Merging r279647:

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r279647 | sanjoy | 2016-08-24 11:10:21 -0700 (Wed, 24 Aug 2016) | 5 lines

[SCCP] Don't delete side-effecting instructions

I'm not sure if the `!isa<CallInst>(Inst) &&
!isa<TerminatorInst>(Inst))` bit is correct either, but this fixes the
case we know is broken.
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llvm-svn: 279689