指令集在汇编中起什么作用? [英] What does the instruction sete do in assembly?

问题描述

我的大学课程要求一些基本的组装知识...即使我没有任何知识.但是他们给了我们这个示例汇编代码:

My uni course requires some basic assembly knowledge... even though I have NONE. However they gave us this sample assembly code:

080485fa <check_pin>:
 80485fa:       55                      push   ebp
 80485fb:       89 e5                   mov    ebp,esp
 80485fd:       81 7d 08 bf 07 00 00    cmp    DWORD PTR [ebp+0x8],0x7bf
 8048604:       0f 94 c0                sete   al
 8048607:       0f b6 c0                movzx  eax,al
 804860a:       5d                      pop    ebp
 804860b:       c3                      ret

应该大致等同于以下C代码:

It is supposed to be more or less equivalent to the following C code:

int check_pin(int pin) {
        return pin == 0x7bf;
}

我试图弄清楚该汇编代码到底是做什么的，对此sete指令我感到du目结舌.这条指令是做什么的?

I'm trying to figure out what exactly this assembly code do and I'm dumbfounded by this sete instruction. What does this instruction do?

Wikibooks具有有关x86汇编的课程，但是我找不到关于sete在有关汇编说明的章节中.

Wikibooks has a course on x86 assembly, but I was not able to find anything about sete in the chapter devoted to assembly instructions.

推荐答案

如果设置了零标志，则sete指令(及其等效的setz)将其参数设置为1，否则设置为0 .如果最后一个比较或算术指令产生相等或结果为零，则设置零标志.因此，根据您的情况，sete根据前面的cmp指令的结果将al设置为0或1.

The sete instruction (and its equivalent, setz) sets its argument to 1 if the zero flag is set or to 0 otherwise. The zero flag is set if the last comparison or arithmetic instruction yielded equality or a result of zero. Thus in your case, sete sets al to 0 or 1 according to the result of the preceeding cmp instruction.

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