Merging r275866:

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r275866 | tnorthover | 2016-07-18 11:28:52 -0700 (Mon, 18 Jul 2016) | 6 lines

CodeGenPrep: use correct function to determine Global's alignment.

Elsewhere (particularly computeKnownBits) we assume that a global will be
aligned to the value returned by Value::getPointerAlignment. This is used to
boost the alignment on memcpy/memset, so any target-specific request can only
increase that value.
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llvm-svn: 275918