Merging r316824:

Merging r316824:

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r316824 | haicheng | 2017-10-27 19:27:14 -0700 (Fri, 27 Oct 2017) | 7 lines

[ConstantFold] Fix a crash when folding a GEP that has vector index

LLVM crashes when factoring out an out-of-bound index into preceding dimension
and the preceding dimension uses vector index.  Simply bail out now when this
case happens.

Differential Revision: https://reviews.llvm.org/D38677
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_50@318096 91177308-0d34-0410-b5e6-96231b3b80d8