Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- llvm/Use.h - Definition of the Use class -----------------*- 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 defines the Use class.  The Use class represents the operand of an

/// instruction or some other User instance which refers to a Value.  The Use

/// class keeps the "use list" of the referenced value up to date.

///

/// Pointer tagging is used to efficiently find the User corresponding to a Use

/// without having to store a User pointer in every Use. A User is preceded in

/// memory by all the Uses corresponding to its operands, and the low bits of

/// one of the fields (Prev) of the Use class are used to encode offsets to be

/// able to find that User given a pointer to any Use. For details, see:

///

///   http://www.llvm.org/docs/ProgrammersManual.html#UserLayout

///

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

#ifndef LLVM_IR_USE_H

#define LLVM_IR_USE_H

#include "llvm-c/Types.h"

#include "llvm/Support/CBindingWrapping.h"

#include "llvm/Support/Compiler.h"

namespace llvm {

template <typename> struct simplify_type;

class User;

class Value;

/// A Use represents the edge between a Value definition and its users.

///

/// This is notionally a two-dimensional linked list. It supports traversing

/// all of the uses for a particular value definition. It also supports jumping

/// directly to the used value when we arrive from the User's operands, and

/// jumping directly to the User when we arrive from the Value's uses.

class Use {

public:

  Use(const Use &U) = delete;

  /// Provide a fast substitute to std::swap<Use>

  /// that also works with less standard-compliant compilers

  void swap(Use &RHS);

private:

  /// Destructor - Only for zap()

  ~Use() {

    if (Val)

      removeFromList();

  }

  /// Constructor

  Use(User *Parent) : Parent(Parent) {}

public:

  friend class Value;

  friend class User;

  operator Value *() const { return Val; }

  Value *get() const { return Val; }

  /// Returns the User that contains this Use.

  ///

  /// For an instruction operand, for example, this will return the

  /// instruction.

  User *getUser() const { return Parent; };

  inline void set(Value *Val);

  inline Value *operator=(Value *RHS);

  inline const Use &operator=(const Use &RHS);

  Value *operator->() { return Val; }

  const Value *operator->() const { return Val; }

  Use *getNext() const { return Next; }

  /// Return the operand # of this use in its User.

  unsigned getOperandNo() const;

  /// Destroys Use operands when the number of operands of

  /// a User changes.

  static void zap(Use *Start, const Use *Stop, bool del = false);

private:

  Value *Val = nullptr;

  Use *Next = nullptr;

  Use **Prev = nullptr;

  User *Parent = nullptr;

  void addToList(Use **List) {

    Next = *List;

    if (Next)

      Next->Prev = &Next;

    Prev = List;

    *Prev = this;

  }

  void removeFromList() {

    *Prev = Next;

    if (Next)

      Next->Prev = Prev;

  }

};

/// Allow clients to treat uses just like values when using

/// casting operators.

template <> struct simplify_type<Use> {

  using SimpleType = Value *;

  static SimpleType getSimplifiedValue(Use &Val) { return Val.get(); }

};

template <> struct simplify_type<const Use> {

  using SimpleType = /*const*/ Value *;

  static SimpleType getSimplifiedValue(const Use &Val) { return Val.get(); }

};

// Create wrappers for C Binding types (see CBindingWrapping.h).

DEFINE_SIMPLE_CONVERSION_FUNCTIONS(Use, LLVMUseRef)

} // end namespace llvm

#endif // LLVM_IR_USE_H