[lld] r248499 - [ELF2] Add support for -discard-none.

Rui Ueyama via llvm-commits llvm-commits at lists.llvm.org
Thu Sep 24 09:45:59 PDT 2015


On Thu, Sep 24, 2015 at 8:08 AM, Davide Italiano via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: davide
> Date: Thu Sep 24 10:08:23 2015
> New Revision: 248499
>
> URL: http://llvm.org/viewvc/llvm-project?rev=248499&view=rev
> Log:
> [ELF2] Add support for -discard-none.
>
> Differential Revision:  http://reviews.llvm.org/D13083
>
> Added:
>     lld/trunk/test/elf2/discard-none.s
> Modified:
>     lld/trunk/ELF/Config.h
>     lld/trunk/ELF/Driver.cpp
>     lld/trunk/ELF/Options.td
>     lld/trunk/ELF/OutputSections.cpp
>     lld/trunk/ELF/OutputSections.h
>     lld/trunk/ELF/Writer.cpp
>
> Modified: lld/trunk/ELF/Config.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Config.h?rev=248499&r1=248498&r2=248499&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Config.h (original)
> +++ lld/trunk/ELF/Config.h Thu Sep 24 10:08:23 2015
> @@ -22,6 +22,7 @@ struct Configuration {
>    bool Shared = false;
>    bool DiscardAll = false;
>    bool DiscardLocals = false;
> +  bool DiscardNone = false;
>    bool ExportDynamic = false;
>  };
>
>
> Modified: lld/trunk/ELF/Driver.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Driver.cpp?rev=248499&r1=248498&r2=248499&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Driver.cpp (original)
> +++ lld/trunk/ELF/Driver.cpp Thu Sep 24 10:08:23 2015
> @@ -88,6 +88,9 @@ void LinkerDriver::link(ArrayRef<const c
>    if (Args.hasArg(OPT_discard_locals))
>      Config->DiscardLocals = true;
>
> +  if (Args.hasArg(OPT_discard_none))
> +    Config->DiscardNone = true;
> +
>    if (Args.hasArg(OPT_export_dynamic))
>      Config->ExportDynamic = true;
>
>
> Modified: lld/trunk/ELF/Options.td
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Options.td?rev=248499&r1=248498&r2=248499&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Options.td (original)
> +++ lld/trunk/ELF/Options.td Thu Sep 24 10:08:23 2015
> @@ -28,6 +28,9 @@ def discard_locals : Flag<["-"], "discar
>  def alias_discard_locals: Flag<["-"], "X">,
>       Alias<discard_locals>;
>
> +def discard_none : Flag<["-"], "discard-none">,
> +     HelpText<"Keep all symbols in the symbol table">;
> +
>
>  //===----------------------------------------------------------------------===//
>  /// Ignored options
>
>  //===----------------------------------------------------------------------===//
>
> Modified: lld/trunk/ELF/OutputSections.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=248499&r1=248498&r2=248499&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.cpp (original)
> +++ lld/trunk/ELF/OutputSections.cpp Thu Sep 24 10:08:23 2015
> @@ -272,6 +272,15 @@ bool lld::elf2::includeInSymtab(const Sy
>    return true;
>  }
>
> +template <class ELFT>
> +bool SymbolTableSection<ELFT>::shouldKeepInSymtab(StringRef SymName) {
> +  if (Config->DiscardNone)
> +    return true;
> +
> +  // ELF defines dynamic locals as symbols which name starts with ".L".
> +  return !(Config->DiscardLocals && SymName.startswith(".L"));
> +}
>

This function doesn't seem to depend on any class or instance, so I'd make
this a static non-member function instead of a member function of
SymbolTableSection<ELFT>.


>  bool lld::elf2::includeInDynamicSymtab(const SymbolBody &B) {
>    if (Config->ExportDynamic || Config->Shared)
>      return true;
> @@ -294,7 +303,7 @@ template <class ELFT> void SymbolTableSe
>          auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
>          uint32_t SecIndex = Sym.st_shndx;
>          ErrorOr<StringRef> SymName = Sym.getName(File.getStringTable());
> -        if (Config->DiscardLocals && SymName->startswith(".L"))
> +        if (SymName && !shouldKeepInSymtab(*SymName))
>            continue;
>          ESym->st_name = (SymName) ? StrTabSec.getFileOff(*SymName) : 0;
>          ESym->st_size = Sym.st_size;
>
> Modified: lld/trunk/ELF/OutputSections.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.h?rev=248499&r1=248498&r2=248499&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.h (original)
> +++ lld/trunk/ELF/OutputSections.h Thu Sep 24 10:08:23 2015
> @@ -186,6 +186,8 @@ public:
>        ++NumLocals;
>    }
>
> +  bool shouldKeepInSymtab(StringRef Name);
> +
>    StringTableSection<ELFT::Is64Bits> &getStrTabSec() const { return
> StrTabSec; }
>    unsigned getNumSymbols() const { return NumVisible + 1; }
>
>
> Modified: lld/trunk/ELF/Writer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=248499&r1=248498&r2=248499&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Writer.cpp (original)
> +++ lld/trunk/ELF/Writer.cpp Thu Sep 24 10:08:23 2015
> @@ -336,7 +336,7 @@ template <class ELFT> void Writer<ELFT>:
>        Elf_Sym_Range Syms = File.getLocalSymbols();
>        for (const Elf_Sym &Sym : Syms) {
>          ErrorOr<StringRef> SymName = Sym.getName(File.getStringTable());
> -        if (SymName && !(Config->DiscardLocals &&
> SymName->startswith(".L")))
> +        if (SymName && SymTabSec.shouldKeepInSymtab(*SymName))
>            SymTabSec.addSymbol(*SymName, true);
>        }
>      }
>
> Added: lld/trunk/test/elf2/discard-none.s
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/discard-none.s?rev=248499&view=auto
>
> ==============================================================================
> --- lld/trunk/test/elf2/discard-none.s (added)
> +++ lld/trunk/test/elf2/discard-none.s Thu Sep 24 10:08:23 2015
> @@ -0,0 +1,58 @@
> +// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux -save-temp-labels
> %s -o %t
> +// RUN: lld -flavor gnu2 -discard-none -shared %t -o %t2
> +// RUN: llvm-readobj -s -sd -t %t2 | FileCheck %s
> +// REQUIRES: x86
> +
> +.text
> +.Lmyvar:
> +.Lmyothervar:
> +
> +// CHECK:   Section {
> +// CHECK:     Name: .strtab
> +// CHECK-NEXT:     Type: SHT_STRTAB
> +// CHECK-NEXT:     Flags [
> +// CHECK-NEXT:     ]
> +// CHECK-NEXT:     Address:
> +// CHECK-NEXT:     Offset:
> +// CHECK-NEXT:     Size:
> +// CHECK-NEXT:     Link:
> +// CHECK-NEXT:     Info:
> +// CHECK-NEXT:     AddressAlignment:
> +// CHECK-NEXT:     EntrySize:
> +// CHECK-NEXT:     SectionData (
> +// CHECK-NEXT:       0000: 002E7465 7874002E 62737300 2E64796E
> |..text..bss..dyn|
> +// CHECK-NEXT:       0010: 73747200 2E4C6D79 76617200 2E4C6D79
> |str..Lmyvar..Lmy|
> +// CHECK-NEXT:       0020: 6F746865 72766172 002E6479 6E73796D
> |othervar..dynsym|
> +// CHECK-NEXT:       0030: 002E6861 7368002E 64796E61 6D696300
> |..hash..dynamic.|
> +// CHECK-NEXT:       0040: 2E737472 74616200 2E73796D 74616200
> |.strtab..symtab.|
> +// CHECK-NEXT:       0050: 2E646174 6100                        |.data.|
> +// CHECK-NEXT:     )
> +// CHECK-NEXT:   }
> +
> +// CHECK:   Symbol {
> +// CHECK-NEXT:     Name:
> +// CHECK-NEXT:     Value: 0x0
> +// CHECK-NEXT:     Size: 0
> +// CHECK-NEXT:     Binding: Local
> +// CHECK-NEXT:     Type: None
> +// CHECK-NEXT:     Other: 0
> +// CHECK-NEXT:     Section: Undefined
> +// CHECK-NEXT:   }
> +// CHECK-NEXT:   Symbol {
> +// CHECK-NEXT:     Name: .Lmyothervar
> +// CHECK-NEXT:     Value: 0x1000
> +// CHECK-NEXT:     Size: 0
> +// CHECK-NEXT:     Binding: Local
> +// CHECK-NEXT:     Type: None
> +// CHECK-NEXT:     Other: 0
> +// CHECK-NEXT:     Section: .text
> +// CHECK-NEXT:   }
> +// CHECK-NEXT:   Symbol {
> +// CHECK-NEXT:     Name: .Lmyvar
> +// CHECK-NEXT:     Value: 0x1000
> +// CHECK-NEXT:     Size: 0
> +// CHECK-NEXT:     Binding: Local
> +// CHECK-NEXT:     Type: None
> +// CHECK-NEXT:     Other: 0
> +// CHECK-NEXT:     Section: .text
> +// CHECK-NEXT:   }
>
>
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