llvm/llvm/include/llvm/IR/Use.h

//===- 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 { … };

/// Allow clients to treat uses just like values when using
/// casting operators.
template <> struct simplify_type<Use> { … };
template <> struct simplify_type<const Use> { … };

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

} // end namespace llvm

#endif // LLVM_IR_USE_H