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