Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- CFG.h ----------------------------------------------------*- 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

//

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

/// \file

///

/// This file provides various utilities for inspecting and working with the

/// control flow graph in LLVM IR. This includes generic facilities for

/// iterating successors and predecessors of basic blocks, the successors of

/// specific terminator instructions, etc. It also defines specializations of

/// GraphTraits that allow Function and BasicBlock graphs to be treated as

/// proper graphs for generic algorithms.

///

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

#ifndef LLVM_IR_CFG_H

#define LLVM_IR_CFG_H

#include "llvm/ADT/GraphTraits.h"

#include "llvm/ADT/iterator.h"

#include "llvm/ADT/iterator_range.h"

#include "llvm/IR/BasicBlock.h"

#include "llvm/IR/Function.h"

#include "llvm/IR/Value.h"

#include <cassert>

#include <cstddef>

#include <iterator>

namespace llvm {

class Instruction;

class Use;

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

// BasicBlock pred_iterator definition

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

template <class Ptr, class USE_iterator> // Predecessor Iterator

class PredIterator {

public:

  using iterator_category = std::forward_iterator_tag;

  using value_type = Ptr;

  using difference_type = std::ptrdiff_t;

  using pointer = Ptr *;

  using reference = Ptr *;

protected:

  using Self = PredIterator<Ptr, USE_iterator>;

  USE_iterator It;

  inline void advancePastNonTerminators() {

    // Loop to ignore non-terminator uses (for example BlockAddresses).

    while (!It.atEnd()) {

      if (auto *Inst = dyn_cast<Instruction>(*It))

        if (Inst->isTerminator())

          break;

      ++It;

    }

  }

public:

  PredIterator() = default;

  explicit inline PredIterator(Ptr *bb) : It(bb->user_begin()) {

    advancePastNonTerminators();

  }

  inline PredIterator(Ptr *bb, bool) : It(bb->user_end()) {}

  inline bool operator==(const Self& x) const { return It == x.It; }

  inline bool operator!=(const Self& x) const { return !operator==(x); }

  inline reference operator*() const {

    assert(!It.atEnd() && "pred_iterator out of range!");

    return cast<Instruction>(*It)->getParent();

  }

  inline pointer *operator->() const { return &operator*(); }

  inline Self& operator++() {   // Preincrement

    assert(!It.atEnd() && "pred_iterator out of range!");

    ++It; advancePastNonTerminators();

    return *this;

  }

  inline Self operator++(int) { // Postincrement

    Self tmp = *this; ++*this; return tmp;

  }

  /// getOperandNo - Return the operand number in the predecessor's

  /// terminator of the successor.

  unsigned getOperandNo() const {

    return It.getOperandNo();

  }

  /// getUse - Return the operand Use in the predecessor's terminator

  /// of the successor.

  Use &getUse() const {

    return It.getUse();

  }

};

using pred_iterator = PredIterator<BasicBlock, Value::user_iterator>;

using const_pred_iterator =

    PredIterator<const BasicBlock, Value::const_user_iterator>;

using pred_range = iterator_range<pred_iterator>;

using const_pred_range = iterator_range<const_pred_iterator>;

inline pred_iterator pred_begin(BasicBlock *BB) { return pred_iterator(BB); }

inline const_pred_iterator pred_begin(const BasicBlock *BB) {

  return const_pred_iterator(BB);

}

inline pred_iterator pred_end(BasicBlock *BB) { return pred_iterator(BB, true);}

inline const_pred_iterator pred_end(const BasicBlock *BB) {

  return const_pred_iterator(BB, true);

}

inline bool pred_empty(const BasicBlock *BB) {

  return pred_begin(BB) == pred_end(BB);

}

/// Get the number of predecessors of \p BB. This is a linear time operation.

/// Use \ref BasicBlock::hasNPredecessors() or hasNPredecessorsOrMore if able.

inline unsigned pred_size(const BasicBlock *BB) {

  return std::distance(pred_begin(BB), pred_end(BB));

}

inline pred_range predecessors(BasicBlock *BB) {

  return pred_range(pred_begin(BB), pred_end(BB));

}

inline const_pred_range predecessors(const BasicBlock *BB) {

  return const_pred_range(pred_begin(BB), pred_end(BB));

}

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

// Instruction and BasicBlock succ_iterator helpers

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

template <class InstructionT, class BlockT>

class SuccIterator

    : public iterator_facade_base<SuccIterator<InstructionT, BlockT>,

                                  std::random_access_iterator_tag, BlockT, int,

                                  BlockT *, BlockT *> {

public:

  using difference_type = int;

  using pointer = BlockT *;

  using reference = BlockT *;

private:

  InstructionT *Inst;

  int Idx;

  using Self = SuccIterator<InstructionT, BlockT>;

  inline bool index_is_valid(int Idx) {

    // Note that we specially support the index of zero being valid even in the

    // face of a null instruction.

    return Idx >= 0 && (Idx == 0 || Idx <= (int)Inst->getNumSuccessors());

  }

  /// Proxy object to allow write access in operator[]

  class SuccessorProxy {

    Self It;

  public:

    explicit SuccessorProxy(const Self &It) : It(It) {}

    SuccessorProxy(const SuccessorProxy &) = default;

    SuccessorProxy &operator=(SuccessorProxy RHS) {

      *this = reference(RHS);

      return *this;

    }

    SuccessorProxy &operator=(reference RHS) {

      It.Inst->setSuccessor(It.Idx, RHS);

      return *this;

    }

    operator reference() const { return *It; }

  };

public:

  // begin iterator

  explicit inline SuccIterator(InstructionT *Inst) : Inst(Inst), Idx(0) {}

  // end iterator

  inline SuccIterator(InstructionT *Inst, bool) : Inst(Inst) {

    if (Inst)

      Idx = Inst->getNumSuccessors();

    else

      // Inst == NULL happens, if a basic block is not fully constructed and

      // consequently getTerminator() returns NULL. In this case we construct

      // a SuccIterator which describes a basic block that has zero

      // successors.

      // Defining SuccIterator for incomplete and malformed CFGs is especially

      // useful for debugging.

      Idx = 0;

  }

  /// This is used to interface between code that wants to

  /// operate on terminator instructions directly.

  int getSuccessorIndex() const { return Idx; }

  inline bool operator==(const Self &x) const { return Idx == x.Idx; }

  inline BlockT *operator*() const { return Inst->getSuccessor(Idx); }

  // We use the basic block pointer directly for operator->.

  inline BlockT *operator->() const { return operator*(); }

  inline bool operator<(const Self &RHS) const {

    assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!");

    return Idx < RHS.Idx;

  }

  int operator-(const Self &RHS) const {

    assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!");

    return Idx - RHS.Idx;

  }

  inline Self &operator+=(int RHS) {

    int NewIdx = Idx + RHS;

    assert(index_is_valid(NewIdx) && "Iterator index out of bound");

    Idx = NewIdx;

    return *this;

  }

  inline Self &operator-=(int RHS) { return operator+=(-RHS); }

  // Specially implement the [] operation using a proxy object to support

  // assignment.

  inline SuccessorProxy operator[](int Offset) {

    Self TmpIt = *this;

    TmpIt += Offset;

    return SuccessorProxy(TmpIt);

  }

  /// Get the source BlockT of this iterator.

  inline BlockT *getSource() {

    assert(Inst && "Source not available, if basic block was malformed");

    return Inst->getParent();

  }

};

using succ_iterator = SuccIterator<Instruction, BasicBlock>;

using const_succ_iterator = SuccIterator<const Instruction, const BasicBlock>;

using succ_range = iterator_range<succ_iterator>;

using const_succ_range = iterator_range<const_succ_iterator>;

inline succ_iterator succ_begin(Instruction *I) { return succ_iterator(I); }

inline const_succ_iterator succ_begin(const Instruction *I) {

  return const_succ_iterator(I);

}

inline succ_iterator succ_end(Instruction *I) { return succ_iterator(I, true); }

inline const_succ_iterator succ_end(const Instruction *I) {

  return const_succ_iterator(I, true);

}

inline bool succ_empty(const Instruction *I) {

  return succ_begin(I) == succ_end(I);

}

inline unsigned succ_size(const Instruction *I) {

  return std::distance(succ_begin(I), succ_end(I));

}

inline succ_range successors(Instruction *I) {

  return succ_range(succ_begin(I), succ_end(I));

}

inline const_succ_range successors(const Instruction *I) {

  return const_succ_range(succ_begin(I), succ_end(I));

}

inline succ_iterator succ_begin(BasicBlock *BB) {

  return succ_iterator(BB->getTerminator());

}

inline const_succ_iterator succ_begin(const BasicBlock *BB) {

  return const_succ_iterator(BB->getTerminator());

}

inline succ_iterator succ_end(BasicBlock *BB) {

  return succ_iterator(BB->getTerminator(), true);

}

inline const_succ_iterator succ_end(const BasicBlock *BB) {

  return const_succ_iterator(BB->getTerminator(), true);

}

inline bool succ_empty(const BasicBlock *BB) {

  return succ_begin(BB) == succ_end(BB);

}

inline unsigned succ_size(const BasicBlock *BB) {

  return std::distance(succ_begin(BB), succ_end(BB));

}

inline succ_range successors(BasicBlock *BB) {

  return succ_range(succ_begin(BB), succ_end(BB));

}

inline const_succ_range successors(const BasicBlock *BB) {

  return const_succ_range(succ_begin(BB), succ_end(BB));

}

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

// GraphTraits specializations for basic block graphs (CFGs)

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

// Provide specializations of GraphTraits to be able to treat a function as a

// graph of basic blocks...

template <> struct GraphTraits<BasicBlock*> {

  using NodeRef = BasicBlock *;

  using ChildIteratorType = succ_iterator;

  static NodeRef getEntryNode(BasicBlock *BB) { return BB; }

  static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); }

  static ChildIteratorType child_end(NodeRef N) { return succ_end(N); }

};

template <> struct GraphTraits<const BasicBlock*> {

  using NodeRef = const BasicBlock *;

  using ChildIteratorType = const_succ_iterator;

  static NodeRef getEntryNode(const BasicBlock *BB) { return BB; }

  static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); }

  static ChildIteratorType child_end(NodeRef N) { return succ_end(N); }

};

// Provide specializations of GraphTraits to be able to treat a function as a

// graph of basic blocks... and to walk it in inverse order.  Inverse order for

// a function is considered to be when traversing the predecessor edges of a BB

// instead of the successor edges.

//

template <> struct GraphTraits<Inverse<BasicBlock*>> {

  using NodeRef = BasicBlock *;

  using ChildIteratorType = pred_iterator;

  static NodeRef getEntryNode(Inverse<BasicBlock *> G) { return G.Graph; }

  static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); }

  static ChildIteratorType child_end(NodeRef N) { return pred_end(N); }

};

template <> struct GraphTraits<Inverse<const BasicBlock*>> {

  using NodeRef = const BasicBlock *;

  using ChildIteratorType = const_pred_iterator;

  static NodeRef getEntryNode(Inverse<const BasicBlock *> G) { return G.Graph; }

  static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); }

  static ChildIteratorType child_end(NodeRef N) { return pred_end(N); }

};

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

// GraphTraits specializations for function basic block graphs (CFGs)

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

// Provide specializations of GraphTraits to be able to treat a function as a

// graph of basic blocks... these are the same as the basic block iterators,

// except that the root node is implicitly the first node of the function.

//

template <> struct GraphTraits<Function*> : public GraphTraits<BasicBlock*> {

  static NodeRef getEntryNode(Function *F) { return &F->getEntryBlock(); }

  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph

  using nodes_iterator = pointer_iterator<Function::iterator>;

  static nodes_iterator nodes_begin(Function *F) {

    return nodes_iterator(F->begin());

  }

  static nodes_iterator nodes_end(Function *F) {

    return nodes_iterator(F->end());

  }

  static size_t size(Function *F) { return F->size(); }

};

template <> struct GraphTraits<const Function*> :

  public GraphTraits<const BasicBlock*> {

  static NodeRef getEntryNode(const Function *F) { return &F->getEntryBlock(); }

  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph

  using nodes_iterator = pointer_iterator<Function::const_iterator>;

  static nodes_iterator nodes_begin(const Function *F) {

    return nodes_iterator(F->begin());

  }

  static nodes_iterator nodes_end(const Function *F) {

    return nodes_iterator(F->end());

  }

  static size_t size(const Function *F) { return F->size(); }

};

// Provide specializations of GraphTraits to be able to treat a function as a

// graph of basic blocks... and to walk it in inverse order.  Inverse order for

// a function is considered to be when traversing the predecessor edges of a BB

// instead of the successor edges.

//

template <> struct GraphTraits<Inverse<Function*>> :

  public GraphTraits<Inverse<BasicBlock*>> {

  static NodeRef getEntryNode(Inverse<Function *> G) {

    return &G.Graph->getEntryBlock();

  }

};

template <> struct GraphTraits<Inverse<const Function*>> :

  public GraphTraits<Inverse<const BasicBlock*>> {

  static NodeRef getEntryNode(Inverse<const Function *> G) {

    return &G.Graph->getEntryBlock();

  }

};

} // end namespace llvm

#endif // LLVM_IR_CFG_H