sdcc/device/lib/_divuint.c

   1 /*-------------------------------------------------------------------------
   2    _divuint.c - routine for unsigned int (16 bit) division
   3
   4    Copyright (C) 1999, Jean-Louis Vern <jlvern AT gmail.com>
   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 /*   Assembler-functions are provided for:
  30      mcs51 small
  31      mcs51 small stack-auto
  32 */
  33
  34 #include <stdbool.h>
  35
  36 #include <sdcc-lib.h>
  37
  38 #if !defined(__SDCC_USE_XSTACK) && !defined(_SDCC_NO_ASM_LIB_FUNCS)
  39 #  if defined(__SDCC_mcs51)
  40 #    if defined(__SDCC_MODEL_SMALL)
  41 #      if defined(__SDCC_STACK_AUTO)
  42 #        define _DIVUINT_ASM_SMALL_AUTO
  43 #      else
  44 #        define _DIVUINT_ASM_SMALL
  45 #      endif
  46 #    endif
  47 #  endif
  48 #endif
  49
  50 #if defined _DIVUINT_ASM_SMALL || defined _DIVUINT_ASM_SMALL_AUTO
  51
  52 static void
  53 _divuint_dummy (void) __naked
  54 {
  55         __asm
  56
  57         .globl __divuint
  58
  59 __divuint:
  60
  61         #define count   r2
  62         #define reste_l r3
  63         #define reste_h r4
  64         #define xl      dpl
  65         #define xh      dph
  66
  67 #if defined(__SDCC_PARMS_IN_BANK1)
  68         #define yl      (b1_0)
  69         #define yh      (b1_1)
  70 #else // __SDCC_PARMS_IN_BANK1
  71   #if defined(__SDCC_STACK_AUTO)
  72
  73         .globl __divint
  74
  75         mov     a,sp
  76         add     a,#-2           ; 2 bytes return address
  77         mov     r0,a            ; r0 points to yh
  78         mov     a,@r0           ; load yh
  79         mov     r1,a
  80         dec     r0
  81         mov     a,@r0           ; load yl
  82         mov     r0,a
  83
  84         #define yl      r0
  85         #define yh      r1
  86
  87 __divint:                       ; entry point for __divsint
  88
  89
  90   #else // __SDCC_STACK_AUTO
  91
  92     #if defined(__SDCC_NOOVERLAY)
  93         .area DSEG    (DATA)
  94     #else
  95         .area OSEG    (OVR,DATA)
  96     #endif
  97
  98         .globl __divuint_PARM_2
  99         .globl __divsint_PARM_2
 100
 101 __divuint_PARM_2:
 102 __divsint_PARM_2:
 103         .ds     2
 104
 105         .area CSEG    (CODE)
 106
 107         #define yl      (__divuint_PARM_2)
 108         #define yh      (__divuint_PARM_2 + 1)
 109
 110   #endif // __SDCC_STACK_AUTO
 111 #endif // __SDCC_PARMS_IN_BANK1
 112
 113         mov     count,#16
 114         clr     a
 115         mov     reste_l,a
 116         mov     reste_h,a
 117
 118 loop:
 119         mov     a,xl            ; x <<= 1
 120         add     a,acc
 121         mov     xl,a
 122         mov     a,xh
 123         rlc     a
 124         mov     xh,a
 125
 126         mov     a,reste_l       ; reste <<= 1
 127         rlc     a               ;   feed in carry
 128         mov     reste_l,a
 129         mov     a,reste_h
 130         rlc     a
 131         mov     reste_h,a
 132
 133         mov     a,reste_l       ; reste - y
 134         subb    a,yl            ; here carry is always clear, because
 135                                         ; reste <<= 1 never overflows
 136         mov     b,a
 137         mov     a,reste_h
 138         subb    a,yh
 139
 140         jc      smaller         ; reste >= y?
 141
 142         mov     reste_h,a       ; -> yes;  reste = reste - y;
 143         mov     reste_l,b
 144         orl     xl,#1
 145 smaller:                        ; -> no
 146         djnz    count,loop
 147         ret
 148
 149         __endasm;
 150 }
 151
 152 #else  // defined _DIVUINT_ASM_SMALL || defined _DIVUINT_ASM_SMALL_AUTO
 153
 154 #define MSB_SET(x) ((x >> (8*sizeof(x)-1)) & 1)
 155
 156 unsigned int
 157 _divuint (unsigned int x, unsigned int y) __SDCC_NONBANKED
 158 {
 159   unsigned int reste = 0;
 160   unsigned char count = 16;
 161   bool c;
 162
 163   do
 164   {
 165     // reste: x <- 0;
 166     c = MSB_SET(x);
 167     x <<= 1;
 168     reste <<= 1;
 169     if (c)
 170       reste |= 1;
 171
 172     if (reste >= y)
 173     {
 174       reste -= y;
 175       // x <- (result = 1)
 176       x |= 1;
 177     }
 178   }
 179   while (--count);
 180   return x;
 181 }
 182
 183 #endif  // defined _DIVUINT_ASM_SMALL || defined _DIVUINT_ASM_SMALL_AUTO