Messages in this thread | | | From | CaT <> | Subject | Re: glibc-2.1 upgrade headaches. Any ideas?? | Date | Sun, 7 Mar 1999 14:35:48 +1100 (EST) |
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Arvind Sankar wrote the following: > > On Sun, Mar 07, 1999 at 02:09:17PM +1100, CaT wrote: > > I've been happily doing it for a while with -O2 optimisation and > > -march=pentiumpro and haven't had a single kernel crash. > > > > I'd use -O6 but I can't find any info on what the hell this does > > as far as optimisation goes. > > The biggest you can go to currently is -O3, I believe. Anything beyond that > turns on the same flags.
Right. That's what I figured. But a lot of people seem to go on about how -O6 should be used for best performace... I've found that somewhat confusing...
> > of -O2 (I compiled X without it and it's working fine. Hasn't crashed) or > > is it something the kernel needs? And, what exactly does this do? I've read > > the manpage but what that has doesn't mean much to me. I wish there was > > info on not just what an optimisation flag does but also how it might effect > > performance and what sideeffects it might have. (this is probably real hard > > to do but it would be way useful. I don't mind long compile times as long > > as runtime performance is imporved) > >From the gcc manual: > > `-fomit-frame-pointer' > Don't keep the frame pointer in a register for functions that > don't need one. This avoids the instructions to save, set up and > restore frame pointers; it also makes an extra register available > in many functions. *It also makes debugging impossible on some > machines.* > > This option is never turned on by default (on i386), so the kernel Makefile > turns it on.
Uhuh. Does this prevent the use of gdb on the executable and can it be used safely on libraries?
> Obviously, it should improve run-time performance, unless the gcc code > optimizer is so buggy that it generates faster code with less registers > available ;)
Hehe :)
-- CaT (cat@zip.net.au) URL: http://www.zip.com.au/dev/null
An electricity provider of New Hampshire, US has advised it's customers that in the event of a power failure they can log on to its website for more information... - Paraphrased from the New Scientist, Feb 6, 1999
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