From owner-freebsd-hackers Sat Apr 8 15: 6:16 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from po4.wam.umd.edu (po4.wam.umd.edu [128.8.10.166]) by hub.freebsd.org (Postfix) with ESMTP id D9FA837B544; Sat, 8 Apr 2000 15:06:07 -0700 (PDT) (envelope-from culverk@wam.umd.edu) Received: from rac3.wam.umd.edu (root@rac3.wam.umd.edu [128.8.10.143]) by po4.wam.umd.edu (8.9.3/8.9.3) with ESMTP id SAA14020; Sat, 8 Apr 2000 18:05:57 -0400 (EDT) Received: from rac3.wam.umd.edu (sendmail@localhost [127.0.0.1]) by rac3.wam.umd.edu (8.9.3/8.9.3) with SMTP id SAA10875; Sat, 8 Apr 2000 18:05:55 -0400 (EDT) Received: from localhost (culverk@localhost) by rac3.wam.umd.edu (8.9.3/8.9.3) with ESMTP id SAA10871; Sat, 8 Apr 2000 18:05:55 -0400 (EDT) X-Authentication-Warning: rac3.wam.umd.edu: culverk owned process doing -bs Date: Sat, 8 Apr 2000 18:05:55 -0400 (EDT) From: Kenneth Wayne Culver To: Matthew Dillon Cc: Kris Kennaway , "Alexey N. Dokuchaev" , freebsd-hackers@FreeBSD.ORG Subject: Re: What are the best gcc optimization options for Pentium 200 MMX In-Reply-To: <200004082134.OAA12743@apollo.backplane.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Why exactly whould you not touch the -march options? I have had no problems using them, and my system (5.0-CURRENT) seems a little faster with -march=i686. I could be wrong though as I havn't done any exact tests... it just seems a bit more responsive.. ================================================================= | Kenneth Culver | FreeBSD: The best OS around. | | Unix Systems Administrator | ICQ #: 24767726 | | and student at The | AIM: muythaibxr | | The University of Maryland, | Website: (Under Construction) | | College Park. | http://www.wam.umd.edu/~culverk/| ================================================================= On Sat, 8 Apr 2000, Matthew Dillon wrote: > :On Sat, 8 Apr 2000, Alexey N. Dokuchaev wrote: > : > :> AFAIK, Linux Mandrake has it's kernel and userland highly optimized for > :> Pentium architecture. However, they have additional gcc optimization > :> flags turned on by default, including -O3 and -mfast_math. > : > :Can you say "gimmick"? :-) gcc often produces demonstrably broken code for > :optimisation levels higher than -O. > : > :Probably the only useful and safe option apart from -O is the > :-march=pentium/pentiumpro/pentiumii/etc option for using > :processor-specific opcodes and instruction scheduling. > :Kris > > I use -Os for everything. I wouldn't bother with anything else. Someone > ran a bunch of benchmarks with various gcc/egcs options a while back > and, frankly, the top half dozen combinations were so close to each > other performance-wise that it just didn't matter. -Os was in that > group, but also produced significantly smaller binaries. > > I wouldn't touch the -march stuff at all, nor would I use -O3 (which > tries to inline standard static functions verses -O2) - that's useless > on IA32 because call/returns are very fast (I had an argument with John > Dyson about call/return overhead verses an L1 cache miss and > we ran a bunch of timings. I lost the argument :-) call/return won the > race handily). > > > -Matt > Matthew Dillon > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message