crash in vecelement test

[JeffBezanson]

I've seen this many times, e.g.

https://travis-ci.org/JuliaLang/julia/jobs/277518263
https://circleci.com/gh/JuliaLang/julia/3693

Seems to be intermittent, and I have no idea whether it's actually related to VecElements, but is a definite pattern.

[yuyichao]

I think this just #21918

[JeffBezanson]

Was the fix for that issue incomplete?

[yuyichao]

Either that or it regressed in special case. I'm not able to reproduce it but I've seen alignment of 32 specified in llvm IR. The fix is mostly a workaround to begin with.

[yuyichao]

a workaround

-> There are a few linked PR for the more correct fix.

[vchuravy]

If there are still alignments of 32 present than my fix was incomplete. I can rebase #21959 but I will probably need help to make sure that it doesn't lead to a performance regression since it is quite hot code.