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Re: C Compilers QoI

From Gareth Owen <gwowen@gmail.com>
Newsgroups comp.lang.c
Subject Re: C Compilers QoI
References (15 earlier) <65fe56dc-d555-40c4-84b1-ae83e5913810@googlegroups.com> <ej0hvkFhe9iU11@mid.individual.net> <ej0if2Fhe9iU13@mid.individual.net> <87d1dgpk3p.fsf@gmail.com> <ej1hcnFhe9iU16@mid.individual.net>
Date 2017-03-17 07:59 +0000
Message-ID <87lgs4wcxw.fsf@gmail.com> (permalink)

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Ian Collins <ian-news@hotmail.com> writes:

> On 03/17/17 06:07 PM, Gareth Owen wrote:
>> Ian Collins <ian-news@hotmail.com> writes:
>>
>>> On 03/17/17 11:30 AM, Ian Collins wrote
>>>>
>>>> For computationally intensive (vectorisable)  code, such as FFmpeg, the
>>>> particulars of specific processors, especially supported SIMD
>>>> instructions can make a very significantly affect performance.
>>>>
>>> Need a grammar checker...
>>>
>>> For computationally intensive (vectorisable)  code such as FFmpeg the
>>> particulars of specific processors, especially supported SIMD
>>> instructions, can very significantly affect performance.
>>
>> True, but for those purposes FFmpeg often falls back to using inline asm
>> or explicit __builtin_xxx SIMD instructions, which suggests the
>> optimisers have some way to on architecture-specific tuning - particular
>> in the presence of potential aliasing.
>
> -fno-strict-aliasing?

You'd have to ask them, I'm only kinda familiar with the codebase.  They
are hyper-sensitive to tiny optimisations -- the absolutely fastest
imaginable code.  There's no such thing as "good enough". If the
compiled code was 99% as fast as the inline asm, I suspect they'd pick
the ASM, even given the maintenence headache.

> Falling back to using inline asm is just as bad as chip specific
> optimisation options!

There's a mindset that doesn't care about that though.  Not one I share.

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C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 13:01 +0000
  Re: C Compilers QoI mark.bluemel@gmail.com - 2017-03-14 06:16 -0700
  Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-14 06:42 -0700
  Re: C Compilers QoI "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-03-14 06:56 -0700
    Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 15:58 +0000
      Re: C Compilers QoI "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-03-14 09:22 -0700
      Re: C Compilers QoI scott@slp53.sl.home (Scott Lurndal) - 2017-03-14 16:54 +0000
        Re: C Compilers QoI supercat@casperkitty.com - 2017-03-14 10:24 -0700
          Re: C Compilers QoI scott@slp53.sl.home (Scott Lurndal) - 2017-03-14 17:58 +0000
            Re: C Compilers QoI supercat@casperkitty.com - 2017-03-14 14:12 -0700
              Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-14 16:34 -0500
              Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-14 17:36 -0500
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 23:06 +0000
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-14 16:20 -0700
              Re: C Compilers QoI antispam@math.uni.wroc.pl - 2017-03-15 02:32 +0000
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-15 12:49 +0000
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-15 11:56 -0700
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-15 23:09 +0000
                Re: C Compilers QoI scott@slp53.sl.home (Scott Lurndal) - 2017-03-16 18:17 +0000
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-16 11:47 -0700
                Re: C Compilers QoI Ian Collins <ian-news@hotmail.com> - 2017-03-17 07:50 +1300
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-16 12:59 -0700
                Re: C Compilers QoI David Brown <david.brown@hesbynett.no> - 2017-03-16 21:24 +0100
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-16 14:23 -0700
                Re: C Compilers QoI Ian Collins <ian-news@hotmail.com> - 2017-03-17 11:30 +1300
                Re: C Compilers QoI Ian Collins <ian-news@hotmail.com> - 2017-03-17 11:38 +1300
                Re: C Compilers QoI Gareth Owen <gwowen@gmail.com> - 2017-03-17 05:07 +0000
                Re: C Compilers QoI Ian Collins <ian-news@hotmail.com> - 2017-03-17 20:26 +1300
                Re: C Compilers QoI Gareth Owen <gwowen@gmail.com> - 2017-03-17 07:59 +0000
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-16 16:14 -0700
                Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-16 22:54 -0500
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-17 09:01 -0700
                Re: C Compilers QoI Ian Collins <ian-news@hotmail.com> - 2017-03-26 14:16 +1300
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-26 14:19 -0700
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-26 22:43 +0100
                Re: C Compilers QoI GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-03-27 01:28 +0200
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-26 22:07 -0700
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-27 11:28 +0100
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-27 07:38 -0700
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-27 16:23 +0100
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-27 08:55 -0700
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-27 17:01 +0100
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-27 10:03 -0700
                Re: C Compilers QoI GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-03-27 17:58 +0200
                Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-27 03:54 -0700
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-27 08:46 -0700
                Re: C Compilers QoI scott@slp53.sl.home (Scott Lurndal) - 2017-03-27 17:47 +0000
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-27 11:48 -0700
                Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-27 15:37 -0500
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-27 14:46 -0700
                Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-27 20:28 -0500
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-28 01:18 -0700
                Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-28 18:24 -0500
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-29 07:40 -0700
                Re: C Compilers QoI David Brown <david.brown@hesbynett.no> - 2017-03-29 17:05 +0200
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-29 11:07 -0700
                Re: C Compilers QoI antispam@math.uni.wroc.pl - 2017-03-31 04:04 +0000
                Re: C Compilers QoI bartc <bc@freeuk.com> - 2017-03-31 10:53 +0100
                Re: C Compilers QoI Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-03-31 07:35 -0700
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-31 08:07 -0700
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-31 07:54 -0700
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-31 07:43 -0700
                Re: C Compilers QoI Ian Collins <ian-news@hotmail.com> - 2017-03-17 11:21 +1300
                Re: C Compilers QoI Ian Collins <ian-news@hotmail.com> - 2017-03-17 11:24 +1300
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-16 22:15 +0000
                Re: C Compilers QoI scott@slp53.sl.home (Scott Lurndal) - 2017-03-17 12:31 +0000
                Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-16 15:24 -0700
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-16 16:03 -0700
                Re: C Compilers QoI scott@slp53.sl.home (Scott Lurndal) - 2017-03-17 12:39 +0000
                Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-17 08:27 -0700
                Re: C Compilers QoI antispam@math.uni.wroc.pl - 2017-03-16 01:35 +0000
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-16 02:18 +0000
                Re: C Compilers QoI antispam@math.uni.wroc.pl - 2017-03-18 00:45 +0000
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-18 13:12 +0000
                Re: C Compilers QoI antispam@math.uni.wroc.pl - 2017-03-18 20:31 +0000
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-18 17:31 -0700
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-16 09:22 -0700
          Re: C Compilers QoI Nick Bowler <nbowler@draconx.ca> - 2017-03-24 16:13 +0000
            Re: C Compilers QoI supercat@casperkitty.com - 2017-03-24 12:32 -0700
              Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-24 22:13 -0500
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-25 13:05 -0700
                Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-27 15:44 -0500
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-27 14:51 -0700
                Re: C Compilers QoI Robert Wessel <robertwessel2@yahoo.com> - 2017-03-27 20:31 -0500
        Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 17:26 +0000
          Re: C Compilers QoI Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-03-15 12:02 -0500
  Re: C Compilers QoI David Brown <david.brown@hesbynett.no> - 2017-03-14 15:00 +0100
    Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-14 07:36 -0700
      Re: C Compilers QoI David Brown <david.brown@hesbynett.no> - 2017-03-14 15:57 +0100
      Re: C Compilers QoI Andrey Tarasevich <andreytarasevich@hotmail.com> - 2017-03-14 08:11 -0700
        Re: C Compilers QoI BGB <cr88192@hotmail.com> - 2017-03-29 23:51 -0500
    Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 15:28 +0000
      Re: C Compilers QoI David Brown <david.brown@hesbynett.no> - 2017-03-14 21:41 +0100
  Re: C Compilers QoI Keith Thompson <kst-u@mib.org> - 2017-03-14 09:26 -0700
    Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 18:23 +0000
      Re: C Compilers QoI Keith Thompson <kst-u@mib.org> - 2017-03-14 12:05 -0700
  Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-14 09:35 -0700
    Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 17:08 +0000
      Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-14 10:24 -0700
        Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 17:34 +0000
        Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-14 11:55 -0700
          Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 19:03 +0000
            Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 19:06 +0000
            Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-14 12:10 -0700
              Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 21:14 +0000
                Re: C Compilers QoI already5chosen@yahoo.com - 2017-03-14 14:42 -0700
                Re: C Compilers QoI supercat@casperkitty.com - 2017-03-14 14:53 -0700
                Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 23:20 +0000
                Re: C Compilers QoI antispam@math.uni.wroc.pl - 2017-03-15 02:43 +0000
  Re: C Compilers QoI jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-14 19:39 +0100
    Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-14 19:10 +0000
  Re: C Compilers QoI antispam@math.uni.wroc.pl - 2017-03-14 19:29 +0000
  Re: C Compilers QoI Noob <root@127.0.0.1> - 2017-03-15 09:27 +0100
  Re: C Compilers QoI ed_davis2@yahoo.com - 2017-03-16 15:10 -0700
    Re: C Compilers QoI BartC <bc@freeuk.com> - 2017-03-16 23:19 +0000

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