On Thu, Apr 18, 2019 at 11:16 AM Richard Sandiford
<richard.sandif...@arm.com> wrote:
>
> When testing PR 85164, the baseline bootstrap-ubsan results had
> a lot of failures from int_const_binop. This is because with the
> new overflow handling we can sometimes do:
>
> poly_res = res;
>
> on an uninitialised res.
>
> Tested with bootstrap-ubsan on aarch64-linux-gnu and x86_64-linux-gnu.
> OK to install? (This is a GCC 9 regression FWIW.)
OK.
Richard.
> Richard
>
>
> 2019-04-18 Richard Sandiford <richard.sandif...@arm.com>
>
> gcc/
> * fold-const.c (int_const_binop): Return early on failure.
>
> Index: gcc/fold-const.c
> ===================================================================
> --- gcc/fold-const.c 2019-04-04 08:34:52.001938080 +0100
> +++ gcc/fold-const.c 2019-04-18 10:11:12.336697917 +0100
> @@ -1173,7 +1173,6 @@ poly_int_binop (poly_wide_int &res, enum
> int_const_binop (enum tree_code code, const_tree arg1, const_tree arg2,
> int overflowable)
> {
> - bool success = false;
> poly_wide_int poly_res;
> tree type = TREE_TYPE (arg1);
> signop sign = TYPE_SIGN (type);
> @@ -1183,17 +1182,18 @@ int_const_binop (enum tree_code code, co
> {
> wide_int warg1 = wi::to_wide (arg1), res;
> wide_int warg2 = wi::to_wide (arg2, TYPE_PRECISION (type));
> - success = wide_int_binop (res, code, warg1, warg2, sign, &overflow);
> + if (!wide_int_binop (res, code, warg1, warg2, sign, &overflow))
> + return NULL_TREE;
> poly_res = res;
> }
> - else if (poly_int_tree_p (arg1) && poly_int_tree_p (arg2))
> - success = poly_int_binop (poly_res, code, arg1, arg2, sign, &overflow);
> - if (success)
> - return force_fit_type (type, poly_res, overflowable,
> - (((sign == SIGNED || overflowable == -1)
> - && overflow)
> - | TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2)));
> - return NULL_TREE;
> + else if (!poly_int_tree_p (arg1)
> + || !poly_int_tree_p (arg2)
> + || !poly_int_binop (poly_res, code, arg1, arg2, sign, &overflow))
> + return NULL_TREE;
> + return force_fit_type (type, poly_res, overflowable,
> + (((sign == SIGNED || overflowable == -1)
> + && overflow)
> + | TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2)));
> }
>
> /* Return true if binary operation OP distributes over addition in operand
