llvm/libc/src/__support/FPUtil/generic/sqrt.h

//===-- Square root of IEEE 754 floating point numbers ----------*- 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_LIBC_SRC___SUPPORT_FPUTIL_GENERIC_SQRT_H
#define LLVM_LIBC_SRC___SUPPORT_FPUTIL_GENERIC_SQRT_H

#include "sqrt_80_bit_long_double.h"
#include "src/__support/CPP/bit.h" // countl_zero
#include "src/__support/CPP/type_traits.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/dyadic_float.h"
#include "src/__support/common.h"
#include "src/__support/macros/config.h"
#include "src/__support/uint128.h"

#include "hdr/fenv_macros.h"

namespace LIBC_NAMESPACE_DECL {
namespace fputil {

namespace internal {

template <typename T> struct SpecialLongDouble { … };

#if defined(LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80)
template <> struct SpecialLongDouble<long double> { … };
#endif // LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80

template <typename T>
LIBC_INLINE void normalize(int &exponent,
                           typename FPBits<T>::StorageType &mantissa) { … }

#ifdef LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64
template <>
LIBC_INLINE void normalize<long double>(int &exponent, uint64_t &mantissa) {
  normalize<double>(exponent, mantissa);
}
#elif !defined(LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80)
template <>
LIBC_INLINE void normalize<long double>(int &exponent, UInt128 &mantissa) {
  const uint64_t hi_bits = static_cast<uint64_t>(mantissa >> 64);
  const int shift =
      hi_bits ? (cpp::countl_zero(hi_bits) - 15)
              : (cpp::countl_zero(static_cast<uint64_t>(mantissa)) + 49);
  exponent -= shift;
  mantissa <<= shift;
}
#endif

} // namespace internal

// Correctly rounded IEEE 754 SQRT for all rounding modes.
// Shift-and-add algorithm.
template <typename OutType, typename InType>
LIBC_INLINE cpp::enable_if_t<cpp::is_floating_point_v<OutType> &&
                                 cpp::is_floating_point_v<InType> &&
                                 sizeof(OutType) <= sizeof(InType),
                             OutType>
sqrt(InType x) { … }

} // namespace fputil
} // namespace LIBC_NAMESPACE_DECL

#endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_GENERIC_SQRT_H