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Re: The Stupidification Of systemd Haters

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Richard Kettlewell <invalid@invalid.invalid> wrote:
> not@telling.you.invalid (Computer Nerd Kev) writes:
>> Is that "fairly straightforward today" like RK said? I'd say
>> writing optimised code in assembly and decoding CPU-specific
>> capabilities identifiers to decide at run-time whether it can be
>> used is really pretty full-on compared to just letting the compiler
>> build pure C code optimised for one specific CPU.
> 
> The statement was:
> 
> | It's fairly straightforward today to build performance critical code
> | multiple times for different targets and select the best one at
> | runtime.  This includes using intrinsics, vector instructions or
> | assembler selected for particular classes of CPU, as well as just
> | giving the compiler a narrower target and letting it get on with it.
> 
> For an example of getting the compiler to build something multiple times
> for different targets, so that an executable can select the best one at
> runtime, see https://godbolt.org/z/PP1Mc3hfj.

Thanks, yes that is a more approachable method of doing the
selection at run-time compared to that FFmpeg code. For those
playing along at home, I see the "target" attribute feature of GCC
is documented here (with an example that seems to avoid needing the
separate function to select for the CPU in use):

https://gcc.gnu.org/onlinedocs/gcc/Function-Multiversioning.html

> Obviously the overall effort increases if you hand-optimize for specific
> targets, or add more architectures, but that's what you would expect;
> the complexity scales with your ambitions.  The basic point here is that
> putting together a design which allows for multiple targets to be
> supported within a single executable or library is really quite easy
> with modern compilers.

It looks like GCC is working on an even easier method using the
"clone" attribute, and eventually a way to apply it automatically
to only the functions where the speed-up is worth the size
increase:

https://gcc.gnu.org/wiki/FunctionSpecificOpt#Stage3:_Details_of_compiling_a_single_function_multiple_times_manually

Oh, "last edited 2011-03-16", so maybe not...

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The Stupidification of GNU/Linux Users Leroy H <lh@somewhere.net> - 2026-05-11 19:00 +0000
  Re: The Stupidification of GNU/Linux Users The Natural Philosopher <tnp@invalid.invalid> - 2026-05-11 20:10 +0100
    Re: The Stupidification of GNU/Linux Users "s|b" <me@privacy.invalid> - 2026-05-12 18:11 +0200
      Re: The Stupidification of GNU/Linux Users The Natural Philosopher <tnp@invalid.invalid> - 2026-05-13 12:38 +0100
  Re: The Stupidification of GNU/Linux Users Andy Burns <usenet@andyburns.uk> - 2026-05-11 20:12 +0100
    Re: The Stupidification Of systemd Haters Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-11 22:47 +0000
      Re: The Stupidification Of systemd Haters c186282 <c186282@nnada.net> - 2026-05-11 22:42 -0400
        Re: The Stupidification Of systemd Haters Rich <rich@example.invalid> - 2026-05-12 13:52 +0000
          Re: The Stupidification Of systemd Haters Richard Kettlewell <invalid@invalid.invalid> - 2026-05-12 17:49 +0100
            Re: The Stupidification Of systemd Haters Rich <rich@example.invalid> - 2026-05-12 22:00 +0000
              Re: The Stupidification Of systemd Haters rbowman <bowman@montana.com> - 2026-05-13 04:47 +0000
                Re: The Stupidification Of systemd Haters The Natural Philosopher <tnp@invalid.invalid> - 2026-05-13 12:43 +0100
                Re: The Stupidification Of systemd Haters rbowman <bowman@montana.com> - 2026-05-13 17:40 +0000
                Re: The Stupidification Of systemd Haters Rich <rich@example.invalid> - 2026-05-13 14:41 +0000
              Re: The Stupidification Of systemd Haters "Carlos E.R." <robin_listas@es.invalid> - 2026-05-13 12:56 +0200
                Re: The Stupidification Of systemd Haters The Natural Philosopher <tnp@invalid.invalid> - 2026-05-13 12:56 +0100
                Re: The Stupidification Of systemd Haters Rich <rich@example.invalid> - 2026-05-13 14:52 +0000
                Re: The Stupidification Of systemd Haters "Carlos E.R." <robin_listas@es.invalid> - 2026-05-13 22:24 +0200
                Re: The Stupidification Of systemd Haters The Natural Philosopher <tnp@invalid.invalid> - 2026-05-14 10:34 +0100
                Re: The Stupidification Of systemd Haters Rich <rich@example.invalid> - 2026-05-13 14:48 +0000
                Re: The Stupidification Of systemd Haters "Carlos E.R." <robin_listas@es.invalid> - 2026-05-13 22:25 +0200
                Re: The Stupidification Of systemd Haters Stéphane CARPENTIER <sc@fiat-linux.fr> - 2026-05-15 20:51 +0000
                Re: The Stupidification Of systemd Haters not@telling.you.invalid (Computer Nerd Kev) - 2026-05-14 10:00 +1000
                Re: The Stupidification Of systemd Haters Richard Kettlewell <invalid@invalid.invalid> - 2026-05-14 10:00 +0100
                Re: The Stupidification Of systemd Haters The Natural Philosopher <tnp@invalid.invalid> - 2026-05-14 10:45 +0100
                Re: The Stupidification Of systemd Haters Richard Kettlewell <invalid@invalid.invalid> - 2026-05-14 11:25 +0100
                Re: The Stupidification Of systemd Haters The Natural Philosopher <tnp@invalid.invalid> - 2026-05-14 11:38 +0100
                Re: The Stupidification Of systemd Haters Richard Kettlewell <invalid@invalid.invalid> - 2026-05-14 12:28 +0100
                Re: The Stupidification Of systemd Haters The Natural Philosopher <tnp@invalid.invalid> - 2026-05-14 12:40 +0100
                Re: The Stupidification Of systemd Haters Richard Kettlewell <invalid@invalid.invalid> - 2026-05-14 18:06 +0100
                Re: The Stupidification Of systemd Haters rbowman <bowman@montana.com> - 2026-05-14 23:46 +0000
                Re: The Stupidification Of systemd Haters Stéphane CARPENTIER <sc@fiat-linux.fr> - 2026-05-15 20:41 +0000
                Re: The Stupidification Of systemd Haters Richard Kettlewell <invalid@invalid.invalid> - 2026-05-14 11:16 +0100
                Re: The Stupidification Of systemd Haters not@telling.you.invalid (Computer Nerd Kev) - 2026-05-15 09:19 +1000
                Re: The Stupidification Of systemd Haters Richard Kettlewell <invalid@invalid.invalid> - 2026-05-15 12:23 +0100
                Re: The Stupidification Of systemd Haters The Natural Philosopher <tnp@invalid.invalid> - 2026-05-14 10:42 +0100
                Re: The Stupidification Of systemd Haters Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-14 01:12 +0000
                Re: The Stupidification Of systemd Haters Richard Kettlewell <invalid@invalid.invalid> - 2026-05-14 10:09 +0100
                Re: The Stupidification Of systemd Haters "Carlos E.R." <robin_listas@es.invalid> - 2026-05-14 12:54 +0200
                Re: The Stupidification Of systemd Haters rbowman <bowman@montana.com> - 2026-05-14 17:52 +0000
                Re: The Stupidification Of systemd Haters "Carlos E.R." <robin_listas@es.invalid> - 2026-05-14 22:50 +0200
          Re: The Stupidification Of systemd Haters "Carlos E.R." <robin_listas@es.invalid> - 2026-05-12 18:55 +0200
          Re: The Stupidification Of systemd Haters rbowman <bowman@montana.com> - 2026-05-12 22:19 +0000
            Re: The Stupidification Of systemd Haters Rich <rich@example.invalid> - 2026-05-13 14:56 +0000
              Re: The Stupidification Of systemd Haters rbowman <bowman@montana.com> - 2026-05-13 17:45 +0000
                Re: The Stupidification Of systemd Haters The Natural Philosopher <tnp@invalid.invalid> - 2026-05-13 18:50 +0100
                Re: The Stupidification Of systemd Haters Rich <rich@example.invalid> - 2026-05-13 19:09 +0000
                Re: The Stupidification Of systemd Haters "Carlos E.R." <robin_listas@es.invalid> - 2026-05-13 22:34 +0200
                Re: The Stupidification Of systemd Haters Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2026-05-13 21:34 +0000
                Re: The Stupidification Of systemd Haters Rich <rich@example.invalid> - 2026-05-13 19:06 +0000
  Re: The Stupidification of GNU/Linux Users Rich <rich@example.invalid> - 2026-05-11 21:41 +0000
  Re: The Stupidification of GNU/Linux Users Bobbie Sellers <bliss-sf4ever@dslextreme.com> - 2026-05-11 14:59 -0700
  Re: The Stupidification of GNU/Linux Users rbowman <bowman@montana.com> - 2026-05-12 03:53 +0000
    Re: The Stupidification of GNU/Linux Users c186282 <c186282@nnada.net> - 2026-05-12 00:39 -0400
      Re: The Stupidification of GNU/Linux Users rbowman <bowman@montana.com> - 2026-05-12 23:02 +0000
        Re: The Stupidification of GNU/Linux Users c186282 <c186282@nnada.net> - 2026-05-12 20:49 -0400
  Re: The Stupidification of GNU/Linux Users makendo <makendo@makendo.invalid> - 2026-05-12 12:47 +0800
    Re: The Stupidification of GNU/Linux Users c186282 <c186282@nnada.net> - 2026-05-12 01:26 -0400
  Re: The Stupidification of GNU/Linux Users Stéphane CARPENTIER <sc@fiat-linux.fr> - 2026-05-15 21:04 +0000

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