[Bug tree-optimization/63202] tree vectorizer does not make use of alignment information from VRP/CCP

[andi-gcc at firstfloor dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63202

--- Comment #3 from Andi Kleen <andi-gcc at firstfloor dot org> ---
I'm not sure rewriting the pattern to assume_aligned would be useful. After all
the user could already use assume_aligned directly.

I was more thinking of cases when VRP/CCP can prove alignment in other ways
from the code, and the vectorizer should use that.

Good point that the fallback is not for unalignment. Should probably use a more
fancy test case where unalignment matters for the cost model.

One interesting case is avoiding the need for tail code when the iteration is
not a multiple of the vector length.