From owner-freebsd-current Tue May 25 11:35:13 1999 Delivered-To: freebsd-current@freebsd.org Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by hub.freebsd.org (Postfix) with ESMTP id EFCF0153FA for ; Tue, 25 May 1999 11:35:06 -0700 (PDT) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.9.3/8.9.3) id NAA18684; Tue, 25 May 1999 13:35:02 -0500 (CDT) (envelope-from dan) Date: Tue, 25 May 1999 13:35:00 -0500 From: Dan Nelson To: Garrett Wollman Cc: current@FreeBSD.ORG Subject: Re: More compiler option comparisons Message-ID: <19990525133459.B17956@dan.emsphone.com> References: <199905251635.MAA11353@khavrinen.lcs.mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.95.5i In-Reply-To: <199905251635.MAA11353@khavrinen.lcs.mit.edu>; from "Garrett Wollman" on Tue May 25 12:35:12 GMT 1999 X-OS: FreeBSD 4.0-CURRENT Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In the last episode (May 25), Garrett Wollman said: > Just for completeness, I did one final run of HINT with just `-O' > specified (our usual default). `-O' results in significantly better > integer performance than `-O4'. (Floating-point performance is just > the opposite.) > > This suggests that compiling the world with `-O' levels higher than > one is probably a bad idea. (The generated assembly is identical from > `-O2' to `-O4'.) The `-O2' code appears to be less efficient at > register allocation; about twice as much stack temporary space is > required. -O4 doesn't exist in egcs (or it didn't a month or so ago). According to the source, -O2 enables all optimizations except -funroll-all-loops, and all -O3 does is enable -funroll-all-loops. I'd like to see separate runs, one with each -march= option (i386, i486, i586, i686), so see if those many any difference at all. -Dan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message