Merging r338915:

Merging r338915:
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r338915 | ctopper | 2018-08-03 22:14:18 +0200 (Fri, 03 Aug 2018) | 5 lines

[SelectionDAG] Teach LegalizeVectorTypes to widen the mask input to a masked store.

The mask operand is visited before the data operand so we need to be able to widen it.

Fixes PR38436.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_70@339106 91177308-0d34-0410-b5e6-96231b3b80d8