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/* ARM sub_n -- Subtract two limb vectors of the same length > 0 and store
* sum in a third limb vector.
*
* Copyright (C) 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi>
*
* This file is part of Libgcrypt.
*
* Libgcrypt 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.
*
* Libgcrypt 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 this program; if not, see <http://www.gnu.org/licenses/>.
*
* Note: This code is heavily based on the GNU MP Library (version 4.2.1).
*/
#include "sysdep.h"
#include "asm-syntax.h"
.syntax unified
.arm
/*******************
* mpi_limb_t
* _gcry_mpih_sub_n( mpi_ptr_t res_ptr, %r0
* mpi_ptr_t s1_ptr, %r1
* mpi_ptr_t s2_ptr, %r2
* mpi_size_t size) %r3
*/
.text
.globl _gcry_mpih_sub_n
.type _gcry_mpih_sub_n,%function
_gcry_mpih_sub_n:
push {%r4, %r5, %r6, %r7, %r8, %r9, %r10, %lr};
cmp %r0, #0; /* prepare carry flag for sub */
tst %r3, #3;
beq .Large_loop;
.Loop:
ldr %r4, [%r1], #4;
sub %r3, #1;
ldr %lr, [%r2], #4;
sbcs %r4, %lr;
tst %r3, #3;
str %r4, [%r0], #4;
bne .Loop;
teq %r3, #0;
beq .Lend;
.Large_loop:
ldm %r1!, {%r4, %r6, %r8, %r10};
sub %r3, #4;
ldm %r2!, {%r5, %r7, %r9, %lr};
sbcs %r4, %r5;
sbcs %r6, %r7;
sbcs %r8, %r9;
sbcs %r10, %lr;
teq %r3, #0;
stm %r0!, {%r4, %r6, %r8, %r10};
bne .Large_loop;
.Lend:
sbc %r0, %r3, #0;
neg %r0, %r0;
pop {%r4, %r5, %r6, %r7, %r8, %r9, %r10, %pc};
.size _gcry_mpih_sub_n,.-_gcry_mpih_sub_n;
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