> Is there a sequence of fewer than 16 instructions to spot a NUL byte inside the 16 byte block? Yes: pxor %xmm1, %xmm1 pcmpeqb (mem), %xmm1 // Do 1

> Is there a sequence of fewer than 16 instructions to spot a NUL byte inside the 16 byte block? Yes: pxor %xmm1, %xmm1 pcmpeqb (mem), %xmm1 // Do 16 byte-wise compares pmovmskb %xmm1, %eax // Move results into the low 16 bits test %eax, %eax jnz saw_null