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/* Copyright (C) 2003, 2009 Free Software Foundation, Inc.

This file is free software; you can redistribute it and/or modify it

under the terms of the GNU General Public License as published by the

Free Software Foundation; either version 3, or (at your option) any

later version.

This file is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional

permissions described in the GCC Runtime Library Exception, version

3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and

a copy of the GCC Runtime Library Exception along with this program;

see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

<http://www.gnu.org/licenses/>.  */

/* Calculate division table for SH5Media integer division

   Contributed by Joern Rennecke

   joern.rennecke@superh.com  */

#include <stdio.h>

#include <math.h>

#define BITS 5

#define N_ENTRIES (1 << BITS)

#define CUTOFF_BITS 20

#define BIAS (-330)

double max_defect = 0.;

double max_defect_x;

double min_defect = 1e9;

double min_defect_x;

double max_defect2 = 0.;

double max_defect2_x;

double min_defect2 = 0.;

double min_defect2_x;

double min_defect3 = 01e9;

double min_defect3_x;

int min_defect3_val;

double max_defect3 = 0.;

double max_defect3_x;

int max_defect3_val;

static double note_defect3 (int val, double d2, double y2d, double x)

{

  int cutoff_val = val >> CUTOFF_BITS;

  double cutoff;

  double defect;

  if (val < 0)

    cutoff_val++;

  cutoff = (cutoff_val * (1<<CUTOFF_BITS) - val) * y2d;

  defect = cutoff + val * d2;

  if (val < 0)

    defect = - defect;

  if (defect > max_defect3)

    {

      max_defect3 = defect;

      max_defect3_x = x;

      max_defect3_val = val;

    }

  if (defect < min_defect3)

    {

      min_defect3 = defect;

      min_defect3_x = x;

      min_defect3_val = val;

    }

}

/* This function assumes 32-bit integers.  */

static double

calc_defect (double x, int constant, int factor)

{

  double y0 = (constant - (int) floor ((x * factor * 64.))) / 16384.;

  double y1 = 2 * y0 -y0 * y0 * (x + BIAS / (1.*(1LL<<30)));

  double y2d0, y2d;

  int y2d1;

  double d, d2;

  y1 = floor (y1 * (1024 * 1024 * 1024)) / (1024 * 1024 * 1024);

  d = y1 - 1 / x;

  if (d > max_defect)

    {

      max_defect = d;

      max_defect_x = x;

    }

  if (d < min_defect)

    {

      min_defect = d;

      min_defect_x = x;

    }

  y2d0 = floor (y1 * x * (1LL << 60-16));

  y2d1 = (int) (long long) y2d0;

  y2d = - floor ((y1 - y0 / (1<<30-14)) * y2d1) / (1LL<<44);

  d2 = y1 + y2d - 1/x;

  if (d2 > max_defect2)

    {

      max_defect2 = d2;

      max_defect2_x = x;

    }

  if (d2 < min_defect2)

    {

      min_defect2 = d2;

      min_defect2_x = x;

    }

  /* zero times anything is trivially zero.  */

  note_defect3 ((1 << CUTOFF_BITS) - 1, d2, y2d, x);

  note_defect3 (1 << CUTOFF_BITS, d2, y2d, x);

  note_defect3 ((1U << 31) - (1 << CUTOFF_BITS), d2, y2d, x);

  note_defect3 ((1U << 31) - 1, d2, y2d, x);

  note_defect3 (-1, d2, y2d, x);

  note_defect3 (-(1 << CUTOFF_BITS), d2, y2d, x);

  note_defect3 ((1U << 31) - (1 << CUTOFF_BITS) + 1, d2, y2d, x);

  note_defect3 (-(1U << 31), d2, y2d, x);

  return d;

}

int

main ()

{

  int i;

  unsigned char factors[N_ENTRIES];

  short constants[N_ENTRIES];

  int steps = N_ENTRIES / 2;

  double step = 1. / steps;

  double eps30 = 1. / (1024 * 1024 * 1024);

  for (i = 0; i < N_ENTRIES; i++)

    {

      double x_low = (i < steps ? 1. : -3.) + i * step;

      double x_high = x_low + step - eps30;

      double x_med;

      int factor, constant;

      double low_defect, med_defect, high_defect, max_defect;

      factor = (1./x_low- 1./x_high) / step * 256. + 0.5;

      if (factor == 256)

        factor = 255;

      factors[i] = factor;

      /* Use minimum of error function for x_med.  */

      x_med = sqrt (256./factor);

      if (x_low < 0)

        x_med = - x_med;

      low_defect = 1. / x_low + x_low * factor / 256.;

      high_defect = 1. / x_high + x_high * factor / 256.;

      med_defect = 1. / x_med + x_med * factor / 256.;

      max_defect

        = ((low_defect > high_defect) ^ (x_med < 0)) ? low_defect : high_defect;

      constant = (med_defect + max_defect) * 0.5 * 16384. + 0.5;

      if (constant < -32768 || constant > 32767)

        abort ();

      constants[i] = constant;

      calc_defect (x_low, constant, factor);

      calc_defect (x_med, constant, factor);

      calc_defect (x_high, constant, factor);

    }

    printf ("/* This table has been generated by divtab.c .\n");

    printf ("Defects for bias %d:\n", BIAS);

    printf ("   Max defect: %e at %e\n", max_defect, max_defect_x);

    printf ("   Min defect: %e at %e\n", min_defect, min_defect_x);

    printf ("   Max 2nd step defect: %e at %e\n", max_defect2, max_defect2_x);

    printf ("   Min 2nd step defect: %e at %e\n", min_defect2, min_defect2_x);

    printf ("   Max div defect: %e at %d:%e\n", max_defect3, max_defect3_val, max_defect3_x);

    printf ("   Min div defect: %e at %d:%e\n", min_defect3, min_defect3_val, min_defect3_x);

    printf ("   Defect at 1: %e\n",

            calc_defect (1., constants[0], factors[0]));

    printf ("   Defect at -2: %e */\n",

            calc_defect (-2., constants[steps], factors[steps]));

    printf ("\t.section\t.rodata\n");

    printf ("\t.balign 2\n");

    printf ("/* negative division constants */\n");

    for (i = steps; i < 2 * steps; i++)

      printf ("\t.word\t%d\n", constants[i]);

    printf ("/* negative division factors */\n");

    for (i = steps; i < 2*steps; i++)

      printf ("\t.byte\t%d\n", factors[i]);

    printf ("\t.skip %d\n", steps);

    printf ("\t.global  GLOBAL(div_table):\n");

    printf ("GLOBAL(div_table):\n");

    printf ("\t.skip %d\n", steps);

    printf ("/* positive division factors */\n");

    for (i = 0; i < steps; i++)

      printf ("\t.byte\t%d\n", factors[i]);

    printf ("/* positive division constants */\n");

    for (i = 0; i < steps; i++)

      printf ("\t.word\t%d\n", constants[i]);

  exit (0);

}