sysdeps/alpha/mul_1.s

   1  # Alpha 21064 __mpn_mul_1 -- Multiply a limb vector with a limb and store
   2  # the result in 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 Lesser General Public License as published by
  10  # the Free Software Foundation; either version 2.1 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 Lesser General Public
  16  # License for more details.
  17
  18  # You should have received a copy of the GNU Lesser 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., 59 Temple Place - Suite 330, Boston,
  21  # MA 02111-1307, USA.
  22
  23
  24  # INPUT PARAMETERS
  25  # res_ptr      r16
  26  # s1_ptr       r17
  27  # size         r18
  28  # s2_limb      r19
  29
  30  # This code runs at 42 cycles/limb on the EV4 and 18 cycles/limb on the EV5.
  31
  32  # To improve performance for long multiplications, we would use
  33  # 'fetch' for S1 and 'fetch_m' for RES.  It's not obvious how to use
  34  # these instructions without slowing down the general code: 1. We can
  35  # only have two prefetches in operation at any time in the Alpha
  36  # architecture.  2. There will seldom be any special alignment
  37  # between RES_PTR and S1_PTR.  Maybe we can simply divide the current
  38  # loop into an inner and outer loop, having the inner loop handle
  39  # exactly one prefetch block?
  40
  41         .set    noreorder
  42         .set    noat
  43 .text
  44         .align  3
  45         .globl  __mpn_mul_1
  46         .ent    __mpn_mul_1 2
  47 __mpn_mul_1:
  48         .frame  $30,0,$26
  49
  50         ldq     $2,0($17)       # $2 = s1_limb
  51         subq    $18,1,$18       # size--
  52         mulq    $2,$19,$3       # $3 = prod_low
  53         bic     $31,$31,$4      # clear cy_limb
  54         umulh   $2,$19,$0       # $0 = prod_high
  55         beq     $18,Lend1       # jump if size was == 1
  56         ldq     $2,8($17)       # $2 = s1_limb
  57         subq    $18,1,$18       # size--
  58         stq     $3,0($16)
  59         beq     $18,Lend2       # jump if size was == 2
  60
  61         .align  3
  62 Loop:   mulq    $2,$19,$3       # $3 = prod_low
  63         addq    $4,$0,$0        # cy_limb = cy_limb + 'cy'
  64         subq    $18,1,$18       # size--
  65         umulh   $2,$19,$4       # $4 = cy_limb
  66         ldq     $2,16($17)      # $2 = s1_limb
  67         addq    $17,8,$17       # s1_ptr++
  68         addq    $3,$0,$3        # $3 = cy_limb + prod_low
  69         stq     $3,8($16)
  70         cmpult  $3,$0,$0        # $0 = carry from (cy_limb + prod_low)
  71         addq    $16,8,$16       # res_ptr++
  72         bne     $18,Loop
  73
  74 Lend2:  mulq    $2,$19,$3       # $3 = prod_low
  75         addq    $4,$0,$0        # cy_limb = cy_limb + 'cy'
  76         umulh   $2,$19,$4       # $4 = cy_limb
  77         addq    $3,$0,$3        # $3 = cy_limb + prod_low
  78         cmpult  $3,$0,$0        # $0 = carry from (cy_limb + prod_low)
  79         stq     $3,8($16)
  80         addq    $4,$0,$0        # cy_limb = prod_high + cy
  81         ret     $31,($26),1
  82 Lend1:  stq     $3,0($16)
  83         ret     $31,($26),1
  84
  85         .end    __mpn_mul_1