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//===---- bitmask_enum.h - Enable bitmask operations on enums ---*- 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
//
//===----------------------------------------------------------------------===//
//
// This file is a part of the ORC runtime support library.
//
//===----------------------------------------------------------------------===//
#ifndef ORC_RT_BITMASK_ENUM_H
#define ORC_RT_BITMASK_ENUM_H
#include "stl_extras.h"
#include <cassert>
#include <type_traits>
namespace orc_rt {
/// ORC_RT_MARK_AS_BITMASK_ENUM lets you opt in an individual enum type so you
/// can perform bitwise operations on it without putting static_cast everywhere.
///
/// \code
/// enum MyEnum {
/// E1 = 1, E2 = 2, E3 = 4, E4 = 8,
/// ORC_RT_MARK_AS_BITMASK_ENUM(/* LargestValue = */ E4)
/// };
///
/// void Foo() {
/// MyEnum A = (E1 | E2) & E3 ^ ~E4; // Look, ma: No static_cast!
/// }
/// \endcode
///
/// Normally when you do a bitwise operation on an enum value, you get back an
/// instance of the underlying type (e.g. int). But using this macro, bitwise
/// ops on your enum will return you back instances of the enum. This is
/// particularly useful for enums which represent a combination of flags.
///
/// The parameter to ORC_RT_MARK_AS_BITMASK_ENUM should be the largest
/// individual value in your enum.
///
/// All of the enum's values must be non-negative.
#define ORC_RT_MARK_AS_BITMASK_ENUM(LargestValue) \
ORC_RT_BITMASK_LARGEST_ENUMERATOR = LargestValue
/// ORC_RT_DECLARE_ENUM_AS_BITMASK can be used to declare an enum type as a bit
/// set, so that bitwise operation on such enum does not require static_cast.
///
/// \code
/// enum MyEnum { E1 = 1, E2 = 2, E3 = 4, E4 = 8 };
/// ORC_RT_DECLARE_ENUM_AS_BITMASK(MyEnum, E4);
///
/// void Foo() {
/// MyEnum A = (E1 | E2) & E3 ^ ~E4; // No static_cast
/// }
/// \endcode
///
/// The second parameter to ORC_RT_DECLARE_ENUM_AS_BITMASK specifies the largest
/// bit value of the enum type.
///
/// ORC_RT_DECLARE_ENUM_AS_BITMASK should be used in __orc_rt namespace.
///
/// This a non-intrusive alternative for ORC_RT_MARK_AS_BITMASK_ENUM. It allows
/// declaring more than one non-scoped enumerations as bitmask types in the same
/// scope. Otherwise it provides the same functionality as
/// ORC_RT_MARK_AS_BITMASK_ENUM.
#define ORC_RT_DECLARE_ENUM_AS_BITMASK(Enum, LargestValue) \
template <> struct is_bitmask_enum<Enum> : std::true_type {}; \
template <> struct largest_bitmask_enum_bit<Enum> { \
static constexpr std::underlying_type_t<Enum> value = LargestValue; \
}
/// Traits class to determine whether an enum has been declared as a bitwise
/// enum via ORC_RT_DECLARE_ENUM_AS_BITMASK.
template <typename E, typename Enable = void>
struct is_bitmask_enum : std::false_type {};
template <typename E>
struct is_bitmask_enum<
E, std::enable_if_t<sizeof(E::ORC_RT_BITMASK_LARGEST_ENUMERATOR) >= 0>>
: std::true_type {};
template <typename E>
inline constexpr bool is_bitmask_enum_v = is_bitmask_enum<E>::value;
/// Traits class to deermine bitmask enum largest bit.
template <typename E, typename Enable = void> struct largest_bitmask_enum_bit;
template <typename E>
struct largest_bitmask_enum_bit<
E, std::enable_if_t<sizeof(E::ORC_RT_BITMASK_LARGEST_ENUMERATOR) >= 0>> {
using UnderlyingTy = std::underlying_type_t<E>;
static constexpr UnderlyingTy value =
static_cast<UnderlyingTy>(E::ORC_RT_BITMASK_LARGEST_ENUMERATOR);
};
template <typename E> constexpr std::underlying_type_t<E> Mask() {
return bit_ceil(largest_bitmask_enum_bit<E>::value) - 1;
}
template <typename E> constexpr std::underlying_type_t<E> Underlying(E Val) {
auto U = static_cast<std::underlying_type_t<E>>(Val);
assert(U >= 0 && "Negative enum values are not allowed");
assert(U <= Mask<E>() && "Enum value too large (or langest val too small");
return U;
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum_v<E>>>
constexpr E operator~(E Val) {
return static_cast<E>(~Underlying(Val) & Mask<E>());
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum_v<E>>>
constexpr E operator|(E LHS, E RHS) {
return static_cast<E>(Underlying(LHS) | Underlying(RHS));
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum_v<E>>>
constexpr E operator&(E LHS, E RHS) {
return static_cast<E>(Underlying(LHS) & Underlying(RHS));
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum_v<E>>>
constexpr E operator^(E LHS, E RHS) {
return static_cast<E>(Underlying(LHS) ^ Underlying(RHS));
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum_v<E>>>
E &operator|=(E &LHS, E RHS) {
LHS = LHS | RHS;
return LHS;
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum_v<E>>>
E &operator&=(E &LHS, E RHS) {
LHS = LHS & RHS;
return LHS;
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum_v<E>>>
E &operator^=(E &LHS, E RHS) {
LHS = LHS ^ RHS;
return LHS;
}
} // namespace orc_rt
#endif // ORC_RT_BITMASK_ENUM_H
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