--- /dev/null
+/* mpn_toom22_mul -- Multiply {ap,an} and {bp,bn} where an >= bn. Or more
+ accurately, bn <= an < 2bn.
+
+ Contributed to the GNU project by Torbjorn Granlund.
+
+ THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY
+ SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
+ GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
+
+Copyright 2006, 2007, 2008 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"
+
+/* Evaluate in: -1, 0, +inf
+
+ <-s--><--n-->
+ ____ ______
+ |_a1_|___a0_|
+ |b1_|___b0_|
+ <-t-><--n-->
+
+ v0 = a0 * b0 # A(0)*B(0)
+ vm1 = (a0- a1)*(b0- b1) # A(-1)*B(-1)
+ vinf= a1 * b1 # A(inf)*B(inf)
+*/
+
+#if TUNE_PROGRAM_BUILD
+#define MAYBE_mul_toom22 1
+#else
+#define MAYBE_mul_toom22 \
+ (MUL_TOOM33_THRESHOLD >= 2 * MUL_TOOM22_THRESHOLD)
+#endif
+
+#define TOOM22_MUL_N_REC(p, a, b, n, ws) \
+ do { \
+ if (! MAYBE_mul_toom22 \
+ || BELOW_THRESHOLD (n, MUL_KARATSUBA_THRESHOLD)) \
+ mpn_mul_basecase (p, a, n, b, n); \
+ else \
+ mpn_toom22_mul (p, a, n, b, n, ws); \
+ } while (0)
+
+void
+mpn_toom22_mul (mp_ptr pp,
+ mp_srcptr ap, mp_size_t an,
+ mp_srcptr bp, mp_size_t bn,
+ mp_ptr scratch)
+{
+ mp_size_t n, s, t;
+ int vm1_neg;
+ mp_limb_t cy, cy2;
+ mp_ptr asm1;
+ mp_ptr bsm1;
+
+#define a0 ap
+#define a1 (ap + n)
+#define b0 bp
+#define b1 (bp + n)
+
+ s = an >> 1;
+ n = an - s;
+ t = bn - n;
+
+ ASSERT (an >= bn);
+
+ ASSERT (0 < s && s <= n);
+ ASSERT (0 < t && t <= s);
+
+ asm1 = pp;
+ bsm1 = pp + n;
+
+ vm1_neg = 0;
+
+ /* Compute asm1. */
+ if (s == n)
+ {
+ if (mpn_cmp (a0, a1, n) < 0)
+ {
+ mpn_sub_n (asm1, a1, a0, n);
+ vm1_neg = 1;
+ }
+ else
+ {
+ mpn_sub_n (asm1, a0, a1, n);
+ }
+ }
+ else
+ {
+ if (mpn_zero_p (a0 + s, n - s) && mpn_cmp (a0, a1, s) < 0)
+ {
+ mpn_sub_n (asm1, a1, a0, s);
+ MPN_ZERO (asm1 + s, n - s);
+ vm1_neg = 1;
+ }
+ else
+ {
+ mpn_sub (asm1, a0, n, a1, s);
+ }
+ }
+
+ /* Compute bsm1. */
+ if (t == n)
+ {
+ if (mpn_cmp (b0, b1, n) < 0)
+ {
+ mpn_sub_n (bsm1, b1, b0, n);
+ vm1_neg ^= 1;
+ }
+ else
+ {
+ mpn_sub_n (bsm1, b0, b1, n);
+ }
+ }
+ else
+ {
+ if (mpn_zero_p (b0 + t, n - t) && mpn_cmp (b0, b1, t) < 0)
+ {
+ mpn_sub_n (bsm1, b1, b0, t);
+ MPN_ZERO (bsm1 + t, n - t);
+ vm1_neg ^= 1;
+ }
+ else
+ {
+ mpn_sub (bsm1, b0, n, b1, t);
+ }
+ }
+
+#define v0 pp /* 2n */
+#define vinf (pp + 2 * n) /* s+t */
+#define vm1 scratch /* 2n */
+#define scratch_out scratch + 2 * n
+
+ /* vm1, 2n limbs */
+ TOOM22_MUL_N_REC (vm1, asm1, bsm1, n, scratch_out);
+
+ /* vinf, s+t limbs */
+ mpn_mul (vinf, a1, s, b1, t);
+
+ /* v0, 2n limbs */
+ TOOM22_MUL_N_REC (v0, ap, bp, n, scratch_out);
+
+ /* H(v0) + L(vinf) */
+ cy = mpn_add_n (pp + 2 * n, v0 + n, vinf, n);
+
+ /* L(v0) + H(v0) */
+ cy2 = cy + mpn_add_n (pp + n, pp + 2 * n, v0, n);
+
+ /* L(vinf) + H(vinf) */
+ cy += mpn_add (pp + 2 * n, pp + 2 * n, n, vinf + n, s + t - n);
+
+ if (vm1_neg)
+ cy += mpn_add_n (pp + n, pp + n, vm1, 2 * n);
+ else
+ cy -= mpn_sub_n (pp + n, pp + n, vm1, 2 * n);
+
+ ASSERT (cy + 1 <= 3);
+ ASSERT (cy2 <= 2);
+
+ mpn_incr_u (pp + 2 * n, cy2);
+ if (LIKELY (cy <= 2))
+ mpn_incr_u (pp + 3 * n, cy);
+ else
+ mpn_decr_u (pp + 3 * n, 1);
+}
projects / msp430-gcc.git / blobdiff