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//===-- nextafter implementation for x86 long double 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_UTILS_FPUTIL_NEXT_AFTER_LONG_DOUBLE_X86_H
#define LLVM_LIBC_UTILS_FPUTIL_NEXT_AFTER_LONG_DOUBLE_X86_H
#include "FPBits.h"
#include <stdint.h>
namespace __llvm_libc {
namespace fputil {
static inline long double nextafter(long double from, long double to) {
using FPBits = FPBits<long double>;
FPBits fromBits(from);
if (fromBits.isNaN())
return from;
FPBits toBits(to);
if (toBits.isNaN())
return to;
if (from == to)
return to;
// Convert pseudo subnormal number to normal number.
if (fromBits.getImplicitBit() == 1 && fromBits.getUnbiasedExponent() == 0) {
fromBits.setUnbiasedExponent(1);
}
using UIntType = FPBits::UIntType;
constexpr UIntType signVal = (UIntType(1) << 79);
constexpr UIntType mantissaMask =
(UIntType(1) << MantissaWidth<long double>::value) - 1;
UIntType intVal = fromBits.uintval();
if (from < 0.0l) {
if (from > to) {
if (intVal == (signVal + FPBits::maxSubnormal)) {
// We deal with normal/subnormal boundary separately to avoid
// dealing with the implicit bit.
intVal = signVal + FPBits::minNormal;
} else if ((intVal & mantissaMask) == mantissaMask) {
fromBits.setMantissa(0);
// Incrementing exponent might overflow the value to infinity,
// which is what is expected. Since NaNs are handling separately,
// it will never overflow "beyond" infinity.
fromBits.setUnbiasedExponent(fromBits.getUnbiasedExponent() + 1);
return fromBits;
} else {
++intVal;
}
} else {
if (intVal == (signVal + FPBits::minNormal)) {
// We deal with normal/subnormal boundary separately to avoid
// dealing with the implicit bit.
intVal = signVal + FPBits::maxSubnormal;
} else if ((intVal & mantissaMask) == 0) {
fromBits.setMantissa(mantissaMask);
// from == 0 is handled separately so decrementing the exponent will not
// lead to underflow.
fromBits.setUnbiasedExponent(fromBits.getUnbiasedExponent() - 1);
return fromBits;
} else {
--intVal;
}
}
} else if (from == 0.0l) {
if (from > to)
intVal = signVal + 1;
else
intVal = 1;
} else {
if (from > to) {
if (intVal == FPBits::minNormal) {
intVal = FPBits::maxSubnormal;
} else if ((intVal & mantissaMask) == 0) {
fromBits.setMantissa(mantissaMask);
// from == 0 is handled separately so decrementing the exponent will not
// lead to underflow.
fromBits.setUnbiasedExponent(fromBits.getUnbiasedExponent() - 1);
return fromBits;
} else {
--intVal;
}
} else {
if (intVal == FPBits::maxSubnormal) {
intVal = FPBits::minNormal;
} else if ((intVal & mantissaMask) == mantissaMask) {
fromBits.setMantissa(0);
// Incrementing exponent might overflow the value to infinity,
// which is what is expected. Since NaNs are handling separately,
// it will never overflow "beyond" infinity.
fromBits.setUnbiasedExponent(fromBits.getUnbiasedExponent() + 1);
return fromBits;
} else {
++intVal;
}
}
}
return *reinterpret_cast<long double *>(&intVal);
// TODO: Raise floating point exceptions as required by the standard.
}
} // namespace fputil
} // namespace __llvm_libc
#endif // LLVM_LIBC_UTILS_FPUTIL_NEXT_AFTER_LONG_DOUBLE_X86_H
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