[llvm-dev] LLD: time to enable --threads by default

[Mehdi Amini via llvm-dev]

SHA1 in LLVM is *very* naive, any improvement is welcome there!
It think Amaury pointed it originally and he had an alternative implementation IIRC.

— 
Mehdi

> On Nov 16, 2016, at 3:58 PM, Rui Ueyama via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> By the way, while running benchmark, I found that our SHA1 function seems much slower than the one in gold. gold slowed down by only 1.3 seconds to compute a SHA1 of output, but we spent 6.0 seconds to do the same thing (I believe). Something doesn't seem right.
> 
> Here is a table to link the same binary with -no-threads and -build-id={none,md5,sha1}. The numbers are in seconds.
> 
>        LLD   gold
> none   7.82  13.78
> MD5    9.68  14.56
> SHA1  13.85  15.05
> 
> 
> On Wed, Nov 16, 2016 at 1:46 PM, Rafael Espíndola <rafael.espindola at gmail.com <mailto:rafael.espindola at gmail.com>> wrote:
> On 16 November 2016 at 15:52, Rafael Espíndola
> <rafael.espindola at gmail.com <mailto:rafael.espindola at gmail.com>> wrote:
> > I will do a quick benchmark run.
> 
> 
> On a mac pro (running linux) the results I got with all cores available:
> 
> firefox
>   master 7.146418217 <tel:7.146418217>
>   patch  5.304271767 1 <tel:304271767%201>.34729488437x faster
> firefox-gc
>   master 7.316743822 <tel:7.316743822>
>   patch  5.46436812 1.33899174824x faster
> chromium
>   master 4.265597914
>   patch  3.972218527 1.07385781648x faster
> chromium fast
>   master 1.823614026
>   patch  1.686059427 1.08158348205x faster
> the gold plugin
>   master 0.340167513
>   patch  0.318601465 1.06768973269x faster
> clang
>   master 0.579914119
>   patch  0.520784947 1.11353855817x faster
> llvm-as
>   master 0.03323043
>   patch  0.041571719 1.251013574x slower
> the gold plugin fsds
>   master 0.36675887
>   patch  0.350970944 1.04498356992x faster
> clang fsds
>   master 0.656180056
>   patch  0.591607603 1.10914743602x faster
> llvm-as fsds
>   master 0.030324313
>   patch  0.040045353 1.32056917497x slower
> scylla
>   master 3.23378908
>   patch  2.019191831 1.60152642773x faster
> 
> With only 2 cores:
> 
> firefox
>   master 7.174839911
>   patch  6.319808477 1.13529388384x faster
> firefox-gc
>   master 7.345525844
>   patch  6.493005841 1.13129820362x faster
> chromium
>   master 4.180752414
>   patch  4.129515199 1.01240756179x faster
> chromium fast
>   master 1.847296843
>   patch  1.78837299 1.0329483018x faster
> the gold plugin
>   master 0.341725451
>   patch  0.339943222 1.0052427255x faster
> clang
>   master 0.581901114
>   patch  0.566932481 1.02640284955x faster
> llvm-as
>   master 0.03381059
>   patch  0.036671392 1.08461260215x slower
> the gold plugin fsds
>   master 0.369184003
>   patch  0.368774353 1.00111084189x faster
> clang fsds
>   master 0.660120583
>   patch  0.641040511 1.02976422187x faster
> llvm-as fsds
>   master 0.031074029
>   patch  0.035421531 1.13990789543x slower
> scylla
>   master 3.243011681
>   patch  2.630991522 1.23261958615x faster
> 
> 
> With only 1 core:
> 
> firefox
>   master 7.174323116
>   patch  7.301968002 1.01779190649x slower
> firefox-gc
>   master 7.339104117
>   patch  7.466171668 1.01731376868x slower
> chromium
>   master 4.176958448
>   patch  4.188387233 1.00273615003x slower
> chromium fast
>   master 1.848922713
>   patch  1.858714219 1.00529578978x slower
> the gold plugin
>   master 0.342383846
>   patch  0.347106743 1.01379415838x slower
> clang
>   master 0.582476955
>   patch  0.600524655 1.03098440178x slower
> llvm-as
>   master 0.033248459
>   patch  0.035622988 1.07141771593x slower
> the gold plugin fsds
>   master 0.369510236
>   patch  0.376390506 1.01861997133x slower
> clang fsds
>   master 0.661267753
>   patch  0.683417482 1.03349585535x slower
> llvm-as fsds
>   master 0.030574688
>   patch  0.033052779 1.08105041006x slower
> scylla
>   master 3.236604638
>   patch  3.325831407 1.02756801617x slower
> 
> Given that we have an improvement even with just two cores available, LGTM.
> 
> Cheers,
> Rafael
> 
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