Merging r267916:

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r267916 | Matthew.Arsenault | 2016-04-28 11:38:48 -0700 (Thu, 28 Apr 2016) | 6 lines

AMDGPU: Fix mishandling array allocations when promoting alloca

The canonical form for allocas is a single allocation of the array type.
In case we see a non-canonical array alloca, make sure we aren't
replacing this with an array N times smaller.

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llvm-svn: 271768