Merging r340158:

Merging r340158:
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r340158 | s.desmalen | 2018-08-20 11:16:59 +0200 (Mon, 20 Aug 2018) | 16 lines

[AArch64][SVE] Asm: Add SVE System registers

This patch adds system registers for controlling aspects of SVE:
- ZCR_EL1  (r/w)   visible at EL1 and EL0.
- ZCR_EL2  (r/w)   visible at EL2 and Non-secure EL1 and EL0.
- ZCR_EL3  (r/w)   visible at all exception levels.

and a system register identifying SVE:
- ID_AA64ZFR0_EL1  (r)  SVE Feature identifier.

Reviewers: SjoerdMeijer, samparker, pbarrio, fhahn, javed.absar

Reviewed By: SjoerdMeijer

Differential Revision: https://reviews.llvm.org/D50885

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_70@340355 91177308-0d34-0410-b5e6-96231b3b80d8