[lld] r320286 - PPC32: Support R_PPC_PLTREL32 in static mode.

[Tim Northover via llvm-commits]

I was just committing a patch that seemed to have a valid review. You want vit9696 to be involved here. I’ve added him to the thread.

Tim.

> On 10 Dec 2017, at 18:58, Rafael Avila de Espindola <rafael.espindola at gmail.com> wrote:
> 
> Tim Northover via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> writes:
> 
>> Author: tnorthover
>> Date: Sun Dec 10 00:42:34 2017
>> New Revision: 320286
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=320286&view=rev
>> Log:
>> PPC32: Support R_PPC_PLTREL32 in static mode.
>> 
>> See https://reviews.llvm.org/D39226
>> 
>> Patch by vit9696 <vit9696 at avp.su>
>> 
>> Modified:
>>    lld/trunk/ELF/Arch/PPC.cpp
>>    lld/trunk/test/ELF/ppc-relocs.s
>> 
>> Modified: lld/trunk/ELF/Arch/PPC.cpp
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Arch/PPC.cpp?rev=320286&r1=320285&r2=320286&view=diff
>> ==============================================================================
>> --- lld/trunk/ELF/Arch/PPC.cpp (original)
>> +++ lld/trunk/ELF/Arch/PPC.cpp Sun Dec 10 00:42:34 2017
>> @@ -34,6 +34,15 @@ RelExpr PPC::getRelExpr(RelType Type, co
>>   case R_PPC_REL24:
>>   case R_PPC_REL32:
>>     return R_PC;
>> +  // In general case R_PPC_PLTREL24 should result in R_PLT_PC, however, since
>> +  // PLT support is currently not available for PPC32 this workaround at least 
>> +  // allows lld to resolve local symbols when performing static linkage after
>> +  // LLVM started to forcibly use PLT relocations by default (see D38554).
>> +  // Non-local symbols will need a full PLT implementation, but once it lands
>> +  // local symbols should still avoid PLT table with static relocation model.
>> +  // This is the optimisation that bfd and gold are doing by default as well.
>> +  case R_PPC_PLTREL24:
>> +    return R_PC;
> 
> The generic optimization (plt -> pc) is implemented in fromPlt in
> Relocations.cpp. If the desire is to support only local symbols, this
> could return R_PLT_PC, no?
> 
> Cheers,
> Rafael

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