We can safely rely on a NoWrap add recurrence causing UB down the road
only if we know the loop does not have a exit expressed in a way that is
opaque to ScalarEvolution (e.g. by a function call that conditionally
calls exit(0)).
I believe with this change PR28012 is fixed.
Note: I had to change some llvm-lit tests in LoopReroll, since it looks
like they were depending on this incorrect behavior.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272237 91177308-0d34-0410-b5e6-96231b3b80d8
05c5b3fd8e