glibc/sysdeps/s390/s390-64/add_n.S

/* Add two limb vectors of the same length > 0 and store sum in a third
   limb vector.
   Copyright (C) 2001-2020 Free Software Foundation, Inc.
   Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
   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,
   see <https://www.gnu.org/licenses/>.  */

/*
   INPUT PARAMETERS
   res_ptr	%r2
   s1_ptr	%r3
   s2_ptr	%r4
   size		%r5
*/

#include "sysdep.h"
#include "asm-syntax.h"

	.text
ENTRY(__mpn_add_n)
	stg    %r6,48(%r15)   # save register 6
	cfi_offset (%r6,-112)
	slgr   %r1,%r1
        lghi   %r0,1          # cannot use ahi to add carry, use alr
.L0:	lg     %r6,0(%r1,%r3) # .L0 -> no carry from last add
	alg    %r6,0(%r1,%r4)
	stg    %r6,0(%r1,%r2)
	la     %r1,8(%r1)
	brc    3,.L3
.L1:	brct   %r5,.L0
	slgr   %r2,%r2        # no last carry to return
	j      .Lexit
.L2:    lg     %r6,0(%r1,%r3) # .L2 -> carry from last add
	alg    %r6,0(%r1,%r4)
	brc    3,.L4
	algr   %r6,%r0        # no carry yet, add carry from last add
	stg    %r6,0(%r1,%r2)
	la     %r1,8(%r1)
	brc    12,.L1          # new carry ?
.L3:	brct   %r5,.L2
	lgr    %r2,%r0        # return last carry
	j      .Lexit
.L4:	algr   %r6,%r0        # already a carry, add carry from last add
	stg    %r6,0(%r1,%r2)
	la     %r1,8(%r1)
	brct   %r5,.L2
	lgr    %r2,%r0        # return last carry
.Lexit:	lg     %r6,48(%r15)   # restore register 6
	br     %r14
END(__mpn_add_n)