From: Murali Karicheri > Sent: 31 July 2015 16:04 > On 07/31/2015 04:38 AM, Viresh Kumar wrote: > > IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there > > is no need to do that again from its callers. Drop it. > > > > IS_ERR_OR_NULL() is defined as > > static inline bool __must_check IS_ERR_OR_NULL(__force const void *ptr) > { > return !ptr || IS_ERR_VALUE((unsigned long)ptr); > } > > So the unlikely() applies only to second part. Wouldn't that be a > problem for optimization?
Ugg... The unlikely() in IS_ERR_VALUE() is likely to stop the compiler doing a single 'window' comparison for the range [-MAX_ERROR .. 0]. So you are likely to end up with 2 comparisons. I suspect that: return IS_ERR_VALUE((unsigned long)ptr - 1); would be a much better test. (Ignoring the off-by-one for the highest error.) David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/