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         u8 result = ((i1<<8|i0)*acc)>>8;  // keep hi byte
  59         //^TODO! https://git.gir.st/Chiptunes.git/blob/d397f89:/foo.c#l83
  60         //final: 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                 if (flag_c) {
  67                         /*(2) ADDC a2, i1*/     a2 += i1 + ((a1+i0)>>8);
  68                         /*(1) ADD  a1, i0*/     a1 += i0;
  69                 }
  70                 /*(2) ROR a1*/  a1>>= 1;a1 |= a2<<7;
  71                 /*(1) LSR a2*/  a2>>= 1;
  72         }
  73         acc = a1;
  74 }
  75 void main(void){
  76         CLEAR   (i0)
  77         CLEAR   (i1)
  78         CLEAR   (i2)
  79
  80         //rom is not mmapped; must load into ram first
  81         MOV     (acc, 0x84)
  82         MOV     (notes[0x0], acc)
  83         MOV     (notes[0x5], acc)
  84         MOV     (acc, 0x9d)
  85         MOV     (notes[0x1], acc)
  86         MOV     (notes[0x4], acc)
  87         MOV     (acc, 0xb0)
  88         MOV     (notes[0x2], acc)
  89         MOV     (notes[0xA], acc)
  90         MOV     (acc, 0x69)
  91         MOV     (notes[0x3], acc)
  92         MOV     (notes[0x6], acc)
  93         MOV     (notes[0xB], acc)
  94         MOV     (notes[0xE], acc)
  95         MOV     (acc, 0x58)
  96         MOV     (notes[0x7], acc)
  97         MOV     (notes[0xF], acc)
  98         MOV     (acc, 0x75)
  99         MOV     (notes[0x8], acc)
 100         MOV     (notes[0xD], acc)
 101         MOV     (acc, 0x8c)
 102         MOV     (notes[0x9], acc)
 103         MOV     (notes[0xC], acc)
 104
 105         for(;;) {
 106                 MOV     (acc, i2)// "mov mem,mem"
 107                 MOV     (n, acc)// does not exist
 108                 SL      (n)
 109                 SL      (n)
 110                 MOV     (acc, i1)
 111                 SWAP    (acc)
 112                 AND     (acc, 0xf)
 113                 SR      (acc)
 114                 SR      (acc)
 115                 OR      (n, acc)
 116
 117                 MOV     (acc, n)
 118                 CALL    (g)
 119                 SWAP    (acc)
 120                 AND     (acc, 0x1)
 121                 MOV     (sample, acc)
 122
 123                 MOV     (acc, i2)
 124                 SL      (acc)
 125                 SL      (acc)
 126                 SL      (acc)
 127                 MOV     (tmp_1, acc) // fresh tmp_1:
 128                 MOV     (acc, i1)
 129                 SWAP    (acc)
 130                 AND     (acc, 0xf)
 131                 SR      (acc)
 132                 OR      (acc, tmp_1) // tmp_1 done.
 133                 XOR     (acc, n)
 134                 CALL    (g)
 135                 SR      (acc)
 136                 AND     (acc, i2)
 137                 SR      (acc)
 138                 AND     (acc, 3)
 139                 ADD     (sample, acc)
 140
 141                 MOV     (acc, i2)
 142                 MOV     (mod3hi, acc)
 143                 SR      (mod3hi)
 144                 SR      (mod3hi)
 145                 SR      (mod3hi)
 146                 SWAP    (acc)
 147                 AND     (acc, 0xf0)
 148                 SL      (acc)
 149                 MOV     (mod3lo, acc)
 150                 MOV     (acc, i1)
 151                 SR      (acc)
 152                 SR      (acc)
 153                 SR      (acc)
 154                 OR      (mod3lo, acc)
 155                 CALL    (mod3)
 156                 ADD     (acc, n)
 157                 CALL    (g)
 158                 SR      (acc)
 159                 SR      (acc)
 160                 MOV     (tmp_1, acc) // acc saved in tmp_1; fresh acc
 161                 MOV     (acc, i2)
 162                 // shift-divide by six
 163                 // note: i2 is max 0x78; so acc will <= 20. (breaks vor values >=128)
 164                 SR      (acc)
 165                 ADD     (acc, i2)
 166                 SR      (acc)
 167                 SR      (acc)
 168                 ADD     (acc, i2)
 169                 SR      (acc)
 170                 SR      (acc)
 171                 ADD     (acc, i2)
 172                 SR      (acc)
 173                 SR      (acc)
 174                 SR      (acc)
 175                 // end divide by six
 176                 AND     (acc, tmp_1) // acc restored from tmp_1
 177                 AND     (acc, 3)
 178                 ADD     (sample, acc)
 179
 180                 MOV     (acc, i2)
 181                 MOV     (mod3hi, acc)
 182                 SR      (mod3hi)
 183                 SR      (mod3hi)
 184                 SWAP    (acc)
 185                 AND     (acc, 0xf0)
 186                 SL      (acc)
 187                 SL      (acc)
 188                 MOV     (mod3lo, acc)
 189                 MOV     (acc, i1)
 190                 SR      (acc)
 191                 SR      (acc)
 192                 OR      (mod3lo, acc)
 193                 CALL    (mod3)
 194                 SUB     (acc, n)
 195                 SUB     (acc, 8)
 196                 NEG     (acc)
 197                 CALL    (g)
 198                 SR      (acc)
 199                 MOV     (tmp_1, acc) // acc saved in tmp_1; fresh acc
 200                 MOV     (acc, i2)
 201                 // shift-divide by ten
 202                 // note: i2 is max 0x78; so acc will <= 12.
 203                 INC     (i2)
 204                 SR      (acc)
 205                 ADD     (acc, i2)
 206                 SR      (acc)
 207                 SR      (acc)
 208                 SR      (acc)
 209                 ADD     (acc, i2)
 210                 SR      (acc)
 211                 ADD     (acc, i2)
 212                 SWAP    (acc)
 213                 DEC     (i2)
 214                 // end divide by ten
 215                 AND     (acc, tmp_1) // acc restored from tmp_1
 216                 AND     (acc, 3)
 217                 ADD     (sample, acc)
 218
 219                 MOV     (acc, sample)
 220                 SWAP    (acc)
 221                 putchar(acc);
 222
 223                 INC     (i0)
 224                 /*ADDC  i1*/            i1 += !i0;
 225                 /*ADDC  i2*/            i2 += !i1 && !i0;
 226
 227                 if(i2 == 0x78) break;
 228         }
 229 }