This re-lands change r230921. r230921 was reverted because it broke a
clang test; a checkin fixing the clang test will be commited shortly.
Summary:
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 (SVN: 222213).
Revert "IndVarSimplify: Don't let LFTR compare against a poison value"
This reverts commit c0f2b8b528d8a37b0a1522aae90af649d6357eb5 (SVN: 217102).
Reviewers: majnemer, atrick, spatel
Differential Revision: http://reviews.llvm.org/D7979
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231018 91177308-0d34-0410-b5e6-96231b3b80d8
caee94bbb4