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/scan0.c b/third_party/gmp/mpz/scan0.c
new file mode 100644
index 0000000..4b0f1ef
--- /dev/null
+++ b/third_party/gmp/mpz/scan0.c
@@ -0,0 +1,129 @@
+/* mpz_scan0 -- search for a 0 bit.
+
+Copyright 2000-2002, 2004, 2012 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"
+#include "longlong.h"
+
+
+/* mpn_scan0 can't be used for the u>0 search since there might not be a 0
+ bit before the end of the data. mpn_scan1 could be used for the inverted
+ search under u<0, but usually the search won't go very far so it seems
+ reasonable to inline that code. */
+
+mp_bitcnt_t
+mpz_scan0 (mpz_srcptr u, mp_bitcnt_t starting_bit) __GMP_NOTHROW
+{
+ mp_srcptr u_ptr = PTR(u);
+ mp_size_t size = SIZ(u);
+ mp_size_t abs_size = ABS(size);
+ mp_srcptr u_end = u_ptr + abs_size;
+ mp_size_t starting_limb = starting_bit / GMP_NUMB_BITS;
+ mp_srcptr p = u_ptr + starting_limb;
+ mp_limb_t limb;
+ int cnt;
+
+ /* When past end, there's an immediate 0 bit for u>=0, or no 0 bits for
+ u<0. Notice this test picks up all cases of u==0 too. */
+ if (starting_limb >= abs_size)
+ return (size >= 0 ? starting_bit : ~(mp_bitcnt_t) 0);
+
+ limb = *p;
+
+ if (size >= 0)
+ {
+ /* Mask to 1 all bits before starting_bit, thus ignoring them. */
+ limb |= (CNST_LIMB(1) << (starting_bit % GMP_NUMB_BITS)) - 1;
+
+ /* Search for a limb which isn't all ones. If the end is reached then
+ the zero bit immediately past the end is returned. */
+ while (limb == GMP_NUMB_MAX)
+ {
+ p++;
+ if (p == u_end)
+ return (mp_bitcnt_t) abs_size * GMP_NUMB_BITS;
+ limb = *p;
+ }
+
+ /* Now seek low 1 bit. */
+ limb = ~limb;
+ }
+ else
+ {
+ mp_srcptr q;
+
+ /* If there's a non-zero limb before ours then we're in the ones
+ complement region. Search from *(p-1) downwards since that might
+ give better cache locality, and since a non-zero in the middle of a
+ number is perhaps a touch more likely than at the end. */
+ q = p;
+ while (q != u_ptr)
+ {
+ q--;
+ if (*q != 0)
+ goto inverted;
+ }
+
+ /* Adjust so ~limb implied by searching for 1 bit below becomes -limb.
+ If limb==0 here then this isn't the beginning of twos complement
+ inversion, but that doesn't matter because limb==0 is a zero bit
+ immediately (-1 is all ones for below). */
+ limb--;
+
+ inverted:
+ /* Now seeking a 1 bit. */
+
+ /* Mask to 0 all bits before starting_bit, thus ignoring them. */
+ limb &= (MP_LIMB_T_MAX << (starting_bit % GMP_NUMB_BITS));
+
+ if (limb == 0)
+ {
+ /* If the high limb is zero after masking, then no 1 bits past
+ starting_bit. */
+ p++;
+ if (p == u_end)
+ return ~(mp_bitcnt_t) 0;
+
+ /* Search further for a non-zero limb. The high limb is non-zero,
+ if nothing else. */
+ for (;;)
+ {
+ limb = *p;
+ if (limb != 0)
+ break;
+ p++;
+ ASSERT (p < u_end);
+ }
+ }
+ }
+
+ ASSERT (limb != 0);
+ count_trailing_zeros (cnt, limb);
+ return (mp_bitcnt_t) (p - u_ptr) * GMP_NUMB_BITS + cnt;
+}