git.sesse.net Git - interpreter_trials/blob - interpreter1.cpp

   1 #include "bytecode.h"
   2 #include <utility>
   3 #include "interpreter.h"
   4
   5 namespace interpreter1
   6 {
   7
   8     struct CpuState
   9     {
  10         int32_t regs[16] = {0};
  11         bool zero_flag = false;
  12         bool negative_flag = false;
  13         uint8_t *pc = nullptr;
  14         uint32_t cycle_count = 0;
  15     };
  16
  17     CpuState global_state;
  18
  19     struct ReturnException
  20     {
  21     };
  22
  23     void op_return()
  24     {
  25         throw ReturnException();
  26     }
  27
  28     void op_add()
  29     {
  30         uint8_t reg = *global_state.pc++;
  31         uint8_t dest = reg>>4, src = reg & 0xf;
  32
  33         int32_t v = global_state.regs[dest];
  34         v += global_state.regs[src];
  35
  36         global_state.zero_flag = (v == 0);
  37         global_state.negative_flag = (v < 0);
  38         global_state.regs[dest] = v;
  39
  40     }
  41
  42     void op_sub()
  43     {
  44         uint8_t reg = *global_state.pc++;
  45         uint8_t dest = reg>>4, src = reg & 0xf;
  46
  47         int32_t v = global_state.regs[dest];
  48         v -= global_state.regs[src];
  49
  50         global_state.zero_flag = (v == 0);
  51         global_state.negative_flag = (v < 0);
  52         global_state.regs[dest] = v;
  53     }
  54
  55     void op_mov()
  56     {
  57         uint8_t reg = *global_state.pc++;
  58         uint8_t dest = reg>>4, src = reg & 0xf;
  59
  60         global_state.regs[dest] = global_state.regs[src];
  61
  62     }
  63
  64     void op_movi()
  65     {
  66         uint8_t reg = *global_state.pc++;
  67         uint8_t dest = reg>>4;
  68
  69         int32_t imm = *(int32_t *)global_state.pc;
  70         global_state.pc += 4;
  71
  72         global_state.regs[dest] = imm;
  73
  74     }
  75
  76     void op_b()
  77     {
  78         int8_t rel = *global_state.pc++;
  79         global_state.pc += rel;
  80     }
  81
  82     void op_bnz()
  83     {
  84         int8_t rel = *global_state.pc++;
  85         if(!global_state.zero_flag)
  86         {
  87             global_state.pc += rel;
  88         }
  89     }
  90
  91     void (*dispatch_table[])() =
  92     {
  93         op_return,
  94         op_add,
  95         op_sub,
  96         op_mov,
  97         op_movi,
  98         op_b,
  99         op_bnz
 100     };
 101
 102     std::pair<int32_t, uint32_t> interpreter_run(uint8_t *program, int32_t param)
 103     {
 104         global_state.pc = program;
 105         global_state.regs[X0] = param;
 106         global_state.cycle_count = 0;
 107         try
 108         {
 109             while(true)
 110             {
 111                 uint8_t opcode = *global_state.pc++;
 112                 global_state.cycle_count += cycle_table[opcode];
 113                 dispatch_table[opcode]();
 114
 115
 116             }
 117
 118
 119         } catch(ReturnException ex)
 120         {
 121             return std::make_pair(global_state.regs[X0], global_state.cycle_count);
 122         }
 123
 124     }
 125
 126
 127 }