Re: [PATCH] Initialize value in bit_value_unop.

[Richard Biener <richard.guenther@gmail.com>]

On Tue, Jul 25, 2023 at 9:08 PM Aldy Hernandez via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> bit_value_binop initializes VAL regardless of the final mask.  It even
> has a comment to that effect:
>
>   /* Ensure that VAL is initialized (to any value).  */
>
> However, bit_value_unop, which in theory shares the same API, does not.
> This causes range-ops to choke on uninitialized VALs for some inputs to
> ABS.
>
> Instead of fixing the callers, it's cleaner to make bit_value_unop and
> bit_value_binop consistent.
>
> OK for trunk?

OK

> gcc/ChangeLog:
>
>         * tree-ssa-ccp.cc (bit_value_unop): Initialize val when appropriate.
> ---
>  gcc/tree-ssa-ccp.cc | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/tree-ssa-ccp.cc b/gcc/tree-ssa-ccp.cc
> index 73fb7c11c64..15e65f16008 100644
> --- a/gcc/tree-ssa-ccp.cc
> +++ b/gcc/tree-ssa-ccp.cc
> @@ -1359,7 +1359,10 @@ bit_value_unop (enum tree_code code, signop type_sgn, int type_precision,
>      case ABS_EXPR:
>      case ABSU_EXPR:
>        if (wi::sext (rmask, rtype_precision) == -1)
> -       *mask = -1;
> +       {
> +         *mask = -1;
> +         *val = 0;
> +       }
>        else if (wi::neg_p (rmask))
>         {
>           /* Result is either rval or -rval.  */
> @@ -1385,6 +1388,7 @@ bit_value_unop (enum tree_code code, signop type_sgn, int type_precision,
>
>      default:
>        *mask = -1;
> +      *val = 0;
>        break;
>      }
>  }
> --
> 2.41.0
>