Merging r258386:

Merging r258386:

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r258386 | thomas.stellard | 2016-01-20 23:28:34 -0500 (Wed, 20 Jan 2016) | 14 lines

AMDGPU/SI: Pass whether to use the SI scheduler via Target Attribute

Summary:
Currently the SI scheduler can be selected via command line option,
but it turned out it would be better if it was selectable via a Target Attribute.

This patch adds "si-scheduler" attribute to the backend.

Reviewers: tstellarAMD, echristo

Subscribers: echristo, arsenm

Differential Revision: http://reviews.llvm.org/D16192

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_38@258885 91177308-0d34-0410-b5e6-96231b3b80d8