(In reply to comment #68)
> I think my difficulty is because -freorder-blocks-and-partition is not being
> passed to GCC. What are you doing to pass -freorder-blocks-and-partition to GCC
> during the initial build?
in configure.in change
MOZ_OPTIMIZE_FLAGS="-Os -freorder-blocks -fno-reorder-functions -fomit-frame-pointer $MOZ_OPTIMIZE_SIZE_TWEAK" to
MOZ_OPTIMIZE_FLAGS="-Os -freorder-blocks-and-partition -fomit-frame-pointer $MOZ_OPTIMIZE_SIZE_TWEAK"
Those pgo instructions are a bit crazy. See https://developer.mozilla.org/en/Building_with_Profile-Guided_Optimization , all you have to do is make a script that can launch firefox. Add the PROFILE_GEN_SCRIPT bit to your .mozconfig and do make -f client.mk profiledbuild