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Re: Compile Assembly and C files together

From Robert Wessel <robertwessel2@yahoo.com>
Newsgroups comp.lang.c, comp.sys.raspberry-pi, comp.programming
Subject Re: Compile Assembly and C files together
Message-ID <fto5adla2e9376a87o7avpvoegvvctceit@4ax.com> (permalink)
References (9 earlier) <p7u3qu$v3u$1@dont-email.me> <9EwoC.76436$CL3.51040@fx17.am4> <p7uc0j$du$1@dont-email.me> <o1g5adljtiebbk6gfssr767mvj684phuud@4ax.com> <p7uj8i$n7g$1@dont-email.me>
Organization Forte - www.forteinc.com
Date 2018-03-09 13:48 -0600

Cross-posted to 3 groups.

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On Fri, 9 Mar 2018 19:20:01 +0100, David Brown
<david.brown@hesbynett.no> wrote:

>On 09/03/18 18:19, Robert Wessel wrote:
>> On Fri, 09 Mar 2018 17:16:19 +0100, David Brown

>>> Well no, of course it was not a priority.  Why should it be?  Virtually
>>> no one is interested in the calling conventions - just compiler writers,
>>> people writing OS context switch routines, and the few dozen people
>>> writing assembly routines instead of using higher level languages.
>>> Efficiency of generated code was far and away the priority when AMD made
>>> the System V AMD64 ABI used by everyone except Windows.  $DEITY only
>>> knows what MS's priorities were when they scrambled it and made
>>> something pointlessly different and less efficient - the only think I
>>> can think of was to make implementation of "printf" a little easier for
>>> the MSVC compiler writers.
>> 
>> 
>> While I'm not going to try to defend it, MS's explanation is that
>> there's no cost to actually allocate the spill space (just a change to
>> the stack adjustment done at entry to the calling function, and the
>> space is not usually wasted (and thus does not impact caching),
>> compilers can use it for local variables if they're not going to spill
>> the first four parameters to that space.  And it does, of course, make
>> the variadic parameter thing easier.
>
>That is an interesting view on it - thanks.
>
>However, it /will/ have a cost in the case of functions that do not 
>otherwise need to allocate space in the stack other than the automatic 
>push/pop from the call/ret pair.  So a small function that could 
>otherwise be run entirely from within the caller-saved registers, but 
>which itself calls another function, will need to allocate stack.  This 
>might seem rare, but I am sure it turns up a lot in C++ code with all 
>these functions that don't seem to do anything except pass on 
>responsibility to other functions!


While true, most of those small C++ functions need to set up a stack
frame anyway so that exception handling can unwind the stack.  That
doesn't, however, change the fact that the shadow area allocation is a
waste of cache space in that scenario.

OTOH, many of those short functions *should* get inlined.  Obviously
that's more difficult if the short functions are virtual ones, but if
you're clunking your way through a indirect call via a vtable anyway,
the added pain from half a wasted cache line is probably modest.

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Re: Compile Assembly and C files together "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-03-06 19:20 +0800
  Re: Compile Assembly and C files together jack4747@gmail.com - 2018-03-06 05:12 -0800
  Re: Compile Assembly and C files together druck <news@druck.org.uk> - 2018-03-06 13:53 +0000
    Re: Compile Assembly and C files together Rob Morley <nospam@ntlworld.com> - 2018-03-06 14:59 +0000
      Re: Compile Assembly and C files together David Brown <david.brown@hesbynett.no> - 2018-03-06 16:35 +0100
    Re: Compile Assembly and C files together "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-03-06 23:01 +0800
  Re: Compile Assembly and C files together ray carter <ray@zianet.com> - 2018-03-06 15:44 +0000
    Re: Compile Assembly and C files together "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-03-07 00:07 +0800
      Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-07 22:39 +0200
        Re: Compile Assembly and C files together "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-03-08 18:18 +0800
          Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-08 12:37 +0000
            Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-08 13:13 +0000
              Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-08 13:34 +0000
                Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-08 15:27 +0000
                Re: Compile Assembly and C files together mm0fmf <none@invalid.com> - 2018-03-08 17:33 +0000
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 09:06 +0000
                Re: Compile Assembly and C files together Richard Kettlewell <invalid@invalid.invalid> - 2018-03-09 09:17 +0000
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 09:30 +0000
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 15:56 +0200
                Re: Compile Assembly and C files together bartc <bc@freeuk.com> - 2018-03-09 14:13 +0000
                Re: Compile Assembly and C files together Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2018-03-09 11:14 -0500
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 17:44 +0000
                Re: Compile Assembly and C files together David Brown <david.brown@hesbynett.no> - 2018-03-09 17:16 +0100
                Re: Compile Assembly and C files together Robert Wessel <robertwessel2@yahoo.com> - 2018-03-09 11:19 -0600
                Re: Compile Assembly and C files together bartc <bc@freeuk.com> - 2018-03-09 18:11 +0000
                Re: Compile Assembly and C files together Robert Wessel <robertwessel2@yahoo.com> - 2018-03-09 13:41 -0600
                Re: Compile Assembly and C files together David Brown <david.brown@hesbynett.no> - 2018-03-09 19:20 +0100
                Re: Compile Assembly and C files together Robert Wessel <robertwessel2@yahoo.com> - 2018-03-09 13:48 -0600
                Re: Compile Assembly and C files together Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2018-03-09 13:16 -0500
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-09 18:29 +0000
                Re: Compile Assembly and C files together Jack Fearnley <jack@alcor.concordia.ca> - 2018-03-09 19:07 +0000
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-09 19:13 +0000
                Re: Compile Assembly and C files together Michael J. Mahon <mjmahon@aol.com> - 2018-03-10 13:16 -0600
                Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-11 19:39 +0000
                Re: Compile Assembly and C files together Michael J. Mahon <mjmahon@aol.com> - 2018-03-12 01:16 -0500
                Re: Compile Assembly and C files together David Taylor <david-taylor@blueyonder.co.uk.invalid> - 2018-03-12 06:39 +0000
                Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-12 20:49 +0000
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-12 16:11 +0000
                Re: Compile Assembly and C files together Michael J. Mahon <mjmahon@aol.com> - 2018-03-12 14:58 -0500
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-12 20:38 +0000
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-12 16:06 +0000
                Re: Compile Assembly and C files together Michael J. Mahon <mjmahon@aol.com> - 2018-03-12 14:58 -0500
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 21:27 +0200
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 17:40 +0000
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 21:30 +0200
                Re: Compile Assembly and C files together Richard Damon <Richard@Damon-Family.org> - 2018-03-09 13:16 -0500
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 21:33 +0200
                Re: Compile Assembly and C files together mm0fmf <none@invalid.com> - 2018-03-09 17:40 +0000
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 17:47 +0000
                Re: Compile Assembly and C files together mm0fmf <none@invalid.com> - 2018-03-09 18:05 +0000
                Compile Assembly and C files together nospam.mark.lewis@p73.f12.n3634.z1.binkp.net (mark lewis) - 2018-03-09 04:17 +1200
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 09:05 +0000
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 16:01 +0200
            Re: Compile Assembly and C files together jack4747@gmail.com - 2018-03-08 05:46 -0800
              Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-08 14:47 +0000
          Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-08 17:25 +0200
  Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-07 07:36 +0000

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