Merging r266105:

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r266105 | thomas.stellard | 2016-04-12 11:40:43 -0700 (Tue, 12 Apr 2016) | 15 lines

AMDGPU/SI: Insert wait states required after v_readfirstlane on SI

Summary:
We will be able to handle this case much better once the hazard
recognizer
is finished, but this conservative implementation  fixes a hang with the
piglit
test:

spec/arb_arrays_of_arrays/execution/sampler/fs-nested-struct-arrays-nonconst-nested-arra

Reviewers: arsenm, nhaehnle

Subscribers: arsenm, llvm-commits

Differential Revision: http://reviews.llvm.org/D18988

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llvm-svn: 271731