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Diffstat (limited to 'gmp/tune/modlinv.c')
| -rw-r--r-- | gmp/tune/modlinv.c | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/gmp/tune/modlinv.c b/gmp/tune/modlinv.c new file mode 100644 index 0000000000..e3f2063e07 --- /dev/null +++ b/gmp/tune/modlinv.c @@ -0,0 +1,178 @@ +/* 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); +} |