[lld] r248054 - [elf2] Relocate against common symbols.

[Michael Spencer via llvm-commits]

On Fri, Sep 18, 2015 at 3:30 PM, Rafael Espíndola
<rafael.espindola at gmail.com> wrote:
> Common symbols always have the same output section. Why do you need the member?

OutputSection::writeTo doesn't have access to the writer. I suppose we
could pass that or the bsssec in instead.

- Michael Spencer

>
> On 18 September 2015 at 18:13, Michael J. Spencer via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>> Author: mspencer
>> Date: Fri Sep 18 17:13:25 2015
>> New Revision: 248054
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=248054&view=rev
>> Log:
>> [elf2] Relocate against common symbols.
>>
>> Added:
>>     lld/trunk/test/elf2/relocation-common.s
>> Modified:
>>     lld/trunk/ELF/Symbols.h
>>     lld/trunk/ELF/Writer.cpp
>>
>> Modified: lld/trunk/ELF/Symbols.h
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Symbols.h?rev=248054&r1=248053&r2=248054&view=diff
>> ==============================================================================
>> --- lld/trunk/ELF/Symbols.h (original)
>> +++ lld/trunk/ELF/Symbols.h Fri Sep 18 17:13:25 2015
>> @@ -24,6 +24,7 @@ class Chunk;
>>  class InputFile;
>>  class SymbolBody;
>>  template <class ELFT> class ObjectFile;
>> +template <class ELFT> class OutputSection;
>>
>>  // A real symbol object, SymbolBody, is usually accessed indirectly
>>  // through a Symbol. There's always one Symbol for each symbol name.
>> @@ -180,6 +181,8 @@ public:
>>
>>    // The maximum alignment we have seen for this symbol.
>>    uintX_t MaxAlignment;
>> +
>> +  OutputSection<ELFT> *OutputSec = nullptr;
>>  };
>>
>>  // Regular defined symbols read from object file symbol tables.
>>
>> Modified: lld/trunk/ELF/Writer.cpp
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=248054&r1=248053&r2=248054&view=diff
>> ==============================================================================
>> --- lld/trunk/ELF/Writer.cpp (original)
>> +++ lld/trunk/ELF/Writer.cpp Fri Sep 18 17:13:25 2015
>> @@ -738,8 +738,11 @@ void OutputSection<ELFT>::relocate(
>>      case SymbolBody::DefinedAbsoluteKind:
>>        SymVA = cast<DefinedAbsolute<ELFT>>(Body)->Sym.st_value;
>>        break;
>> -    case SymbolBody::DefinedCommonKind:
>> -      continue;
>> +    case SymbolBody::DefinedCommonKind: {
>> +      auto *DC = cast<DefinedCommon<ELFT>>(Body);
>> +      SymVA = DC->OutputSec->getVA() + DC->OffsetInBSS;
>> +      break;
>> +    }
>>      case SymbolBody::SharedKind:
>>        if (!relocNeedsGOT(Type))
>>          continue;
>> @@ -1063,6 +1066,7 @@ template <class ELFT> void Writer<ELFT>:
>>      uintX_t Align = C->MaxAlignment;
>>      Off = RoundUpToAlignment(Off, Align);
>>      C->OffsetInBSS = Off;
>> +    C->OutputSec = BSSSec;
>>      Off += Sym.st_size;
>>    }
>>
>>
>> Added: lld/trunk/test/elf2/relocation-common.s
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/relocation-common.s?rev=248054&view=auto
>> ==============================================================================
>> --- lld/trunk/test/elf2/relocation-common.s (added)
>> +++ lld/trunk/test/elf2/relocation-common.s Fri Sep 18 17:13:25 2015
>> @@ -0,0 +1,14 @@
>> +// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t
>> +// RUN: lld -flavor gnu2 %t -o %tout
>> +// RUN: llvm-objdump -t -d %tout | FileCheck %s
>> +// REQUIRES: x86
>> +
>> +.global _start
>> +_start:
>> +  movl $1, sym1(%rip)
>> +
>> +.global sym1
>> +.comm sym1,4,4
>> +
>> +// CHECK: 11000: {{.*}} movl    $1, 4086(%rip)
>> +// CHECK: 0000000000012000 g       .bss            00000004 sym1
>>
>>
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