Revert "[SCCP] Throw away dead code. NFC."

This reverts commit r268568, as it broke the bots.

llvm-svn: 268570

llvm/lib/Transforms/Scalar/SCCP.cpp

@@ -500,6 +500,9 @@ private:
     visitTerminatorInst(II);
   }
   void visitCallSite      (CallSite CS);
+  void visitResumeInst    (TerminatorInst &I) { /*returns void*/ }
+  void visitUnreachableInst(TerminatorInst &I) { /*returns void*/ }
+  void visitFenceInst     (FenceInst &I) { /*returns void*/ }
   void visitAtomicCmpXchgInst(AtomicCmpXchgInst &I) {
     markAnythingOverdefined(&I);
   }