On Thu, May 25, 2017 at 6:33 PM, Marek Polacek <pola...@redhat.com> wrote:
> We ICE on this testcase in
> 9812 /* Transform x * -C into -x * C if x is easily negatable. */
> 9813 if (TREE_CODE (op1) == INTEGER_CST
> 9814 && tree_int_cst_sgn (op1) == -1
> 9815 && negate_expr_p (op0)
> 9816 && (tem = negate_expr (op1)) != op1
> 9817 && ! TREE_OVERFLOW (tem))
> because fold_negate_expr returns NULL_TREE for INT_MIN, so negate_expr just
> wrapped in into a NEGATE_EXPR, creating NEGATE_EXPR <INT_MIN>. TREE_OVERFLOW
> crashes on that. I thought it made sense to check whether we can negate OP1
> first, as done in the patch below.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk and 7?
Ok.
> 2017-05-25 Marek Polacek <pola...@redhat.com>
>
> PR sanitizer/80875
> * fold-const.c (fold_binary_loc) <case MULT_EXPR>: Check if OP1
> can be negated.
>
> * c-c++-common/ubsan/pr80875.c: New test.
>
> diff --git gcc/fold-const.c gcc/fold-const.c
> index efc0b10..911ae36 100644
> --- gcc/fold-const.c
> +++ gcc/fold-const.c
> @@ -9813,6 +9813,7 @@ fold_binary_loc (location_t loc,
> if (TREE_CODE (op1) == INTEGER_CST
> && tree_int_cst_sgn (op1) == -1
> && negate_expr_p (op0)
> + && negate_expr_p (op1)
> && (tem = negate_expr (op1)) != op1
> && ! TREE_OVERFLOW (tem))
> return fold_build2_loc (loc, MULT_EXPR, type,
> diff --git gcc/testsuite/c-c++-common/ubsan/pr80875.c
> gcc/testsuite/c-c++-common/ubsan/pr80875.c
> index e69de29..e679452 100644
> --- gcc/testsuite/c-c++-common/ubsan/pr80875.c
> +++ gcc/testsuite/c-c++-common/ubsan/pr80875.c
> @@ -0,0 +1,9 @@
> +/* PR sanitizer/80875 */
> +/* { dg-do compile } */
> +/* { dg-options "-fsanitize=undefined" } */
> +
> +int
> +foo (void)
> +{
> + return ~__INT_MAX__ * (0 / 0); /* { dg-warning "division by zero" } */
> +}
>
> Marek
