4 ms·

i += 7; Wouldn't this cause a sizable performance hit due to being misaligned most of the time?

• secure 9y ago
  No: many (most?) modern SIMD instructions don’t require alignment. From the Intel Intrinsics Guide (can’t figure out how to link directly to it, sorry) on _mm_loadu_si128: > Load 128-bits of integer data from memory into dst. mem_addr does not need to be aligned on any particular boundary.
  • detaro 9y ago
    Doesn't need, but is there a performance difference? I seem to remember there is no difference between _mm_load_si128 and _mm_loadu_si128 on modern CPUs, but I'm not sure.
    • deleted 9y ago
      [deleted]
  • mattkrause 9y ago
    loadu is not the best example because its sole purpose is loading unaligned data. There is a separate load for aligned data.
• wmu 9y ago
  Author here. This was true several generations ago (core2, for instance), now the performance penalty is negligible.
  • fulafel 9y ago
    What about ARM?
    • wmu 9y ago
      Sorry, have no idea.