From owner-freebsd-hackers Wed Jun 3 22:32:08 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id WAA01732 for freebsd-hackers-outgoing; Wed, 3 Jun 1998 22:32:08 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from iconmail.bellatlantic.net (iconmail.bellatlantic.net [199.173.162.30]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id WAA01614; Wed, 3 Jun 1998 22:31:56 -0700 (PDT) (envelope-from dmm125@bellatlantic.net) Received: from myname.my.domain (client201-122-92.bellatlantic.net [151.201.122.92]) by iconmail.bellatlantic.net (IConNet Sendmail) with SMTP id BAA14471; Thu, 4 Jun 1998 01:30:38 -0400 (EDT) Date: Thu, 4 Jun 1998 01:31:26 +0000 (GMT) From: Donn Miller X-Sender: dmm125@myname.my.domain To: "John S. Dyson" cc: Mike Smith , hackers@FreeBSD.ORG Subject: Re: Recompiling sources with "-O2 -m486 -pipe" In-Reply-To: <199806040447.XAA00815@dyson.iquest.net> 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 On Wed, 3 Jun 1998, John S. Dyson wrote: > Mike Smith said: > > > > > > About the -m486 option -- I use -m486 -O3 -pipe all the time; does it slow > > > down the execution somewhat? I noticed the Mozilla sources defined > > > -mno-486. Do you know if compiling with -mno-486 gives better results > > > than -m486 as far as speed, etc.? I figured that -m486 generated 486 > > > instructions, which would make a pentium run faster. > > > > There are no 486 instructions to generate, and anything over -O runs > > the risk of exposing bugs in the gcc optimiser it seems. > > > -m486 expands the code somewhat, with larger alignment boundaries. Netscape > is already very big :-). Some postings in DejaNews claim that the -mno-486 runs faster on a Pentium (than -m486). Other postings say just the opposite. The -m486 option, from what I understand, benefits the 486 more than a Pentium. I thought that the Pentium architecture was a ``superset'' more or less of the 486, so I figured whatever makes a 486 run faster will make a Pentium run faster. I figure that: use: CFLAGS -m486 -O3 for small to medium-sized code. use: CFLAGS -mno-486 -O3 for large code (ex. - Mozilla, compiling entire XFree86 dist. from source). --Donn To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message