diff options
Diffstat (limited to 'rts/gmp/mpn/generic/mod_1_rs.c')
-rw-r--r-- | rts/gmp/mpn/generic/mod_1_rs.c | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/rts/gmp/mpn/generic/mod_1_rs.c b/rts/gmp/mpn/generic/mod_1_rs.c new file mode 100644 index 0000000000..62aaa94b92 --- /dev/null +++ b/rts/gmp/mpn/generic/mod_1_rs.c @@ -0,0 +1,111 @@ +/* mpn_mod_1_rshift -- mpn remainder under hypothetical right shift. + + THE FUNCTION IN THIS FILE IS FOR INTERNAL USE AND HAS A MUTABLE + INTERFACE. IT IS ONLY SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. + IT'S ALMOST GUARANTEED THAT IT'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP + RELEASE. */ + +/* +Copyright (C) 1999, 2000 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 2.1 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; see the file COPYING.LIB. If not, write to +the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, +MA 02111-1307, USA. */ + +#include "gmp.h" +#include "gmp-impl.h" +#include "longlong.h" + + +/* When testing on a CPU with UDIV_NEEDS_NORMALIZATION equal to 0, it can be + changed to 1 temporarily to test the code under that case too. */ +#if 0 +#undef UDIV_NEEDS_NORMALIZATION +#define UDIV_NEEDS_NORMALIZATION 1 +#endif + + +/* Calculate the remainder "(ptr,size >> shift) % divisor". Note ptr,size + is unchanged, the shift is only for its effect on the remainder. + The shift doesn't even need to be considered until the last limb. + + This function has the normal size!=0 restriction, unlike the basic + mpn_mod_1. */ + +mp_limb_t +#if __STDC__ +mpn_mod_1_rshift (mp_srcptr ptr, mp_size_t size, unsigned shift, + mp_limb_t divisor) +#else +mpn_mod_1_rshift (ptr, size, shift, divisor) + mp_srcptr ptr; + mp_size_t size; + unsigned shift; + mp_limb_t divisor; +#endif +{ + mp_limb_t quot, rem; + + ASSERT (shift >= 1); + ASSERT (shift < BITS_PER_MP_LIMB); + ASSERT (size >= 1); + + if (size == 1) + return (ptr[0] >> shift) % divisor; + +#if UDIV_NEEDS_NORMALIZATION + { + int norm; + int delta; + + count_leading_zeros (norm, divisor); + divisor <<= norm; + + delta = shift - norm; + if (delta == 0) + return mpn_mod_1 (ptr, size, divisor) >> norm; + + if (delta > 0) + { + rem = mpn_mod_1 (ptr+1, size-1, divisor); + udiv_qrnnd (quot, rem, + rem >> delta, + (rem << (BITS_PER_MP_LIMB-delta)) | (ptr[0] >> delta), + divisor); + return rem >> norm; + } + else + { + rem = mpn_mod_1 (ptr, size, divisor); + udiv_qrnnd (quot, rem, + rem >> (BITS_PER_MP_LIMB+delta), + rem << -delta, + divisor); + return rem >> norm; + } + } + +#else /* !UDIV_NEEDS_NORMALIZATION */ + + rem = mpn_mod_1 (ptr+1, size-1, divisor); + udiv_qrnnd (quot, rem, + rem >> shift, + (rem << (BITS_PER_MP_LIMB-shift)) | (ptr[0] >> shift), + divisor); + return rem; + +#endif +} |