Merging r155809:

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r155809 | rafael | 2012-04-29 20:53:06 -0700 (Sun, 29 Apr 2012) | 2 lines

Make sure HoistInsertPosition finds a position that is dominated by all
inputs.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_31@155828 91177308-0d34-0410-b5e6-96231b3b80d8