Merging r260495:

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r260495 | Matthew.Arsenault | 2016-02-10 22:15:39 -0800 (Wed, 10 Feb 2016) | 9 lines

AMDGPU: Fix constant bus use check with subregisters

If the two operands to an instruction were both
subregisters of the same super register, it would incorrectly
think this counted as the same constant bus use.

This fixes the verifier error in fmin_legacy.ll which
was missing -verify-machineinstrs.

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llvm-svn: 271640