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

[Mehdi Amini via llvm-dev]

The current implementation was “copy/pasted” from somewhere (it was explicitly public domain).

> On Nov 16, 2016, at 4:05 PM, Rui Ueyama <ruiu at google.com> wrote:
> 
> Can we just copy-and-paste optimized code from somewhere?
> 
> On Wed, Nov 16, 2016 at 4:03 PM, Mehdi Amini <mehdi.amini at apple.com <mailto:mehdi.amini at apple.com>> wrote:
> 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 <mailto: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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> 
> 

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