Re: [U-Boot-Users] [PATCH v2] ppc: Added fls, fls64, __ilog2_u64, and ffs64 to bitops

Kumar Gala galak@kernel.crashing.org wrote:

+/*

• • fls: find last (most-significant) bit set.
• • Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
• */

+static __inline__ int fls(unsigned int x) +{

• return __ilog2(x) + 1;

I was sort of hoping you'd add a comment here explaining why it's safe to rely on undefined behaviour in this particular case. Something like

/* On powerpc, __ilog2(0) returns -1, but this is not safe in general */

Haavard