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gb6
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implement shifts

This commit is contained in:
Matthew Laux 2022-07-25 23:48:22 -05:00
parent bc980ec1e5
commit bbb398f524
1 changed files with 62 additions and 5 deletions
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67
src/cpu.c
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@ -164,11 +164,55 @@ static u8 rrc(struct cpu *cpu, u8 val)
static u8 shift_left(struct cpu *cpu, u8 value)
{
return 0;
int result = value << 1;
if (result == 0) {
set_flag(cpu, FLAG_ZERO);
} else {
clear_flag(cpu, FLAG_ZERO);
}
if (value & 0x80) {
set_flag(cpu, FLAG_CARRY);
} else {
clear_flag(cpu, FLAG_CARRY);
}
clear_flag(cpu, FLAG_SIGN);
clear_flag(cpu, FLAG_HALF_CARRY);
return result;
}
static u8 shift_right(struct cpu *cpu, u8 value)
{
int result = (signed) value >> 1;
if (result == 0) {
set_flag(cpu, FLAG_ZERO);
} else {
clear_flag(cpu, FLAG_ZERO);
}
if (value & 0x1) {
set_flag(cpu, FLAG_CARRY);
} else {
clear_flag(cpu, FLAG_CARRY);
}
clear_flag(cpu, FLAG_SIGN);
clear_flag(cpu, FLAG_HALF_CARRY);
return result;
}
static u8 srl(struct cpu *cpu, u8 value)
{
int result = value >> 1;
if (result == 0) {
set_flag(cpu, FLAG_ZERO);
} else {
clear_flag(cpu, FLAG_ZERO);
}
if (value & 0x1) {
set_flag(cpu, FLAG_CARRY);
} else {
clear_flag(cpu, FLAG_CARRY);
}
clear_flag(cpu, FLAG_SIGN);
clear_flag(cpu, FLAG_HALF_CARRY);
return 0;
}
@ -368,7 +412,7 @@ static void extended_insn(struct cpu *cpu, u8 insn)
shift_left,
shift_right,
swap,
shift_right // TODO SRL
srl,
};
#ifdef GB6_DEBUG
@ -462,6 +506,9 @@ void cpu_step(struct cpu *cpu)
write_bc(cpu, read16(cpu, cpu->pc));
cpu->pc += 2;
break;
case 0x02: // LD (BC), A
write8(cpu, read_bc(cpu), cpu->a);
break;
case 0x0f: // RRCA
cpu->a = rrc(cpu, cpu->a);
break;
@ -516,7 +563,7 @@ void cpu_step(struct cpu *cpu)
case 0x33: cpu->sp++; break;
case 0x34: temp = read8(cpu, read_hl(cpu)); inc_with_carry(cpu, &temp); write8(cpu, read_hl(cpu), temp); break;
case 0x35: temp = read8(cpu, read_hl(cpu)); dec_with_carry(cpu, &temp); write8(cpu, read_hl(cpu), temp); break;
case 0x35: temp = read8(cpu, read_hl(cpu)); dec_with_carry(cpu, &temp); write8(cpu, read_hl(cpu), temp); break;
case 0x3b: cpu->sp--; break;
case 0x3c: inc_with_carry(cpu, &cpu->a); break;
@ -592,8 +639,8 @@ void cpu_step(struct cpu *cpu)
case 0x6d: break; // copy L to L
case 0x6e: cpu->l = read8(cpu, read_hl(cpu)); break;
case 0x6f: cpu->l = cpu->a; break;
// dest = *HL
// dest is *HL
case 0x70: write8(cpu, read_hl(cpu), cpu->b); break;
case 0x71: write8(cpu, read_hl(cpu), cpu->c); break;
case 0x72: write8(cpu, read_hl(cpu), cpu->d); break;
@ -690,6 +737,16 @@ void cpu_step(struct cpu *cpu)
if (!flag_isset(cpu, FLAG_ZERO)) {
push(cpu, cpu->pc);
cpu->pc = temp16;
cpu->cycle_count += instructions[opc].cycles_branch - instructions[opc].cycles;
}
break;
case 0xcc: // CALL Z, u16
temp16 = read16(cpu, cpu->pc);
cpu->pc += 2;
if (flag_isset(cpu, FLAG_ZERO)) {
push(cpu, cpu->pc);
cpu->pc = temp16;
cpu->cycle_count += instructions[opc].cycles_branch - instructions[opc].cycles;
}
break;
case 0xd0: // RET NC