On Mon, 10 Nov 2008, Darrick J. Wong wrote:
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index fba141d..fb02266 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -48,6 +48,12 @@ extern const char linux_proc_banner[];
> #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
> #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
> #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
> +#define DIV_ROUND_CLOSEST(x, divisor)( \
> +{ \
> + typeof(divisor) __divisor = divisor; \
> + (((x) + ((__divisor) / 2)) / (__divisor)); \
> +} \
> +)
Maybe you can do away with the statement-expression extension? I've seen
cases where it cases gcc to generate worse code. It seems like it
shouldn't, but it does. I know DIV_ROUND_CLOSEST (maybe DIV_ROUND_NEAR?)
uses divisor twice, but all the also divide macros do that too, so why does
this one need to be different?
Note that if divisor is a signed variable, divisor/2 generates worse code
than divisor>>1.
