Merging r155166:

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r155166 | void | 2012-04-19 16:31:07 -0700 (Thu, 19 Apr 2012) | 1 line

Put this expensive check below the less expensive ones.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_31@155830 91177308-0d34-0410-b5e6-96231b3b80d8