[patch] Forward the -O options to the linker

[Rafael Espíndola]

The only small argument I can think for it is for cases where the
compiler and linker cooperate, like -function-sections + -gc-sections.

I am fine with just updating our own build for now to take advantage
of the linker optimizations. It is probably a good idea even if this
patch goes in for people building with gcc or older clang versions
(patch is a second).



On 1 November 2014 22:04, Chandler Carruth <chandlerc at google.com> wrote:
> So, I vaguely don't like this....
>
> I'm pretty comfortable with 'clang -O3 x.o y.o z.o -o my_binary' passing O3
> to the LTO plugin, but less comfortable with passing it to the linker
> itself. I'm not really sure why though, so I'm open to be convinced
> otherwise. I don't have any principled stance here, it just seems somewhat
> off.
>
> I asked Rafael on IRC to check with GCC, and it requires "-Wl,-O3", and so
> my current vote is for us to not invent a new convenience thing here. I'd be
> interested if others disagree, and if so why.
>
> On Mon, Oct 20, 2014 at 9:35 AM, Rafael Espíndola
> <rafael.espindola at gmail.com> wrote:
>>
>> It is fairly common for -O to be passed to clang when linking and both
>> bfd and gold support -O options, but currently the driver doesn't
>> translate it and projects have to use -Wl,-O if they want to enable
>> those options. In fact, our own build pass -O3, but not -Wl,-O.
>>
>> The attached patch translates and forwards the -O options to the linker.
>>
>> Cheers,
>> Rafael
>
>