From: Peter Zijlstra > Sent: 21 December 2017 14:12 ... > > > This part above looks like FLS > > It also does the rest of the required shifts. > > Still, fls() + shift is way faster on hardware that has an fls > instruction. > > Writing out that binary search doesn't make sense. If the hardware doesn't have an appropriate fls instruction the soft fls()will be worse. If you used fls() you'd still need quite a bit of code to generate the correct shift and loop count adjustment. Given the cost of the loop iterations the 3 tests are noise. The open coded version is obviously correct... I didn't add the 4th one because the code always does 2 iterations. If you were really worried about performance there are faster algorithms (even doing 2 or 4 bits a time is faster). David -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
