[PATCH] Vectorize starting from insertelements building a vector

[Nadav Rotem]

> No. Most of the other callers of Gather take care to set the insert point themselves, it's just that one and one other that don’t.
> 
Okay. 

> The other one is in the ExtractElement case of vectorizeTree(TreeEntry *E). I haven't been able to come up with a case that actually reaches there. I'm not sure it's even reachable, since I think everything CanReuseExtract checks earlier sets the NeedToGather causing it to use the first one.

Okay.  Please commit!  And thanks for adding this feature and fixing the bug :)