[PATCH] Disable indvar widening if arithmetics on the wider type are more expensive

[Andrew Trick]

LGTM.

I don't like the fact that TTI info silently changes behavior of an early IR pass while not required to be present; that's a broader issue though that I'd rather not debate in this context. This is actually a pretty benign use of TTI.

http://reviews.llvm.org/D6196