From owner-freebsd-hackers Fri Sep 8 00:38:47 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id AAA25401 for hackers-outgoing; Fri, 8 Sep 1995 00:38:47 -0700 Received: from localhost.lightside.com (user52.lightside.com [198.81.209.52]) by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id AAA25394 for ; Fri, 8 Sep 1995 00:38:45 -0700 Received: (from jehamby@localhost) by localhost.lightside.com (8.6.11/8.6.9) id AAA04280; Fri, 8 Sep 1995 00:39:13 -0700 Date: Fri, 8 Sep 1995 00:38:46 -0700 (PDT) From: Jake Hamby X-Sender: jehamby@localhost To: hackers@freebsd.org Subject: -m486 option to GCC Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: hackers-owner@freebsd.org Precedence: bulk I remember in my Linux days that the '-m486' option was often passed to GCC to provide optimizations for 486-class PC's. Apparently it didn't generate 486-specific code but simply padded functions out in such a way that performance was improved on 486's without sacrificing compatibility with 386's. If you build GCC on a "i486-*-*" machine it will include the "-m486" option by default but on a "i386-*-*" machine, it won't. My question is: In Linux, 'uname -m' will tell you 'i486' if you have a 486 or 'i386' otherwise (I'm not sure about Pentiums), whereas under FreeBSD, it always returns 'i386'. Therefore GCC by default is built NOT to include the '-m486' option by default. I would recommend that either: a) The kernel be changed to return the "proper" machine name, and GCC be recompiled with 486 optimizations on by default (since it doesn't hurt performance on 386's). Of course purists would argue that 'i386' is the generic architecture name and shouldn't change depending on which machine you run 'uname' on. b) When running "configure" in the build tree for GCC, the canonical name be manually overridden to "i486-unknown-freebsd2.x.x" instead of "i386-unknown-freebsd2.x.x" to build in this optimization. Note that the default Makefiles generated by imake under XFree86 will always include '-m486' anyway. Comments? ------------------------------------------------------------------------------- Jake Hamby | E-Mail: jehamby@lightside.com Student, Cal Poly University, Pomona | System Administrator, JPL -------------------------------------------------------------------------------