| /* UltraSPARC 64 mpn_mod_1 -- mpn by limb remainder. |
| |
| Copyright 1991, 1993, 1994, 1999, 2000, 2001, 2003 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 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. |
| |
| 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 Lesser General Public |
| License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public License |
| along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ |
| |
| #include "gmp.h" |
| #include "gmp-impl.h" |
| #include "longlong.h" |
| |
| #include "mpn/sparc64/sparc64.h" |
| |
| |
| /* 64-bit divisor 32-bit divisor |
| cycles/limb cycles/limb |
| (approx) (approx) |
| Ultrasparc 2i: 160 120 |
| */ |
| |
| |
| /* 32-bit divisors are treated in special case code. This requires 4 mulx |
| per limb instead of 8 in the general case. |
| |
| For big endian systems we need HALF_ENDIAN_ADJ included in the src[i] |
| addressing, to get the two halves of each limb read in the correct order. |
| This is kept in an adj variable. Doing that measures about 6 c/l faster |
| than just writing HALF_ENDIAN_ADJ(i) in the loop. The latter shouldn't |
| be 6 cycles worth of work, but perhaps it doesn't schedule well (on gcc |
| 3.2.1 at least). |
| |
| A simple udivx/umulx loop for the 32-bit case was attempted for small |
| sizes, but at size==2 it was only about the same speed and at size==3 was |
| slower. */ |
| |
| mp_limb_t |
| mpn_mod_1 (mp_srcptr src_limbptr, mp_size_t size_limbs, mp_limb_t d_limb) |
| { |
| int norm, norm_rshift; |
| mp_limb_t src_high_limb; |
| mp_size_t i; |
| |
| ASSERT (size_limbs >= 0); |
| ASSERT (d_limb != 0); |
| |
| if (UNLIKELY (size_limbs == 0)) |
| return 0; |
| |
| src_high_limb = src_limbptr[size_limbs-1]; |
| |
| /* udivx is good for size==1, and no need to bother checking limb<divisor, |
| since if that's likely the caller should check */ |
| if (UNLIKELY (size_limbs == 1)) |
| return src_high_limb % d_limb; |
| |
| if (d_limb <= CNST_LIMB(0xFFFFFFFF)) |
| { |
| unsigned *src, n1, n0, r, dummy_q, nshift, norm_rmask; |
| mp_size_t size, adj; |
| mp_limb_t dinv_limb; |
| |
| size = 2 * size_limbs; /* halfwords */ |
| src = (unsigned *) src_limbptr; |
| |
| /* prospective initial remainder, if < d */ |
| r = src_high_limb >> 32; |
| |
| /* If the length of the source is uniformly distributed, then there's |
| a 50% chance of the high 32-bits being zero, which we can skip. */ |
| if (r == 0) |
| { |
| r = (unsigned) src_high_limb; |
| size--; |
| ASSERT (size > 0); /* because always even */ |
| } |
| |
| /* Skip a division if high < divisor. Having the test here before |
| normalizing will still skip as often as possible. */ |
| if (r < d_limb) |
| { |
| size--; |
| ASSERT (size > 0); /* because size==1 handled above */ |
| } |
| else |
| r = 0; |
| |
| count_leading_zeros_32 (norm, d_limb); |
| norm -= 32; |
| d_limb <<= norm; |
| |
| norm_rshift = 32 - norm; |
| norm_rmask = (norm == 0 ? 0 : 0xFFFFFFFF); |
| i = size-1; |
| adj = HALF_ENDIAN_ADJ (i); |
| n1 = src [i + adj]; |
| r = (r << norm) | ((n1 >> norm_rshift) & norm_rmask); |
| |
| invert_half_limb (dinv_limb, d_limb); |
| adj = -adj; |
| |
| for (i--; i >= 0; i--) |
| { |
| n0 = src [i + adj]; |
| adj = -adj; |
| nshift = (n1 << norm) | ((n0 >> norm_rshift) & norm_rmask); |
| udiv_qrnnd_half_preinv (dummy_q, r, r, nshift, d_limb, dinv_limb); |
| n1 = n0; |
| } |
| |
| /* same as loop, but without n0 */ |
| nshift = n1 << norm; |
| udiv_qrnnd_half_preinv (dummy_q, r, r, nshift, d_limb, dinv_limb); |
| |
| ASSERT ((r & ((1 << norm) - 1)) == 0); |
| return r >> norm; |
| } |
| else |
| { |
| mp_srcptr src; |
| mp_size_t size; |
| mp_limb_t n1, n0, r, dinv, dummy_q, nshift, norm_rmask; |
| |
| src = src_limbptr; |
| size = size_limbs; |
| r = src_high_limb; /* initial remainder */ |
| |
| /* Skip a division if high < divisor. Having the test here before |
| normalizing will still skip as often as possible. */ |
| if (r < d_limb) |
| { |
| size--; |
| ASSERT (size > 0); /* because size==1 handled above */ |
| } |
| else |
| r = 0; |
| |
| count_leading_zeros (norm, d_limb); |
| d_limb <<= norm; |
| |
| norm_rshift = GMP_LIMB_BITS - norm; |
| norm_rmask = (norm == 0 ? 0 : 0xFFFFFFFF); |
| |
| src += size; |
| n1 = *--src; |
| r = (r << norm) | ((n1 >> norm_rshift) & norm_rmask); |
| |
| invert_limb (dinv, d_limb); |
| |
| for (i = size-2; i >= 0; i--) |
| { |
| n0 = *--src; |
| nshift = (n1 << norm) | ((n0 >> norm_rshift) & norm_rmask); |
| udiv_qrnnd_preinv (dummy_q, r, r, nshift, d_limb, dinv); |
| n1 = n0; |
| } |
| |
| /* same as loop, but without n0 */ |
| nshift = n1 << norm; |
| udiv_qrnnd_preinv (dummy_q, r, r, nshift, d_limb, dinv); |
| |
| ASSERT ((r & ((CNST_LIMB(1) << norm) - 1)) == 0); |
| return r >> norm; |
| } |
| } |