4 ms·

> > There are tricks that let them do this 8 bytes at a time (on AMD64, 4 bytes on x86) > It's actually 16 bytes at a time on any machine that supports SSE (ma

> > There are tricks that let them do this 8 bytes at a time (on AMD64, 4 bytes on x86) > It's actually 16 bytes at a time on any machine that supports SSE (maybe 32 bytes soon with AVX). Is there a sequence of fewer than 16 instructions to spot a NUL byte inside the 16 byte block?

haberman 14y ago
> 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
- marshray 14y ago
  Very cool.