[PATCH] D42216: Use New Module Metadata String "AvoidPLT" to avoid calls via PLT

[Sriraman Tallam via llvm-commits]

On Mon, Jan 29, 2018 at 2:35 PM, Rafael Avila de Espindola
<rafael.espindola at gmail.com> wrote:
> Sriraman Tallam via Phabricator <reviews at reviews.llvm.org> writes:
>
> This LGTM with a llvm-link patch added.
>
>> --- lib/Target/X86/X86Subtarget.cpp
>> +++ lib/Target/X86/X86Subtarget.cpp
>> @@ -157,8 +157,11 @@
>>        // In Regcall calling convention those registers are used for passing
>>        // parameters. Thus we need to prevent lazy binding in Regcall.
>>        return X86II::MO_GOTPCREL;
>> -    if (F && F->hasFnAttribute(Attribute::NonLazyBind) && is64Bit())
>> -      return X86II::MO_GOTPCREL;
>> +    // If PLT must be avoided then the call should be via GOTPCREL.
>> +    if (((F && F->hasFnAttribute(Attribute::NonLazyBind)) ||
>> +         (!F && M.getRtLibUseGOT())) &&
>> +        is64Bit())
>> +       return X86II::MO_GOTPCREL;
>>      return X86II::MO_PLT;
>>    }
>
> Should we deprecate the non lazy bind attribute and always use the
> module flag?

There is still a use case for the attribute.  I was hoping to expose a
function attribute in clang that can be used to set the nonlazybind
attribute only for a subset of functions.  Would be useful for linkers
which do not know how to undo indirect calls to direct for functions
that are not external or for 32-bit.

Thanks
Sri

>
> Cheers,
> Rafael