[lld] r316305 - Remove a fast lookup table from MergeInputSection.

[Rui Ueyama via llvm-commits]

I'll do that now.

On Tue, Oct 31, 2017 at 12:03 PM, Rafael Avila de Espindola <
rafael.espindola at gmail.com> wrote:

> Ping.
>
> The more patches that lld accumulates the harder this is to revert. It
> is a very significant regression, reverting it should be a priority.
>
> Cheers,
> Rafael
>
> Rafael Avila de Espindola <rafael.espindola at gmail.com> writes:
>
> > Would you mind reverting for now?
> >
> > Cheers,
> > Rafael
> >
> > Rui Ueyama <ruiu at google.com> writes:
> >
> >> I will try to link Firefox with/without this change.
> >>
> >> On Mon, Oct 30, 2017 at 1:26 PM, Rafael Avila de Espindola <
> >> rafael.espindola at gmail.com> wrote:
> >>
> >>> Rui Ueyama via llvm-commits <llvm-commits at lists.llvm.org> writes:
> >>>
> >>> > Author: ruiu
> >>> > Date: Sun Oct 22 16:02:07 2017
> >>> > New Revision: 316305
> >>> >
> >>> > URL: http://llvm.org/viewvc/llvm-project?rev=316305&view=rev
> >>> > Log:
> >>> > Remove a fast lookup table from MergeInputSection.
> >>> >
> >>> > We used to have a map from section piece offsets to section pieces
> >>> > as a cache for binary search. But I found that the map took quite a
> >>> > large amount of memory and didn't make linking faster. So, in this
> >>> > patch, I removed the map.
> >>> >
> >>> > This patch saves 566 MiB of RAM (2.019 GiB -> 1.453 GiB) when linking
> >>> > clang with debug info, and the link time is 4% faster in that test
> case.
> >>>
> >>> I really cannot reproduce these results. I got no speedups and up to
> >>> 1.26 X slowdown on one testcase.
> >>>
> >>>
> >>> linux-kernel
> >>>   master 0.546992001
> >>>   patch  0.549968921 1.0054423465x slower
> >>> clang-gdb-index
> >>>   master 9.992913087
> >>>   patch  10.087697421 1.00948515545x slower
> >>> firefox-O0
> >>>   master 4.309384538
> >>>   patch  4.319022313 1.00223646206x slower
> >>> firefox
> >>>   master 7.34432128
> >>>   patch  8.732557725 1.18902174783x slower
> >>> firefox-gc
> >>>   master 7.597263246
> >>>   patch  8.982908786 1.18238745916x slower
> >>> chromium
> >>>   master 3.642106275
> >>>   patch  3.643732349 1.00044646528x slower
> >>> chromium fast
> >>>   master 2.124109064
> >>>   patch  2.130475186 1.00299707868x slower
> >>> the gold plugin
> >>>   master 0.369448142
> >>>   patch  0.375036623 1.0151265641x slower
> >>> clang
> >>>   master 0.641592855
> >>>   patch  0.648808956 1.01124716546x slower
> >>> llvm-as
> >>>   master 0.041228891
> >>>   patch  0.041646759 1.01013531991x slower
> >>> the gold plugin fsds
> >>>   master 0.406015859
> >>>   patch  0.410742062 1.01164043939x slower
> >>> clang fsds
> >>>   master 0.744126586
> >>>   patch  0.750361992 1.00837949633x slower
> >>> llvm-as fsds
> >>>   master 0.041222066
> >>>   patch  0.041647983 1.01033225749x slower
> >>> scylla
> >>>   master 3.127981483
> >>>   patch  3.964674056 1.26748642137x slower
> >>>
> >>>
> >>> Cheers,
> >>> Rafael
> >>>
> >>>
>
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