vm.c

   1 #include <stdio.h>
   2 #include <assert.h>
   3 #include "heap.h"
   4 #include "code.h"
   5 #include "vm.h"
   6
   7 #define STACK_SIZE 4096
   8
   9 static int top = -1;
  10 static int stack[STACK_SIZE];
  11
  12 static int pc = 0;              /* program counter */
  13
  14 static void
  15 bin_arith_op(char op)
  16 {
  17   assert(top >= 1);
  18   switch(op) {
  19   case '+':
  20     stack[top-1] = stack[top-1] + stack[top];
  21     break;
  22   case '-':
  23     stack[top-1] = stack[top-1] - stack[top];
  24     break;
  25   case '*':
  26     stack[top-1] = stack[top-1] * stack[top];
  27     break;
  28   case '/':
  29     stack[top-1] = stack[top-1] / stack[top];
  30     break;
  31   case '%':
  32     stack[top-1] = stack[top-1] % stack[top];
  33     break;
  34   default:
  35     fprintf(stderr, "Operacao %c nao reconhecida\n", op);
  36     break;
  37   }
  38   --top;
  39   pc++;
  40 }
  41
  42 void
  43 vm_halt(int arg)
  44 {
  45 }
  46
  47 void
  48 vm_add(int arg)
  49 {
  50   bin_arith_op('+');
  51 }
  52
  53 void
  54 vm_sub(int arg)
  55 {
  56   bin_arith_op('-');
  57 }
  58
  59 void
  60 vm_mul(int arg)
  61 {
  62   bin_arith_op('*');
  63 }
  64
  65 void
  66 vm_div(int arg)
  67 {
  68   bin_arith_op('/');
  69 }
  70
  71 void
  72 vm_mod(int arg)
  73 {
  74   bin_arith_op('%');
  75 }
  76
  77 void
  78 vm_load_var(int arg)
  79 {
  80   stack[++top] = data_get(arg);
  81   pc++;
  82 }
  83
  84 void
  85 vm_load_int(int arg)
  86 {
  87   stack[++top] = arg;
  88   pc++;
  89 }
  90
  91 void
  92 vm_store(int arg)
  93 {
  94   assert(top >= 0);
  95   data_put(arg, stack[top]);
  96   top--;
  97   pc++;
  98 }
  99
 100 void
 101 vm_jmp_false(int arg)
 102 {
 103   if (stack[top] == 0)
 104     pc = arg;
 105   else
 106     pc++;
 107 }
 108
 109 void
 110 vm_goto(int arg)
 111 {
 112   pc = arg;
 113 }
 114
 115 void
 116 vm_write_int(int arg)
 117 {
 118   printf("%d\n", stack[top]);
 119   top--;
 120   pc++;
 121 }
 122
 123 void
 124 vm_call(int arg)
 125 {
 126   pc++;
 127 }
 128
 129 int
 130 vm_loop(void)
 131 {
 132   while (code[pc].op != HALT) {
 133     ops[code[pc].op].op(code[pc].arg);
 134   }
 135
 136   return 0;
 137 }