bsv.c

   1 #include <stdio.h>
   2 #include "fakeasm.h"
   3 typedef unsigned char u8;
   4
   5 u8 notes[16]; //MEM
   6 u8 i0, i1, i2; //MEM
   7 u8 n; //MEM
   8 u8 sample; //MEM
   9 u8 tmp_1; //MEM
  10 u8 acc; //ACC
  11
  12 u8 mod3hi, mod3lo; //MEM
  13 //todo: can mod3hi be aliased to tmp_1?
  14 void mod3(void) {
  15         MOV     (acc,mod3hi)
  16         ADD     (mod3lo,acc) // mod3lo = hi+lo
  17         CLEAR   (acc)
  18         ADDC0   (acc) // mod3hi, 1bit
  19         SWAP    (acc)
  20         MOV     (mod3hi, acc)
  21
  22         MOV     (acc, mod3lo)
  23         SWAP    (acc)
  24         AND     (acc, 0xf) // (mod3lo>>4)
  25         XCH     (mod3lo) // acc=mod3lo, mod3lo=mod3lo>>4
  26         AND     (acc, 0xF) // acc=mod3lo&0xf, mod3lo=mod3lo>>4
  27         ADD     (acc, mod3lo) // (mod3lo & 0xF)
  28         ADD     (acc, mod3hi)
  29         MOV     (mod3lo, acc)
  30
  31         AND     (acc, 0x3) // acc = (mod3lo & 0x3)
  32         SR      (mod3lo)
  33         SR      (mod3lo) // (mod3lo >>  2)
  34         ADD     (acc, mod3lo)
  35         MOV     (mod3lo, acc)
  36
  37         AND     (acc, 0x3) // acc = (mod3lo & 0x3)
  38         SR      (mod3lo)
  39         SR      (mod3lo) // (mod3lo >>  2)
  40         ADD     (acc, mod3lo)
  41
  42         SUB     (acc,3)
  43         /*T0SN  FLAG.C (0x00.1)*/       if (flag_c){ // skip if carry clear
  44         ADD (acc,3)                     }
  45         RET
  46 }
  47
  48 void g(void){
  49         // notes_ix_hi = always 0
  50         u8 notes_ix;//lo
  51         AND     (acc, 0x7)
  52         MOV     (notes_ix, acc)
  53         // test i2 & 3:
  54         MOV     (acc, i2)
  55         AND     (acc, 3)
  56         /*T0SN  FLAG.Z (0x00.0)*/       if(3&i2) {// skip if !(3&i0)
  57         SET1    (notes_ix, 3)           } // ix += 8 <=> ix |= 8
  58         IDXM    (acc, notes+notes_ix)
  59
  60         //unrolled: https://git.gir.st/Chiptunes.git/blob/f8e0502:/foo.S#l113
  61         u8 a2 = 0; // can probably be overloaded onto mul3lo/hi
  62         u8 a1 = 0; // -"-
  63         u8 t  = acc; // note input (as returned by idxm)
  64         for (u8 loop = 0; loop < 8; loop++) {
  65                 SR      (t)
  66                 /*T1SN  FLAG.C (0x00.1)*/       if (!flag_c) // skip if carry set
  67                 goto skip;
  68                 MOV     (acc, i0)
  69                 ADD     (a1, acc)
  70                 MOV     (acc, i1)
  71                 ADDC    (a2, acc)
  72         skip:   SR      (a2)
  73                 SRC     (a1)
  74         }
  75         MOV     (acc, a1)
  76         RET
  77 }
  78 void main(void){
  79         CLEAR   (i0)
  80         CLEAR   (i1)
  81         CLEAR   (i2)
  82
  83         //rom is not mmapped; must load into ram first
  84         MOV     (acc, 0x84)
  85         MOV     (notes[0x0], acc)
  86         MOV     (notes[0x5], acc)
  87         MOV     (acc, 0x9d)
  88         MOV     (notes[0x1], acc)
  89         MOV     (notes[0x4], acc)
  90         MOV     (acc, 0xb0)
  91         MOV     (notes[0x2], acc)
  92         MOV     (notes[0xA], acc)
  93         MOV     (acc, 0x69)
  94         MOV     (notes[0x3], acc)
  95         MOV     (notes[0x6], acc)
  96         MOV     (notes[0xB], acc)
  97         MOV     (notes[0xE], acc)
  98         MOV     (acc, 0x58)
  99         MOV     (notes[0x7], acc)
 100         MOV     (notes[0xF], acc)
 101         MOV     (acc, 0x75)
 102         MOV     (notes[0x8], acc)
 103         MOV     (notes[0xD], acc)
 104         MOV     (acc, 0x8c)
 105         MOV     (notes[0x9], acc)
 106         MOV     (notes[0xC], acc)
 107
 108         for(;;) {
 109                 MOV     (acc, i2)// "mov mem,mem"
 110                 MOV     (n, acc)// does not exist
 111                 SL      (n)
 112                 SL      (n)
 113                 MOV     (acc, i1)
 114                 SWAP    (acc)
 115                 AND     (acc, 0xf)
 116                 SR      (acc)
 117                 SR      (acc)
 118                 OR      (n, acc)
 119
 120                 MOV     (acc, n)
 121                 CALL    (g)
 122                 SWAP    (acc)
 123                 AND     (acc, 0x1)
 124                 MOV     (sample, acc)
 125
 126                 MOV     (acc, i2)
 127                 SL      (acc)
 128                 SL      (acc)
 129                 SL      (acc)
 130                 MOV     (tmp_1, acc) // fresh tmp_1:
 131                 MOV     (acc, i1)
 132                 SWAP    (acc)
 133                 AND     (acc, 0xf)
 134                 SR      (acc)
 135                 OR      (acc, tmp_1) // tmp_1 done.
 136                 XOR     (acc, n)
 137                 CALL    (g)
 138                 SR      (acc)
 139                 AND     (acc, i2)
 140                 SR      (acc)
 141                 AND     (acc, 3)
 142                 ADD     (sample, acc)
 143
 144                 MOV     (acc, i2)
 145                 MOV     (mod3hi, acc)
 146                 SR      (mod3hi)
 147                 SR      (mod3hi)
 148                 SR      (mod3hi)
 149                 SWAP    (acc)
 150                 AND     (acc, 0xf0)
 151                 SL      (acc)
 152                 MOV     (mod3lo, acc)
 153                 MOV     (acc, i1)
 154                 SR      (acc)
 155                 SR      (acc)
 156                 SR      (acc)
 157                 OR      (mod3lo, acc)
 158                 CALL    (mod3)
 159                 ADD     (acc, n)
 160                 CALL    (g)
 161                 SR      (acc)
 162                 SR      (acc)
 163                 MOV     (tmp_1, acc) // acc saved in tmp_1; fresh acc
 164                 MOV     (acc, i2)
 165                 // shift-divide by six
 166                 // note: i2 is max 0x78; so acc will <= 20. (breaks vor values >=128)
 167                 SR      (acc)
 168                 ADD     (acc, i2)
 169                 SR      (acc)
 170                 SR      (acc)
 171                 ADD     (acc, i2)
 172                 SR      (acc)
 173                 SR      (acc)
 174                 ADD     (acc, i2)
 175                 SR      (acc)
 176                 SR      (acc)
 177                 SR      (acc)
 178                 // end divide by six
 179                 AND     (acc, tmp_1) // acc restored from tmp_1
 180                 AND     (acc, 3)
 181                 ADD     (sample, acc)
 182
 183                 MOV     (acc, i2)
 184                 MOV     (mod3hi, acc)
 185                 SR      (mod3hi)
 186                 SR      (mod3hi)
 187                 SWAP    (acc)
 188                 AND     (acc, 0xf0)
 189                 SL      (acc)
 190                 SL      (acc)
 191                 MOV     (mod3lo, acc)
 192                 MOV     (acc, i1)
 193                 SR      (acc)
 194                 SR      (acc)
 195                 OR      (mod3lo, acc)
 196                 CALL    (mod3)
 197                 SUB     (acc, n)
 198                 SUB     (acc, 8)
 199                 NEG     (acc)
 200                 CALL    (g)
 201                 SR      (acc)
 202                 MOV     (tmp_1, acc) // acc saved in tmp_1; fresh acc
 203                 MOV     (acc, i2)
 204                 // shift-divide by ten
 205                 // note: i2 is max 0x78; so acc will <= 12.
 206                 INC     (i2)
 207                 SR      (acc)
 208                 ADD     (acc, i2)
 209                 SR      (acc)
 210                 SR      (acc)
 211                 SR      (acc)
 212                 ADD     (acc, i2)
 213                 SR      (acc)
 214                 ADD     (acc, i2)
 215                 SWAP    (acc)
 216                 DEC     (i2)
 217                 // end divide by ten
 218                 AND     (acc, tmp_1) // acc restored from tmp_1
 219                 AND     (acc, 3)
 220                 ADD     (sample, acc)
 221
 222                 MOV     (acc, sample)
 223                 SWAP    (acc)
 224                 putchar(acc);
 225
 226                 INC     (i0)
 227                 /*ADDC  i1*/            i1 += !i0;
 228                 /*ADDC  i2*/            i2 += !i1 && !i0;
 229
 230                 if(i2 == 0x78) break;
 231         }
 232 }