Merging r259177:

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r259177 | echristo | 2016-01-28 23:20:01 -0800 (Thu, 28 Jan 2016) | 5 lines

Since LI/LIS sign extend the constant passed into the instruction we should
check that the sign extended constant fits into 16-bits if we want a
zero extended value, otherwise go ahead and put it together piecemeal.

Fixes PR26356.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_38@259713 91177308-0d34-0410-b5e6-96231b3b80d8