
> File);
>    if (WasInserted) {
>      S->Binding = Binding;
>
> Modified: lld/trunk/ELF/SymbolTable.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SymbolTable.h?rev=272812&r1=272811&r2=272812&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/SymbolTable.h (original)
> +++ lld/trunk/ELF/SymbolTable.h Wed Jun 15 12:56:10 2016
> @@ -59,7 +59,7 @@ public:
>
>    Symbol *addUndefined(StringRef Name);
>    Symbol *addUndefined(StringRef Name, uint8_t Binding, uint8_t StOther,
> -                       uint8_t Type, InputFile *File);
> +                       uint8_t Type, bool CanOmitFromDynSym, InputFile
> *File);
>
>    Symbol *addRegular(StringRef Name, const Elf_Sym &Sym,
>                       InputSectionBase<ELFT> *Section);
>
> Added: lld/trunk/test/ELF/lto/unnamed-addr-comdat.ll
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/lto/unnamed-addr-comdat.ll?rev=272812&view=auto
>
> ==============================================================================
> --- lld/trunk/test/ELF/lto/unnamed-addr-comdat.ll (added)
> +++ lld/trunk/test/ELF/lto/unnamed-addr-comdat.ll Wed Jun 15 12:56:10 2016
> @@ -0,0 +1,11 @@
> +; RUN: llvm-as %s -o %t.o
> +; RUN: ld.lld -m elf_x86_64 %t.o %t.o -o %t.so -save-temps -shared
> +; 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"
> +
> +$foo = comdat any
> + at foo = linkonce_odr unnamed_addr constant i32 42, comdat
> +
> +; CHECK: @foo = internal unnamed_addr constant i32 42, comdat
>
>
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