[PATCH] D40697: Cache modulo values for the .gnu.hash section.

[Rui Ueyama via llvm-commits]

On Fri, Dec 1, 2017 at 2:10 PM, Rafael Avila de Espindola <
rafael.espindola at gmail.com> wrote:

> Rui Ueyama <ruiu at google.com> writes:
>
> > On Fri, Dec 1, 2017 at 1:41 PM, Rafael Avila de Espindola <
> > rafael.espindola at gmail.com> wrote:
> >
> >> Rui Ueyama via Phabricator <reviews at reviews.llvm.org> writes:
> >>
> >> > ruiu updated this revision to Diff 125067.
> >> > ruiu added a comment.
> >> >
> >> > - clang-format
> >> >
> >> > It seems this patch actually makes that test case 2% faster, which
> >> > isn't a negligible improvement.
> >>
> >> Please benchmark more than clang. There is a set of different benchmarks
> >> in https://s3-us-west-2.amazonaws.com/linker-tests/
> lld-speed-test.tar.xz.
> >
> >
> > We don't need to run all these benchmarks as this patch is a micro
> > optimization. More precisely, in order to create a hash table for 22212
> > symbols,
> >
> >  - GnuHashTableSection::addSymbols took 60 ms
> >  - GnuHashTableSection::writeHashTable took 8 ms.
> >
> > With this patch it now takes 37 ms and 7 ms, respectively.
>
> I am uncomfortable LGTMing an optimization without a full
> benchmark. Specially one that trades memory for speed.
>

There's no memory-to-CPU tradeoff. There was a 32-bit padding at end of
`Entry` struct.


> I will benchmark the patch. This will hopefully get better soon with a
> bot tracking performance.
>
> Cheers,
> Rafael
>
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