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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!news.ecn.uoknor.edu!news.wildstar.net!cancer.vividnet.com!hunter.premier.net!www.nntp.primenet.com!nntp.primenet.com!howland.erols.net!EU.net!usenet2.news.uk.psi.net!uknet!usenet1.news.uk.psi.net!uknet!dispatch.news.demon.net!demon!longacre.demon.co.uk From: searle@longacre.demon.co.uk (Michael Searle) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: gcc optimizations for kernel Date: Sun, 15 Sep 1996 16:41:48 BST Lines: 29 Message-ID: <n0E175F6A@longacre.demon.co.uk> References: <51d0eg$9uf@usenet4.interramp.com> <323A693E.7B4C@OntheNet.com.au> <8791ad5jed.fsf@plm.xs4all.nl> NNTP-Posting-Host: longacre.demon.co.uk X-NNTP-Posting-Host: longacre.demon.co.uk X-Newsreader: Offlite 0.09 / Termite Internet for Acorn RISC OS Peter Mutsaers <plm@xs4all.nl> wrote: >>> On Sat, 14 Sep 1996 18:13:50 +1000, Tony Griffiths >>> <tonyg@OntheNet.com.au> said: TG>> The higher levels of optimisation are "probably" OK for non-device TG>> driver code, but would almost certainly bring you undone in a driver. TG>> Re-arranging the order of 'bashing' device registers is generally TG>> not a good thing. TG>> If you feel brave enough to go through and modify the make file, then TG>> you might get a "-O3" kernel to work but it will be a LOT of work!!! > Hmm, I've been running for months with a kernel compiled with -O2, > without problems. I assume that the sections of device drivers that > depend on order are not reordered by gcc, or the makefiles force that > -O2 not be used for such files. Well, so had I, but I've changed the Makefile to do -O on device drivers (there's a separate CFLAGS line). I tried to change it to do -O3 for the rest, but the result gave me the Black Screen of Death when starting X. (I think it was X that did it, it was certainly after login.) Is all the driver code compiled with the DRIVER_C options? Most of it seemed to be, but I think all the /scsi files were compiled with the NORMAL_C flags which may have caused the failure at -O3. -- Michael Searle - searle@longacre.demon.co.uk