Ken Moffat wrote: > For i?86, when we force it to build for m486 we also add -O3. I've > been using -O3 for glibc on x86_64 in case it turns out to be > beneficial. On my old single processor machines, I doubt that it > helped, but my suspicions about it are actually raised by results on > my phonon which definitely has enough horsepower. > > On LFS-7.1 I noted ldd segfaulted for one of the gst plugins > packages near the end of my system build, but that eventually built > ok. On my i3, no problems. > > Now I'm doing my first test build of current svn, mainly to iron > out the bugs in my scripts, and then to sort out the changes for the > first part of my desktop scripts. Here, glibc bombs out very > quickly (internal compiler error, segmentation fault in vfscanf.c) > . > Did it twice, so at that point I dropped back to -O2 and it was ok. > Perhaps I should mention that everything else using my own CFLAGS > uses -O2, it's only glibc where I've tried -O3. > > Has anyone seen similar problems with -O3 in glibc (or, converesely, > has anyone used -O3 without any problems) ? I can see that I'll have > to have a go at recompiling glibc when the LFS packages have finished, > and then (if it still crashes), have to work out how to get the > preprocessed source. I'm hoping its just a problem with the > temporary version of gcc in /tools. > > I'm just glad I'm not doing this on a slow i686 box :)
http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html -O3 turns on -finline-functions -funswitch-loops -fpredictive-commoning -fgcse-after-reload -ftree-vectorize -fipa-cp-clone I know that inline functions can cause problems at times. Personally, I go with the upstream default optimizations. I don't think any improvements would be worth the risk. If I were developing compute intensive sw, I'd pay attention, but for a general purpose library, the devs know best. Note that I *have* done compute intensive sw and sometimes it does make the difference of an 18 hour run instead of a 24 hour run. However, I don't think the standard libraries are the place for this type of optimization. That said, have fun... -- Bruce -- http://linuxfromscratch.org/mailman/listinfo/lfs-dev FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
