Re: Bravo mais..

alors dans ce cas il y'a a dans les builtins gcc [1]:

— Built-in Function: int __builtin_ctz (unsigned int x)

Returns the number of trailing 0-bits in x, starting at the least significant bit position. If x is 0, the result is undefined.

et sinon dans /usr/src/linux/include/asm-i386/bitops.h, en 3 instructions assembleur:

/**
* fls - find last bit set
* @x: the word to search
*
* This is defined the same way as ffs.
*/

[1] http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other-(...)