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-rw-r--r--stdlib/submul_1.c65
1 files changed, 65 insertions, 0 deletions
diff --git a/stdlib/submul_1.c b/stdlib/submul_1.c
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+++ b/stdlib/submul_1.c
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+/* mpn_submul_1 -- multiply the S1_SIZE long limb vector pointed to by S1_PTR
+ by S2_LIMB, subtract the S1_SIZE least significant limbs of the product
+ from the limb vector pointed to by RES_PTR. Return the most significant
+ limb of the product, adjusted for carry-out from the subtraction.
+
+Copyright (C) 1992, 1993, 1994, 1996, 2005 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 2.1 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; see the file COPYING.LIB. If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include <gmp.h>
+#include "gmp-impl.h"
+#include "longlong.h"
+
+mp_limb_t
+mpn_submul_1 (res_ptr, s1_ptr, s1_size, s2_limb)
+ register mp_ptr res_ptr;
+ register mp_srcptr s1_ptr;
+ mp_size_t s1_size;
+ register mp_limb_t s2_limb;
+{
+ register mp_limb_t cy_limb;
+ register mp_size_t j;
+ register mp_limb_t prod_high, prod_low;
+ register mp_limb_t x;
+
+ /* The loop counter and index J goes from -SIZE to -1. This way
+ the loop becomes faster. */
+ j = -s1_size;
+
+ /* Offset the base pointers to compensate for the negative indices. */
+ res_ptr -= j;
+ s1_ptr -= j;
+
+ cy_limb = 0;
+ do
+ {
+ umul_ppmm (prod_high, prod_low, s1_ptr[j], s2_limb);
+
+ prod_low += cy_limb;
+ cy_limb = (prod_low < cy_limb) + prod_high;
+
+ x = res_ptr[j];
+ prod_low = x - prod_low;
+ cy_limb += (prod_low > x);
+ res_ptr[j] = prod_low;
+ }
+ while (++j != 0);
+
+ return cy_limb;
+}