Ugh, the code in Figure 13 is mis-compiled by the super-optimizer. It seems that their checking procedure is flawed. How was that not caught in peer-review?

The problem is that the ranges pointed by x and y could (partially) overlap, in which case the SSE-based optimization is incorrect.

Edit: Even more damning, gcc actually does produce an equivalent optimal code sequence for me when the incoming pointers are correctly marked as restrict and -march=native is used. (Although perhaps that's due to different gcc versions; maybe a gcc improvement was inspired by that article.)

Edit #2: I see they actually discuss this in the main article text. Oh well, I'm leaving the comment here since the figure by itself is misleading.