vm.c

#include <stdio.h>
#include <assert.h>
#include <stdint.h>

int imTop = 0;
int16_t im[32768], m[65536];

#define BIT(i) (0x0001<<(i))
#define debug(...) printf(__VA_ARGS__)
// #define debug(...) 

int run(uint16_t *im, int16_t *m) {
  int16_t D = 0, A = 0, PC = 0;
  uint16_t I = 0;
  uint16_t a, c, d, j;
  while (1) {
    int16_t aluOut = 0, AM = 0;
    if (PC >= imTop) { 
      debug("exit program !\n");
      break;
    }
    I = im[PC];
    debug("PC=%04X I=%04X", PC, I);
    PC ++;
    if ((I & 0x8000) == 0) { // A 指令
      A = I;
    } else { // C 指令
      a = (I & 0x1000) >> 12;
      c = (I & 0x0FC0) >>  6;
      d = (I & 0x0038) >>  3;
      j = (I & 0x0007) >>  0;

      AM = (a == 0) ? A : m[A];
      switch (c) { // 處理 c1..6, 計算 aluOut
        case 0x2A: aluOut = 0;      break; // "0",   "101010"
        case 0x3F: aluOut = 1;      break; // "1",   "111111"
        case 0x3A: aluOut = -1;     break; // "-1",  "111010"
        case 0x0C: aluOut = D;      break; // "D",   "001100"
        case 0x30: aluOut = AM;     break; // "AM",  "110000"
        case 0x0D: aluOut = D ^ 0xFFFF; break; // "!D",  "001101"
        case 0x31: aluOut = AM ^ 0xFFFF; break; // "!AM", "110001"
        case 0x0F: aluOut = -D;     break; // "-D",  "001111"
        case 0x33: aluOut = -AM;    break; // "-AM", "110011"
        case 0x1F: aluOut = D + 1;  break; // "D+1", "011111"
        case 0x37: aluOut = AM + 1; break; // "AM+1","110111"
        case 0x0E: aluOut = D - 1;  break; // "D-1", "001110"
        case 0x32: aluOut = AM - 1; break; // "AM-1","110010"
        case 0x02: aluOut = D + AM; break; // "D+AM","000010"
        case 0x13: aluOut = D - AM; break; // "D-AM","010011"
        case 0x07: aluOut = AM - D; break; // "AM-D","000111"
        case 0x00: aluOut = D & AM; break; // "D&AM","000000"
        case 0x15: aluOut = D | AM; break; // "D|AM","010101"
        default: assert(0);
      }
      if (d & BIT(2)) A = aluOut;
      if (d & BIT(1)) D = aluOut;
      if (d & BIT(0)) m[A] = aluOut;
      switch (j) {
        case 0x0: break;                          // 
        case 0x1: if (aluOut >  0) PC = A; break; // JGT
        case 0x2: if (aluOut == 0) PC = A; break; // JEQ
        case 0x3: if (aluOut >= 0) PC = A; break; // JGE
        case 0x4: if (aluOut <  0) PC = A; break; // JLT
        case 0x5: if (aluOut != 0) PC = A; break; // JNE
        case 0x6: if (aluOut <= 0) PC = A; break; // JLE
        case 0x7: PC = A; break;                  // JMP
      }
    }
    debug(" A=%04X D=%04X m[A]=%04X", A, D, m[A]);
    if ((I & 0x8000) != 0) debug(" a=%X c=%02X d=%X j=%X", a, c, d, j);
    debug("\n");
  }
}

// run: ./vm <file.bin>
int main(int argc, char *argv[]) {
  char *binFileName = argv[1];
  FILE *binFile = fopen(binFileName, "rb");
  imTop = fread(im, sizeof(uint16_t), 32768, binFile);
  fclose(binFile);
  run(im, m);
}