LEA EAX，[EAX] 有什么意义? [英] What's the point of LEA EAX, [EAX]?

问题描述

LEA EAX, [EAX]

我在用 Microsoft C 编译器编译的二进制文件中遇到了这条指令.它显然不能改变 EAX 的值.那为什么会在那里呢?

I encountered this instruction in a binary compiled with the Microsoft C compiler. It clearly can't change the value of EAX. Then why is it there?

推荐答案

这是一个NOP.

以下通常用作NOP.它们都做同样的事情，但它们导致不同长度的机器代码.根据对齐要求选择其中之一:

The following are typcially used as NOP. They all do the same thing but they result in machine code of different length. Depending on the alignment requirement one of them is chosen:

xchg eax, eax         = 90
mov eax, eax          = 89 C0 
lea eax, [eax + 0x00] = 8D 40 00 

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