Re: A bug in vrp_meet?

[Qing Zhao <qing dot zhao at oracle dot com>]

> On Mar 5, 2019, at 8:44 AM, Richard Biener <richard.guenther@gmail.com> wrote:
> 
>>>> 
>>>> 
>>>> will you commit this fix to gcc9 and gcc8  (we need it in gcc8)?
>>> 
>>> I'll see to carve out some cycles trying to find a testcase and amend
>>> the fix a bit
>>> and will take care of testing/submitting the fix.  Thanks for testing
>>> that it works
>>> for your case.
>> 
>> I filed PR89595 with a testcase.
> 
> 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.

I tried the new patch on my side,Now, in the dump file of dom3:

========
Visiting statement:
i_49 = _98 > 0 ? k_105 : 0;
Meeting
  [0, 65535]
and
  [0, 0]
to
  [0, 65535]
Intersecting
  [0, 65535]
and
  [0, 65535]
to
  [0, 65535]
Optimizing statement i_49 = _98 > 0 ? k_105 : 0;
  Replaced 'k_105' with variable '_98'
gimple_simplified to _152 = MAX_EXPR <_98, 0>;
i_49 = _152;
  Folded to: i_49 = _152;
LKUP STMT i_49 = _152
==== ASGN i_49 = _152

Visiting statement:
_152 = MAX_EXPR <_98, 0>;
Optimizing statement _152 = MAX_EXPR <_98, 0>;
LKUP STMT _152 = _98 max_expr 0
2>>> STMT _152 = _98 max_expr 0
========

thanks.

Qing

> 
> 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.
> <fix-pr89595>