Re: Inline functions and locals

From	James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups	comp.lang.c++
Subject	Re: Inline functions and locals
Date	2022-01-14 11:26 -0500
Organization	A noiseless patient Spider
Message-ID	<srs873$ijn$1@dont-email.me> (permalink)
References	<srmvu4$oie$1@gioia.aioe.org> <srqkvk$3vi$1@dont-email.me> <srrmd6$1bo0$1@gioia.aioe.org> <srru5t$939$1@dont-email.me>

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On 1/14/22 8:34 AM, James Kuyper wrote:
...
> standard's wording above makes "inline" no more than a hint. An
> implementation is free to perform inline substitution of any function
> call, whether or not the function is declared 'inline', so long as the
> result produces the same observable effects as calling a separate
> function.

I wanted to point out that the opposite transformation is also
permitted: and implementation can take code out of the function where it
is written, and replace it with a call to a separate function created by
the implementation containing that code.

Why would an implementation do this? For the opposite of the reason it
would inline some code. In general, inlining trades off an increase in
the execution speed against increased code size. There are important
exceptions: the inlined code could be smaller than the code that would
needed to implement the function call. Even if it isn't, inline
substitution could open up opportunities for optimization involving
interactions between the code inside the inlined function, and code
surrounding the function call. However, when neither of those cases
apply, each call to a function that gets inlined increases the size of
the generated code.

When I first mentioned this possibility, I had no idea whether any
existing compiler would do this, but I thought it unlikely. I was
corresponding surprised by a response that identified a particular
compiler that actually did it. As I might have anticipated, that
compiler was cross-compiling for a memory-starved embedded system.
Unfortunately, that was a decade ago, and I no longer remember any details.

Thread

Inline functions and locals Muttley@dastardlyhq.com - 2022-01-12 16:34 +0000
  Re: Inline functions and locals Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-12 17:38 +0100
  Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-12 12:47 -0500
  Re: Inline functions and locals Juha Nieminen <nospam@thanks.invalid> - 2022-01-13 07:00 +0000
    Re: Inline functions and locals "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-01-13 10:45 +0100
      Re: Inline functions and locals Juha Nieminen <nospam@thanks.invalid> - 2022-01-17 12:55 +0000
        Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-17 15:14 +0100
        Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-17 10:24 -0800
          Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-17 19:46 +0100
    Re: Inline functions and locals Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-13 11:08 +0100
      Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-13 19:30 -0800
  Re: Inline functions and locals Paavo Helde <eesnimi@osa.pri.ee> - 2022-01-13 12:46 +0200
    Re: Inline functions and locals Muttley@dastardlyhq.com - 2022-01-13 15:38 +0000
  Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-13 17:51 -0800
    Re: Inline functions and locals Muttley@dastardlyhq.com - 2022-01-14 11:22 +0000
      Re: Inline functions and locals Öö Tiib <ootiib@hot.ee> - 2022-01-14 04:02 -0800
        Re: Inline functions and locals Manfred <invalid@invalid.add> - 2022-01-14 17:30 +0100
          Re: Inline functions and locals Muttley@dastardlyhq.com - 2022-01-14 16:49 +0000
        Re: Inline functions and locals Muttley@dastardlyhq.com - 2022-01-14 16:40 +0000
          Re: Inline functions and locals Öö Tiib <ootiib@hot.ee> - 2022-01-14 11:28 -0800
          Re: Inline functions and locals "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-01-14 20:29 +0100
      Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-14 08:34 -0500
        Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-14 11:26 -0500
          Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-14 18:47 +0100
      Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-14 08:43 -0800
        Re: Inline functions and locals Juha Nieminen <nospam@thanks.invalid> - 2022-01-17 05:38 +0000
          Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-17 08:12 +0100
            Re: Inline functions and locals "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-01-16 23:51 -0800
              Re: Inline functions and locals "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-01-16 23:55 -0800
              Re: Inline functions and locals David Brown <david.brown@hesbynett.no> - 2022-01-17 11:35 +0100
            Re: Inline functions and locals Juha Nieminen <nospam@thanks.invalid> - 2022-01-17 09:50 +0000
              Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-17 14:39 -0500
                Re: Inline functions and locals Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 15:34 -0800
                Re: Inline functions and locals "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-01-17 15:50 -0800
                Re: Inline functions and locals Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-25 03:42 -0700
                Re: Inline functions and locals "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-04-25 08:48 -0700
          Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-16 23:53 -0800
            Re: Inline functions and locals Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 15:29 -0800
    Re: Inline functions and locals Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-17 12:40 +0100
      Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-17 10:13 -0800
        Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-17 16:15 -0500
          Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-17 16:28 -0800
            Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-17 22:55 -0500
              Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-18 11:32 -0800
                Re: Inline functions and locals James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-18 19:03 -0500
                Re: Inline functions and locals Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-18 17:22 -0800
        Re: Inline functions and locals Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-18 09:20 +0100

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