http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52459
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |matz at gcc dot gnu.org
Summary|PPRE performs stupid |PRE performs stupid inserts
|inserts |
--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-21
10:41:04 UTC ---
I have a patch. The issue is we inhibit PHI insertion for the builtin call
at -O3 (when -ftree-vectorize is on), not partial-PRE. The stupid inserts
are really caused because of the inhibited PRE insertion will cause
only part of the dependent expressions to be available but some uses get
eliminated so the still inserted PHI node is not removed ... which means
that limiting 'PHI insertion' is bougs - we should really limit what
we PHI translate, to not cause dependent expressions to be partially
available. Not sure if we know at that point whether we'd need a PHI node,
but at least the edges we want to eventually restrict translation are
easy to spot - the latch edges.
