Merging r276389:

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r276389 | majnemer | 2016-07-21 21:54:44 -0700 (Thu, 21 Jul 2016) | 6 lines

Don't remove side effecting instructions due to ConstantFoldInstruction

Just because we can constant fold the result of an instruction does not
imply that we can delete the instruction.  It may have side effects.

This fixes PR28655.
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llvm-svn: 276660