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Annotation of OpenXM_contrib/gmp/mpn/alpha/mul_1.s, Revision 1.1.1.1

1.1       maekawa     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 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., 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