On Thu, 04 Feb 2016 13:40:38 +0100 Arnd Bergmann <a...@arndb.de> wrote:
> diff --git a/include/linux/err.h b/include/linux/err.h
> index b7d4a9ff6342..bd4936a2c352 100644
> --- a/include/linux/err.h
> +++ b/include/linux/err.h
> @@ -18,9 +18,7 @@
>
> #ifndef __ASSEMBLY__
>
> -#define IS_ERR_VALUE(x) ((typeof(x))(-1) <= 0 \
> - ? unlikely((x) <= -1) \
> - : unlikely((x) >= (typeof(x))-MAX_ERRNO))
> +#define IS_ERR_VALUE(x) (unlikely((unsigned long long)(x) >= (unsigned
> long long)(typeof(x))-MAX_ERRNO))
>
> static inline void * __must_check ERR_PTR(long error)
> {
>
>
> I'm not sure if the cast to 'unsigned long long' might cause less
> efficient code to be generated by gcc. I would hope that it is smart
> enough to not actually extend shorter variables to 64 bit before
> doing the comparison but I have not checked yet.
I did a quick test with i386 on drivers/nvmem/core.o. The patch takes
the text size from 9098 bytes to 9133. That file has 11 instances of
IS_ERR_VALUE().
