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mpih-mul1.S
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/* Alpha 21064 mpih-mul1.S -- Multiply a limb vector with a limb and store
* the result in a second limb vector.
*
* Copyright (C) 1992, 1994, 1995, 1998,
* 2001, 2002 Free Software Foundation, Inc.
*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
/*******************
* mpi_limb_t
* _gcry_mpih_mul_1( mpi_ptr_t res_ptr, (r16)
* mpi_ptr_t s1_ptr, (r17)
* mpi_size_t s1_size, (r18)
* mpi_limb_t s2_limb) (r19)
*
* This code runs at 42 cycles/limb on the EV4 and 18 cycles/limb on the EV5.
*
* 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 _gcry_mpih_mul_1
.ent _gcry_mpih_mul_1 2
_gcry_mpih_mul_1:
.frame $30,0,$26
ldq $2,0($17) # $2 = s1_limb
subq $18,1,$18 # size--
mulq $2,$19,$3 # $3 = prod_low
bic $31,$31,$4 # clear cy_limb
umulh $2,$19,$0 # $0 = prod_high
beq $18,Lend1 # jump if size was == 1
ldq $2,8($17) # $2 = s1_limb
subq $18,1,$18 # size--
stq $3,0($16)
beq $18,Lend2 # jump if size was == 2
.align 3
Loop: mulq $2,$19,$3 # $3 = prod_low
addq $4,$0,$0 # cy_limb = cy_limb + 'cy'
subq $18,1,$18 # size--
umulh $2,$19,$4 # $4 = cy_limb
ldq $2,16($17) # $2 = s1_limb
addq $17,8,$17 # s1_ptr++
addq $3,$0,$3 # $3 = cy_limb + prod_low
stq $3,8($16)
cmpult $3,$0,$0 # $0 = carry from (cy_limb + prod_low)
addq $16,8,$16 # res_ptr++
bne $18,Loop
Lend2: mulq $2,$19,$3 # $3 = prod_low
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)
stq $3,8($16)
addq $4,$0,$0 # cy_limb = prod_high + cy
ret $31,($26),1
Lend1: stq $3,0($16)
ret $31,($26),1
.end _gcry_mpih_mul_1

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