[PATCH] Remove bogus optimization from may_alias_p

[Richard Guenther]

On Tue, 21 Oct 2008, Daniel Berlin wrote:

> On Tue, Oct 21, 2008 at 11:07 AM, Richard Guenther
> <richard.guenther@gmail.com> wrote:
> > On Tue, Oct 21, 2008 at 4:47 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
> >>> Bootstrapped and tested on x86_64-unknown-linux-gnu for the trunk
> >>> and the gcc-4_3-branch.  Committed to trunk and the branch.
> >>>
> >>> Richard.
> >>>
> >>> 2008-10-19  Richard Guenther  <rguenther@suse.de>
> >>>
> >>>       * tree-ssa-alias.c (may_alias_p): Remove bogus shortcut.
> >>
> >> On the 4.3 branch this causes lots of warnings during bootstrap of the form:
> >>
> > The stuff comes from the tree-ssa-alias-warnings.c code which is - err
> > - bogus.  On
> > the trunk most of it is disabled because we prune all interesting
> > stuff away from it,
> > on the branch TBAA pruning of points-to sets was disabled, so the
> > (bogus) warning
> > code became "more effective" there.  Retaining even more valid
> > points-to information
> > makes it appearantly go even more mad ... :/
> >
> > Unfortunately the author of said infrastructure left GCC development
> > as I was told in
> > the past.  I will try to have a quick look (or end up reverting the
> > patch on the branch).
> 
> If the author is gone and nobody can update the code to be sane, we
> should just remove it

I have a nearly finished replacement for the trunk which deletes the code.
It only depends on some PTA fixes ... ;)  But for the branch this is
probably not the way to go.

Btw, I can reproduce it now.  The interesting thing is that once I
append -save-temps it doesn't reproduce anymore... :(

Richard.