为什么在 LEA 中使用方括号? [英] Why are Square Brackets used in LEA?

问题描述

在汇编中，方括号[] 似乎与C 编程语言中的* 具有相同的含义.它们用于取消引用指针.取消引用指针意味着要引用特定的内存位置来读取或写入它.

In assembly, the square brackets [] seem to have the same meaning as * in C programming language. They are used to dereference a pointer. Dereferencing a pointer means going to refer to a specific memory location to read or write it.

因此，在 MOV 的情况下使用方括号是非常合乎逻辑的.但他们也将其用于 LEA 的合乎逻辑的原因是什么?

So, it is quite logical to use square brackets in the case of a MOV. But what is the logical reason why they also use it for LEA?

LEA EAX, [EBP -4], 看起来像是取消引用一个指针，EBP - 4，来引用指向的内存位置，但它不会读取值包含在位置而不是地址中.

LEA EAX, [EBP -4], looks like dereferencing a pointer, EBP - 4, to refer to the pointed memory location but it will not read the value contained in the location but rather the address.

我对此有点困惑.你能给我一个正确的思考方式吗?
LEA 与取消引用的概念有什么联系吗?显然不是为了读取内存，而主要是指内存位置不是为了它的值，而是为了它的地址.我不希望这成为一个哲学问题.

I'm a little confused about this. Could you give me the right way to think about this?
Does LEA have any connection with the concept of dereferencing? Clearly not intended as a memory reading, but mostly as referring to a location of memory not for its value, but for its address. I wouldn't want this to become a philosophical question.

推荐答案

LEA 指令被设计成一个内存访问指令——因此可以执行所有 寻址模式. 当然，正如您所注意到的，区别在于 LEA 加载有效地址"而不是该位置的内存值.

The LEA instruction is designed to look like a memory access instruction — so can perform all the addressing modes.  The difference, of course, as you're noting is that LEA loads the "effective address" rather than a memory value from that location.

因此，LEA 类似于内存访问操作，但具体而言，在 C 术语中，是获取地址——就像 C 中的 &a[i]. 就像在带有 & 的 C 中一样，LEA 的结果总是一个指针大小的值，而不是我们可以获取/存储字节、字等的实际访问.

Thus, LEA is similar to memory access operations, but specifically, in C terms, is taking the address — so like &a[i] in C.  Like in C with &, the result of LEA is always a pointer sized value rather than with real accesses where we can fetch/store a byte, word, etc..

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