Well, you have a point. But if you look at the documentation, it says: -OfastDisregard strict standards compliance. -Ofast enables all -O3 optimizations. It also enables optimizations that are not valid for all standard-compliant programs. It turns on -ffast-math and the Fortran-specific -fno-protect-parens and -fstack-arrays.
So, While O3 turns on -ftree-vectorize, -Ofast is not strictly compliant and turns on fast-math, I do it separately I use the above incantation. Finally, since I compile atk/glib/pango/cairo by myself, I do use the above optimization for all the builds. Btw, I build Gimp on Windows and Mac, so your mileage may vary. On Sat, Mar 2, 2013 at 10:00 AM, Elle Stone <[email protected]> wrote: > On 3/2/13, Partha Bagchi <[email protected]> wrote: > > I thought Gentoo was all about optimizing a linux distribution to your > > specific proecessor. :) > > > > Anyway, try the following optimization and see if it makes a difference > in > > your setup: > > > > ./autogen CFLAGS="-O3 -ffast-math -ftree-vectorize" ... > > Sorry! I spoke in too broad a generalization. *Most* Linux > distributions aren't optimized to a specific processor. Gentoo is set > up so you roll your own, as is Linux from Scratch (others? Arch?). The > Gentoo documentation recommends -O2 for general usage, to be on the > safe side. The Linux from Scratch article recommends -O3. Neither > article is especially new, so were written in reference to older > versions of gcc. > > Probably what level of optimization does what changes as gcc changes, > but according to the gcc documentation, -Ofast includes -ffast-math > and -ftree-vectorize. Is there a reason why using "-O3 -ffast-math > -ftree-vectorize" might be better than using "-Ofast"? > > Elle >
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