LEA和偏移的区别 [英] Difference between lea and offset
问题描述
ar db "Defference $"
有什么
mov dx,offset ar
和
lea dx,ar
我觉得这两个都在做同样的工作，但正是这两者之间的区别
I think both are doing same work, but what is the difference between these two
推荐答案
在此用例LEA和MOV做同样的事情。如果你想在一个更复杂的方法来计算一个地址LEA比MOV更强大。
In this use-case LEA and MOV do the same thing. LEA is more powerful than MOV if you want to calculate an address in a more complex way.
让例如说，你想要得到的第n个字符的地址数组中，和n存储在BX。随着MOV，你必须编写以下两个指令：
Lets for example say you want to get the address of the n'th character in your array, and the n is stored in bx. With MOV you have to write the following two instructions:
Mov dx, offset ar
add dx, bx
使用LEA，你可以只用一个指令做到这一点：
With lea you can do it with just one instruction:
lea dx, [ar + bx]
另一个要考虑这里：在添加DX，BX 指令将改变CPU的状态标志。在 LEA DX内部完成的增加，[AR + BX]，另一方面指令，因为它不被视为一个算术指令不更改标记以任何方式。
Another thing to consider here: the add dx,bx instruction will change the status flags of the CPU. The addition done inside the lea dx, [ar + bx] instruction on the other hand does not change the flags in any way because it is not considered an arithmetic instruction.
如果您想preserve标志，同时做一些简单的计算，这有时是非常有用（地址的计算是很常见的）。存储和恢复的标志寄存器是可行的，但一个缓慢的操作。
This is sometimes helpful if you want to preserve the flags while doing some simple calculations (address calculations are very common). Storing and restoring the flag-register is doable but a slow operation.
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