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diff --git a/gmp/mpn/generic/toom42_mul.c b/gmp/mpn/generic/toom42_mul.c
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+++ b/gmp/mpn/generic/toom42_mul.c
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+/* mpn_toom42_mul -- Multiply {ap,an} and {bp,bn} where an is nominally twice
+   as large as bn.  Or more accurately, (3/2)bn < an < 4bn.
+
+   Contributed to the GNU project by Torbjorn Granlund.
+   Additional improvements by Marco Bodrato.
+
+   The idea of applying toom to unbalanced multiplication is due to by Marco
+   Bodrato and Alberto Zanoni.
+
+   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/.  */
+
+
+/*
+  Things to work on:
+
+  1. Trim allocation.  The allocations for as1, asm1, bs1, and bsm1 could be
+     avoided by instead reusing the pp area and the scratch allocation.
+
+  2. Apply optimizations also to mul_toom32.c.
+*/
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+/* Evaluate in: -1, 0, +1, +2, +inf
+
+  <-s-><--n--><--n--><--n-->
+   ___ ______ ______ ______
+  |a3_|___a2_|___a1_|___a0_|
+	       |_b1_|___b0_|
+	       <-t--><--n-->
+
+  v0  =  a0             * b0      #   A(0)*B(0)
+  v1  = (a0+ a1+ a2+ a3)*(b0+ b1) #   A(1)*B(1)      ah  <= 3  bh <= 1
+  vm1 = (a0- a1+ a2- a3)*(b0- b1) #  A(-1)*B(-1)    |ah| <= 1  bh  = 0
+  v2  = (a0+2a1+4a2+8a3)*(b0+2b1) #   A(2)*B(2)      ah  <= 14 bh <= 2
+  vinf=              a3 *     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_toom42_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, vinf0;
+  mp_ptr a0_a2, a1_a3;
+  mp_ptr as1, asm1, as2;
+  mp_ptr bs1, bsm1, bs2;
+  TMP_DECL;
+
+#define a0  ap
+#define a1  (ap + n)
+#define a2  (ap + 2*n)
+#define a3  (ap + 3*n)
+#define b0  bp
+#define b1  (bp + n)
+
+  n = an >= 2 * bn ? (an + 3) >> 2 : (bn + 1) >> 1;
+
+  s = an - 3 * n;
+  t = bn - n;
+
+  ASSERT (0 < s && s <= n);
+  ASSERT (0 < t && t <= n);
+
+  TMP_MARK;
+
+  as1 = TMP_SALLOC_LIMBS (n + 1);
+  asm1 = TMP_SALLOC_LIMBS (n + 1);
+  as2 = TMP_SALLOC_LIMBS (n + 1);
+
+  bs1 = TMP_SALLOC_LIMBS (n + 1);
+  bsm1 = TMP_SALLOC_LIMBS (n);
+  bs2 = TMP_SALLOC_LIMBS (n + 1);
+
+  a0_a2 = pp;
+  a1_a3 = pp + n + 1;
+
+  /* Compute as1 and asm1.  */
+  a0_a2[n] = mpn_add_n (a0_a2, a0, a2, n);
+  a1_a3[n] = mpn_add (a1_a3, a1, n, a3, s);
+#if HAVE_NATIVE_mpn_addsub_n
+  if (mpn_cmp (a0_a2, a1_a3, n + 1) < 0)
+    {
+      mpn_addsub_n (as1, asm1, a1_a3, a0_a2, n + 1);
+      vm1_neg = 1;
+    }
+  else
+    {
+      mpn_addsub_n (as1, asm1, a0_a2, a1_a3, n + 1);
+      vm1_neg = 0;
+    }
+#else
+  mpn_add_n (as1, a0_a2, a1_a3, n + 1);
+  if (mpn_cmp (a0_a2, a1_a3, n + 1) < 0)
+    {
+      mpn_sub_n (asm1, a1_a3, a0_a2, n + 1);
+      vm1_neg = 1;
+    }
+  else
+    {
+      mpn_sub_n (asm1, a0_a2, a1_a3, n + 1);
+      vm1_neg = 0;
+    }
+#endif
+
+  /* Compute as2.  */
+#if HAVE_NATIVE_mpn_addlsh1_n
+  cy  = mpn_addlsh1_n (as2, a2, a3, s);
+  if (s != n)
+    cy = mpn_add_1 (as2 + s, a2 + s, n - s, cy);
+  cy = 2 * cy + mpn_addlsh1_n (as2, a1, as2, n);
+  cy = 2 * cy + mpn_addlsh1_n (as2, a0, as2, n);
+#else
+  cy  = mpn_lshift (as2, a3, s, 1);
+  cy += mpn_add_n (as2, a2, as2, s);
+  if (s != n)
+    cy = mpn_add_1 (as2 + s, a2 + s, n - s, cy);
+  cy = 2 * cy + mpn_lshift (as2, as2, n, 1);
+  cy += mpn_add_n (as2, a1, as2, n);
+  cy = 2 * cy + mpn_lshift (as2, as2, n, 1);
+  cy += mpn_add_n (as2, a0, as2, n);
+#endif
+  as2[n] = cy;
+
+  /* Compute bs1 and bsm1.  */
+  if (t == n)
+    {
+#if HAVE_NATIVE_mpn_addsub_n
+      if (mpn_cmp (b0, b1, n) < 0)
+	{
+	  cy = mpn_addsub_n (bs1, bsm1, b1, b0, n);
+	  vm1_neg ^= 1;
+	}
+      else
+	{
+	  cy = mpn_addsub_n (bs1, bsm1, b0, b1, n);
+	}
+      bs1[n] = cy >> 1;
+#else
+      bs1[n] = mpn_add_n (bs1, b0, b1, 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);
+	}
+#endif
+    }
+  else
+    {
+      bs1[n] = mpn_add (bs1, b0, n, b1, t);
+
+      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);
+	}
+    }
+
+  /* Compute bs2, recycling bs1. bs2=bs1+b1  */
+  mpn_add (bs2, bs1, n + 1, b1, t);
+
+  ASSERT (as1[n] <= 3);
+  ASSERT (bs1[n] <= 1);
+  ASSERT (asm1[n] <= 1);
+/*ASSERT (bsm1[n] == 0);*/
+  ASSERT (as2[n] <= 14);
+  ASSERT (bs2[n] <= 2);
+
+#define v0    pp				/* 2n */
+#define v1    (pp + 2 * n)			/* 2n+1 */
+#define vinf  (pp + 4 * n)			/* s+t */
+#define vm1   scratch				/* 2n+1 */
+#define v2    (scratch + 2 * n + 1)		/* 2n+2 */
+#define scratch_out	scratch + 4 * n + 4
+
+  /* vm1, 2n+1 limbs */
+  TOOM22_MUL_N_REC (vm1, asm1, bsm1, n, scratch_out);
+  cy = 0;
+  if (asm1[n] != 0)
+    cy = mpn_add_n (vm1 + n, vm1 + n, bsm1, n);
+  vm1[2 * n] = cy;
+
+  TOOM22_MUL_N_REC (v2, as2, bs2, n + 1, scratch_out);	/* v2, 2n+1 limbs */
+
+  /* vinf, s+t limbs */
+  if (s > t)  mpn_mul (vinf, a3, s, b1, t);
+  else        mpn_mul (vinf, b1, t, a3, s);
+
+  vinf0 = vinf[0];				/* v1 overlaps with this */
+
+  /* v1, 2n+1 limbs */
+  TOOM22_MUL_N_REC (v1, as1, bs1, n, scratch_out);
+  if (as1[n] == 1)
+    {
+      cy = bs1[n] + mpn_add_n (v1 + n, v1 + n, bs1, n);
+    }
+  else if (as1[n] == 2)
+    {
+#if HAVE_NATIVE_mpn_addlsh1_n
+      cy = 2 * bs1[n] + mpn_addlsh1_n (v1 + n, v1 + n, bs1, n);
+#else
+      cy = 2 * bs1[n] + mpn_addmul_1 (v1 + n, bs1, n, CNST_LIMB(2));
+#endif
+    }
+  else if (as1[n] == 3)
+    {
+      cy = 3 * bs1[n] + mpn_addmul_1 (v1 + n, bs1, n, CNST_LIMB(3));
+    }
+  else
+    cy = 0;
+  if (bs1[n] != 0)
+    cy += mpn_add_n (v1 + n, v1 + n, as1, n);
+  v1[2 * n] = cy;
+
+  TOOM22_MUL_N_REC (v0, ap, bp, n, scratch_out);	/* v0, 2n limbs */
+
+  mpn_toom_interpolate_5pts (pp, v2, vm1, n, s + t, 1^vm1_neg, vinf0, scratch + 4 * n + 4);
+
+  TMP_FREE;
+}