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Removed temp var. Fixed PC.

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Changed PC to be 8bits and checking for alignment.
Introduced x/y vars.
This commit is contained in:
Sam Stevens
2018-10-16 22:25:27 +01:00
parent 0359d4e0b2
commit 40a1add41d
4 changed files with 51 additions and 33 deletions
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74
vm.c
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@@ -80,7 +80,12 @@ void vm_step(VM *vm) {
VM_Instruction inst;
memset(&inst, 0, sizeof(VM_Instruction));
uint16_t PC = vm->PC;
uint8_t PC = vm->PC;
if (PC % 2 != 0) {
fprintf(stderr, "Halted. PC not aligned.\n");
vm->halted = true;
return;
}
uint16_t raw = (vm->M[PC] << 8) + vm->M[PC + 1];
vm->PC += 2;
inst.op = (uint8_t) (raw >> 12);
@@ -89,98 +94,107 @@ void vm_step(VM *vm) {
return;
}
uint8_t temp = 0, x = 0, y = 0;
uint8_t x = 0;
uint8_t y = 0;
uint8_t d = 0;
uint16_t temp16 = 0;
switch (inst.op) {
case OP_LDA:
vm_decode_Q(&inst, raw);
vm_put_r(vm, inst.rd, vm->M[inst.imm]);
d = vm->M[inst.imm];
break;
case OP_STA:
vm_decode_Q(&inst, raw);
vm->M[inst.imm] = (uint8_t) vm_get_r(vm, inst.rd);
vm->M[inst.imm] = vm_get_r(vm, inst.rd);
break;
case OP_LDI:
vm_decode_Q(&inst, raw);
vm_put_r(vm, inst.rd, inst.imm);
d = inst.imm;
break;
case OP_ADD:
vm_decode_S(&inst, raw);
vm->carry = 0;
temp = vm_get_r(vm, inst.rx) + vm_get_r(vm, inst.ry);
vm_put_r(vm, inst.rd, temp);
x = vm_get_r(vm, inst.rx);
y = vm_get_r(vm, inst.ry);
d = x + y;
break;
case OP_ADC:
vm_decode_S(&inst, raw);
temp16 = vm_get_r(vm, inst.rx) + vm_get_r(vm, inst.ry) + vm->carry;
x = vm_get_r(vm, inst.rx);
y = vm_get_r(vm, inst.ry);
temp16 = x + y + vm->carry;
vm->carry = (uint8_t) (temp16 >> 8);
vm_put_r(vm, inst.rd, (uint8_t)temp16);
d = (uint8_t) temp16;
break;
case OP_SUB:
vm_decode_S(&inst, raw);
vm->carry = 0;
temp = vm_get_r(vm, inst.rx) - vm_get_r(vm, inst.ry);
vm_put_r(vm, inst.rd, temp);
x = vm_get_r(vm, inst.rx);
y = vm_get_r(vm, inst.ry);
d = x - y;
break;
case OP_SBC:
vm_decode_S(&inst, raw);
x = vm_get_r(vm, inst.rx);
y = vm_get_r(vm, inst.ry);
temp = vm_subtract(x, y, &vm->carry);
vm_put_r(vm, inst.rd, temp);
d = vm_subtract(x, y, &vm->carry);
break;
case OP_NOT:
vm_decode_T(&inst, raw);
temp = vm_get_r(vm, inst.rx);
vm_put_r(vm, inst.rd, ~temp);
d = ~x;
break;
case OP_AND:
vm_decode_S(&inst, raw);
temp = vm_get_r(vm, inst.rx) & vm_get_r(vm, inst.ry);
vm_put_r(vm, inst.rd, temp);
x = vm_get_r(vm, inst.rx);
y = vm_get_r(vm, inst.ry);
d = x & y;
break;
case OP_SHL:
vm_decode_T(&inst, raw);
temp = vm_get_r(vm, inst.rx) << vm_get_r(vm, (uint8_t) inst.imm);
vm_put_r(vm, inst.rd, temp);
x = vm_get_r(vm, inst.rx);
d = x << vm_get_r(vm, inst.imm);
break;
case OP_SHR:
vm_decode_T(&inst, raw);
temp = vm_get_r(vm, inst.rx) >> vm_get_r(vm, (uint8_t) inst.imm);
vm_put_r(vm, inst.rd, temp);
x = vm_get_r(vm, inst.rx);
d = x >> vm_get_r(vm, inst.imm);
break;
case OP_SYS:
vm_decode_Q(&inst, raw);
if (vm->syscall != NULL) {
temp = vm->syscall(vm, inst.imm);
vm_put_r(vm, inst.rd, temp);
d = vm->syscall(vm, inst.imm);
} else {
printf("SYSCALL #%d\n", inst.imm);
}
break;
case OP_JMP:
vm_decode_Q(&inst, raw);
vm->PC = vm->M[inst.rd];
vm->PC = vm_get_r(vm, inst.rd);
break;
case OP_JEQ:
vm_decode_S(&inst, raw);
if (vm_get_r(vm, inst.rx) == vm_get_r(vm, inst.ry)) {
vm->PC = vm->M[inst.rd];
x = vm_get_r(vm, inst.rx);
y = vm_get_r(vm, inst.ry);
if (x == y) {
vm->PC = vm_get_r(vm, inst.rd);
}
break;
case OP_JLT:
vm_decode_S(&inst, raw);
if (vm_get_r(vm, inst.rx) < vm_get_r(vm, inst.ry)) {
vm->PC = vm->M[inst.rd];
x = vm_get_r(vm, inst.rx);
y = vm_get_r(vm, inst.ry);
if (x < y) {
vm->PC = vm_get_r(vm, inst.rd);
}
break;
case OP_HLT:
printf("Halted at 0x%04hX\n", PC);
printf("Halted at 0x%04X\n", PC);
vm->halted = true;
break;
default:
printf("Unknown Instruction at 0x%04hX: 0x%hhX\n", PC, inst.op);
printf("Unknown Instruction at 0x%04X: 0x%hhX\n", PC, inst.op);
vm->halted = true;
break;
}
vm_put_r(vm, inst.rd, d);
}