bsv.c

   1 #include <stdio.h>
   2 #include "fakeasm.h"
   3 typedef unsigned char u8;
   4
   5 u8 i0, i1, i2; //MEM
   6 u8 n; //MEM
   7 u8 sample; //MEM
   8 u8 tmp_1; //MEM
   9 u8 acc; //ACC
  10
  11 u8 notes[] = {
  12         0x84, 0x9d, 0xb0, 0x69, 0x9d, 0x84, 0x69, 0x58,
  13         0x75, 0x8c, 0xb0, 0x69, 0x8c, 0x75, 0x69, 0x58
  14 };
  15
  16 u8 mod3hi, mod3lo; //MEM
  17 //todo: can mod3hi be aliased to tmp_1?
  18 void mod3(void) {
  19         MOV     (acc,mod3hi)
  20         ADD     (mod3lo,acc) // mod3lo = hi+lo
  21         CLEAR   (acc)
  22         ADDC0   (acc) // mod3hi, 1bit
  23         SWAP    (acc)
  24         MOV     (mod3hi, acc)
  25
  26         MOV     (acc, mod3lo)
  27         SWAP    (acc)
  28         AND     (acc, 0xf) // (mod3lo>>4)
  29         XCH     (mod3lo) // acc=mod3lo, mod3lo=mod3lo>>4
  30         AND     (acc, 0xF) // acc=mod3lo&0xf, mod3lo=mod3lo>>4
  31         ADD     (acc, mod3lo) // (mod3lo & 0xF)
  32         ADD     (acc, mod3hi)
  33         MOV     (mod3lo, acc)
  34
  35         AND     (acc, 0x3) // acc = (mod3lo & 0x3)
  36         SR      (mod3lo)
  37         SR      (mod3lo) // (mod3lo >>  2)
  38         ADD     (acc, mod3lo)
  39         MOV     (mod3lo, acc)
  40
  41         AND     (acc, 0x3) // acc = (mod3lo & 0x3)
  42         SR      (mod3lo)
  43         SR      (mod3lo) // (mod3lo >>  2)
  44         ADD     (acc, mod3lo)
  45
  46         if (acc > 2) { // TODO: acc in [0,1,2,3,4]
  47         SUB     (acc,3)
  48         }
  49 }
  50
  51 void g(void){
  52         u8 notes_ix = acc & 0x7;
  53         if(3&i2)
  54                 notes_ix += 8;
  55         u8 result = ((i1<<8|i0)*notes[notes_ix])>>8;  // keep hi byte
  56         acc = result;
  57 }
  58 void main(void){
  59         CLEAR   (i0)
  60         CLEAR   (i1)
  61         CLEAR   (i2)
  62         for(;;) {
  63                 MOV     (acc, i2)// "mov mem,mem"
  64                 MOV     (n, acc)// does not exist
  65                 SL      (n)
  66                 SL      (n)
  67                 MOV     (acc, i1)
  68                 SWAP    (acc)
  69                 AND     (acc, 0xf)
  70                 SR      (acc)
  71                 SR      (acc)
  72                 OR      (n, acc)
  73
  74                 MOV     (acc, n)
  75                 CALL    (g)
  76                 SWAP    (acc)
  77                 AND     (acc, 0x1)
  78                 MOV     (sample, acc)
  79
  80                 MOV     (acc, i2)
  81                 SL      (acc)
  82                 SL      (acc)
  83                 SL      (acc)
  84                 MOV     (tmp_1, acc) // fresh tmp_1:
  85                 MOV     (acc, i1)
  86                 SWAP    (acc)
  87                 AND     (acc, 0xf)
  88                 SR      (acc)
  89                 OR      (acc, tmp_1) // tmp_1 done.
  90                 XOR     (acc, n)
  91                 CALL    (g)
  92                 SR      (acc)
  93                 AND     (acc, i2)
  94                 SR      (acc)
  95                 AND     (acc, 3)
  96                 ADD     (sample, acc)
  97
  98                 mod3hi = i2>>3;
  99                 mod3lo = i2<<5|i1>>3;
 100                 CALL    (mod3)
 101                 ADD     (acc, n)
 102                 CALL    (g)
 103                 SR      (acc)
 104                 SR      (acc)
 105                 MOV     (tmp_1, acc) // acc saved in tmp_1; fresh acc
 106                 MOV     (acc, i2)
 107                 // shift-divide by six
 108                 // note: i2 is max 0x78; so acc will <= 20. (breaks vor values >=128)
 109                 SR      (acc)
 110                 ADD     (acc, i2)
 111                 SR      (acc)
 112                 SR      (acc)
 113                 ADD     (acc, i2)
 114                 SR      (acc)
 115                 SR      (acc)
 116                 ADD     (acc, i2)
 117                 SR      (acc)
 118                 SR      (acc)
 119                 SR      (acc)
 120                 // end divide by six
 121                 AND     (acc, tmp_1) // acc restored from tmp_1
 122                 AND     (acc, 3)
 123                 ADD     (sample, acc)
 124
 125                 mod3hi = i2>>2;
 126                 mod3lo = i2<<6|i1>>2;
 127                 CALL    (mod3)
 128                 SUB     (acc, n)
 129                 SUB     (acc, 8)
 130                 NEG     (acc)
 131                 CALL    (g)
 132                 SR      (acc)
 133                 MOV     (tmp_1, acc) // acc saved in tmp_1; fresh acc
 134                 MOV     (acc, i2)
 135                 // shift-divide by ten
 136                 // note: i2 is max 0x78; so acc will <= 12.
 137                 INC     (i2)
 138                 SR      (acc)
 139                 ADD     (acc, i2)
 140                 SR      (acc)
 141                 SR      (acc)
 142                 SR      (acc)
 143                 ADD     (acc, i2)
 144                 SR      (acc)
 145                 ADD     (acc, i2)
 146                 SWAP    (acc)
 147                 DEC     (i2)
 148                 // end divide by ten
 149                 AND     (acc, tmp_1) // acc restored from tmp_1
 150                 AND     (acc, 3)
 151                 ADD     (sample, acc)
 152
 153                 MOV     (acc, sample)
 154                 SWAP    (acc)
 155                 putchar(acc);
 156
 157                 INC     (i0)
 158                 i1 += !i0; // ADDC i1
 159                 i2 += !i1 && !i0; // ADDC i2
 160
 161                 if(i2 == 0x78) break;
 162         }
 163 }