On Tue, Sep 25, 2012 at 1:23 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> This patch fixes two spots where signed 1-bit precision isn't handled
> properly in VRP. With that type, build_int_cst (TREE_TYPE (min), 1)
> will overflow and thus adding it to something or subtracting leads to
> ICEs or bad code. In the first spot min is different from max, which
> for 1-bit precision implies either all values, or none (but we don't have
> empty ranges and fallback to varying for those anyway).
emty ranges are turned into VR_UNDEFINED in intersect_range for example
(but not consistently so I see, not in set_and_canonicalize_value_range
at least).
> In the second case we can optimize if the anti range is singleton, then
> the corresponding range is singleton too (the other value).
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok.
Thanks,
Richard.
> 2012-09-25 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/54676
> * tree-vrp.c (set_and_canonicalize_value_range): Handle
> one bit precision properly.
>
> * gcc.dg/pr54676.c: New test.
>
> --- gcc/tree-vrp.c.jj 2012-09-17 11:13:12.000000000 +0200
> +++ gcc/tree-vrp.c 2012-09-24 10:06:10.814376659 +0200
> @@ -501,8 +501,19 @@ set_and_canonicalize_value_range (value_
> to adjust them. */
> if (tree_int_cst_lt (max, min))
> {
> - tree one = build_int_cst (TREE_TYPE (min), 1);
> - tree tmp = int_const_binop (PLUS_EXPR, max, one);
> + tree one, tmp;
> +
> + /* For one bit precision if max < min, then the swapped
> + range covers all values, so for VR_RANGE it is varying and
> + for VR_ANTI_RANGE empty range, so drop to varying as well. */
> + if (TYPE_PRECISION (TREE_TYPE (min)) == 1)
> + {
> + set_value_range_to_varying (vr);
> + return;
> + }
> +
> + one = build_int_cst (TREE_TYPE (min), 1);
> + tmp = int_const_binop (PLUS_EXPR, max, one);
> max = int_const_binop (MINUS_EXPR, min, one);
> min = tmp;
>
> @@ -531,6 +542,24 @@ set_and_canonicalize_value_range (value_
> set_value_range_to_varying (vr);
> return;
> }
> + else if (TYPE_PRECISION (TREE_TYPE (min)) == 1
> + && !TYPE_UNSIGNED (TREE_TYPE (min))
> + && (is_min || is_max))
> + {
> + /* For signed 1-bit precision, one is not in-range and
> + thus adding/subtracting it would result in overflows. */
> + if (operand_equal_p (min, max, 0))
> + {
> + min = max = is_min ? vrp_val_max (TREE_TYPE (min))
> + : vrp_val_min (TREE_TYPE (min));
> + t = VR_RANGE;
> + }
> + else
> + {
> + set_value_range_to_varying (vr);
> + return;
> + }
> + }
> else if (is_min
> /* As a special exception preserve non-null ranges. */
> && !(TYPE_UNSIGNED (TREE_TYPE (min))
> --- gcc/testsuite/gcc.dg/pr54676.c.jj 2012-09-24 10:52:48.911691835 +0200
> +++ gcc/testsuite/gcc.dg/pr54676.c 2012-09-24 10:52:30.000000000 +0200
> @@ -0,0 +1,23 @@
> +/* PR tree-optimization/54676 */
> +/* { dg-do compile } */
> +/* { dg-options "-O -fno-tree-ccp -fno-tree-copy-prop -fno-tree-fre
> -ftree-vrp" } */
> +
> +struct S
> +{
> + int s:1;
> +};
> +
> +struct S bar (void);
> +
> +int a;
> +
> +void
> +foo (int x)
> +{
> + struct S s = bar ();
> + while (!a)
> + {
> + int l = 94967295;
> + a = x || (s.s &= l);
> + }
> +}
>
> Jakub
