[llvm-dev] Please dogfood LLD

[Rui Ueyama via llvm-dev]

As to the Phoronix benchmark results, I tried linking fftw as an example
and got a different result. In my test, ld.bfd, ld.gold and ld.lld are all
on par, and that is reasonable because compile time is the dominant factor
of building fftw. In the Phoronix tests, LLD was slower than the GNU
linkers when linking fftw, and I don't know why. The Phoronix tests
measured the entire build time (as opposed to the time that the linker
actually consumed), and it seems to me that that is too noisy. (Michael, if
you are watching this, you probably want to measure only the time spent by
the linker?)

Regarding the libtool issue, I'm inclined to accept the "GNU" hack. That's
not really a bad hack. As Ed explained, that is not going to be fixed
easily as the code generated by libtool is copied to so many projects. If
we can convince libtool-generated script that we are a GNU compatible
linker just by adding "GNU" to somewhere in the --version message, it
sounds like a good deal. We can add a string "LLD is a GNU-compatible
linker" or "LLD accepts the same command line options as the GNU linker" or
something like that to the --version string. I think we need this in
reality.

On Mon, Mar 20, 2017 at 7:17 AM, Rafael Avila de Espindola via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Michael Johnson <mpj at rowley.co.uk> writes:
>
> > Hi Rafael,
> >> Michael Johnson via llvm-dev <llvm-dev at lists.llvm.org> writes:
> >>
> >>> Hi Rui,
> >>>
> >>> Are there any plans to support the -defsym command line option?
> >> It doesn't look that hard, it was just never requested. What project is
> >> using it?
> > Not sure I understand what the project set is. It's not an uncommon
> > feature for a linker in the embedded world.
> >
> > It's the first problem I discovered when trying to use lld rather than
> > ld e.g.
> >
> > -defsym=__vfprintf=__vfprintf_float_long_long
> >
> > to select a particular implementation of printf.
> >
> > The second problem was failing to parse the .ld script - I can provide
> > it if required.
>
> If you could open bugs for both that would be awesome.
>
> Thanks,
> Rafael
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