//===-- llvm/ADT/BitmaskEnum.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_BITMASKENUM_H
#define LLVM_ADT_BITMASKENUM_H
#include <cassert>
#include <type_traits>
#include <utility>
#include "llvm/Support/MathExtras.h"
/// LLVM_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,
/// LLVM_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 LLVM_MARK_AS_BITMASK_ENUM should be the largest individual
/// value in your enum.
///
/// All of the enum's values must be non-negative.
#define LLVM_MARK_AS_BITMASK_ENUM(LargestValue) \
LLVM_BITMASK_LARGEST_ENUMERATOR = LargestValue
/// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() pulls the operator overloads used
/// by LLVM_MARK_AS_BITMASK_ENUM into the current namespace.
///
/// Suppose you have an enum foo::bar::MyEnum. Before using
/// LLVM_MARK_AS_BITMASK_ENUM on MyEnum, you must put
/// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() somewhere inside namespace foo or
/// namespace foo::bar. This allows the relevant operator overloads to be found
/// by ADL.
///
/// You don't need to use this macro in namespace llvm; it's done at the bottom
/// of this file.
#define LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() \
using ::llvm::BitmaskEnumDetail::operator~; \
using ::llvm::BitmaskEnumDetail::operator|; \
using ::llvm::BitmaskEnumDetail::operator&; \
using ::llvm::BitmaskEnumDetail::operator^; \
using ::llvm::BitmaskEnumDetail::operator|=; \
using ::llvm::BitmaskEnumDetail::operator&=; \
/* Force a semicolon at the end of this macro. */ \
using ::llvm::BitmaskEnumDetail::operator^=
namespace llvm {
/// Traits class to determine whether an enum has a
/// LLVM_BITMASK_LARGEST_ENUMERATOR enumerator.
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::LLVM_BITMASK_LARGEST_ENUMERATOR) >= 0>>
: std::true_type {};
namespace BitmaskEnumDetail {
/// Get a bitmask with 1s in all places up to the high-order bit of E's largest
/// value.
template <typename E> constexpr std::underlying_type_t<E> Mask() {
// On overflow, NextPowerOf2 returns zero with the type uint64_t, so
// subtracting 1 gives us the mask with all bits set, like we want.
return NextPowerOf2(static_cast<std::underlying_type_t<E>>(
E::LLVM_BITMASK_LARGEST_ENUMERATOR)) -
1;
}
/// Check that Val is in range for E, and return Val cast to E's underlying
/// type.
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 largest val too small?)");
return U;
}
constexpr unsigned bitWidth(uint64_t Value) {
return Value ? 1 + bitWidth(Value >> 1) : 0;
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
constexpr E operator~(E Val) {
return static_cast<E>(~Underlying(Val) & Mask<E>());
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
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<E>::value>>
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<E>::value>>
constexpr E operator^(E LHS, E RHS) {
return static_cast<E>(Underlying(LHS) ^ Underlying(RHS));
}
// |=, &=, and ^= return a reference to LHS, to match the behavior of the
// operators on builtin types.
template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
E &operator|=(E &LHS, E RHS) {
LHS = LHS | RHS;
return LHS;
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
E &operator&=(E &LHS, E RHS) {
LHS = LHS & RHS;
return LHS;
}
template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
E &operator^=(E &LHS, E RHS) {
LHS = LHS ^ RHS;
return LHS;
}
} // namespace BitmaskEnumDetail
// Enable bitmask enums in namespace ::llvm and all nested namespaces.
LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
constexpr unsigned BitWidth = BitmaskEnumDetail::bitWidth(uint64_t{
static_cast<std::underlying_type_t<E>>(
E::LLVM_BITMASK_LARGEST_ENUMERATOR)});
} // namespace llvm
#endif