Merging r341094:

Merging r341094:
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r341094 | efriedma | 2018-08-30 20:59:24 +0200 (Thu, 30 Aug 2018) | 11 lines

[SROA] Fix alignment for uses of PHI nodes.

Splitting an alloca can decrease the alignment of GEPs into the
partition.  Normally, rewriting accounts for this, but the code was
missing for uses of PHI nodes and select instructions.

Fixes https://bugs.llvm.org/show_bug.cgi?id=38707 .

Differential Revision: https://reviews.llvm.org/D51335

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_70@341220 91177308-0d34-0410-b5e6-96231b3b80d8