Re: A bug in vrp_meet?

[Richard Biener <richard dot guenther at gmail dot com>]

On Tue, Mar 5, 2019 at 10:36 PM Jeff Law <law@redhat.com> wrote:
>
> On 3/5/19 7:44 AM, Richard Biener wrote:
>
> > So fixing it properly with also re-optimize_stmt those stmts so we'd CSE
> > the MAX_EXPR introduced by folding makes it somewhat ugly.
> >
> > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
> >
> > Any ideas how to make it less so?  I can split out making optimize_stmt
> > take a gsi * btw, in case that's a more obvious change and it makes the
> > patch a little smaller.
> >
> > Richard.
> >
> > 2019-03-05  Richard Biener  <rguenther@suse.de>
> >
> >         PR tree-optimization/89595
> >         * tree-ssa-dom.c (dom_opt_dom_walker::optimize_stmt): Take
> >         stmt iterator as reference, take boolean output parameter to
> >         indicate whether the stmt was removed and thus the iterator
> >         already advanced.
> >         (dom_opt_dom_walker::before_dom_children): Re-iterate over
> >         stmts created by folding.
> >
> >         * gcc.dg/torture/pr89595.c: New testcase.
> >
>
> Well, all the real logic changs are in the before_dom_children method.
> The bits in optimize_stmt are trivial enough to effectively ignore.
>
> I don't see a better way to discover and process statements that are
> created in the bowels of fold_stmt.

I'm not entirely happy so I created the following alternative which
is a bit larger and slower due to the pre-pass clearing the visited flag
but is IMHO easier to follow.  I guess there's plenty of TLC opportunity
here but then I also hope to retire the VN parts of DOM in favor
of the non-iterating RPO-VN code...

So - I'd lean to this variant even though it has the extra loop over stmts,
would you agree?

Bootstrap / regtest running on x86_64-unknown-linux-gnu.

Richard.

2019-03-06  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/89595
        * tree-ssa-dom.c (dom_opt_dom_walker::optimize_stmt): Take
        stmt iterator as reference, take boolean output parameter to
        indicate whether the stmt was removed and thus the iterator
        already advanced.
        (dom_opt_dom_walker::before_dom_children): Re-iterate over
        stmts created by folding.

        * gcc.dg/torture/pr89595.c: New testcase.

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