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/* IBM POWER sub_n -- Subtract two limb vectors of equal, non-zero length.
*
* Copyright (C) 1992, 1994, 1995, 1996, 1999
* Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* GnuPG is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* GnuPG 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include "sysdep.h"
#include "asm-syntax.h"
/*
# INPUT PARAMETERS
# res_ptr r3
# s1_ptr r4
# s2_ptr r5
# size r6
*/
.toc
.extern mpihelp_sub_n[DS]
.extern .mpihelp_sub_n
.csect [PR]
.align 2
.globl mpihelp_sub_n
.globl .mpihelp_sub_n
.csect mpihelp_sub_n[DS]
mpihelp_sub_n:
.long .mpihelp_sub_n, TOC[tc0], 0
.csect [PR]
.mpihelp_sub_n:
andil. 10,6,1 # odd or even number of limbs?
l 8,0(4) # load least significant s1 limb
l 0,0(5) # load least significant s2 limb
cal 3,-4(3) # offset res_ptr, it's updated before it's used
sri 10,6,1 # count for unrolled loop
sf 7,0,8 # subtract least significant limbs, set cy
mtctr 10 # copy count into CTR
beq 0,Leven # branch if even # of limbs (# of limbs >= 2)
# We have an odd # of limbs. Add the first limbs separately.
cmpi 1,10,0 # is count for unrolled loop zero?
bne 1,L1 # branch if not
st 7,4(3)
sfe 3,0,0 # load !cy into ...
sfi 3,3,0 # ... return value register
br # return
# We added least significant limbs. Now reload the next limbs to enter loop.
L1: lu 8,4(4) # load s1 limb and update s1_ptr
lu 0,4(5) # load s2 limb and update s2_ptr
stu 7,4(3)
sfe 7,0,8 # subtract limbs, set cy
Leven: lu 9,4(4) # load s1 limb and update s1_ptr
lu 10,4(5) # load s2 limb and update s2_ptr
bdz Lend # If done, skip loop
Loop: lu 8,4(4) # load s1 limb and update s1_ptr
lu 0,4(5) # load s2 limb and update s2_ptr
sfe 11,10,9 # subtract previous limbs with cy, set cy
stu 7,4(3) #
lu 9,4(4) # load s1 limb and update s1_ptr
lu 10,4(5) # load s2 limb and update s2_ptr
sfe 7,0,8 # subtract previous limbs with cy, set cy
stu 11,4(3) #
bdn Loop # decrement CTR and loop back
Lend: sfe 11,10,9 # subtract limbs with cy, set cy
st 7,4(3) #
st 11,8(3) #
sfe 3,0,0 # load !cy into ...
sfi 3,3,0 # ... return value register
br
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