File: jslibmath.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef jslibmath_h
#define jslibmath_h

#include "mozilla/FloatingPoint.h"

#include <math.h>

#include "jsnum.h"

#include "vm/JSContext.h"

/*
 * Use system provided math routines.
 */

/* The right copysign function is not always named the same thing. */
#ifdef __GNUC__
#define js_copysign __builtin_copysign
#elif defined _WIN32
#define js_copysign _copysign
#else
#define js_copysign copysign
#endif

/* Consistency wrapper for platform deviations in fmod() */
static inline double js_fmod(double d, double d2) {
#ifdef XP_WIN
  /*
   * Workaround MS fmod bug where 42 % (1/0) => NaN, not 42.
   * Workaround MS fmod bug where -0 % -N => 0, not -0.
   */
  if ((mozilla::IsFinite(d) && mozilla::IsInfinite(d2)) ||
      (d == 0 && mozilla::IsFinite(d2))) {
    return d;
  }
#endif
  return fmod(d, d2);
}

namespace js {

inline double NumberDiv(double a, double b) {
  AutoUnsafeCallWithABI unsafe;
  if (b == 0) {
    if (a == 0 || mozilla::IsNaN(a)
#ifdef XP_WIN
        || mozilla::IsNaN(b) /* XXX MSVC miscompiles such that (NaN == 0) */
#endif
    )
      return JS::GenericNaN();

    if (mozilla::IsNegative(a) != mozilla::IsNegative(b))
      return mozilla::NegativeInfinity<double>();
    return mozilla::PositiveInfinity<double>();
  }

  return a / b;
}

inline double NumberMod(double a, double b) {
  AutoUnsafeCallWithABI unsafe;
  if (b == 0) return JS::GenericNaN();
  double r = fmod(a, b);
#if defined(XP_WIN)
  // Some versions of Windows (Win 10 v1803, v1809) miscompute the sign of zero
  // results from fmod. The sign should match the sign of the LHS. This bug
  // only affects 64-bit builds. See bug 1527007.
  if (mozilla::IsPositiveZero(r) && mozilla::IsNegative(a)) {
    return -0.0;
  }
#endif
  return r;
}

}  // namespace js

#endif /* jslibmath_h */