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/* AMD64 (x86_64) sub_n -- Subtract two limb vectors of the same length > 0 and store
* sum in a third limb vector.
*
* Copyright (C) 1992, 1994, 1995, 1998,
* 2001, 2002, 2006 Free Software Foundation, Inc.
* Copyright (C) 2023 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 <https://www.gnu.org/licenses/>.
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* Note: This code is heavily based on the GNU MP Library.
* Actually it's the same code with only minor changes in the
* way the data is stored; this is to support the abstraction
* of an optional secure memory allocation which may be used
* to avoid revealing of sensitive data due to paging etc.
*/
#include "sysdep.h"
#include "asm-syntax.h"
/*******************
* mpi_limb_t
* _gcry_mpih_sub_n( mpi_ptr_t res_ptr, rdi
* mpi_ptr_t s1_ptr, rsi
* mpi_ptr_t s2_ptr, rdx
* mpi_size_t size) rcx
*/
TEXT
ALIGN(4)
.globl C_SYMBOL_NAME(_gcry_mpih_sub_n)
C_SYMBOL_NAME(_gcry_mpih_sub_n:)
FUNC_ENTRY()
movl %ecx, %r9d
andl $3, %r9d
je .Lprehandle0
cmpl $2, %r9d
jb .Lprehandle1
je .Lprehandle2
#define FIRST_SUB() \
movq (%rsi), %rax; \
subq (%rdx), %rax; \
movq %rax, (%rdi)
#define NEXT_SUB(offset) \
movq offset(%rsi), %rax; \
sbbq offset(%rdx), %rax; \
movq %rax, offset(%rdi)
.Lprehandle3:
leaq -2(%rcx), %rcx
FIRST_SUB();
NEXT_SUB(8);
NEXT_SUB(16);
decq %rcx
je .Lend
leaq 24(%rsi), %rsi
leaq 24(%rdx), %rdx
leaq 24(%rdi), %rdi
jmp .Loop
ALIGN(3)
.Lprehandle2:
leaq -1(%rcx), %rcx
FIRST_SUB();
NEXT_SUB(8);
decq %rcx
je .Lend
leaq 16(%rsi), %rsi
leaq 16(%rdx), %rdx
leaq 16(%rdi), %rdi
jmp .Loop
ALIGN(3)
.Lprehandle1:
FIRST_SUB();
decq %rcx
je .Lend
leaq 8(%rsi), %rsi
leaq 8(%rdx), %rdx
leaq 8(%rdi), %rdi
jmp .Loop
ALIGN(3)
.Lprehandle0:
clc /* clear cy */
ALIGN(4) /* minimal alignment for claimed speed */
.Loop: leaq -3(%rcx), %rcx
NEXT_SUB(0);
NEXT_SUB(8);
NEXT_SUB(16);
NEXT_SUB(24);
leaq 32(%rsi), %rsi
leaq 32(%rdx), %rdx
leaq 32(%rdi), %rdi
decq %rcx
jne .Loop
ALIGN(2)
.Lend:
movl $0, %eax /* zero %rax */
adcl %eax, %eax
FUNC_EXIT()
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