[PATCH] IndVarSimplify: Allow LFTR to fire more often

[Andrew Trick]

LGTM.

A short comment might help the reader. Something like “Check if InitIV + BECount+1 requires sign/zero extension. If not, clear the corresponding flag from WrappingFlags because it is not necessary for those flags in the IncrementedIndvarSCEV expression.”

http://reviews.llvm.org/D6222