2 ms·

Then suddenly the REP prefix became much more useful than it used to be (around Nehalem I think?) to the point that REP MOV could be as fast or faster than SIMD

by p_l 4y ago

Then suddenly the REP prefix became much more useful than it used to be (around Nehalem I think?) to the point that REP MOV could be as fast or faster than SIMDified copy routine.

innocenat 4y ago
Isn't like REP MOV the only thing useful in application code? I think it's special cased in CPU to use whatever available to copy as fast as possible.
- rep_lodsb 4y ago
  It takes some time to start up, but can be the fastest for large block copies. REPNE SCASB is useful to implement strlen, and REPE CMPSB for strcmp. Don't know offhand how optimized these are though. REP LODSB, on the other hand, is completely useless :)