llvm/llvm/include/llvm/ADT/PointerEmbeddedInt.h

//===- llvm/ADT/PointerEmbeddedInt.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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_POINTEREMBEDDEDINT_H
#define LLVM_ADT_POINTEREMBEDDEDINT_H

#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
#include <cassert>
#include <climits>
#include <cstdint>
#include <type_traits>

namespace llvm {

/// Utility to embed an integer into a pointer-like type. This is specifically
/// intended to allow embedding integers where fewer bits are required than
/// exist in a pointer, and the integer can participate in abstractions along
/// side other pointer-like types. For example it can be placed into a \c
/// PointerSumType or \c PointerUnion.
///
/// Note that much like pointers, an integer value of zero has special utility
/// due to boolean conversions. For example, a non-null value can be tested for
/// in the above abstractions without testing the particular active member.
/// Also, the default constructed value zero initializes the integer.
template <typename IntT, int Bits = sizeof(IntT) * CHAR_BIT>
class PointerEmbeddedInt { … };

// Provide pointer like traits to support use with pointer unions and sum
// types.
PointerLikeTypeTraits<PointerEmbeddedInt<IntT, Bits>>;

// Teach DenseMap how to use PointerEmbeddedInt objects as keys if the Int type
// itself can be a key.
DenseMapInfo<PointerEmbeddedInt<IntT, Bits>>;

} // end namespace llvm

#endif // LLVM_ADT_POINTEREMBEDDEDINT_H