sysdeps/alpha/addmul_1.s

   1  # Alpha 21064 __mpn_addmul_1 -- Multiply a limb vector with a limb and add
   2  # the result to a second limb vector.
   3
   4  # Copyright (C) 1992, 1994, 1995 Free Software Foundation, Inc.
   5
   6  # This file is part of the GNU MP Library.
   7
   8  # The GNU MP Library is free software; you can redistribute it and/or modify
   9  # it under the terms of the GNU Library General Public License as published by
  10  # the Free Software Foundation; either version 2 of the License, or (at your
  11  # option) any later version.
  12
  13  # The GNU MP Library is distributed in the hope that it will be useful, but
  14  # WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  15  # or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
  16  # License for more details.
  17
  18  # You should have received a copy of the GNU Library General Public License
  19  # along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
  20  # the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21
  22
  23  # INPUT PARAMETERS
  24  # res_ptr      r16
  25  # s1_ptr       r17
  26  # size         r18
  27  # s2_limb      r19
  28
  29  # This code runs at 42 cycles/limb on the 21064.
  30
  31  # To improve performance for long multiplications, we would use
  32  # 'fetch' for S1 and 'fetch_m' for RES.  It's not obvious how to use
  33  # these instructions without slowing down the general code: 1. We can
  34  # only have two prefetches in operation at any time in the Alpha
  35  # architecture.  2. There will seldom be any special alignment
  36  # between RES_PTR and S1_PTR.  Maybe we can simply divide the current
  37  # loop into an inner and outer loop, having the inner loop handle
  38  # exactly one prefetch block?
  39
  40         .set    noreorder
  41         .set    noat
  42 .text
  43         .align  3
  44         .globl  __mpn_addmul_1
  45         .ent    __mpn_addmul_1 2
  46 __mpn_addmul_1:
  47         .frame  $30,0,$26
  48
  49         ldq     $2,0($17)       # $2 = s1_limb
  50         addq    $17,8,$17       # s1_ptr++
  51         subq    $18,1,$18       # size--
  52         mulq    $2,$19,$3       # $3 = prod_low
  53         ldq     $5,0($16)       # $5 = *res_ptr
  54         umulh   $2,$19,$0       # $0 = prod_high
  55         beq     $18,Lend1       # jump if size was == 1
  56         ldq     $2,0($17)       # $2 = s1_limb
  57         addq    $17,8,$17       # s1_ptr++
  58         subq    $18,1,$18       # size--
  59         addq    $5,$3,$3
  60         cmpult  $3,$5,$4
  61         stq     $3,0($16)
  62         addq    $16,8,$16       # res_ptr++
  63         beq     $18,Lend2       # jump if size was == 2
  64
  65         .align  3
  66 Loop:   mulq    $2,$19,$3       # $3 = prod_low
  67         ldq     $5,0($16)       # $5 = *res_ptr
  68         addq    $4,$0,$0        # cy_limb = cy_limb + 'cy'
  69         subq    $18,1,$18       # size--
  70         umulh   $2,$19,$4       # $4 = cy_limb
  71         ldq     $2,0($17)       # $2 = s1_limb
  72         addq    $17,8,$17       # s1_ptr++
  73         addq    $3,$0,$3        # $3 = cy_limb + prod_low
  74         cmpult  $3,$0,$0        # $0 = carry from (cy_limb + prod_low)
  75         addq    $5,$3,$3
  76         cmpult  $3,$5,$5
  77         stq     $3,0($16)
  78         addq    $16,8,$16       # res_ptr++
  79         addq    $5,$0,$0        # combine carries
  80         bne     $18,Loop
  81
  82 Lend2:  mulq    $2,$19,$3       # $3 = prod_low
  83         ldq     $5,0($16)       # $5 = *res_ptr
  84         addq    $4,$0,$0        # cy_limb = cy_limb + 'cy'
  85         umulh   $2,$19,$4       # $4 = cy_limb
  86         addq    $3,$0,$3        # $3 = cy_limb + prod_low
  87         cmpult  $3,$0,$0        # $0 = carry from (cy_limb + prod_low)
  88         addq    $5,$3,$3
  89         cmpult  $3,$5,$5
  90         stq     $3,0($16)
  91         addq    $5,$0,$0        # combine carries
  92         addq    $4,$0,$0        # cy_limb = prod_high + cy
  93         ret     $31,($26),1
  94 Lend1:  addq    $5,$3,$3
  95         cmpult  $3,$5,$5
  96         stq     $3,0($16)
  97         addq    $0,$5,$0
  98         ret     $31,($26),1
  99
 100         .end    __mpn_addmul_1