marcothms/8086-rs
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fix(interpreter): set flags correctly for inc/dec/neg

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This commit is contained in:
Marco Thomas
2025-07-02 17:15:40 +09:00
parent 4f161f47f6
commit cf3383c23a
1 changed files with 39 additions and 16 deletions
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55
src/interpreter/interpreter.rs
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@@ -358,25 +358,39 @@ impl Interpreter {
/* /*
* INC * INC
*/ */
Mnemonic::INC_Reg(reg) => self Mnemonic::INC_Reg(reg) => {
.computer let cf = self.computer.flags.cf;
.regs let dest = ModRmTarget::Register(reg);
.write(reg, self.computer.regs.read(reg) + 1), let src = ArithmeticOperand::Immediate(ImmediateOperand::Byte(1));
Mnemonic::INC_Mod(target) => { self.computer.add(dest, src)?;
let val = self.computer.read_modrm(target)?; // The CF flag is not affected
self.computer.write_modrm(target, val + 1)? self.computer.flags.cf = cf;
}
Mnemonic::INC_Mod(dest) => {
let cf = self.computer.flags.cf;
let src = ArithmeticOperand::Immediate(ImmediateOperand::Byte(1));
self.computer.add(dest, src)?;
// The CF flag is not affected
self.computer.flags.cf = cf;
} }
/* /*
* DEC * DEC
*/ */
Mnemonic::DEC_Reg(reg) => self Mnemonic::DEC_Reg(reg) => {
.computer let cf = self.computer.flags.cf;
.regs let dest = ModRmTarget::Register(reg);
.write(reg, self.computer.regs.read(reg) - 1), let src = ArithmeticOperand::Immediate(ImmediateOperand::Byte(1));
Mnemonic::DEC_Mod(target) => { self.computer.sub(dest, src)?;
let val = self.computer.read_modrm(target)?; // The CF flag is not affected
self.computer.write_modrm(target, val - 1)? self.computer.flags.cf = cf;
}
Mnemonic::DEC_Mod(dest) => {
let cf = self.computer.flags.cf;
let src = ArithmeticOperand::Immediate(ImmediateOperand::Byte(1));
self.computer.sub(dest, src)?;
// The CF flag is not affected
self.computer.flags.cf = cf;
} }
/* /*
@@ -624,8 +638,17 @@ impl Interpreter {
.write_modrm(target, !self.computer.read_modrm(target)?)?; .write_modrm(target, !self.computer.read_modrm(target)?)?;
} }
Mnemonic::NEG(target) => { Mnemonic::NEG(target) => {
let val = !self.computer.read_modrm(target)?; let lhs = !self.computer.read_modrm(target)?;
self.computer.write_modrm(target, val + 0b1)?; let rhs = ImmediateOperand::Byte(1);
let result = lhs + rhs;
self.computer.flags.cf = result < self.computer.read_modrm(target)?;
self.computer.flags.of =
(lhs.msb() && rhs.msb()) && (result.msb() != lhs.msb());
self.computer.flags.zf = result.zero();
self.computer.flags.sf = result.msb();
self.computer.flags.pf = result.parity();
self.computer.write_modrm(target, result)?;
} }
/* /*