[CGP] Disable default copy ctor and copy assignment operator for InstructionRemover

[yubing]

Summary

class InstructionRemover manages resources such as dynamically allocated memory, it's generally a good practice to either implement a custom copy constructor or disable the default one.

[pengfei]

LGTM.

llvm/lib/CodeGen/CodeGenPrepare.cpp

InstructionRemover(Instruction *Inst, SetOfInstrs &RemovedInsts,
       /// The instructions removed here will be freed after completing
       /// optimizeBlock() for all blocks as we need to keep track of the
       /// removed instructions during promotion.
       Inst->removeFromParent();
     }
 
     ~InstructionRemover() override { delete Replacer; }
 
+    InstructionRemover &operator=(const InstructionRemover &other) = delete;
+    InstructionRemover(const InstructionRemover &other) = delete;
+
     /// Resurrect the instruction and reassign it to the proper uses if
     /// new value was provided when build this action.
     void undo() override {
       LLVM_DEBUG(dbgs() << "Undo: InstructionRemover: " << *Inst << "\n");
       Inserter.insert(Inst);
       if (Replacer)
         Replacer->undo();
       Hider.undo();