Hi Vincent, On Mon, Dec 08, 2014 at 11:45:13PM +0100, Vincent Bernat wrote: > ??? 8 décembre 2014 23:20 +0100, Vincent Bernat <[email protected]> : > > > Assuming that RAND_MAX is always a power of two - 1, 32 could be > > replaced by a precomputed value of ffs(RAND_MAX+1)-1. > > ebtree defines a fls64() function which seems best suited (RAND_MAX+1 > could overflow). Here is a proposed patch for this:
Good catch, but I'd rather simply divide by ((u64)RAND_MAX + 1) and let gcc notice it's a power of two and implement a hard-coded constant shift. There are a lot of things gcc doesn't figure well, but divides and multiplies are generally performed optimally :-) Thanks, Willy
