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# Alpha 21064 __mpn_submul_1 -- Multiply a limb vector with a limb and
# subtract the result from a second limb vector.
# Copyright (C) 1992, 1994, 1995 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 Library General Public License as published by
# the Free Software Foundation; either version 2 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 Library General Public
# License for more details.
# You should have received a copy of the GNU Library General Public License
# along with the GNU MP Library; see the file COPYING.LIB. If not, write to
# the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
# INPUT PARAMETERS
# res_ptr r16
# s1_ptr r17
# size r18
# s2_limb r19
# This code runs at 42 cycles/limb on the 21064.
# To improve performance for long multiplications, we would use
# 'fetch' for S1 and 'fetch_m' for RES. It's not obvious how to use
# these instructions without slowing down the general code: 1. We can
# only have two prefetches in operation at any time in the Alpha
# architecture. 2. There will seldom be any special alignment
# between RES_PTR and S1_PTR. Maybe we can simply divide the current
# loop into an inner and outer loop, having the inner loop handle
# exactly one prefetch block?
.set noreorder
.set noat
.text
.align 3
.globl __mpn_submul_1
.ent __mpn_submul_1 2
__mpn_submul_1:
.frame $30,0,$26
ldq $2,0($17) # $2 = s1_limb
addq $17,8,$17 # s1_ptr++
subq $18,1,$18 # size--
mulq $2,$19,$3 # $3 = prod_low
ldq $5,0($16) # $5 = *res_ptr
umulh $2,$19,$0 # $0 = prod_high
beq $18,Lend1 # jump if size was == 1
ldq $2,0($17) # $2 = s1_limb
addq $17,8,$17 # s1_ptr++
subq $18,1,$18 # size--
subq $5,$3,$3
cmpult $5,$3,$4
stq $3,0($16)
addq $16,8,$16 # res_ptr++
beq $18,Lend2 # jump if size was == 2
.align 3
Loop: mulq $2,$19,$3 # $3 = prod_low
ldq $5,0($16) # $5 = *res_ptr
addq $4,$0,$0 # cy_limb = cy_limb + 'cy'
subq $18,1,$18 # size--
umulh $2,$19,$4 # $4 = cy_limb
ldq $2,0($17) # $2 = s1_limb
addq $17,8,$17 # s1_ptr++
addq $3,$0,$3 # $3 = cy_limb + prod_low
cmpult $3,$0,$0 # $0 = carry from (cy_limb + prod_low)
subq $5,$3,$3
cmpult $5,$3,$5
stq $3,0($16)
addq $16,8,$16 # res_ptr++
addq $5,$0,$0 # combine carries
bne $18,Loop
Lend2: mulq $2,$19,$3 # $3 = prod_low
ldq $5,0($16) # $5 = *res_ptr
addq $4,$0,$0 # cy_limb = cy_limb + 'cy'
umulh $2,$19,$4 # $4 = cy_limb
addq $3,$0,$3 # $3 = cy_limb + prod_low
cmpult $3,$0,$0 # $0 = carry from (cy_limb + prod_low)
subq $5,$3,$3
cmpult $5,$3,$5
stq $3,0($16)
addq $5,$0,$0 # combine carries
addq $4,$0,$0 # cy_limb = prod_high + cy
ret $31,($26),1
Lend1: subq $5,$3,$3
cmpult $5,$3,$5
stq $3,0($16)
addq $0,$5,$0
ret $31,($26),1
.end __mpn_submul_1
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