-O3 will give you a good boost if you didn't have that before.
-fomit-frame-pointer gives the compiler one more register "to play with" (but makes debugging harder, and it may not apply to all functions).
-fstrict-aliasing is automatically enabled in -O3, so no need to specify that specifically.
When you say it's the same compiler, is it the same VERSION of gcc. There are big differences between gcc 3.x and 4.x (or 2.x for that matter) - some code runs faster, some slower for each version (although in general, newer version should give better [faster] code).
--
Mats
