[Bug tree-optimization/32461] [4.3 Regression] Segmentation fault in build_classic_dist_vector_1() at tree-data-ref.c:2700

["richard dot guenther at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #23 from richard dot guenther at gmail dot com  2007-06-24 12:59 -------
Subject: Re:  [4.3 Regression] Segmentation fault in
build_classic_dist_vector_1() at tree-data-ref.c:2700

On 6/24/07, Sebastian Pop <sebpop@gmail.com> wrote:
> On 6/24/07, Richard Guenther <richard.guenther@gmail.com> wrote:
> > If you use TREE_OPERAND (op0, 0), op1 instead it should work.  The
> > problem seems to be that arg0/arg1 have all NOPs stripped, including
> > those changing the sign.  So we get to compare a and (unsigned)a,
> > which are obviously not the same.
> >
>
> Right.
> The attached patch solves the problem.
>
> > It looks like most of the users of the arg variants are suspicious in this
> > regard...
> >
>
> So if I'm correctly understanding, you suppose that there are also
> other cases in which fold fails just because it uses arg instead of op?

quite possibly.  The patch is ok if it bootstraps & tests and you change

          /* X + ~X is -1.  */
          if (TREE_CODE (arg1) == BIT_NOT_EXPR
-             && operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0)
+             && operand_equal_p (op0, TREE_OPERAND (op1, 0), 0)
              && !TYPE_OVERFLOW_TRAPS (type))

to use op1 to check against BIT_NOT_EXPR.  An alternative is to use

          if (TREE_CODE (arg1) == BIT_NOT_EXPR
              && !TYPE_OVERFLOW_TRAPS (type))
             {
                tem = TREE_OPERAND (arg1, 0);
                STRIP_NOPS (tem);
                if (operand_equal_p (arg0, tem, 0))
 ...

which would be even better and shouldn't cause other missed
optimizations.

Thanks,
Richard.

> Thanks,
> Sebastian
>
>


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32461