This is a test for an upcoming patch that proposes to change the default LMUL used by the loop vectorizer from 1 to 2
LGTM w/comment addressed.
I think this would be more clear to drop the DEFAULT and simply have the default configuration use an LMUL1 check line. Then when we switch the default, we simply change that to LMUL2.
Ok, there's something surprising going on here. When we go from LMUL1 to LMUL2, we appear to be *both* doubling the vector length (expected), and doing additional unrolling (unexpected). This means that the effective VF of the loop increases not by 2, but by 4.
I think we need to figure out what's causing the unrolling and isolate that. We should be changing one thing at a time here, not two.