> In case Andy is asking about "how" rather than "under what circumstances", my > guess is: -O1+ may have just chosen instructions that also happen to > zero-extend, > which are common. -O0 doesn't represent the naive straightforward structure of > what the programmer wrote, it's more like an "exploded" representation > suitable > for later optimization passes. That's why it always looks goofy.
Hah yeah. I missed the "how" part of the question but your explanation makes sense. > > > Replacing that with _mm512_zextsi128_si512 fixes the problem. > > Here's a patch for testing, which also reverts the previous workaround. Help > welcome, but I still promise to test it in the near future regardless. LGTM. Raghuveer
