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//===- CallGraphSCCPass.h - Pass that operates BU on call graph -*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// 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/ADT/ArrayRef.h"

#include "llvm/Pass.h"

#include <vector>

namespace llvm {

class CallGraph;

class CallGraphNode;

class CallGraphSCC;

class PMStack;

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 &OS,

                          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;

protected:

  /// Optional passes call this function to check whether the pass should be

  /// skipped. This is the case when optimization bisect is over the limit.

  bool skipSCC(CallGraphSCC &SCC) const;

};

/// CallGraphSCC - This is a single SCC that a CallGraphSCCPass is run on.

class CallGraphSCC {

  const CallGraph &CG; // The call graph for this SCC.

  void *Context; // The CGPassManager object that is vending this.

  std::vector<CallGraphNode *> Nodes;

public:

  CallGraphSCC(CallGraph &cg, void *context) : CG(cg), Context(context) {}

  void initialize(ArrayRef<CallGraphNode *> NewNodes) {

    Nodes.assign(NewNodes.begin(), NewNodes.end());

  }

  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);

  /// DeleteNode - This informs the SCC and the pass manager that the specified

  /// Old node has been deleted.

  void DeleteNode(CallGraphNode *Old);

  using iterator = std::vector<CallGraphNode *>::const_iterator;

  iterator begin() const { return Nodes.begin(); }

  iterator end() const { return Nodes.end(); }

  const CallGraph &getCallGraph() { return CG; }

};

void initializeDummyCGSCCPassPass(PassRegistry &);

/// This pass is required by interprocedural register allocation. It forces

/// codegen to follow bottom up order on call graph.

class DummyCGSCCPass : public CallGraphSCCPass {

public:

  static char ID;

  DummyCGSCCPass() : CallGraphSCCPass(ID) {

    PassRegistry &Registry = *PassRegistry::getPassRegistry();

    initializeDummyCGSCCPassPass(Registry);

  }

  bool runOnSCC(CallGraphSCC &SCC) override { return false; }

  void getAnalysisUsage(AnalysisUsage &AU) const override {

    AU.setPreservesAll();

  }

};

} // end namespace llvm

#endif // LLVM_ANALYSIS_CALLGRAPHSCCPASS_H