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Groups > comp.lang.c > #107061
| Newsgroups | comp.lang.c |
|---|---|
| Date | 2017-03-25 13:05 -0700 |
| References | (3 earlier) <4fVxA.62281$Bp6.47291@fx36.iad> <74bd9556-d8eb-4507-8780-11df9311b5d2@googlegroups.com> <ob3gil$drf$1@dont-email.me> <099f1bea-dbc7-4955-b2e4-df520abc90e4@googlegroups.com> <p0obdcdijaqig54jcfqu9ic2e4fku6fo21@4ax.com> |
| Message-ID | <faf2e101-579e-4dae-b770-ede0a6cc7cdc@googlegroups.com> (permalink) |
| Subject | Re: C Compilers QoI |
| From | supercat@casperkitty.com |
On Friday, March 24, 2017 at 10:13:52 PM UTC-5, robert...@yahoo.com wrote:
> On Fri, 24 Mar 2017 12:32:04 -0700 (PDT), supercat wrote:
>
> >On the other hand, that would probably a good idea even if one didn't care
> >about having repeated builds produce bit-identical output, since the
> >likelihood of an optimization's benefits exceeding the costs will tend to
> >fall as code grows beyond a certain point.
>
> I'm not sure how you'd support such a statement. Why would most of
> the non-code-expanding optimizations tend to be less effective on
> large routines? And even the ones that tend to expand code?
Many optimizations involve the elimination of redundant loads, stores, or
computations, and rely upon the compiler's ability to determine everything
between those operations that might affect them. As a simple example:
int someVar;
void someFunction(void)
{
someVar++;
... some other code
someVar++;
}
depending upon what's in the omitted section, it may or may not be possible
to consolidate the two actions on someVar. The greater the amount of code
between the two accesses to someVar, the longer it will take to determine
whether the consolidation would be safe, and the greater the likelihood that
it won't be. Further, if a lot of code ends up executing between the two
operations on someVar, it's unlikely that those two operations on someVar
would represent a meaningful fraction of the program's execution time.
Obviously there are cases where a long-range search for optimizations can
turn up some which end up being quite useful and which wouldn't have been
found on a more aggressively-pruned search. In general, though, I would
suggest that the greater the distance between operations, the less likely
it is that the value of any optimization opportunities will exceed the
cost.
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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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