Merging r296642:

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r296642 | hans | 2017-03-01 09:15:08 -0800 (Wed, 01 Mar 2017) | 5 lines

[GVNHoist] Don't hoist unsafe scalars at -Oz (PR31729)

Based on Aditya Kumar's patch:

Differential Revision: https://reviews.llvm.org/D29092
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llvm-svn: 296761