[PATCH v7 04/28] powerpc/xmon: Use bitwise calculations in_breakpoint_table()

[Michael Ellerman]

Jordan Niethe <jniethe5 at gmail.com> writes:
> A modulo operation is used for calculating the current offset from a
> breakpoint within the breakpoint table. As instruction lengths are
> always a power of 2, this can be replaced with a bitwise 'and'. The
> current check for word alignment can be replaced with checking that the
> lower 2 bits are not set.
>
> Suggested-by: Christophe Leroy <christophe.leroy at c-s.fr>
> Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>
> ---
> v6: New to series
> ---
>  arch/powerpc/xmon/xmon.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index bbfea22f4a96..e122f0c8a044 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -857,8 +857,8 @@ static struct bpt *in_breakpoint_table(unsigned long nip, unsigned long *offp)
>  	off = nip - (unsigned long) bpt_table;
>  	if (off >= sizeof(bpt_table))
>  		return NULL;
> -	*offp = off % BPT_SIZE;
> -	if (*offp != 0 && *offp != 4)
> +	*offp = off & (BPT_SIZE - 1);
> +	if (off & 3)
>  		return NULL;

It would be even better if you didn't hard code the 3 wouldn't it?

eg:

+	*offp = off & (BPT_SIZE - 1);
+	if (off & (BPT_SIZE - 1))
 		return NULL;

cheers