装配莱亚尔和MOVL差异 [英] assembly leal and movl difference

问题描述

leal(%eax,%ecx,4), %edx

，因为我是从我的计算机系统的电子书阅读，
如果$ EAX包含x值和％ECX包含Ÿ可以去看premises，
那么上面的方法，X + 4Y付诸％EDX。

as I was reading from my computer systems book, if there`s premises that $eax contains x value and %ecx contains y, then the above means, x+4y putting into %edx.

那么，如果它是

movl(%eax,%ecx,4), %edx

，然后isn`t的同一个以上利尔前pression？

, then isn`t the same one with leal expression above?

据我所知，莱亚尔创建一个可参考的地址，而不是本身引用MOVL一样，但

As I know, leal creates address that can be referenced,not referencing by itself like movl, but

当我看到莱亚尔（％eax中，％ECX，4），％EDX 等于把 X + 4Y 到 EDX 注册，
然后没有按 T这意味着它引用％EAX 和％ecx`提取值x和y使用计算??

when I saw leal(%eax,%ecx,4), %edx equals putting x+4y into edx register, then doesnt it mean that it 'referenced'%eaxand%ecx` and extracted value x and y for using computation??

• 不`吨了（）的意思是'引用'??

推荐答案

LEA 加载由地址计算到寄存器产生一个有效的地址。 MOV 使用SIB寻址作为源操作数，当某个地方移动的东西，它的动作无论是在的由地址计算到目标操作数生成的地址。

LEA loads an effective address generated by an address calculation into a register. MOV moves something somewhere, when using SIB addressing as source operand, it moves whatever is at the address generated by the address calculation into the target operand.

所以：

leal (%eax,%ecx,4), %edx  ←  moves %eax+%ecx*4 into %edx
movl (%eax,%ecx,4), %edx  ←  moves whatever is at address %eax+%ecx*4 into %edx

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