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Re: moving constants out of loops
- To: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- Subject: Re: moving constants out of loops
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Tue, 30 Jun 1998 17:51:54 -0600
- cc: Haj dot Ten dot Brugge at net dot hcc dot nl, egcs-patches at cygnus dot com, gcc-patches at gnu dot org
- Reply-To: law at cygnus dot com
In message <9806302349.AA14600@vlsi1.ultra.nyu.edu>you write:
> I don't see it as an alias issue per se.
Certainly the alias issue is a secondary effect -- but a very important
one -- on the PA at least the lossage due to poor alias analysis
outweighed all the benefits we originally got from finding more givs.
> What I see is that the more
> givs that are found, the more relationships between givs that can be
> found.
Yup.
> Currently loop.c doesn't take advantage of that. Part of what
> I was doing (and never finished) is to do much better tracking of the
> relationship between givs.
This is one of the key things rth has been working on.
> That allows for much better choosing of
> which to reduce and also to allow many more cases of biv elimination.
Yup.
> I think this is precisely the trickiest issue in all of loop.c.
Richard has found that out the hard way. I think we're up to the
13th or so public revision. I think his stuff is real close to being
ready.
jeff