Date:	Thu, 6 Jul 2000 19:44:18 +0600 (LKT)
From:	Kalum Somaratna aka Grendel <kalum AT lintux DOT cx>
X-Sender:	kalum AT roadrunner DOT grendel DOT net
To:	djgpp AT delorie DOT com
Subject:	Re: Voodoo optimization?
In-Reply-To:	<20000706015618.01353.00001528@ng-bj1.aol.com>
Message-ID:	<Pine.LNX.4.21.0007061935210.1891-100000@roadrunner.grendel.net>
MIME-Version:	1.0
Reply-To:	djgpp AT delorie DOT com
Errors-To:	nobody AT delorie DOT com
X-Mailing-List:	djgpp AT delorie DOT com
X-Unsubscribes-To:	listserv AT delorie DOT com

On 6 Jul 2000, The awesome and feared S. T. L. commented thusly,

> Hi. I've been trying to squeeze more optimized code out of DJGPP by playing
> with various switches.  (I don't know C yet, but I hope to learn it soon!)  I'm
> compiling BladeEnc, an MP3 encoder, and want to see how fast I can get it. 
> (No, I don't use it to transfer music over the Internet.)  By turning on
> various switches, I've found that the commandline
> GCC -s -O2 -march=i686 -fomit-frame-pointer -ffast-math -funroll-loops
> -funroll-all-loops -malign-double -fstrict-aliasing -o BLADE.EXE *.c
> seems to produce the fastest code.  (I'm doing this on a Pentium III system.)
> Am I missing any blindingly obvious switches I should be trying?  I've tried
> several other switches, but they all have no effect or detrimental effects. 

Did you try -O3..what effect did that have, sometimes it causes the 
compiler to output code that overflows the cache etc..which can make it
slower than -O2.

> I'm looking for speed, not for size.

Sometimes(often?), unroling loops,and inlining functions can be slower on
586,686 architectures due to the cache overflows etc...

Grendel

Hi, I'm a signature virus. plz set me as your signature and help me spread
:)

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