which version of gcc support the -Ofast optimization level?

I found Ofast level opt in the doc of gcc on http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Optimize-Options. But when i compile my code using this level,gcc told me not recognize this flag. I'm using gcc 4.5.2 which is the most recently released gcc. So which version 开发者_高级运维of gcc support this level? Tnanks.

The -Ofast flag is a new feature in GCC 4.6 -- see the list of changes here.

GCC's changelog seems to indicate that this will be available in the 4.6 release series (which does not yet have a stable release). Optionally, you could try building the development sources from their SVN repo or grabbing a pre-built snapshot from one of the mirrors.