Re: [PATCH] Clear upper bits during sign extension

Joel Brobecker
2014-12-29T03:53:34Z

> Yeah, that is better, or even we can left shift signbit by one.

Indeed!

> 2014-12-29 Yao Qi <yao@codesourcery.com>
>
> * utils.c (gdb_sign_extend): Clear bits from BIT in VALUE.

Looks good to me.

> diff --git a/gdb/utils.c b/gdb/utils.c
> index 47adb67..61873f7 100644
> --- a/gdb/utils.c
> +++ b/gdb/utils.c
> @@ -3032,6 +3032,9 @@ gdb_sign_extend (LONGEST value, int bit)
> {
> LONGEST signbit = ((LONGEST) 1) << (bit - 1);
>
> + /* Clear upper bits from bit BIT. */
> + value &= (signbit << 1) - 1;
> +
> value = (value ^ signbit) - signbit;
> }

--
Joel