1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
/* Copyright (C) 2023 Aryadev Chavali
* You may distribute and modify this code under the terms of the
* GPLv2 license. You should have received a copy of the GPLv2
* license with this file. If not, please write to:
* aryadev@aryadevchavali.com.
* Created: 2023-10-15
* Author: Aryadev Chavali
* Description: Entrypoint to program
*/
#include <stdio.h>
#include <string.h>
#include "./base.h"
#include "./inst.h"
#define VM_BYTE_REGISTERS 8
#define VM_WORD_REGISTERS 8
#define VM_FLOAT_REGISTERS 8
typedef struct
{
struct Registers
{
word ret;
byte b[VM_BYTE_REGISTERS];
word w[VM_WORD_REGISTERS];
f64 f[VM_FLOAT_REGISTERS];
} registers;
struct Stack
{
byte *data;
word ptr, max;
} stack;
struct Program
{
inst_t *instructions;
word ptr, max;
} program;
} vm_t;
void vm_load_program(vm_t *vm, inst_t *instructions, size_t size)
{
vm->program.instructions = instructions;
vm->program.max = size;
vm->program.ptr = 0;
}
void vm_load_stack(vm_t *vm, byte *bytes, size_t size)
{
vm->stack.data = bytes;
vm->stack.max = size;
vm->stack.ptr = 0;
}
void vm_push_byte(vm_t *vm, data_t b)
{
if (vm->stack.ptr >= vm->stack.max)
// TODO: Error STACK_OVERFLOW
return;
vm->stack.data[vm->stack.ptr++] = b.as_byte;
}
void vm_push_word(vm_t *vm, data_t w)
{
if (vm->stack.ptr + WORD_SIZE >= vm->stack.max)
// TODO: Error STACK_OVERFLOW
return;
// By default store in big endian
for (size_t i = 64; i > 0; i -= 8)
{
const word mask = ((word)0b11111111) << (i - 8);
byte b = (w.as_word & mask) >> (i - 8);
vm_push_byte(vm, DBYTE(b));
}
}
void vm_push_float(vm_t *vm, data_t f)
{
if (vm->stack.ptr + FLOAT_SIZE >= vm->stack.max)
// TODO: Error STACK_OVERFLOW
return;
// TODO: Make this machine independent (encode IEEE754 floats
// yourself?)
memcpy(vm->stack.data + vm->stack.ptr, &f.as_float, FLOAT_SIZE);
vm->stack.ptr += FLOAT_SIZE;
}
void vm_mov_byte(vm_t *vm, data_t b, word reg)
{
if (reg >= VM_BYTE_REGISTERS)
// TODO: Error (reg is not a valid byte register)
return;
vm->registers.b[reg] = b.as_byte;
}
void vm_mov_word(vm_t *vm, data_t w, word reg)
{
if (reg >= VM_WORD_REGISTERS)
// TODO: Error (reg is not a valid byte register)
return;
vm->registers.w[reg] = w.as_word;
}
void vm_mov_float(vm_t *vm, data_t f, word reg)
{
if (reg >= VM_FLOAT_REGISTERS)
// TODO: Error (reg is not a valid byte register)
return;
vm->registers.f[reg] = f.as_float;
}
data_t vm_pop_byte(vm_t *vm)
{
if (vm->stack.ptr == 0)
// TODO: Error STACK_UNDERFLOW
return DBYTE(0);
return DBYTE(vm->stack.data[--vm->stack.ptr]);
}
data_t vm_pop_word(vm_t *vm)
{
if (vm->stack.ptr < WORD_SIZE)
// TODO: Error STACK_UNDERFLOW
return DWORD(0);
word w = 0;
for (size_t i = 0; i < WORD_SIZE; ++i)
{
data_t b = vm_pop_byte(vm);
w = w | ((word)(b.as_byte) << (i * 8));
}
return DWORD(w);
}
data_t vm_pop_float(vm_t *vm)
{
if (vm->stack.ptr < FLOAT_SIZE)
// TODO: Error STACK_UNDERFLOW
return DFLOAT(0);
f64 f = 0;
// TODO: Make this machine independent (encode IEEE754 floats
// yourself?)
memcpy(&f, vm->stack.data + vm->stack.ptr - FLOAT_SIZE, FLOAT_SIZE);
vm->stack.ptr -= FLOAT_SIZE;
return DFLOAT(f);
}
typedef void (*push_f)(vm_t *, data_t);
static const push_f PUSH_ROUTINES[] = {
[OP_PUSH_BYTE] = vm_push_byte,
[OP_PUSH_WORD] = vm_push_word,
[OP_PUSH_FLOAT] = vm_push_float,
};
typedef void (*mov_f)(vm_t *, data_t, word);
static const mov_f MOV_ROUTINES[] = {
[OP_MOV_BYTE] = vm_mov_byte,
[OP_MOV_WORD] = vm_mov_word,
[OP_MOV_FLOAT] = vm_mov_float,
};
typedef data_t (*pop_f)(vm_t *);
static const pop_f POP_ROUTINES[] = {
[OP_POP_BYTE] = vm_pop_byte,
[OP_POP_WORD] = vm_pop_word,
[OP_POP_FLOAT] = vm_pop_float,
};
void vm_execute(vm_t *vm)
{
struct Program *prog = &vm->program;
if (prog->ptr >= prog->max)
// TODO: Error (Went past end of program)
return;
inst_t instruction = prog->instructions[prog->ptr];
if (OPCODE_IS_PUSH(instruction.opcode))
{
PUSH_ROUTINES[instruction.opcode](vm, instruction.operand);
vm->registers.ret = instruction.operand.as_word;
prog->ptr++;
}
else if (OPCODE_IS_MOV(instruction.opcode))
{
MOV_ROUTINES[instruction.opcode](vm, instruction.operand, instruction.reg);
vm->registers.ret = instruction.operand.as_word;
prog->ptr++;
}
else if (OPCODE_IS_POP(instruction.opcode))
{
// NOTE: We use the `ret` register for the result of this pop
data_t d = POP_ROUTINES[instruction.opcode](vm);
vm->registers.ret = d.as_word;
prog->ptr++;
}
else
{
// TODO: Error (Unknown opcode)
return;
}
}
#define ARR_SIZE(xs) (sizeof(xs) / sizeof(xs[0]))
int main(void)
{
byte stack_data[256];
vm_t vm = {0};
vm_load_stack(&vm, stack_data, ARR_SIZE(stack_data));
return 0;
}
|
