Merging r276435:

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r276435 | arsenm | 2016-07-22 10:01:21 -0700 (Fri, 22 Jul 2016) | 4 lines

AMDGPU: Fix i1 fp_to_int

R600's i1 fp_to_uint selected but was incorrect according to
what instcombine constant folds to.
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llvm-svn: 277082