http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53949
--- Comment #2 from chrbr at gcc dot gnu.org 2012-07-13 11:00:55 UTC --- I see the MAC only as a global optimization, since its interest is to spawns across several loop BBs as you said. Their is also problem on clear the accumulator. That should certainly be new extension in the gimple SSA loop optimizers, based on the presence on a multiply and and pattern. Not sure what is the best way to do this as this point.
