TZCNT and BSF are not completely identical even for non-zero input: BSF sets the ZF when the input is zero, TZCNT sets ZF when the output is zero (i.e., the lea

TZCNT and BSF are not completely identical even for non-zero input: BSF sets the ZF when the input is zero, TZCNT sets ZF when the output is zero (i.e., the least significant bit is set).