Merging r276510:

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r276510 | majnemer | 2016-07-22 19:56:49 -0700 (Fri, 22 Jul 2016) | 9 lines

[LoopUnrollAnalyzer] Handle out of bounds accesses in visitLoad

While we handed loads past the end of an array, we didn't handle loads
_before_ the array.

This fixes PR28062.

N.B. While the bug in the code is obvious, I am struggling to craft a
test case which is reasonable in size.
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llvm-svn: 276688