How to understand CMPXCHG compare and exchange operation instructions

This article introduces you how to understand CMPXCHG comparison and exchange operation instructions, the content is very detailed, interested friends can refer to, hope to be helpful to you.

Instruction mnemonic CMPXCHG

Meaning: compare and exchange instructions

Usage: compare destination operands with cumulative operands (AH, AL, EAX). If equal (ZF=1), copy the source Operand to the destination Operand, otherwise copy the destination Operand to the accumulator.

Instruction format:

CMPXCHG reg regCMPXCHG mem reg

Examples are as follows:

CMPXCHG CX,DX1. Before the instruction execution: (AX) = 00FFH, (CX) = 00FFH, (DX) = 00EFH; after the instruction execution: (AX) = 00FFH, (CX) = 00EFH, (DX) = 00EFH. Before instruction execution: (AX) = 00EEH, (CX) = 00FFH, (DX) = 00EFH; after instruction execution: (AX) = 00FFH, (CX) = 00EFH, (DX) = 00EFH

Detailed description of the flow chart:

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