Re: Arch maintainers Ahoy!

[David Howells <dhowells@redhat.com>]

Linus Torvalds <torvalds@linux-foundation.org> wrote:

> It's not faster to just do something like
> 
>    int byte = 4;
> 
> #if CONFIG_64BIT
>    byte = 8;
>    if (has_zero_32bit(value >> 32)) {
>        value >>= 32;
>        byte = 4;
>    }
> #endif
>    if (has_zero_16(value >> 16)) {
>       value >>= 16;
>       byte -= 2;
>    }
>    if (!value & 0xff00)
>       byte--;
>    return byte;


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.

David