git.sesse.net Git - interpreter_trials/blob - interpreter2.cpp

   1 #include "bytecode.h"
   2 #include <utility>
   3 #include "interpreter.h"
   4
   5 namespace interpreter2
   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
  19     void op_return(CpuState *state)
  20     {
  21         state->exit = true;
  22     }
  23
  24     void op_add(CpuState *state)
  25     {
  26         uint8_t reg = *state->pc++;
  27         uint8_t dest = reg>>4, src = reg & 0xf;
  28
  29         int32_t v = state->regs[dest];
  30         v += state->regs[src];
  31
  32         state->zero_flag = (v == 0);
  33         state->negative_flag = (v < 0);
  34         state->regs[dest] = v;
  35
  36     }
  37
  38     void op_sub(CpuState *state)
  39     {
  40         uint8_t reg = *state->pc++;
  41         uint8_t dest = reg>>4, src = reg & 0xf;
  42
  43         int32_t v = state->regs[dest];
  44         v -= state->regs[src];
  45
  46         state->zero_flag = (v == 0);
  47         state->negative_flag = (v < 0);
  48         state->regs[dest] = v;
  49     }
  50
  51     void op_mov(CpuState *state)
  52     {
  53         uint8_t reg = *state->pc++;
  54         uint8_t dest = reg>>4, src = reg & 0xf;
  55
  56         state->regs[dest] = state->regs[src];
  57
  58     }
  59
  60     void op_movi(CpuState *state)
  61     {
  62         uint8_t reg = *state->pc++;
  63         uint8_t dest = reg>>4;
  64
  65         int32_t imm = *(int32_t *)state->pc;
  66         state->pc += 4;
  67
  68         state->regs[dest] = imm;
  69
  70     }
  71
  72     void op_b(CpuState *state)
  73     {
  74         int8_t rel = *state->pc++;
  75         state->pc += rel;
  76     }
  77
  78     void op_bnz(CpuState *state)
  79     {
  80         int8_t rel = *state->pc++;
  81         if(!state->zero_flag)
  82         {
  83             state->pc += rel;
  84         }
  85     }
  86
  87     void (*dispatch_table[])(CpuState *) =
  88     {
  89         op_return,
  90         op_add,
  91         op_sub,
  92         op_mov,
  93         op_movi,
  94         op_b,
  95         op_bnz
  96     };
  97
  98     std::pair<int32_t, uint32_t> interpreter_run(uint8_t *program, int32_t param)
  99     {
 100         CpuState local_state;
 101         CpuState *state = &local_state;
 102         state->pc = program;
 103         state->regs[X0] = param;
 104         state->cycle_count = 0;
 105         state->exit = false;
 106         while(!state->exit)
 107         {
 108             uint8_t opcode = *state->pc++;
 109             state->cycle_count += cycle_table[opcode];
 110             dispatch_table[opcode](state);
 111
 112
 113         }
 114         return std::make_pair(state->regs[X0], state->cycle_count);
 115     }
 116
 117
 118 }