[Hexagon] Make a test more flexible in HexagonLoopIdiomRecognition
[Hexagon] Make a test more flexible in HexagonLoopIdiomRecognition

An "or" that sets the sign-bit can be replaced with a "xor", if
the sign-bit was known to be clear before. With some changes to
instruction combining, the simple sign-bit check was failing.
Replace it with a more flexible one to catch more cases.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@317592 91177308-0d34-0410-b5e6-96231b3b80d8

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