On March 2, 2005 12:12 pm, Mike Hernandez wrote: > > I'm also using -O3 and --enable-omitfp with good results btw. > > > > robert > > is --enable-omitfp the same as -fomit-frame-pointer ?
--enable-omitfp also uses -O99, and defines string_inlines. -fomit-frame-pointer can't be added to CFLAGS for glibc because a handfull of files can't use it, the configure option enables it where ever it can. > And does it still hold true that -O2 combined with > -fomit-frame-pointer produces faster executables than -O3? (as stated > here: > http://archives.linuxfromscratch.org/mail-archives/blfs-dev/2002-October/00 >1419.html) Not in my experience. And it looks like the glibc folks think -O99 (basically -O3) works well with -fomit-frame-pointer. -O2 vs -O3 totally depends on the cpu. On my duron -O3 is very bad because there's only 64kb of L2 cache. I still use --enable-omitfp but I hack Makeconfig and s/-O99/-O2/. I use -finline-functions because it still helps. I also covert packages to gzip on that system because bzip2 is heavy on the L2 cache. I expect Celeron's would have the same problem. On this pentium4 I have much more L2 cache, and -O3 is usable. Optimizations also vary in benefits from one package to another. -O3 would work better on the GNU packages, and kernel, because they're coded for GCC. Software like ash, and procps, are not programed for GCC specifically, so -O3 would make them slower because -finline-functions, etc, would not be taken advantage of. Others like mplayer use -O4 because they have done everything they can think of to take advantage of GCC. robert -- http://linuxfromscratch.org/mailman/listinfo/lfs-chat FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
