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authorPedro Alvarez <pedro.alvarez@codethink.co.uk>2014-12-22 00:55:04 +0000
committerPedro Alvarez <pedro.alvarez@codethink.co.uk>2014-12-22 00:56:42 +0000
commit54eea31d0053620bab65153ab39d61e5575aaf1b (patch)
tree5f97c96dffdb6b27df36795689abfb9086011585 /gmp/mpn/generic/jacobi_2.c
parentc16297b7cfb0c1708f1d84b5d0f90be0844d07ce (diff)
downloadgcc-tarball-54eea31d0053620bab65153ab39d61e5575aaf1b.tar.gz
Add gmp, mpc and mpfr sourcesbaserock/pedroalvarez/4.9.1
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+/* jacobi_2.c
+
+ THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES. IT IS ONLY
+ SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
+ GUARANTEED THAT THEY'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
+
+Copyright 1996, 1998, 2000-2004, 2008, 2010 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 "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+#ifndef JACOBI_2_METHOD
+#define JACOBI_2_METHOD 2
+#endif
+
+/* Computes (a / b) where b is odd, and a and b are otherwise arbitrary
+ two-limb numbers. */
+#if JACOBI_2_METHOD == 1
+int
+mpn_jacobi_2 (mp_srcptr ap, mp_srcptr bp, unsigned bit)
+{
+ mp_limb_t ah, al, bh, bl;
+ int c;
+
+ al = ap[0];
+ ah = ap[1];
+ bl = bp[0];
+ bh = bp[1];
+
+ ASSERT (bl & 1);
+
+ bl = ((bh << (GMP_NUMB_BITS - 1)) & GMP_NUMB_MASK) | (bl >> 1);
+ bh >>= 1;
+
+ if ( (bh | bl) == 0)
+ return 1 - 2*(bit & 1);
+
+ if ( (ah | al) == 0)
+ return 0;
+
+ if (al == 0)
+ {
+ al = ah;
+ ah = 0;
+ bit ^= GMP_NUMB_BITS & (bl ^ (bl >> 1));
+ }
+ count_trailing_zeros (c, al);
+ bit ^= c & (bl ^ (bl >> 1));
+
+ c++;
+ if (UNLIKELY (c == GMP_NUMB_BITS))
+ {
+ al = ah;
+ ah = 0;
+ }
+ else
+ {
+ al = ((ah << (GMP_NUMB_BITS - c)) & GMP_NUMB_MASK) | (al >> c);
+ ah >>= c;
+ }
+ while ( (ah | bh) > 0)
+ {
+ mp_limb_t th, tl;
+ mp_limb_t bgta;
+
+ sub_ddmmss (th, tl, ah, al, bh, bl);
+ if ( (tl | th) == 0)
+ return 0;
+
+ bgta = LIMB_HIGHBIT_TO_MASK (th);
+
+ /* If b > a, invoke reciprocity */
+ bit ^= (bgta & al & bl);
+
+ /* b <-- min (a, b) */
+ add_ssaaaa (bh, bl, bh, bl, th & bgta, tl & bgta);
+
+ if ( (bh | bl) == 0)
+ return 1 - 2*(bit & 1);
+
+ /* a <-- |a - b| */
+ al = (bgta ^ tl) - bgta;
+ ah = (bgta ^ th);
+
+ if (UNLIKELY (al == 0))
+ {
+ /* If b > a, al == 0 implies that we have a carry to
+ propagate. */
+ al = ah - bgta;
+ ah = 0;
+ bit ^= GMP_NUMB_BITS & (bl ^ (bl >> 1));
+ }
+ count_trailing_zeros (c, al);
+ c++;
+ bit ^= c & (bl ^ (bl >> 1));
+
+ if (UNLIKELY (c == GMP_NUMB_BITS))
+ {
+ al = ah;
+ ah = 0;
+ }
+ else
+ {
+ al = ((ah << (GMP_NUMB_BITS - c)) & GMP_NUMB_MASK) | (al >> c);
+ ah >>= c;
+ }
+ }
+
+ ASSERT (bl > 0);
+
+ while ( (al | bl) & GMP_LIMB_HIGHBIT)
+ {
+ /* Need an extra comparison to get the mask. */
+ mp_limb_t t = al - bl;
+ mp_limb_t bgta = - (bl > al);
+
+ if (t == 0)
+ return 0;
+
+ /* If b > a, invoke reciprocity */
+ bit ^= (bgta & al & bl);
+
+ /* b <-- min (a, b) */
+ bl += (bgta & t);
+
+ /* a <-- |a - b| */
+ al = (t ^ bgta) - bgta;
+
+ /* Number of trailing zeros is the same no matter if we look at
+ * t or a, but using t gives more parallelism. */
+ count_trailing_zeros (c, t);
+ c ++;
+ /* (2/b) = -1 if b = 3 or 5 mod 8 */
+ bit ^= c & (bl ^ (bl >> 1));
+
+ if (UNLIKELY (c == GMP_NUMB_BITS))
+ return 1 - 2*(bit & 1);
+
+ al >>= c;
+ }
+
+ /* Here we have a little impedance mismatch. Better to inline it? */
+ return mpn_jacobi_base (2*al+1, 2*bl+1, bit << 1);
+}
+#elif JACOBI_2_METHOD == 2
+int
+mpn_jacobi_2 (mp_srcptr ap, mp_srcptr bp, unsigned bit)
+{
+ mp_limb_t ah, al, bh, bl;
+ int c;
+
+ al = ap[0];
+ ah = ap[1];
+ bl = bp[0];
+ bh = bp[1];
+
+ ASSERT (bl & 1);
+
+ /* Use bit 1. */
+ bit <<= 1;
+
+ if (bh == 0 && bl == 1)
+ /* (a|1) = 1 */
+ return 1 - (bit & 2);
+
+ if (al == 0)
+ {
+ if (ah == 0)
+ /* (0|b) = 0, b > 1 */
+ return 0;
+
+ count_trailing_zeros (c, ah);
+ bit ^= ((GMP_NUMB_BITS + c) << 1) & (bl ^ (bl >> 1));
+
+ al = bl;
+ bl = ah >> c;
+
+ if (bl == 1)
+ /* (1|b) = 1 */
+ return 1 - (bit & 2);
+
+ ah = bh;
+
+ bit ^= al & bl;
+
+ goto b_reduced;
+ }
+ if ( (al & 1) == 0)
+ {
+ count_trailing_zeros (c, al);
+
+ al = ((ah << (GMP_NUMB_BITS - c)) & GMP_NUMB_MASK) | (al >> c);
+ ah >>= c;
+ bit ^= (c << 1) & (bl ^ (bl >> 1));
+ }
+ if (ah == 0)
+ {
+ if (bh > 0)
+ {
+ bit ^= al & bl;
+ MP_LIMB_T_SWAP (al, bl);
+ ah = bh;
+ goto b_reduced;
+ }
+ goto ab_reduced;
+ }
+
+ while (bh > 0)
+ {
+ /* Compute (a|b) */
+ while (ah > bh)
+ {
+ sub_ddmmss (ah, al, ah, al, bh, bl);
+ if (al == 0)
+ {
+ count_trailing_zeros (c, ah);
+ bit ^= ((GMP_NUMB_BITS + c) << 1) & (bl ^ (bl >> 1));
+
+ al = bl;
+ bl = ah >> c;
+ ah = bh;
+
+ bit ^= al & bl;
+ goto b_reduced;
+ }
+ count_trailing_zeros (c, al);
+ bit ^= (c << 1) & (bl ^ (bl >> 1));
+ al = ((ah << (GMP_NUMB_BITS - c)) & GMP_NUMB_MASK) | (al >> c);
+ ah >>= c;
+ }
+ if (ah == bh)
+ goto cancel_hi;
+
+ if (ah == 0)
+ {
+ bit ^= al & bl;
+ MP_LIMB_T_SWAP (al, bl);
+ ah = bh;
+ break;
+ }
+
+ bit ^= al & bl;
+
+ /* Compute (b|a) */
+ while (bh > ah)
+ {
+ sub_ddmmss (bh, bl, bh, bl, ah, al);
+ if (bl == 0)
+ {
+ count_trailing_zeros (c, bh);
+ bit ^= ((GMP_NUMB_BITS + c) << 1) & (al ^ (al >> 1));
+
+ bl = bh >> c;
+ bit ^= al & bl;
+ goto b_reduced;
+ }
+ count_trailing_zeros (c, bl);
+ bit ^= (c << 1) & (al ^ (al >> 1));
+ bl = ((bh << (GMP_NUMB_BITS - c)) & GMP_NUMB_MASK) | (bl >> c);
+ bh >>= c;
+ }
+ bit ^= al & bl;
+
+ /* Compute (a|b) */
+ if (ah == bh)
+ {
+ cancel_hi:
+ if (al < bl)
+ {
+ MP_LIMB_T_SWAP (al, bl);
+ bit ^= al & bl;
+ }
+ al -= bl;
+ if (al == 0)
+ return 0;
+
+ count_trailing_zeros (c, al);
+ bit ^= (c << 1) & (bl ^ (bl >> 1));
+ al >>= c;
+
+ if (al == 1)
+ return 1 - (bit & 2);
+
+ MP_LIMB_T_SWAP (al, bl);
+ bit ^= al & bl;
+ break;
+ }
+ }
+
+ b_reduced:
+ /* Compute (a|b), with b a single limb. */
+ ASSERT (bl & 1);
+
+ if (bl == 1)
+ /* (a|1) = 1 */
+ return 1 - (bit & 2);
+
+ while (ah > 0)
+ {
+ ah -= (al < bl);
+ al -= bl;
+ if (al == 0)
+ {
+ if (ah == 0)
+ return 0;
+ count_trailing_zeros (c, ah);
+ bit ^= ((GMP_NUMB_BITS + c) << 1) & (bl ^ (bl >> 1));
+ al = ah >> c;
+ goto ab_reduced;
+ }
+ count_trailing_zeros (c, al);
+
+ al = ((ah << (GMP_NUMB_BITS - c)) & GMP_NUMB_MASK) | (al >> c);
+ ah >>= c;
+ bit ^= (c << 1) & (bl ^ (bl >> 1));
+ }
+ ab_reduced:
+ ASSERT (bl & 1);
+ ASSERT (bl > 1);
+
+ return mpn_jacobi_base (al, bl, bit);
+}
+#else
+#error Unsupported value for JACOBI_2_METHOD
+#endif