Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > Could you use cpu_to_be32/64() and then ffs()? That ought to work for both > > variants of endianness. The cpu_to_beXX() should be a noop on BE and is > > likely to be a single instruction on LE. The meat of ffs() is usually a > > single instruction, though it may have to have zero-detect logic added. > > First off, the *last* thing you want to do is go to big-endian mode. > All the bit counting gets *much* more complicated, and your argument > that it's "free" on some architectures is pointless, since it is only > free on the architectures that have the *least* users. I didn't suggest it was free, but it might be cheaper. Besides x86/x86_64 has BSF/BSR instructions - though having played with Dave's algorithm some, I don't think they're usable for this. My suggestion assumes that there would be zeros beyond the terminal NUL, which isn't something you can rely on. David -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
