mdw@git.distorted.org.uk Git - ssr/blob - StraySrc/Libraries/Sapphire/sh/divide

   1 ;
   2 ; divide.sh
   3 ;
   4 ; Various routines of a division-related nature (MDW/TMA)
   5 ;
   6 ; © 1994-1998 Straylight
   7 ;
   8
   9 ;----- Licensing note -------------------------------------------------------
  10 ;
  11 ; This file is part of Straylight's Sapphire library.
  12 ;
  13 ; Sapphire is free software; you can redistribute it and/or modify
  14 ; it under the terms of the GNU General Public License as published by
  15 ; the Free Software Foundation; either version 2, or (at your option)
  16 ; any later version.
  17 ;
  18 ; Sapphire is distributed in the hope that it will be useful,
  19 ; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ; GNU General Public License for more details.
  22 ;
  23 ; You should have received a copy of the GNU General Public License
  24 ; along with Sapphire.  If not, write to the Free Software Foundation,
  25 ; 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  26
  27 ;----- Overview -------------------------------------------------------------
  28 ;
  29 ; Functions provided:
  30 ;
  31 ;  divide
  32 ;  div_unsigned
  33 ;  div10
  34 ;  div_round
  35 ;  div_u64x32
  36
  37                 [       :LNOT::DEF:divide__dfn
  38                 GBLL    divide__dfn
  39
  40 ; --- divide ---
  41 ;
  42 ; On entry:     R0 == dividend
  43 ;               R1 == divisor
  44 ;
  45 ; On exit:      R0 == quotient
  46 ;               R1 == remainder
  47 ;
  48 ; Use:          A standard divide routine.  Fairly speedy, hopefully.
  49 ;               The results are always such that
  50 ;
  51 ;                       |quotient| <= |(divisor/dividend)|,
  52 ;
  53 ;                       |remainder| < |divisor|
  54 ;
  55 ;               and
  56 ;
  57 ;                       quotient * divisor + remainder == dividend
  58
  59                 IMPORT  divide
  60
  61 ; --- div_unsigned ---
  62 ;
  63 ; On entry:     R0 == dividend
  64 ;               R1 == divisor
  65 ;
  66 ; On exit:      R0 == quotient
  67 ;               R1 == remainder
  68 ;
  69 ; Use:          As for divide, except that it considers its operands to be
  70 ;               unsigned.
  71
  72                 IMPORT  div_unsigned
  73
  74 ; --- div10 ---
  75 ;
  76 ; On entry:     R0 == integer to divide
  77 ;
  78 ; On exit:      R0 == quotient after division by 10
  79 ;               R1 == remainder after division by 10
  80 ;
  81 ; Use:          Divides an integer very quickly by 10.
  82 ;
  83 ; [Generated by Straylight divc]
  84
  85                 IMPORT  div10
  86
  87 ; --- div_round ---
  88 ;
  89 ; On entry:     R0 == dividend
  90 ;               R1 == divisor
  91 ;
  92 ; On exit:      R0 == quotient, rounded to nearest integer
  93 ;               R1 == remainder
  94 ;
  95 ; Use:          Calculates a rounded-to-nearest quotient, rather than one
  96 ;               rounded towards zero, which is what divide returns you.
  97 ;
  98 ;               The remainder is fiddled during this process, so that the
  99 ;               properties
 100 ;
 101 ;                       quotient * divisor + remainder == dividend
 102 ;
 103 ;               and
 104 ;
 105 ;                       |remainder| < |divisor|
 106 ;
 107 ;               still hold (so the remainder's sign may well change).
 108
 109                 IMPORT  div_round
 110
 111 ; --- div_u64x32 ---
 112 ;
 113 ; On entry:     R0,R1 == dividend (high word in R1)
 114 ;               R2 == divisor
 115 ;
 116 ; On exit:      R0 == quotient
 117 ;               R1 == remainder
 118 ;
 119 ; Use:          Divides a 64-bit unsigned value by a 32-bit unsigned value
 120 ;               yielding 32-bit unsigned quotient and remainder.  If there
 121 ;               are more than 32 bits of quotient, the return values are
 122 ;               undefined.
 123
 124                 IMPORT  div_u64x32
 125
 126                 ]
 127
 128 ;----- That's all, folks ----------------------------------------------------
 129
 130                 END