[PATCH] This patch reverts some changes that were made to fix PR20680.

[Sanjoy Das]

(I missed subscribing the llvm-commits list, so sending the patch here manually)

As far as I can tell, the real bug causing the issue was fixed in r230533.

SCEVExpander should mark an increment operation as nuw or nsw only if
it can *prove* that the operation does not overflow. There shouldn't
be any situation where we have to do something different because of
no-wrap flags generated by SCEVExpander.

Revert "IndVarSimplify: Allow LFTR to fire more often"

This reverts commit 1ade0f0faa98877b688e0b9da58e876052c1e04e.

Revert "IndVarSimplify: Don't let LFTR compare against a poison value"

This reverts commit c0f2b8b528d8a37b0a1522aae90af649d6357eb5.

http://reviews.llvm.org/D7979

-- Sanjoy