new optimizations for lunar - part1

[Dennis Veatch]

On Wednesday 04 May 2005 03:32 am, Auke Kok wrote:
> Zbigniew Łuszpiński wrote:
> >Hi everyone
> >
> >I made patch for lunar tools which:
> >* removes deprecated (for x86, x64 architecture only!), slowdown gcc
> > option: -mcpu=
> >* adds new option -freorder-blocks
> >
> >Installation:
> >Copy /var/lib/lunar to safe place (to have backup before patching)
> >unpack newopti.diff.bz2 to /var/lib/
> >go to /var/lib and execute: patch -p0 < newopti.diff
> >
> >After installation a new option will appear in Lunar Optimizations/Speed
> >optimizations: Blocks -freorder-blocks
> >
> >Additional information:
> >This patch I use on my computer and it works. Do not know what happen on
> > other computers so be smart applying it.
> >
> >The -freorder-blocks function is rather safe optimization flag which is
> >enabled by default in -O2 and -O3 optimizations and disabled in -O0, -O1
> > and -Os. If someone like me uses -Os optimization and want to get little
> > speedup can safely use -freorder-blocks. Compiled program can be little
> > bigger than -Os but smaller than -O2 and much smaller than -O3. This is
> > good trade-off (speed/size) in my opinion.
> >
> >-mcpu= makes code optimized for given processor but runable with 386. I
> > think that nobody needs such crazy optimization. The -march= option
> > implies -mcpu=. With gcc 3.4 you will even get ugly warning about
> > deprecated -mcpu=.
> >
> >After throwing away -mcpu these options are useless:
> >-mmmx, -msse, -msse2, -msse3, -m3dnow,
> >the -march option implies them if specified CPU have support for them.
> >The compilation process is little faster because gcc do not waste time
> >processing many commandline options.
> >Refer to gcc manual, mailinglist for more information about gcc options.
> >
> >This is my first patch for lunar publicly available so feel free to post
> >comments.
>
> Zbigniew,
>
> thanks for your patch. I've quickly taken a look at it and have some
> comments with regard to your changes:
>
> - -mcpu in lunar is set to the same architecture as -march, we do that
> so that no unoptimized i386 code is present in i686 optimized programs,
> so it makes sense to use -mcpu to 'remove compatibility code for slower
> cpus'.
>
> -> however, I'll see if we can turn on/off the -mcpu option with a flag
> as to achieve downwards compatible code anyways, as this may be of use
> to people running the same binaries on multiple platforms.
>
> - the sse/sse2/mmx flags are useful to people who wish to use mmx/sse
> with slower optimizations
>
> - the '-freorder-blocks' looks interesting, however I don't think there
> are many people who use -Os or -O1 optimization right now, so the
> usability is low again. However for the ISO's it might be of use, or
> anyone who's experimenting with smaller but still optimized code.
>
> In any case the -mcpu idea is interesting and I'll try to see if I can
> fit it in.
>
> Thanks for your patch!
>
> sofar
>
> _______________________________________________
> Lunar mailing list
> Lunar at lunar-linux.org
> http://foo-projects.org/mailman/listinfo/lunar

I do not want to lose the sse/sse2/mmx flags. :)