[Bug middle-end/19721] [meta-bug] optimizations that CSE still catches

["stevenb at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From stevenb at suse dot de  2005-03-06 09:30 -------
Subject: Re:  [meta-bug] optimizations that CSE still catches

On Sunday 06 March 2005 06:59, law at redhat dot com wrote:
> Ah.  Yes.  What did it look like in the tree dumps?   Unless
> one of the expanders is creating the negation I would think this
> would be pretty easy to catch in fold-const.c

This is PR20130.  We don't fold -1*x to -x, ie. we never
fold the MULT_EXPR to a NEGATE_EXPR.  PR20130 has a patch.

> expand_mult?  Sigh.  That's been in the back of my mind for a couple
> years now -- it's probably one of the largest RTL expanders which
> needs to have a lot of its functionality moved into trees.

That'd be nice.

In this case, Roger found out that for DImode negative constants
it completely bypasses expand_mult_const.  Fixing that would help
for now.



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19721