Merging r339535:

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r339535 | ctopper | 2018-08-13 08:53:47 +0200 (Mon, 13 Aug 2018) | 5 lines

[SelectionDAG] In PromoteIntRes_BITCAST, when the input is TypePromoteFloat, make sure the output type is scalar. For vectors, use a store and load of temporary.

Previously if the result type was a vector, we emitted a FP_TO_FP16 with a vector result type which isn't valid.

This is basically the opposite case of the root cause of PR38533.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_70@339856 91177308-0d34-0410-b5e6-96231b3b80d8