text: //===- CallGraphSCCPass.h - Pass that operates BU on call graph -*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file defines the CallGraphSCCPass class, which is used for passes which
  // are implemented as bottom-up traversals on the call graph.  Because there may
  // be cycles in the call graph, passes of this type operate on the call-graph in
  // SCC order: that is, they process function bottom-up, except for recursive
  // functions, which they process all at once.
  //
  // These passes are inherently interprocedural, and are required to keep the
  // call graph up-to-date if they do anything which could modify it.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_ANALYSIS_CALLGRAPHSCCPASS_H
  #define LLVM_ANALYSIS_CALLGRAPHSCCPASS_H
  
  #include "llvm/Analysis/CallGraph.h"
  #include "llvm/Pass.h"
  
  namespace llvm {
  
  class CallGraphNode;
  class CallGraph;
  class PMStack;
  class CallGraphSCC;
    
  class CallGraphSCCPass : public Pass {
  public:
    explicit CallGraphSCCPass(char &pid) : Pass(PT_CallGraphSCC, pid) {}
  
    /// createPrinterPass - Get a pass that prints the Module
    /// corresponding to a CallGraph.
    Pass *createPrinterPass(raw_ostream &O,
                            const std::string &Banner) const override;
  
    using llvm::Pass::doInitialization;
    using llvm::Pass::doFinalization;
  
    /// doInitialization - This method is called before the SCC's of the program
    /// has been processed, allowing the pass to do initialization as necessary.
    virtual bool doInitialization(CallGraph &CG) {
      return false;
    }
  
    /// runOnSCC - This method should be implemented by the subclass to perform
    /// whatever action is necessary for the specified SCC.  Note that
    /// non-recursive (or only self-recursive) functions will have an SCC size of
    /// 1, where recursive portions of the call graph will have SCC size > 1.
    ///
    /// SCC passes that add or delete functions to the SCC are required to update
    /// the SCC list, otherwise stale pointers may be dereferenced.
    ///
    virtual bool runOnSCC(CallGraphSCC &SCC) = 0;
  
    /// doFinalization - This method is called after the SCC's of the program has
    /// been processed, allowing the pass to do final cleanup as necessary.
    virtual bool doFinalization(CallGraph &CG) {
      return false;
    }
  
    /// Assign pass manager to manager this pass
    void assignPassManager(PMStack &PMS, PassManagerType PMT) override;
  
    ///  Return what kind of Pass Manager can manage this pass.
    PassManagerType getPotentialPassManagerType() const override {
      return PMT_CallGraphPassManager;
    }
  
    /// getAnalysisUsage - For this class, we declare that we require and preserve
    /// the call graph.  If the derived class implements this method, it should
    /// always explicitly call the implementation here.
    void getAnalysisUsage(AnalysisUsage &Info) const override;
  };
  
  /// CallGraphSCC - This is a single SCC that a CallGraphSCCPass is run on. 
  class CallGraphSCC {
    void *Context; // The CGPassManager object that is vending this.
    std::vector<CallGraphNode*> Nodes;
  public:
    CallGraphSCC(void *context) : Context(context) {}
    
    void initialize(CallGraphNode*const*I, CallGraphNode*const*E) {
      Nodes.assign(I, E);
    }
    
    bool isSingular() const { return Nodes.size() == 1; }
    unsigned size() const { return Nodes.size(); }
    
    /// ReplaceNode - This informs the SCC and the pass manager that the specified
    /// Old node has been deleted, and New is to be used in its place.
    void ReplaceNode(CallGraphNode *Old, CallGraphNode *New);
    
    typedef std::vector<CallGraphNode*>::const_iterator iterator;
    iterator begin() const { return Nodes.begin(); }
    iterator end() const { return Nodes.end(); }
  };
  
  } // End llvm namespace
  
  #endif
  