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