Merging r276358, r276364, and r276368

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r276358 | spop | 2016-07-21 16:22:10 -0700 (Thu, 21 Jul 2016) | 6 lines

GVH-hoist: only clone GEPs (PR28606)

Do not clone stored values unless they are GEPs that are special cased to avoid
hoisting them without hoisting their associated ld/st.

Differential revision: https://reviews.llvm.org/D22652
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r276364 | spop | 2016-07-21 16:32:39 -0700 (Thu, 21 Jul 2016) | 1 line

GVN-hoist: add missing check for all GEP operands available
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r276368 | spop | 2016-07-21 17:07:01 -0700 (Thu, 21 Jul 2016) | 1 line

GVN-hoist: move check before mutating the IR
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llvm-svn: 276420