Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> 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
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