This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] Don't consider TREE_OVERFLOW in folding of comparisons with highest/lowest type's value (PR tree-optimization/37664)


On Thu, Oct 16, 2008 at 9:08 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> On this testcase, VRP is upset by (unsigned int) x > UINT_MAX (OVF),
> for ASSERT_EXPR it clears the TREE_OVERFLOW flag (since PR37327)
> and then ICEs because this ASSERT_EXPR's condition folds to boolean_false_node.
> Is there any reason why fold prohibits folding of comparisons with
> highest or lowest type's value if the value has TREE_OVERFLOW set?
> I've tried to construct a testcase where C/C++ would care, but if one
> of the arguments has TREE_OVERFLOW set, then the warning/error is reported
> already when folding that value, not when folding the comparison.
> This passed bootstrap/regtest, so if it matters, it doesn't reproduce
> on anything we have in the tree.
>
> Ok for trunk?

Ok.

Thanks,
Richard.

> 2008-10-16  Jakub Jelinek  <jakub@redhat.com>
>
>        PR tree-optimization/37664
>        * fold-const.c (fold_binary): When optimizing comparison with
>        highest or lowest type's value, don't consider TREE_OVERFLOW.
>
>        * gcc.c-torture/compile/pr37664.c: New test.
>
> --- gcc/fold-const.c.jj 2008-09-30 16:57:11.000000000 +0200
> +++ gcc/fold-const.c    2008-10-16 01:02:42.000000000 +0200
> @@ -12447,7 +12447,6 @@ fold_binary (enum tree_code code, tree t
>        unsigned int width = TYPE_PRECISION (arg1_type);
>
>        if (TREE_CODE (arg1) == INTEGER_CST
> -           && !TREE_OVERFLOW (arg1)
>            && width <= 2 * HOST_BITS_PER_WIDE_INT
>            && (INTEGRAL_TYPE_P (arg1_type) || POINTER_TYPE_P (arg1_type)))
>          {
> --- gcc/testsuite/gcc.c-torture/compile/pr37664.c.jj    2008-10-15 14:14:23.000000000 +0200
> +++ gcc/testsuite/gcc.c-torture/compile/pr37664.c       2008-10-15 14:14:04.000000000 +0200
> @@ -0,0 +1,14 @@
> +/* PR tree-optimization/37664 */
> +
> +int v;
> +
> +int
> +foo ()
> +{
> +  int a = 0x8899A862;
> +  int b = 0x8E * a;
> +  int c = (b % b);
> +  if (v > (4294967295U >> c))
> +    return v;
> +  return 0;
> +}
>
>        Jakub
>


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]