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     };
  16
  17
  18     struct ReturnException
  19     {
  20     };
  21
  22     void op_return(CpuState *state)
  23     {
  24         throw ReturnException();
  25     }
  26
  27     void op_add(CpuState *state)
  28     {
  29         uint8_t reg = *state->pc++;
  30         uint8_t dest = reg>>4, src = reg & 0xf;
  31
  32         int32_t v = state->regs[dest];
  33         v += state->regs[src];
  34
  35         state->zero_flag = (v == 0);
  36         state->negative_flag = (v < 0);
  37         state->regs[dest] = v;
  38
  39     }
  40
  41     void op_sub(CpuState *state)
  42     {
  43         uint8_t reg = *state->pc++;
  44         uint8_t dest = reg>>4, src = reg & 0xf;
  45
  46         int32_t v = state->regs[dest];
  47         v -= state->regs[src];
  48
  49         state->zero_flag = (v == 0);
  50         state->negative_flag = (v < 0);
  51         state->regs[dest] = v;
  52     }
  53
  54     void op_mov(CpuState *state)
  55     {
  56         uint8_t reg = *state->pc++;
  57         uint8_t dest = reg>>4, src = reg & 0xf;
  58
  59         state->regs[dest] = state->regs[src];
  60
  61     }
  62
  63     void op_movi(CpuState *state)
  64     {
  65         uint8_t reg = *state->pc++;
  66         uint8_t dest = reg>>4;
  67
  68         int32_t imm = *(int32_t *)state->pc;
  69         state->pc += 4;
  70
  71         state->regs[dest] = imm;
  72
  73     }
  74
  75     void op_b(CpuState *state)
  76     {
  77         int8_t rel = *state->pc++;
  78         state->pc += rel;
  79     }
  80
  81     void op_bnz(CpuState *state)
  82     {
  83         int8_t rel = *state->pc++;
  84         if(!state->zero_flag)
  85         {
  86             state->pc += rel;
  87         }
  88     }
  89
  90     void (*dispatch_table[])(CpuState *) =
  91     {
  92         op_return,
  93         op_add,
  94         op_sub,
  95         op_mov,
  96         op_movi,
  97         op_b,
  98         op_bnz
  99     };
 100
 101     std::pair<int32_t, uint32_t> interpreter_run(uint8_t *program, int32_t param)
 102     {
 103         CpuState local_state;
 104         CpuState *state = &local_state;
 105         state->pc = program;
 106         state->regs[X0] = param;
 107         state->cycle_count = 0;
 108         try
 109         {
 110             while(true)
 111             {
 112                 uint8_t opcode = *state->pc++;
 113                 state->cycle_count += cycle_table[opcode];
 114                 dispatch_table[opcode](state);
 115
 116
 117             }
 118
 119
 120         } catch(ReturnException ex)
 121         {
 122             return std::make_pair(state->regs[X0], state->cycle_count);
 123         }
 124
 125     }
 126
 127
 128 }