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Re: clang

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: clang
Date 2019-03-24 15:47 +0100
Organization A noiseless patient Spider
Message-ID <q785ae$9gi$1@dont-email.me> (permalink)
References <q77osi$1id$1@dont-email.me> <m8LlE.156248$MT2.71591@fx21.am4> <q77vl5$sh4$2@dont-email.me> <GyLlE.163277$pP5.161588@fx01.am4>

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On 24/03/2019 14:24, Melzzzzz wrote:
> On 2019-03-24, jacobnavia <jacob@jacob.remcomp.fr> wrote:
>> Le 24/03/2019 à 13:56, Melzzzzz a écrit :
>>> On 2019-03-24, jacobnavia <jacob@jacob.remcomp.fr> wrote:
>>>> What are your experiences with clang?
>>>>
>>>> I have recently installed that compiler in an ARM64/Linux system, and it
>>>> seems very good (much better than gcc) when it works.
>>>>
>>>> For instance, in a benchmark of floating point operations (matrix
>>>> operations) the results were:
>>>>
>>>>      1 clang -O2: 12.22
>>>>      2 gcc   -O2: 18.6
>>>>      3 lcc   -O : 21.4
>>>
>>> Without code it is meaningless to say such figures. In my experience gcc
>>> is slightly faster.
>>>
>>
>> Joined the code of matrix.c
> Indeed clang is slightly faster in this benchmark:
> ./matrix_gcc  0.94s user 0.00s system 118% cpu 0.790 total
> ./matrix_clang  0.61s user 0.00s system 116% cpu 0.529 total
> ~/News >>> gcc -O2 -march=native matrix.c -o matrix_gcc -lm
> ~/News >>> clang -O2 -march=native matrix.c -o matrix_clang -lm
> clang version 7.0.1 (tags/RELEASE_701/final)
> gcc version 8.2.1 20181127 (GCC)
> 

clang tends to be very good at automatic vectorisation and using SIMD 
units.  If it is code where that is a benefit (and a matrix benchmark 
sounds like a likely candidate), then it stands a good chance of giving 
fast results.  On other code, it can lead to slower results.

It is, as far as I have seen in comparisons, usual for clang to compile 
a little faster than gcc, but for gcc's output to run a little faster 
than clang's.  The difference between the two has dropped significantly 
in recent years - the rivalry between the compilers has paid off for 
everyone.

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clang jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-24 12:15 +0100
  Re: clang Melzzzzz <Melzzzzz@zzzzz.com> - 2019-03-24 12:56 +0000
    Re: clang jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-24 14:11 +0100
      Re: clang Melzzzzz <Melzzzzz@zzzzz.com> - 2019-03-24 13:24 +0000
        Re: clang David Brown <david.brown@hesbynett.no> - 2019-03-24 15:47 +0100
      Re: clang Bart <bc@freeuk.com> - 2019-03-24 13:42 +0000
        Re: clang Noob <root@127.0.0.1> - 2019-04-10 21:07 +0200
  Re: clang already5chosen@yahoo.com - 2019-03-24 06:24 -0700
    Re: clang Melzzzzz <Melzzzzz@zzzzz.com> - 2019-03-24 13:38 +0000
  Re: clang jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-26 21:06 +0100
    Re: clang Melzzzzz <Melzzzzz@zzzzz.com> - 2019-03-26 20:48 +0000
      Re: clang jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-26 21:50 +0100
        Re: clang Ian Collins <ian-news@hotmail.com> - 2019-03-27 09:52 +1300
          Re: clang jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-26 21:58 +0100
            Re: clang already5chosen@yahoo.com - 2019-03-27 06:40 -0700
              Re: clang jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-27 17:31 +0100
          Re: clang already5chosen@yahoo.com - 2019-03-27 06:29 -0700
            Re: clang Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-27 14:57 +0000
              Re: clang already5chosen@yahoo.com - 2019-03-27 08:16 -0700
                Re: clang scott@slp53.sl.home (Scott Lurndal) - 2019-03-27 15:47 +0000
                Re: clang Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-27 18:29 +0000
                Re: clang already5chosen@yahoo.com - 2019-03-27 11:45 -0700
                Re: clang Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-27 21:37 +0000
                Re: clang already5chosen@yahoo.com - 2019-03-28 05:50 -0700
                Re: clang already5chosen@yahoo.com - 2019-03-28 06:01 -0700
                Re: clang scott@slp53.sl.home (Scott Lurndal) - 2019-03-28 15:21 +0000
                Re: clang Ian Collins <ian-news@hotmail.com> - 2019-03-28 07:52 +1300
                Re: clang David Brown <david.brown@hesbynett.no> - 2019-03-27 22:45 +0100
                Re: clang jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-28 00:12 +0100
      Re: clang scott@slp53.sl.home (Scott Lurndal) - 2019-03-26 20:55 +0000
        Re: clang jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-26 22:05 +0100
          Re: clang Melzzzzz <Melzzzzz@zzzzz.com> - 2019-03-26 21:59 +0000
      Re: clang Bart <bc@freeuk.com> - 2019-03-26 21:42 +0000
        Re: clang Melzzzzz <Melzzzzz@zzzzz.com> - 2019-03-26 22:00 +0000
          Re: clang Bart <bc@freeuk.com> - 2019-03-27 14:32 +0000
    Re: clang already5chosen@yahoo.com - 2019-03-27 06:54 -0700
  Re: clang: release build jacobnavia <jacob@jacob.remcomp.fr> - 2019-03-28 23:31 +0100
  Re: clang Mehdi Amini <atorrses@gmail.com> - 2019-04-07 19:38 +0430

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