Add libgmp 6.2.0 to third_party
Don't build it yet. That will come in the next review.
Change-Id: Idf3266558165e5ab45f4a41c98cc8c838c8244d5
diff --git a/third_party/gmp/mpz/cong_2exp.c b/third_party/gmp/mpz/cong_2exp.c
new file mode 100644
index 0000000..9de9645
--- /dev/null
+++ b/third_party/gmp/mpz/cong_2exp.c
@@ -0,0 +1,149 @@
+/* mpz_congruent_2exp_p -- test congruence of mpz mod 2^n.
+
+Copyright 2001, 2002, 2013 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-impl.h"
+
+
+int
+mpz_congruent_2exp_p (mpz_srcptr a, mpz_srcptr c, mp_bitcnt_t d) __GMP_NOTHROW
+{
+ mp_size_t i, dlimbs;
+ unsigned dbits;
+ mp_ptr ap, cp;
+ mp_limb_t dmask, alimb, climb, sum;
+ mp_size_t as, cs, asize, csize;
+
+ as = SIZ(a);
+ asize = ABS(as);
+
+ cs = SIZ(c);
+ csize = ABS(cs);
+
+ if (asize < csize)
+ {
+ MPZ_SRCPTR_SWAP (a, c);
+ MP_SIZE_T_SWAP (asize, csize);
+ }
+
+ dlimbs = d / GMP_NUMB_BITS;
+ dbits = d % GMP_NUMB_BITS;
+ dmask = (CNST_LIMB(1) << dbits) - 1;
+
+ ap = PTR(a);
+ cp = PTR(c);
+
+ if (csize == 0)
+ goto a_zeros;
+
+ if ((cs ^ as) >= 0)
+ {
+ /* same signs, direct comparison */
+
+ /* a==c for limbs in common */
+ if (mpn_cmp (ap, cp, MIN (csize, dlimbs)) != 0)
+ return 0;
+
+ /* if that's all of dlimbs, then a==c for remaining bits */
+ if (csize > dlimbs)
+ return ((ap[dlimbs]-cp[dlimbs]) & dmask) == 0;
+
+ a_zeros:
+ /* a remains, need all zero bits */
+
+ /* if d covers all of a and c, then must be exactly equal */
+ if (asize <= dlimbs)
+ return asize == csize;
+
+ /* whole limbs zero */
+ for (i = csize; i < dlimbs; i++)
+ if (ap[i] != 0)
+ return 0;
+
+ /* partial limb zero */
+ return (ap[dlimbs] & dmask) == 0;
+ }
+ else
+ {
+ /* different signs, negated comparison */
+
+ /* common low zero limbs, stopping at first non-zeros, which must
+ match twos complement */
+ i = 0;
+ do
+ {
+ ASSERT (i < csize); /* always have a non-zero limb on c */
+ alimb = ap[i];
+ climb = cp[i];
+ sum = (alimb + climb) & GMP_NUMB_MASK;
+
+ if (i >= dlimbs)
+ return (sum & dmask) == 0;
+ ++i;
+
+ /* require both zero, or first non-zeros as twos-complements */
+ if (sum != 0)
+ return 0;
+ } while (alimb == 0);
+
+ /* further limbs matching as ones-complement */
+ for (; i < csize; ++i)
+ {
+ alimb = ap[i];
+ climb = cp[i];
+ sum = alimb ^ climb ^ GMP_NUMB_MASK;
+
+ if (i >= dlimbs)
+ return (sum & dmask) == 0;
+
+ if (sum != 0)
+ return 0;
+ }
+
+ /* no more c, so require all 1 bits in a */
+
+ if (asize < dlimbs)
+ return 0; /* not enough a */
+
+ /* whole limbs */
+ for ( ; i < dlimbs; i++)
+ if (ap[i] != GMP_NUMB_MAX)
+ return 0;
+
+ /* if only whole limbs, no further fetches from a */
+ if (dbits == 0)
+ return 1;
+
+ /* need enough a */
+ if (asize == dlimbs)
+ return 0;
+
+ return ((ap[dlimbs]+1) & dmask) == 0;
+ }
+}