On Wed, 2012-05-23 at 18:19 +0200, Borislav Petkov wrote: > On Wed, May 23, 2012 at 09:11:51AM -0700, H. Peter Anvin wrote: > > On 05/23/2012 09:10 AM, Peter Zijlstra wrote: > > > On Wed, 2012-05-23 at 09:07 -0700, tip-bot for Borislav Petkov wrote: > > >> +#define BIT_64(n) (U64_C(1) << (n)) > > > > > > Because writing 1ULL << n is too much work? > > > > > > > Because writing 1ULL << n is broken in anything that needs to be used in > > assembly, for example. > > Actually we need a BIT() macro that works both > on 32- and 64-bit. But that won't be that easy: > http://lkml.indiana.edu/hypermail/linux/kernel/1010.1/02335.html > > And it should return UL for shift values < 32 and ULL otherwise. If I remember my type rules correctly you'll get something like that with: #define BIT(n) ({ typeof(n) __n = (n); (__n < 32) ? (1UL << __n) : (1ULL << __n); }) That said, having it do this might be unexpected, also hpa mentioned something about assembly magics which will obviously not work with the above either. Anyway, ignore me, I just thought the BIT_64() thing looked funny, but apparently there's good reasons for it. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html