[PATCH] D42977: Don't set dso_local flag in LTO resolutions for absolute symbols defined in ELF objects

[via llvm-commits]

I addressed the comments and updated the diff.


> On Feb 6, 2018, at 3:24 PM, Rafael Avila de Espindola <rafael.espindola at gmail.com> wrote:
> 
> Dmitry Mikulin via Phabricator <reviews at reviews.llvm.org> writes:
> 
>> Index: lld/test/ELF/lto/abs-resol.ll
>> ===================================================================
>> --- /dev/null
>> +++ lld/test/ELF/lto/abs-resol.ll
>> @@ -0,0 +1,15 @@
>> +; REQUIRES: x86
>> +
>> +; RUN: llvm-as %s -o %t.o
>> +; RUN: llvm-mc -triple=x86_64-pc-linux %p/Inputs/absolute.s -o %t2.o -filetype=obj
>> +; RUN: ld.lld %t.o %t2.o -o %t.out -pie
>> +
>> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
>> +target triple = "x86_64-unknown-linux-gnu"
>> +
>> + at blah = external global i8, align 1
>> +
>> +; Function Attrs: noinline nounwind optnone uwtable
> 
> You can remove the above comment.
> 
>> Index: lld/test/ELF/lto/Inputs/absolute.s
>> ===================================================================
>> --- /dev/null
>> +++ lld/test/ELF/lto/Inputs/absolute.s
>> @@ -0,0 +1,3 @@
>> +.globl blah
>> +.equ blah, 0xdeadbeef
>> +.type blah, at notype
> 
> notype is the default I think. Most other tests use = instead of .equ.
> 
>> Index: lld/ELF/LTO.cpp
>> ===================================================================
>> --- lld/ELF/LTO.cpp
>> +++ lld/ELF/LTO.cpp
>> @@ -154,8 +154,12 @@
>>     R.VisibleToRegularObj = Config->Relocatable || Sym->IsUsedInRegularObj ||
>>                             (R.Prevailing && Sym->includeInDynsym()) ||
>>                             UsedStartStop.count(ObjSym.getSectionName());
>> +    const auto *DR = dyn_cast<Defined>(Sym);
>>     R.FinalDefinitionInLinkageUnit =
>> -        Sym->isDefined() && (IsExecutable || Sym->Visibility != STV_DEFAULT);
>> +        (IsExecutable || Sym->Visibility != STV_DEFAULT) && DR &&
>> +        // Skip absolute symbols from ELF objects, otherwise PC-rel relocations
>> +        // will be generated by for them, triggering linker errors.
>> +        !(Sym->File && Sym->File->isElf() && DR->Section == nullptr);
> 
> In the last part of the if it is not immediately clear why you need to
> check isElf. Experimenting with the patch it turns out the reason is that
> bitcode files always have a null section.
> 
> Please update the comment to say that.
> 
> LGTM with the above changes.
> 
> Thanks,
> Rafael
>