/* Alternate implementations of binvert_limb to compare speeds. */

/*

Copyright 2000, 2002 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify

it under the terms of either:

  * the GNU Lesser General Public License as published by the Free

    Software Foundation; either version 3 of the License, or (at your

    option) any later version.

or

  * the GNU General Public License as published by the Free Software

    Foundation; either version 2 of the License, or (at your option) any

    later version.

or both in parallel, as here.

The GNU MP Library 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.

You should have received copies of the GNU General Public License and the

GNU Lesser General Public License along with the GNU MP Library.  If not,

see https://www.gnu.org/licenses/.  */

#include <stdio.h>

#include "gmp.h"

#include "gmp-impl.h"

#include "longlong.h"

#include "speed.h"

/* Like the standard version in gmp-impl.h, but with the expressions using a

   "1-" form.  This has the same number of steps, but "1-" is on the

   dependent chain, whereas the "2*" in the standard version isn't.

   Depending on the CPU this should be the same or a touch slower.  */

#if GMP_LIMB_BITS <= 32

#define binvert_limb_mul1(inv,n)                                \

  do {                                                          \

    mp_limb_t  __n = (n);                                       \

    mp_limb_t  __inv;                                           \

    ASSERT ((__n & 1) == 1);                                    \

    __inv = binvert_limb_table[(__n&0xFF)/2]; /*  8 */          \

    __inv = (1 - __n * __inv) * __inv + __inv;  /* 16 */        \

    __inv = (1 - __n * __inv) * __inv + __inv;  /* 32 */        \

    ASSERT (__inv * __n == 1);                                  \

    (inv) = __inv;                                              \

  } while (0)

#endif

#if GMP_LIMB_BITS > 32 && GMP_LIMB_BITS <= 64

#define binvert_limb_mul1(inv,n)                                \

  do {                                                          \

    mp_limb_t  __n = (n);                                       \

    mp_limb_t  __inv;                                           \

    ASSERT ((__n & 1) == 1);                                    \

    __inv = binvert_limb_table[(__n&0xFF)/2]; /*  8 */          \

    __inv = (1 - __n * __inv) * __inv + __inv;  /* 16 */        \

    __inv = (1 - __n * __inv) * __inv + __inv;  /* 32 */        \

    __inv = (1 - __n * __inv) * __inv + __inv;  /* 64 */        \

    ASSERT (__inv * __n == 1);                                  \

    (inv) = __inv;                                              \

  } while (0)

#endif

/* The loop based version used in GMP 3.0 and earlier.  Usually slower than

   multiplying, due to the number of steps that must be performed.  Much

   slower when the processor has a good multiply.  */

#define binvert_limb_loop(inv,n)                \

  do {                                          \

    mp_limb_t  __v = (n);                       \

    mp_limb_t  __v_orig = __v;                  \

    mp_limb_t  __make_zero = 1;                 \

    mp_limb_t  __two_i = 1;                     \

    mp_limb_t  __v_inv = 0;                     \

                                                \

    ASSERT ((__v & 1) == 1);                    \

                                                \

    do                                          \

      {                                         \

        while ((__two_i & __make_zero) == 0)    \

          __two_i <<= 1, __v <<= 1;             \

        __v_inv += __two_i;                     \

        __make_zero -= __v;                     \

      }                                         \

    while (__make_zero);                        \

                                                \

    ASSERT (__v_orig * __v_inv == 1);           \

    (inv) = __v_inv;                            \

  } while (0)

/* Another loop based version with conditionals, but doing a fixed number of

   steps. */

#define binvert_limb_cond(inv,n)                \

  do {                                          \

    mp_limb_t  __n = (n);                       \

    mp_limb_t  __rem = (1 - __n) >> 1;          \

    mp_limb_t  __inv = GMP_LIMB_HIGHBIT;        \

    int        __count;                         \

                                                \

    ASSERT ((__n & 1) == 1);                    \

                                                \

    __count = GMP_LIMB_BITS-1;               \

    do                                          \

      {                                         \

        __inv >>= 1;                            \

        if (__rem & 1)                          \

          {                                     \

            __inv |= GMP_LIMB_HIGHBIT;          \

            __rem -= __n;                       \

          }                                     \

        __rem >>= 1;                            \

      }                                         \

    while (-- __count);                         \

                                                \

    ASSERT (__inv * __n == 1);                  \

    (inv) = __inv;                              \

  } while (0)

/* Another loop based bitwise version, but purely arithmetic, no

   conditionals. */

#define binvert_limb_arith(inv,n)                                       \

  do {                                                                  \

    mp_limb_t  __n = (n);                                               \

    mp_limb_t  __rem = (1 - __n) >> 1;                                  \

    mp_limb_t  __inv = GMP_LIMB_HIGHBIT;                                \

    mp_limb_t  __lowbit;                                                \

    int        __count;                                                 \

                                                                        \

    ASSERT ((__n & 1) == 1);                                            \

                                                                        \

    __count = GMP_LIMB_BITS-1;                                       \

    do                                                                  \

      {                                                                 \

        __lowbit = __rem & 1;                                           \

        __inv = (__inv >> 1) | (__lowbit << (GMP_LIMB_BITS-1));      \

        __rem = (__rem - (__n & -__lowbit)) >> 1;                       \

      }                                                                 \

    while (-- __count);                                                 \

                                                                        \

    ASSERT (__inv * __n == 1);                                          \

    (inv) = __inv;                                                      \

  } while (0)

double

speed_binvert_limb_mul1 (struct speed_params *s)

{

  SPEED_ROUTINE_MODLIMB_INVERT (binvert_limb_mul1);

}

double

speed_binvert_limb_loop (struct speed_params *s)

{

  SPEED_ROUTINE_MODLIMB_INVERT (binvert_limb_loop);

}

double

speed_binvert_limb_cond (struct speed_params *s)

{

  SPEED_ROUTINE_MODLIMB_INVERT (binvert_limb_cond);

}

double

speed_binvert_limb_arith (struct speed_params *s)

{

  SPEED_ROUTINE_MODLIMB_INVERT (binvert_limb_arith);

}