sdcc/device/lib/z80/mulchar.s

   1 ;--------------------------------------------------------------------------
   2 ;  mulchar.s
   3 ;
   4 ;  Copyright (c) 2017-2021, Philipp Klaus Krause
   5 ;
   6 ;  This library is free software; you can redistribute it and/or modify it
   7 ;  under the terms of the GNU General Public License as published by the
   8 ;  Free Software Foundation; either version 2, or (at your option) any
   9 ;  later version.
  10 ;
  11 ;  This library is distributed in the hope that it will be useful,
  12 ;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 ;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 ;  GNU General Public License for more details.
  15 ;
  16 ;  You should have received a copy of the GNU General Public License
  17 ;  along with this library; see the file COPYING. If not, write to the
  18 ;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  19 ;   MA 02110-1301, USA.
  20 ;
  21 ;  As a special exception, if you link this library with other files,
  22 ;  some of which are compiled with SDCC, to produce an executable,
  23 ;  this library does not by itself cause the resulting executable to
  24 ;  be covered by the GNU General Public License. This exception does
  25 ;  not however invalidate any other reasons why the executable file
  26 ;   might be covered by the GNU General Public License.
  27 ;--------------------------------------------------------------------------
  28
  29         .module mulchar
  30         .optsdcc -mz80 sdcccall(1)
  31
  32 .area   _CODE
  33
  34 ; unsigned char x unsigned char multiplication is done by code generation.
  35
  36 .globl  __mulsuchar
  37 .globl  __muluschar
  38 .globl  __mulschar
  39
  40 ; operands have different sign
  41
  42 __muluschar:
  43         ld      e, a
  44         ld      c, l
  45         ld      b, #0
  46
  47         jr      signexte
  48
  49 __mulsuchar:
  50         ld      c, a
  51         ld      b, #0
  52         ld      e, l
  53
  54         jr      signexte
  55
  56 __mulschar:
  57         ld      e, l
  58         ld      c, a
  59
  60         ;; Need to sign extend before going in.
  61         rla
  62         sbc     a, a
  63         ld      b, a
  64 signexte:
  65         ld      a, e
  66         rla
  67         sbc     a, a
  68         ld      d, a
  69
  70         jp      __mul16
  71