xref: /external/clang/include/clang/Analysis/CFG.h

//===--- CFG.h - Classes for representing and building CFGs------*- 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 CFG and CFGBuilder classes for representing and
//  building Control-Flow Graphs (CFGs) from ASTs.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_CFG_H
#define LLVM_CLANG_CFG_H

#include "llvm/ADT/GraphTraits.h"
#include "llvm/Support/Allocator.h"
#include <list>
#include <vector>
#include <iosfwd>
#include <cassert>

namespace clang {
  class Stmt;
  class Expr;
  class CFG;
  class PrinterHelper;
  class BlockEdge;

/// CFGBlock - Represents a single basic block in a source-level CFG.
///  It consists of:
///
///  (1) A set of statements/expressions (which may contain subexpressions).
///  (2) A "terminator" statement (not in the set of statements).
///  (3) A list of successors and predecessors.
///
/// Terminator: The terminator represents the type of control-flow that occurs
/// at the end of the basic block.  The terminator is a Stmt* referring to an
/// AST node that has control-flow: if-statements, breaks, loops, etc.
/// If the control-flow is conditional, the condition expression will appear
/// within the set of statements in the block (usually the last statement).
///
/// Predecessors: the order in the set of predecessors is arbitrary.
///
/// Successors: the order in the set of successors is NOT arbitrary.  We
///  currently have the following orderings based on the terminator:
///
///     Terminator       Successor Ordering
///  -----------------------------------------------------
///       if            Then Block;  Else Block
///     ? operator      LHS expression;  RHS expression
///     &&, ||          expression that uses result of && or ||, RHS
///
class CFGBlock {
  typedef std::vector<Stmt*> StatementListTy;
  /// Stmts - The set of statements in the basic block.
  StatementListTy Stmts;

  /// Label - An (optional) label that prefixes the executable
  ///  statements in the block.  When this variable is non-NULL, it is
  ///  either an instance of LabelStmt or SwitchCase.
  Stmt* Label;

  /// Terminator - The terminator for a basic block that
  ///  indicates the type of control-flow that occurs between a block
  ///  and its successors.
  Stmt* Terminator;

  /// BlockID - A numerical ID assigned to a CFGBlock during construction
  ///   of the CFG.
  unsigned BlockID;

  /// Predecessors/Successors - Keep track of the predecessor / successor
  /// CFG blocks.
  typedef std::vector<CFGBlock*> AdjacentBlocks;
  AdjacentBlocks Preds;
  AdjacentBlocks Succs;

public:
  explicit CFGBlock(unsigned blockid) : Label(NULL), Terminator(NULL),
                                        BlockID(blockid) {}
  ~CFGBlock() {};

  // Statement iterators
  typedef StatementListTy::iterator                                  iterator;
  typedef StatementListTy::const_iterator                      const_iterator;
  typedef std::reverse_iterator<const_iterator>        const_reverse_iterator;
  typedef std::reverse_iterator<iterator>                    reverse_iterator;

  Stmt*                        front()       const { return Stmts.front();   }
  Stmt*                        back()        const { return Stmts.back();    }

  iterator                     begin()             { return Stmts.begin();   }
  iterator                     end()               { return Stmts.end();     }
  const_iterator               begin()       const { return Stmts.begin();   }
  const_iterator               end()         const { return Stmts.end();     }

  reverse_iterator             rbegin()            { return Stmts.rbegin();  }
  reverse_iterator             rend()              { return Stmts.rend();    }
  const_reverse_iterator       rbegin()      const { return Stmts.rbegin();  }
  const_reverse_iterator       rend()        const { return Stmts.rend();    }

  unsigned                     size()        const { return Stmts.size();    }
  bool                         empty()       const { return Stmts.empty();   }

  Stmt*  operator[](size_t i) const  { assert (i < size()); return Stmts[i]; }

  // CFG iterators
  typedef AdjacentBlocks::iterator                              pred_iterator;
  typedef AdjacentBlocks::const_iterator                  const_pred_iterator;
  typedef AdjacentBlocks::reverse_iterator              pred_reverse_iterator;
  typedef AdjacentBlocks::const_reverse_iterator  const_pred_reverse_iterator;

  typedef AdjacentBlocks::iterator                              succ_iterator;
  typedef AdjacentBlocks::const_iterator                  const_succ_iterator;
  typedef AdjacentBlocks::reverse_iterator              succ_reverse_iterator;
  typedef AdjacentBlocks::const_reverse_iterator  const_succ_reverse_iterator;

  pred_iterator                pred_begin()        { return Preds.begin();   }
  pred_iterator                pred_end()          { return Preds.end();     }
  const_pred_iterator          pred_begin()  const { return Preds.begin();   }
  const_pred_iterator          pred_end()    const { return Preds.end();     }

  pred_reverse_iterator        pred_rbegin()       { return Preds.rbegin();  }
  pred_reverse_iterator        pred_rend()         { return Preds.rend();    }
  const_pred_reverse_iterator  pred_rbegin() const { return Preds.rbegin();  }
  const_pred_reverse_iterator  pred_rend()   const { return Preds.rend();    }

  succ_iterator                succ_begin()        { return Succs.begin();   }
  succ_iterator                succ_end()          { return Succs.end();     }
  const_succ_iterator          succ_begin()  const { return Succs.begin();   }
  const_succ_iterator          succ_end()    const { return Succs.end();     }

  succ_reverse_iterator        succ_rbegin()       { return Succs.rbegin();  }
  succ_reverse_iterator        succ_rend()         { return Succs.rend();    }
  const_succ_reverse_iterator  succ_rbegin() const { return Succs.rbegin();  }
  const_succ_reverse_iterator  succ_rend()   const { return Succs.rend();    }

  unsigned                     succ_size()   const { return Succs.size();    }
  bool                         succ_empty()  const { return Succs.empty();   }

  unsigned                     pred_size()   const { return Preds.size();    }
  bool                         pred_empty()  const { return Preds.empty();   }

  // Manipulation of block contents

  void appendStmt(Stmt* Statement) { Stmts.push_back(Statement); }
  void setTerminator(Stmt* Statement) { Terminator = Statement; }
  void setLabel(Stmt* Statement) { Label = Statement; }

  Stmt* getTerminator() { return Terminator; }
  const Stmt* getTerminator() const { return Terminator; }

  Expr* getTerminatorCondition();

  const Expr* getTerminatorCondition() const {
    return const_cast<CFGBlock*>(this)->getTerminatorCondition();
  }

  bool hasBinaryBranchTerminator() const;

  Stmt* getLabel() { return Label; }
  const Stmt* getLabel() const { return Label; }

  void reverseStmts();

  void addSuccessor(CFGBlock* Block) {
    Block->Preds.push_back(this);
    Succs.push_back(Block);
  }

  unsigned getBlockID() const { return BlockID; }

  void dump(const CFG* cfg) const;
  void print(std::ostream& OS, const CFG* cfg) const;
  void printTerminator(std::ostream& OS) const;
};


/// CFG - Represents a source-level, intra-procedural CFG that represents the
///  control-flow of a Stmt.  The Stmt can represent an entire function body,
///  or a single expression.  A CFG will always contain one empty block that
///  represents the Exit point of the CFG.  A CFG will also contain a designated
///  Entry block.  The CFG solely represents control-flow; it consists of
///  CFGBlocks which are simply containers of Stmt*'s in the AST the CFG
///  was constructed from.
class CFG {
public:
  //===--------------------------------------------------------------------===//
  // CFG Construction & Manipulation.
  //===--------------------------------------------------------------------===//

  /// buildCFG - Builds a CFG from an AST.  The responsibility to free the
  ///   constructed CFG belongs to the caller.
  static CFG* buildCFG(Stmt* AST);

  /// createBlock - Create a new block in the CFG.  The CFG owns the block;
  ///  the caller should not directly free it.
  CFGBlock* createBlock();

  /// setEntry - Set the entry block of the CFG.  This is typically used
  ///  only during CFG construction.  Most CFG clients expect that the
  ///  entry block has no predecessors and contains no statements.
  void setEntry(CFGBlock *B) { Entry = B; }

  /// setExit - Set the exit block of the CFG.  This is typically used
  ///  only during CFG construction.  Most CFG clients expect that the
  ///  exit block has no successors and contains no statements.
  void setIndirectGotoBlock(CFGBlock* B) { IndirectGotoBlock = B; }

  //===--------------------------------------------------------------------===//
  // Block Iterators
  //===--------------------------------------------------------------------===//

  typedef std::list<CFGBlock>                      CFGBlockListTy;

  typedef CFGBlockListTy::iterator                 iterator;
  typedef CFGBlockListTy::const_iterator           const_iterator;
  typedef std::reverse_iterator<iterator>          reverse_iterator;
  typedef std::reverse_iterator<const_iterator>    const_reverse_iterator;

  CFGBlock&                 front()                { return Blocks.front(); }
  CFGBlock&                 back()                 { return Blocks.back(); }

  iterator                  begin()                { return Blocks.begin(); }
  iterator                  end()                  { return Blocks.end(); }
  const_iterator            begin()       const    { return Blocks.begin(); }
  const_iterator            end()         const    { return Blocks.end(); }

  reverse_iterator          rbegin()               { return Blocks.rbegin(); }
  reverse_iterator          rend()                 { return Blocks.rend(); }
  const_reverse_iterator    rbegin()      const    { return Blocks.rbegin(); }
  const_reverse_iterator    rend()        const    { return Blocks.rend(); }

  CFGBlock&                 getEntry()             { return *Entry; }
  const CFGBlock&           getEntry()    const    { return *Entry; }
  CFGBlock&                 getExit()              { return *Exit; }
  const CFGBlock&           getExit()     const    { return *Exit; }

  CFGBlock*        getIndirectGotoBlock() { return IndirectGotoBlock; }
  const CFGBlock*  getIndirectGotoBlock() const { return IndirectGotoBlock; }

  //===--------------------------------------------------------------------===//
  // Member templates useful for various batch operations over CFGs.
  //===--------------------------------------------------------------------===//

  template <typename CALLBACK>
  void VisitBlockStmts(CALLBACK& O) const {
    for (const_iterator I=begin(), E=end(); I != E; ++I)
      for (CFGBlock::const_iterator BI=I->begin(), BE=I->end(); BI != BE; ++BI)
        O(*BI);
  }

  //===--------------------------------------------------------------------===//
  // CFG Introspection.
  //===--------------------------------------------------------------------===//

  struct   BlkExprNumTy {
    const signed Idx;
    explicit BlkExprNumTy(signed idx) : Idx(idx) {}
    explicit BlkExprNumTy() : Idx(-1) {}
    operator bool() const { return Idx >= 0; }
    operator unsigned() const { assert(Idx >=0); return (unsigned) Idx; }
  };

  bool          isBlkExpr(const Stmt* S) { return getBlkExprNum(S); }
  BlkExprNumTy  getBlkExprNum(const Stmt* S);
  unsigned      getNumBlkExprs();

  unsigned getNumBlockIDs() const { return NumBlockIDs; }

  //===--------------------------------------------------------------------===//
  // CFG Debugging: Pretty-Printing and Visualization.
  //===--------------------------------------------------------------------===//

  void viewCFG() const;
  void print(std::ostream& OS) const;
  void dump() const;

  //===--------------------------------------------------------------------===//
  // Internal: constructors and data.
  //===--------------------------------------------------------------------===//

  CFG() : Entry(NULL), Exit(NULL), IndirectGotoBlock(NULL), NumBlockIDs(0),
          BlkExprMap(NULL), BlkEdgeSet(NULL) {};

  ~CFG();

  llvm::BumpPtrAllocator& getAllocator() {
    return Alloc;
  }

private:
  CFGBlock* Entry;
  CFGBlock* Exit;
  CFGBlock* IndirectGotoBlock;  // Special block to contain collective dispatch
  // for indirect gotos
  CFGBlockListTy Blocks;
  unsigned  NumBlockIDs;

  // BlkExprMap - An opaque pointer to prevent inclusion of DenseMap.h.
  //  It represents a map from Expr* to integers to record the set of
  //  block-level expressions and their "statement number" in the CFG.
  void*     BlkExprMap;

  /// BlkEdgeSet - An opaque pointer to prevent inclusion of FoldingSet.h.
  ///  The set contains std::pair<CFGBlock*,CFGBlock*> objects that have
  ///  stable references for use by the 'BlockEdge' class.  This set is intended
  ///  to be sparse, as it only contains edges whether both the source
  ///  and destination block have multiple successors/predecessors.
  void*     BlkEdgeSet;

  /// Alloc - An internal allocator used for BlkEdgeSet.
  llvm::BumpPtrAllocator Alloc;

  friend class BlockEdge;

  /// getBlockEdgeImpl - Utility method used by the class BlockEdge.  The CFG
  ///  stores a set of interned std::pair<CFGBlock*,CFGBlock*> that can
  ///  be used by BlockEdge to refer to edges that cannot be represented
  ///  by a single pointer.
  const std::pair<CFGBlock*,CFGBlock*>* getBlockEdgeImpl(const CFGBlock* B1,
                                                         const CFGBlock* B2);

};
} // end namespace clang

//===----------------------------------------------------------------------===//
// GraphTraits specializations for CFG basic block graphs (source-level CFGs)
//===----------------------------------------------------------------------===//

namespace llvm {

// Traits for: CFGBlock

template <> struct GraphTraits<clang::CFGBlock* > {
  typedef clang::CFGBlock NodeType;
  typedef clang::CFGBlock::succ_iterator ChildIteratorType;

  static NodeType* getEntryNode(clang::CFGBlock* BB)
  { return BB; }

  static inline ChildIteratorType child_begin(NodeType* N)
  { return N->succ_begin(); }

  static inline ChildIteratorType child_end(NodeType* N)
  { return N->succ_end(); }
};

template <> struct GraphTraits<const clang::CFGBlock* > {
  typedef const clang::CFGBlock NodeType;
  typedef clang::CFGBlock::const_succ_iterator ChildIteratorType;

  static NodeType* getEntryNode(const clang::CFGBlock* BB)
  { return BB; }

  static inline ChildIteratorType child_begin(NodeType* N)
  { return N->succ_begin(); }

  static inline ChildIteratorType child_end(NodeType* N)
  { return N->succ_end(); }
};

template <> struct GraphTraits<Inverse<const clang::CFGBlock*> > {
  typedef const clang::CFGBlock NodeType;
  typedef clang::CFGBlock::const_pred_iterator ChildIteratorType;

  static NodeType *getEntryNode(Inverse<const clang::CFGBlock*> G)
  { return G.Graph; }

  static inline ChildIteratorType child_begin(NodeType* N)
  { return N->pred_begin(); }

  static inline ChildIteratorType child_end(NodeType* N)
  { return N->pred_end(); }
};

// Traits for: CFG

template <> struct GraphTraits<clang::CFG* >
            : public GraphTraits<clang::CFGBlock* >  {

  typedef clang::CFG::iterator nodes_iterator;

  static NodeType *getEntryNode(clang::CFG* F) { return &F->getEntry(); }
  static nodes_iterator nodes_begin(clang::CFG* F) { return F->begin(); }
  static nodes_iterator nodes_end(clang::CFG* F) { return F->end(); }
};

template <> struct GraphTraits< const clang::CFG* >
            : public GraphTraits< const clang::CFGBlock* >  {

  typedef clang::CFG::const_iterator nodes_iterator;

  static NodeType *getEntryNode( const clang::CFG* F) { return &F->getEntry(); }
  static nodes_iterator nodes_begin( const clang::CFG* F) { return F->begin(); }
  static nodes_iterator nodes_end( const clang::CFG* F) { return F->end(); }
};

template <> struct GraphTraits<Inverse<const clang::CFG*> >
            : public GraphTraits<Inverse<const clang::CFGBlock*> > {

  typedef clang::CFG::const_iterator nodes_iterator;

  static NodeType *getEntryNode(const clang::CFG* F) { return &F->getExit(); }
  static nodes_iterator nodes_begin(const clang::CFG* F) { return F->begin();}
  static nodes_iterator nodes_end(const clang::CFG* F) { return F->end(); }
};

} // end llvm namespace

#endif