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chore(interpreter): correctly sign extend for CBW/CWD intructions

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Marco Thomas
2025-07-02 17:46:15 +09:00
parent 6d60343067
commit 60b5b6bd51
1 changed files with 6 additions and 2 deletions
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8
src/interpreter/interpreter.rs
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@@ -576,15 +576,19 @@ impl Interpreter {
* Sign extensions * Sign extensions
*/ */
Mnemonic::CBW => { Mnemonic::CBW => {
if ImmediateOperand::Byte(self.computer.regs.ax.lower).msb() {
// extend sign bit into AX, i.e. all bits set // extend sign bit into AX, i.e. all bits set
if ImmediateOperand::Byte(self.computer.regs.ax.lower).msb() {
self.computer.regs.ax.upper = 0xff; self.computer.regs.ax.upper = 0xff;
} else {
self.computer.regs.ax.upper = 0x00;
} }
} }
Mnemonic::CWD => { Mnemonic::CWD => {
if ImmediateOperand::Word(self.computer.regs.ax.read()).msb() {
// extend sign bit into DX, i.e. all bits set // extend sign bit into DX, i.e. all bits set
if ImmediateOperand::Word(self.computer.regs.ax.read()).msb() {
self.computer.regs.dx.write(0xffff); self.computer.regs.dx.write(0xffff);
} else {
self.computer.regs.dx.write(0x0000);
} }
} }