/*******************************************************************************
MIT License
-----------

Copyright (c) 2002-2019 Advanced Micro Devices, Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this Software and associated documentaon files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*******************************************************************************/

#include "libm.h"
#include "libm_util.h"

#define USE_REMAINDER_PIBY2F_INLINE
#define USE_VALF_WITH_FLAGS
#define USE_NANF_WITH_FLAGS
#define USE_HANDLE_ERRORF
#include "libm_inlines.h"
#undef USE_VALF_WITH_FLAGS
#undef USE_NANF_WITH_FLAGS
#undef USE_REMAINDER_PIBY2F_INLINE
#undef USE_HANDLE_ERRORF

#include "libm_errno.h"

#ifdef _MSC_VER
// Disable "C4163: not available as intrinsic function" warning that older
// compilers may issue here.
#pragma warning(disable:4163)
#pragma function(tanf)
#endif

/* tan(x) approximation valid on the interval [-pi/4,pi/4].
   If recip is true return -1/tan(x) instead. */
static inline double tanf_piby4(double x, int recip)
{
  double r, t;

  /* Core Remez [1,2] approximation to tan(x) on the
     interval [0,pi/4]. */
  r = x*x;
  t = x + x*r*
    (0.385296071263995406715129e0 -
     0.172032480471481694693109e-1 * r) /
    (0.115588821434688393452299e+1 +
     (-0.51396505478854532132342e0 +
      0.1844239256901656082986661e-1 * r) * r);

  if (recip)
    return -1.0 / t;
  else
    return t;
}


float tanf(float x)
{
  double r, dx;
  int region, xneg;

  unsigned long long ux, ax;

  dx = x;

  GET_BITS_DP64(dx, ux);
  ax = (ux & ~SIGNBIT_DP64);

  if (ax <= 0x3fe921fb54442d18) /* abs(x) <= pi/4 */
    {
      if (ax < 0x3f80000000000000) /* abs(x) < 2.0^(-7) */
        {
          if (ax < 0x3f20000000000000) /* abs(x) < 2.0^(-13) */
            {
              if (ax == 0x0000000000000000)
                return x;
              else
                return valf_with_flags(x, AMD_F_INEXACT);
            }
          else
            return (float)(dx + dx*dx*dx*0.333333333333333333);
        }
      else
        return (float)tanf_piby4(x, 0);
    }
  else if ((ux & EXPBITS_DP64) == EXPBITS_DP64)
    {
      /* x is either NaN or infinity */
      if (ux & MANTBITS_DP64)
        {
          /* x is NaN */
          unsigned int ufx;
          GET_BITS_SP32(x, ufx);
          return _handle_errorf("tanf", OP_TAN, ufx|0x00400000, _DOMAIN, 0,
                               EDOM, x, 0.0F, 1);
        }
      else
        {
          /* x is infinity. Return a NaN */
          return _handle_errorf("tanf", OP_TAN, INDEFBITPATT_SP32, _DOMAIN, AMD_F_INVALID,
                               EDOM, x, 0.0F, 1);
        }
    }

  xneg = (int)(ux >> 63);

  if (xneg)
    dx = -dx;

  if (dx < 5.0e5)
    {
      /* For these size arguments we can just carefully subtract the
         appropriate multiple of pi/2, using extra precision where
         dx is close to an exact multiple of pi/2 */
      static const double
        twobypi =  6.36619772367581382433e-01, /* 0x3fe45f306dc9c883 */
        piby2_1  =  1.57079632673412561417e+00, /* 0x3ff921fb54400000 */
        piby2_1tail =  6.07710050650619224932e-11, /* 0x3dd0b4611a626331 */
        piby2_2  =  6.07710050630396597660e-11, /* 0x3dd0b4611a600000 */
        piby2_2tail =  2.02226624879595063154e-21, /* 0x3ba3198a2e037073 */
        piby2_3  =  2.02226624871116645580e-21, /* 0x3ba3198a2e000000 */
        piby2_3tail =  8.47842766036889956997e-32; /* 0x397b839a252049c1 */
      double t, rhead, rtail;
      int npi2;
      unsigned long long uy, xexp, expdiff;
      xexp  = ax >> EXPSHIFTBITS_DP64;
      /* How many pi/2 is dx a multiple of? */
      if (ax <= 0x400f6a7a2955385e) /* 5pi/4 */
        {
          if (ax <= 0x4002d97c7f3321d2) /* 3pi/4 */
            npi2 = 1;
          else
            npi2 = 2;
        }
      else if (ax <= 0x401c463abeccb2bb) /* 9pi/4 */
        {
          if (ax <= 0x4015fdbbe9bba775) /* 7pi/4 */
            npi2 = 3;
          else
            npi2 = 4;
        }
      else
        npi2  = (int)(dx * twobypi + 0.5);
      /* Subtract the multiple from dx to get an extra-precision remainder */
      rhead  = dx - npi2 * piby2_1;
      rtail  = npi2 * piby2_1tail;
      GET_BITS_DP64(rhead, uy);
      expdiff = xexp - ((uy & EXPBITS_DP64) >> EXPSHIFTBITS_DP64);
      if (expdiff > 15)
        {
          /* The remainder is pretty small compared with dx, which
             implies that dx is a near multiple of pi/2
             (dx matches the multiple to at least 15 bits) */
          t  = rhead;
          rtail  = npi2 * piby2_2;
          rhead  = t - rtail;
          rtail  = npi2 * piby2_2tail - ((t - rhead) - rtail);
          if (expdiff > 48)
            {
              /* dx matches a pi/2 multiple to at least 48 bits */
              t  = rhead;
              rtail  = npi2 * piby2_3;
              rhead  = t - rtail;
              rtail  = npi2 * piby2_3tail - ((t - rhead) - rtail);
            }
        }
      r = rhead - rtail;
      region = npi2 & 3;
    }
  else
    {
      /* Reduce x into range [-pi/4,pi/4] */
      __remainder_piby2f_inline(ax, &r, &region);
    }

  if (xneg)
    return (float)-tanf_piby4(r, region & 1);
  else
    return (float)tanf_piby4(r, region & 1);
}