libc/src/__support/FPUtil/BasicOperations.h

//===-- Basic operations on 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_BASICOPERATIONS_H
#define LLVM_LIBC_SRC___SUPPORT_FPUTIL_BASICOPERATIONS_H

#include "FEnvImpl.h"
#include "FPBits.h"
#include "dyadic_float.h"

#include "src/__support/CPP/type_traits.h"
#include "src/__support/big_int.h"
#include "src/__support/common.h"
#include "src/__support/macros/config.h"
#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
#include "src/__support/macros/properties/architectures.h"
#include "src/__support/macros/properties/types.h"
#include "src/__support/uint128.h"

namespace LIBC_NAMESPACE_DECL {
namespace fputil {

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T abs(T x) {
  return FPBits<T>(x).abs().get_val();
}

namespace internal {

template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<T>, T>
constexpr_max(T x, T y) {
  FPBits<T> x_bits(x);
  FPBits<T> y_bits(y);

  // To make sure that fmax(+0, -0) == +0 == fmax(-0, +0), whenever x and y
  // have different signs and both are not NaNs, we return the number with
  // positive sign.
  if (x_bits.sign() != y_bits.sign())
    return x_bits.is_pos() ? x : y;
  return x > y ? x : y;
}

template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<T>, T>
max(T x, T y) {
  return constexpr_max(x, y);
}

#ifdef LIBC_TYPES_HAS_FLOAT16
#if defined(__LIBC_USE_BUILTIN_FMAXF16_FMINF16)
template <> LIBC_INLINE constexpr float16 max(float16 x, float16 y) {
  if (cpp::is_constant_evaluated())
    return constexpr_max(x, y);
  return __builtin_fmaxf16(x, y);
}
#elif !defined(LIBC_TARGET_ARCH_IS_AARCH64)
template <> LIBC_INLINE constexpr float16 max(float16 x, float16 y) {
  FPBits<float16> x_bits(x);
  FPBits<float16> y_bits(y);

  int16_t xi = static_cast<int16_t>(x_bits.uintval());
  int16_t yi = static_cast<int16_t>(y_bits.uintval());
  return ((xi > yi) != (xi < 0 && yi < 0)) ? x : y;
}
#endif
#endif // LIBC_TYPES_HAS_FLOAT16

#if defined(__LIBC_USE_BUILTIN_FMAX_FMIN) && !defined(LIBC_TARGET_ARCH_IS_X86)
template <> LIBC_INLINE constexpr float max(float x, float y) {
  if (cpp::is_constant_evaluated())
    return constexpr_max(x, y);
  return __builtin_fmaxf(x, y);
}

template <> LIBC_INLINE constexpr double max(double x, double y) {
  if (cpp::is_constant_evaluated())
    return constexpr_max(x, y);
  return __builtin_fmax(x, y);
}
#endif

template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<T>, T>
constexpr_min(T x, T y) {
  FPBits<T> x_bits(x);
  FPBits<T> y_bits(y);

  // To make sure that fmin(+0, -0) == -0 == fmin(-0, +0), whenever x and y have
  // different signs and both are not NaNs, we return the number with negative
  // sign.
  if (x_bits.sign() != y_bits.sign())
    return x_bits.is_neg() ? x : y;
  return x < y ? x : y;
}

template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<T>, T>
min(T x, T y) {
  return constexpr_min(x, y);
}

#ifdef LIBC_TYPES_HAS_FLOAT16
#if defined(__LIBC_USE_BUILTIN_FMAXF16_FMINF16)
template <> LIBC_INLINE constexpr float16 min(float16 x, float16 y) {
  if (cpp::is_constant_evaluated())
    return constexpr_min(x, y);
  return __builtin_fminf16(x, y);
}
#elif !defined(LIBC_TARGET_ARCH_IS_AARCH64)
template <> LIBC_INLINE constexpr float16 min(float16 x, float16 y) {
  FPBits<float16> x_bits(x);
  FPBits<float16> y_bits(y);

  int16_t xi = static_cast<int16_t>(x_bits.uintval());
  int16_t yi = static_cast<int16_t>(y_bits.uintval());
  return ((xi < yi) != (xi < 0 && yi < 0)) ? x : y;
}
#endif
#endif // LIBC_TYPES_HAS_FLOAT16

#if defined(__LIBC_USE_BUILTIN_FMAX_FMIN) && !defined(LIBC_TARGET_ARCH_IS_X86)
template <> LIBC_INLINE constexpr float min(float x, float y) {
  if (cpp::is_constant_evaluated())
    return constexpr_min(x, y);
  return __builtin_fminf(x, y);
}

template <> LIBC_INLINE constexpr double min(double x, double y) {
  if (cpp::is_constant_evaluated())
    return constexpr_min(x, y);
  return __builtin_fmin(x, y);
}
#endif

} // namespace internal

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fmin(T x, T y) {
  const FPBits<T> bitx(x), bity(y);

  if (bitx.is_nan())
    return y;
  if (bity.is_nan())
    return x;
  return internal::min(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fmax(T x, T y) {
  FPBits<T> bitx(x), bity(y);

  if (bitx.is_nan())
    return y;
  if (bity.is_nan())
    return x;
  return internal::max(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fmaximum(T x, T y) {
  FPBits<T> bitx(x), bity(y);

  if (bitx.is_nan())
    return x;
  if (bity.is_nan())
    return y;
  return internal::max(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fminimum(T x, T y) {
  const FPBits<T> bitx(x), bity(y);

  if (bitx.is_nan())
    return x;
  if (bity.is_nan())
    return y;
  return internal::min(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fmaximum_num(T x, T y) {
  FPBits<T> bitx(x), bity(y);
  if (bitx.is_signaling_nan() || bity.is_signaling_nan()) {
    fputil::raise_except_if_required(FE_INVALID);
    if (bitx.is_nan() && bity.is_nan())
      return FPBits<T>::quiet_nan().get_val();
  }
  if (bitx.is_nan())
    return y;
  if (bity.is_nan())
    return x;
  return internal::max(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fminimum_num(T x, T y) {
  FPBits<T> bitx(x), bity(y);
  if (bitx.is_signaling_nan() || bity.is_signaling_nan()) {
    fputil::raise_except_if_required(FE_INVALID);
    if (bitx.is_nan() && bity.is_nan())
      return FPBits<T>::quiet_nan().get_val();
  }
  if (bitx.is_nan())
    return y;
  if (bity.is_nan())
    return x;
  return internal::min(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fmaximum_mag(T x, T y) {
  FPBits<T> bitx(x), bity(y);

  if (abs(x) > abs(y))
    return x;
  if (abs(y) > abs(x))
    return y;
  return fmaximum(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fminimum_mag(T x, T y) {
  FPBits<T> bitx(x), bity(y);

  if (abs(x) < abs(y))
    return x;
  if (abs(y) < abs(x))
    return y;
  return fminimum(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fmaximum_mag_num(T x, T y) {
  FPBits<T> bitx(x), bity(y);

  if (abs(x) > abs(y))
    return x;
  if (abs(y) > abs(x))
    return y;
  return fmaximum_num(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr T fminimum_mag_num(T x, T y) {
  FPBits<T> bitx(x), bity(y);

  if (abs(x) < abs(y))
    return x;
  if (abs(y) < abs(x))
    return y;
  return fminimum_num(x, y);
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE T constexpr fdim(T x, T y) {
  FPBits<T> bitx(x), bity(y);

  if (bitx.is_nan()) {
    return x;
  }

  if (bity.is_nan()) {
    return y;
  }

  return (x > y ? x - y : T(0));
}

// Avoid reusing `issignaling` macro.
template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr int issignaling_impl(const T &x) {
  FPBits<T> sx(x);
  return sx.is_signaling_nan();
}

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE constexpr int canonicalize(T &cx, const T &x) {
  FPBits<T> sx(x);
  if constexpr (get_fp_type<T>() == FPType::X86_Binary80) {
    // All the pseudo and unnormal numbers are not canonical.
    // More precisely :
    // Exponent   |       Significand      | Meaning
    //            | Bits 63-62 | Bits 61-0 |
    // All Ones   |     00     |    Zero   | Pseudo Infinity, Value = SNaN
    // All Ones   |     00     |  Non-Zero | Pseudo NaN, Value = SNaN
    // All Ones   |     01     | Anything  | Pseudo NaN, Value = SNaN
    //            |   Bit 63   | Bits 62-0 |
    // All zeroes |   One      | Anything  | Pseudo Denormal, Value =
    //            |            |           | (−1)**s × m × 2**−16382
    // All Other  |   Zero     | Anything  | Unnormal, Value = SNaN
    //  Values    |            |           |
    bool bit63 = sx.get_implicit_bit();
    UInt128 mantissa = sx.get_explicit_mantissa();
    bool bit62 = static_cast<bool>((mantissa & (1ULL << 62)) >> 62);
    int exponent = sx.get_biased_exponent();
    if (exponent == 0x7FFF) {
      if (!bit63 && !bit62) {
        if (mantissa == 0) {
          cx = FPBits<T>::quiet_nan(sx.sign(), mantissa).get_val();
          raise_except_if_required(FE_INVALID);
          return 1;
        }
        cx = FPBits<T>::quiet_nan(sx.sign(), mantissa).get_val();
        raise_except_if_required(FE_INVALID);
        return 1;
      } else if (!bit63 && bit62) {
        cx = FPBits<T>::quiet_nan(sx.sign(), mantissa).get_val();
        raise_except_if_required(FE_INVALID);
        return 1;
      } else if (LIBC_UNLIKELY(sx.is_signaling_nan())) {
        cx = FPBits<T>::quiet_nan(sx.sign(), sx.get_explicit_mantissa())
                 .get_val();
        raise_except_if_required(FE_INVALID);
        return 1;
      } else
        cx = x;
    } else if (exponent == 0 && bit63)
      cx = FPBits<T>::make_value(mantissa, 0).get_val();
    else if (exponent != 0 && !bit63) {
      cx = FPBits<T>::quiet_nan(sx.sign(), mantissa).get_val();
      raise_except_if_required(FE_INVALID);
      return 1;
    } else if (LIBC_UNLIKELY(sx.is_signaling_nan())) {
      cx =
          FPBits<T>::quiet_nan(sx.sign(), sx.get_explicit_mantissa()).get_val();
      raise_except_if_required(FE_INVALID);
      return 1;
    } else
      cx = x;
  } else if (LIBC_UNLIKELY(sx.is_signaling_nan())) {
    cx = FPBits<T>::quiet_nan(sx.sign(), sx.get_explicit_mantissa()).get_val();
    raise_except_if_required(FE_INVALID);
    return 1;
  } else
    cx = x;
  return 0;
}

template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<T>, bool>
totalorder(T x, T y) {
  using FPBits = FPBits<T>;
  FPBits x_bits(x);
  FPBits y_bits(y);

  using StorageType = typename FPBits::StorageType;
  StorageType x_u = x_bits.uintval();
  StorageType y_u = y_bits.uintval();

  bool has_neg = ((x_u | y_u) & FPBits::SIGN_MASK) != 0;
  return x_u == y_u || ((x_u < y_u) != has_neg);
}

template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<T>, bool>
totalordermag(T x, T y) {
  return FPBits<T>(x).abs().uintval() <= FPBits<T>(y).abs().uintval();
}

template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<T>, T>
getpayload(T x) {
  using FPBits = FPBits<T>;
  using StorageType = typename FPBits::StorageType;
  FPBits x_bits(x);

  if (!x_bits.is_nan())
    return T(-1.0);

  StorageType payload = x_bits.uintval() & (FPBits::FRACTION_MASK >> 1);

  if constexpr (is_big_int_v<StorageType>) {
    DyadicFloat<FPBits::STORAGE_LEN> payload_dfloat(Sign::POS, 0, payload);

    return static_cast<T>(payload_dfloat);
  } else {
    return static_cast<T>(payload);
  }
}

template <bool IsSignaling, typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<T>, bool>
setpayload(T &res, T pl) {
  using FPBits = FPBits<T>;
  FPBits pl_bits(pl);

  // Signaling NaNs don't have the mantissa's MSB set to 1, so they need a
  // non-zero payload to distinguish them from infinities.
  if (!IsSignaling && pl_bits.is_zero()) {
    res = FPBits::quiet_nan(Sign::POS).get_val();
    return false;
  }

  int pl_exp = pl_bits.get_exponent();

  if (pl_bits.is_neg() || pl_exp < 0 || pl_exp >= FPBits::FRACTION_LEN - 1 ||
      ((pl_bits.get_mantissa() << pl_exp) & FPBits::FRACTION_MASK) != 0) {
    res = T(0.0);
    return true;
  }

  using StorageType = typename FPBits::StorageType;
  StorageType v(pl_bits.get_explicit_mantissa() >>
                (FPBits::FRACTION_LEN - pl_exp));

  if constexpr (IsSignaling)
    res = FPBits::signaling_nan(Sign::POS, v).get_val();
  else
    res = FPBits::quiet_nan(Sign::POS, v).get_val();
  return false;
}

} // namespace fputil
} // namespace LIBC_NAMESPACE_DECL

#endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_BASICOPERATIONS_H