On Tue, 25 Mar 2014, Jakub Jelinek wrote:
> Hi!
>
> While working on previous patch, I've noticed a severe omission in the
> -fsanitize=signed-integer-overflow support. Nothing ever
> folds addition/subtraction of 0 and multiplication by [0,1], none of these
> may ever overflow and thus we can fold them to normal operations and let
> those be folded as normal operations.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, tested with
> --with-build-config=bootstrap-ubsan bootstrap on i686-linux, ok for trunk?
I think you only need to adjust gimple_fold_stmt_to_constant_1.
Richard.
> 2014-03-25 Jakub Jelinek <ja...@redhat.com>
>
> * tree-vrp.c (simplify_internal_call_using_ranges): If only
> one range is range_int_cst_p, but not both, at least optimize
> addition/subtraction of 0 and multiplication by 0 or 1.
>
> --- gcc/tree-vrp.c.jj 2014-03-12 10:14:18.000000000 +0100
> +++ gcc/tree-vrp.c 2014-03-24 16:14:50.822674164 +0100
> @@ -9336,31 +9336,58 @@ simplify_internal_call_using_ranges (gim
> else if (TREE_CODE (op0) == INTEGER_CST)
> set_value_range_to_value (&vr0, op0, NULL);
> else
> - return false;
> + set_value_range_to_varying (&vr0);
>
> if (TREE_CODE (op1) == SSA_NAME)
> vr1 = *get_value_range (op1);
> else if (TREE_CODE (op1) == INTEGER_CST)
> set_value_range_to_value (&vr1, op1, NULL);
> else
> - return false;
> + set_value_range_to_varying (&vr1);
>
> - if (!range_int_cst_p (&vr0) || !range_int_cst_p (&vr1))
> - return false;
> -
> - tree r1 = int_const_binop (subcode, vr0.min, vr1.min);
> - tree r2 = int_const_binop (subcode, vr0.max, vr1.max);
> - if (r1 == NULL_TREE || TREE_OVERFLOW (r1)
> - || r2 == NULL_TREE || TREE_OVERFLOW (r2))
> - return false;
> - if (subcode == MULT_EXPR)
> + if (!range_int_cst_p (&vr0))
> + {
> + /* If one range is VR_ANTI_RANGE, VR_VARYING etc.,
> + optimize at least x = y + 0; x = y - 0; x = y * 0;
> + and x = y * 1; which never overflow. */
> + if (!range_int_cst_p (&vr1))
> + return false;
> + if (tree_int_cst_sgn (vr1.min) == -1)
> + return false;
> + if (compare_tree_int (vr1.max, subcode == MULT_EXPR) == 1)
> + return false;
> + }
> + else if (!range_int_cst_p (&vr1))
> + {
> + /* If one range is VR_ANTI_RANGE, VR_VARYING etc.,
> + optimize at least x = 0 + y; x = 0 * y; and x = 1 * y;
> + which never overflow. */
> + if (subcode == MINUS_EXPR)
> + return false;
> + if (!range_int_cst_p (&vr0))
> + return false;
> + if (tree_int_cst_sgn (vr0.min) == -1)
> + return false;
> + if (compare_tree_int (vr0.max, subcode == MULT_EXPR) == 1)
> + return false;
> + }
> + else
> {
> - tree r3 = int_const_binop (subcode, vr0.min, vr1.max);
> - tree r4 = int_const_binop (subcode, vr0.max, vr1.min);
> - if (r3 == NULL_TREE || TREE_OVERFLOW (r3)
> - || r4 == NULL_TREE || TREE_OVERFLOW (r4))
> + tree r1 = int_const_binop (subcode, vr0.min, vr1.min);
> + tree r2 = int_const_binop (subcode, vr0.max, vr1.max);
> + if (r1 == NULL_TREE || TREE_OVERFLOW (r1)
> + || r2 == NULL_TREE || TREE_OVERFLOW (r2))
> return false;
> + if (subcode == MULT_EXPR)
> + {
> + tree r3 = int_const_binop (subcode, vr0.min, vr1.max);
> + tree r4 = int_const_binop (subcode, vr0.max, vr1.min);
> + if (r3 == NULL_TREE || TREE_OVERFLOW (r3)
> + || r4 == NULL_TREE || TREE_OVERFLOW (r4))
> + return false;
> + }
> }
> +
> gimple g = gimple_build_assign_with_ops (subcode, gimple_call_lhs (stmt),
> op0, op1);
> gsi_replace (gsi, g, false);
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
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