[PATCH] D42681: [ELF] - Remove unused synthetic sections correctly.

[George Rimar via llvm-commits]

>> -    std::vector<BaseCommand *>::iterator Empty = OS->SectionCommands.end();
>> -    for (auto I = OS->SectionCommands.begin(), E = OS->SectionCommands.end();
>> -         I != E; ++I) {
>> -      BaseCommand *B = *I;
>> +    // If we reach here, then SS is an unused synthetic section and we want to
>> +    // remove it from corresponding input section description of output section.
>> +    for (BaseCommand *B : OS->SectionCommands) {
>>        if (auto *ISD = dyn_cast<InputSectionDescription>(B)) {
>> -        llvm::erase_if(ISD->Sections,
>> -                       [=](InputSection *IS) { return IS == SS; });
>> -        if (ISD->Sections.empty())
>> -          Empty = I;
>> +        auto It = llvm::find(ISD->Sections, SS);
>> +        if (It == ISD->Sections.end())
>> +          continue;
>> +        ISD->Sections.erase(It);
>> +        break;
>
>This can keep using erase_if:
>
>    for (BaseCommand *B : OS->SectionCommands)
>      if (auto *ISD = dyn_cast<InputSectionDescription>(B))
>        llvm::erase_if(ISD->Sections,
>                      [=](InputSection *IS) { return IS == SS; });
>
>LGTM with that.
>
>Cheers,
>Rafael

Ok, thanks ! 
This stops doing early loop break, but makes code simpler and not a perfomance hit anyways.
Updated the patch.

Rui, are you OK to land it ?

George.