llvm/libc/src/__support/math_extras.h

//===-- Mimics llvm/Support/MathExtras.h ------------------------*- C++ -*-===//
// Provides useful math functions.
//
// 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_LIBC_SRC___SUPPORT_MATH_EXTRAS_H
#define LLVM_LIBC_SRC___SUPPORT_MATH_EXTRAS_H

#include "src/__support/CPP/bit.h"         // countl_one, countr_zero
#include "src/__support/CPP/limits.h"      // CHAR_BIT, numeric_limits
#include "src/__support/CPP/type_traits.h" // is_unsigned_v, is_constant_evaluated
#include "src/__support/macros/attributes.h" // LIBC_INLINE
#include "src/__support/macros/config.h"

namespace LIBC_NAMESPACE_DECL {

// Create a bitmask with the count right-most bits set to 1, and all other bits
// set to 0.  Only unsigned types are allowed.
template <typename T, size_t count>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
mask_trailing_ones() { … }

// Create a bitmask with the count left-most bits set to 1, and all other bits
// set to 0.  Only unsigned types are allowed.
template <typename T, size_t count>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
mask_leading_ones() { … }

// Create a bitmask with the count right-most bits set to 0, and all other bits
// set to 1.  Only unsigned types are allowed.
template <typename T, size_t count>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
mask_trailing_zeros() { … }

// Create a bitmask with the count left-most bits set to 0, and all other bits
// set to 1.  Only unsigned types are allowed.
template <typename T, size_t count>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
mask_leading_zeros() { … }

// Returns whether 'a + b' overflows, the result is stored in 'res'.
template <typename T>
[[nodiscard]] LIBC_INLINE constexpr bool add_overflow(T a, T b, T &res) { … }

// Returns whether 'a - b' overflows, the result is stored in 'res'.
template <typename T>
[[nodiscard]] LIBC_INLINE constexpr bool sub_overflow(T a, T b, T &res) { … }

#define RETURN_IF …

// Returns the result of 'a + b' taking into account 'carry_in'.
// The carry out is stored in 'carry_out' it not 'nullptr', dropped otherwise.
// We keep the pass by pointer interface for consistency with the intrinsic.
template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
add_with_carry(T a, T b, T carry_in, T &carry_out) { … }

// Returns the result of 'a - b' taking into account 'carry_in'.
// The carry out is stored in 'carry_out' it not 'nullptr', dropped otherwise.
// We keep the pass by pointer interface for consistency with the intrinsic.
template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
sub_with_borrow(T a, T b, T carry_in, T &carry_out) { … }

#undef RETURN_IF

template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
first_leading_zero(T value) { … }

template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
first_leading_one(T value) { … }

template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
first_trailing_zero(T value) { … }

template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
first_trailing_one(T value) { … }

template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
count_zeros(T value) { … }

} // namespace LIBC_NAMESPACE_DECL

#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXTRAS_H