Merging r338817:

Merging r338817:
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r338817 | inouehrs | 2018-08-03 07:39:48 +0200 (Fri, 03 Aug 2018) | 10 lines

[InstSimplify] fold extracting from std::pair (2/2)

This is the second patch of the series which intends to enable jump threading for an inlined method whose return type is std::pair<int, bool> or std::pair<bool, int>.
The first patch is https://reviews.llvm.org/rL338485.

This patch handles code sequences that merges two values using `shl` and `or`, then extracts one value using `and`.

Differential Revision: https://reviews.llvm.org/D49981

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_70@339097 91177308-0d34-0410-b5e6-96231b3b80d8