Merging r311951 and r312038:

Merging r311951 and r312038:

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r311951 | adrian | 2017-08-28 16:07:43 -0700 (Mon, 28 Aug 2017) | 6 lines

Fix a logic error in DwarfExpression::addMachineReg()

This fixes PR34323 and thus splitting undescribable registers into
smaller, describable sub-registers.

https://bugs.llvm.org/show_bug.cgi?id=34323
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r312038 | joerg | 2017-08-29 14:18:07 -0700 (Tue, 29 Aug 2017) | 2 lines

Simplify test case, so that it works for both trunk and release-5.0.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_50@314567 91177308-0d34-0410-b5e6-96231b3b80d8