[lld] r268604 - ELF: Do not use -1 to mark pieces of merge sections as being tail merged.

[Rafael Espíndola via llvm-commits]

I did, but it is easy to fix I think (working on it).

Cheers,
Rafael


On 5 May 2016 at 11:29, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
> On 5 May 2016 at 00:10, Peter Collingbourne via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>> Author: pcc
>> Date: Wed May  4 23:10:12 2016
>> New Revision: 268604
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=268604&view=rev
>> Log:
>> ELF: Do not use -1 to mark pieces of merge sections as being tail merged.
>>
>> We were previously using an output offset of -1 for both GC'd and tail
>> merged pieces. We need to distinguish these two cases in order to filter
>> GC'd symbols from the symbol table -- we were previously asserting when we
>> asked for the VA of a symbol pointing into a dead piece, which would end
>> up asking the tail merging string table for an offset even though we hadn't
>> initialized it properly.
>>
>> This patch fixes the bug by using an offset of -1 to exclusively mean GC'd
>> pieces, using 0 for tail merges, and distinguishing the tail merge case from
>> an offset of 0 by asking the output section whether it is tail merge.
>>
>> Differential Revision: http://reviews.llvm.org/D19953
>>
>> Added:
>>     lld/trunk/test/ELF/string-gc.s
>> Modified:
>>     lld/trunk/ELF/InputSection.cpp
>>     lld/trunk/ELF/InputSection.h
>>     lld/trunk/ELF/MarkLive.cpp
>>     lld/trunk/ELF/OutputSections.cpp
>>     lld/trunk/ELF/OutputSections.h
>>     lld/trunk/ELF/Writer.cpp
>>
>> Modified: lld/trunk/ELF/InputSection.cpp
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=268604&r1=268603&r2=268604&view=diff
>> ==============================================================================
>> --- lld/trunk/ELF/InputSection.cpp (original)
>> +++ lld/trunk/ELF/InputSection.cpp Wed May  4 23:10:12 2016
>> @@ -419,7 +419,8 @@ MergeInputSection<ELFT>::MergeInputSecti
>>    StringRef Data((const char *)D.data(), D.size());
>>    std::vector<std::pair<uintX_t, uintX_t>> &Offsets = this->Offsets;
>>
>> -  uintX_t V = Config->GcSections ? -1 : 0;
>> +  uintX_t V = Config->GcSections ? MergeInputSection<ELFT>::PieceDead
>> +                                 : MergeInputSection<ELFT>::PieceLive;
>>    if (Header->sh_flags & SHF_STRINGS) {
>>      uintX_t Offset = 0;
>>      while (!Data.empty()) {
>> @@ -478,15 +479,15 @@ typename ELFT::uint MergeInputSection<EL
>>    // Compute the Addend and if the Base is cached, return.
>>    uintX_t Addend = Offset - Start;
>>    uintX_t &Base = I->second;
>> -  if (Base != uintX_t(-1))
>> +  auto *MOS = static_cast<MergeOutputSection<ELFT> *>(this->OutSec);
>> +  if (!MOS->shouldTailMerge())
>>      return Base + Addend;
>
> This disabled the caching, no?
>
> Cheers,
> Rafael