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Newsgroups: comp.os.386bsd.questions Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!elroy.jpl.nasa.gov!swrinde!gatech!howland.reston.ans.net!pipex!uknet!cf-cm!paul From: paul@myrddin.isl.cf.ac.uk (Paul) Subject: Re: FPU in FreeBSD? Message-ID: <1993Nov10.003426.21244@cm.cf.ac.uk> Sender: news@cm.cf.ac.uk (Network News System) Organization: Intelligent Systems Lab, ELSYM, University of Wales, Cardiff References: <2bo8s7$c0r@nic.lth.se> Date: Wed, 10 Nov 1993 00:34:24 +0000 Lines: 34 In article <2bo8s7$c0r@nic.lth.se> jh@efd.lth.se (Joergen Haegg) writes: >I noticed that some files in gcc was compiled with -NOFPU. >Does this mean that I don't use the FPU in my 486 DX2? > >What should I do to get maximum floating-point performance in FreeBSD >and my own programs? >Is it enough to add '-m486'? > Simply - no. gcc2 uses quite a few FPU instructions and relies on the underlying OS to provide emulation for hardware that doesn't have one. The current emulator doesn't handle sin/cos/sqrt so the generation of these instructions was inhibited in current releases using the NOFPU flag. If you have an FPU you can recompile gcc2 without this flag and it will generate these instructions. They only get generated at -O2 (I think from memory) and even then they may call the standard lib functions to handle error checking. The -m486 flag will buy you some performance at the cost of size, it aligns things better for the 486 and makes slightly different instruction choices to improve performance. To really get *significant* performance improvements for math functions you need a true FPU libm, the GNU mathlib is good, I've used it exstensively but it's unlikely to ever be part of FreeBSD because of the GPL. I'm sure we'll get one done at some point though. -- Paul Richards, University of Wales, College Cardiff Internet: paul@isl.cf.ac.uk JANET: RICHARDSDP@CARDIFF.AC.UK