Back-port r276209:

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r276209 | spatel | 2016-07-20 16:40:01 -0700 (Wed, 20 Jul 2016) | 4 lines

[InstSimplify][InstCombine] don't crash when folding vector selects of icmp

Differential Revision: https://reviews.llvm.org/D22602

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llvm-svn: 276986