From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Hubicka To: law@redhat.com Cc: Jan Hubicka , Joern Rennecke , gcc@gcc.gnu.org Subject: Re: Higher level RTL issues Date: Wed, 24 Oct 2001 07:59:00 -0000 Message-id: <20011024165850.M11456@atrey.karlin.mff.cuni.cz> References: <20011023120240.G12992@atrey.karlin.mff.cuni.cz> <32418.1003876268@localhost.localdomain> X-SW-Source: 2001-10/msg01235.html > In message < 20011023120240.G12992@atrey.karlin.mff.cuni.cz >you write: > > > How about commoning of libcall addresses and other special constants? > > > Are you going to rely on post-lowering phases to do that, or do you > > > plan to display this stuff in the CALL_FUSAGE or some now field of > > > CALL_INSNs? > > I believe we still must do (g)cse after lowering, as at almost each riscy > > architecture this is going to introduce dozen of new constants and > > temporaries that can be cseed, but we probably don't need the "full > > strength cse+gcse" we've somehow failed to reach, as for instance > > load/store motion and friends> can be done only on midlevel. > It is likely that we will continue to have a [g]cse pass of some kind that > runs after lowering from generic to target specific RTL. It is *hoped* that > it can be a simpler, more compile time efficient pass than we currently have > with cse or gcse. > > What makes you think we can only do lsm on target rtl? There's no reason > they can not be done on the generic RTL. Thats what I wanted to say - that we can drop some of complexity of current gcse on lowlevel tree, as lsm is, since it don't make sense to rerun it after midlevel->lowlevel generation. > > > Another pass that may make sense at lowlevel is strength reduction, but > > maybe we can do it at midlevel just by knowing the addressing modes of > > target machine. > I don't really want to get into the loop optimizer right now or better stated > I think solving our loop optimizer problems needs to be handled independently > of adding a generic RTL IR to GCC and I personally prefer to focus on the > generic RTL issues right now. Sure. I am trying to get some of bits for writing new loop optimizer ready in meantime, so I am focusion on the oposite side of this problem. Honza > > jeff