了解 x86 汇编中 mov 和 lea 指令之间的差异

Question

我试图理解 x86 汇编语言中

mov

和

lea

指令之间的差异。我编写了一个简单的汇编代码片段，并添加了注释来解释我对这些指令的理解。

.data
num: .int 2     # Declare an integer variable num with value 2

.text
.globl _start

_start:
    movl num, %eax # num stores an address, take the value inside that address into eax
    movl $num, %ebx # num stores an address, $ tells us to take the address itself into ebx
    leal num, %ecx # num stores an address, take the address itself into ecx (lea)

    #initialize
    movl $0, %eax
    movl $0, %ebx
    movl $0, %ecx

    movl $num, %edx # num stores an address, take the address itself into edx
    movl %edx, %eax # edx is an address, take the value inside that address into eax
    leal (%edx), %ecx # () tells us to go to the address inside edx, take the address itself into ecx (lea)
    movl (%edx), %ebx # () tells us to go to the address inside edx, take the value inside that address into ebx

    # Exit
    movl $1, %eax     # System call number for exit
    xorl %ebx, %ebx   # Exit status 0
    int $0x80         # Invoke the syscall

但是，我对这些指令如何与寄存器一起工作有点困惑。如果有人能给我他的解释，我会很高兴。

Answer 1

您的大部分评论都很好。
其他人可能需要一些改写：

movl %edx, %eax # edx is an address, take the value inside that address into eax

“取该地址内的值”
这只是将 EDX 寄存器中内容的副本放入 EAX 寄存器中。在这种情况下，EDX 包含地址这一事实并不重要。

leal (%edx), %ecx # () tells us to go to the address inside edx, take the address itself into ecx (lea)

“前往里面的地址”
我们不会“去”某个地址。 CPU 计算最左边操作数代表的地址并将其存储到目标寄存器 ECX 中。