one could use a substitution, but I think it makes the code harder to read.

movemask_epi8 returns an integer with 16 bit set to the most significant bit of each of the 16 bytes in the vector.
cmpeq_epi8 sets true to 0xFF
for all/and it checks that all significant bits are zero, meaning no element was zero/false, if not it stops
for any/or it checks if any significant bit was zero and stops, if all 16 bits are set all elements are zero/false