大会JLE JMP指令为例 [英] Assembly JLE jmp instruction example

问题描述

如何使用href=\"http://www.laynetworks.com/assembly%20tutorials3.htm#jump\">跳转指令家庭的

这是他们得到了什么：

JL标签


它跳，如果它小于或如果它不大于或等于。

我的问题是的是什么它的这句话？说我在 EBX 的变量，我想跳到标签有：如果 EBX 是＆LT; = 10

具体我感兴趣的使用 86 跳家族的说明

解决方案

跳转本身会检查EFL寄存器中的标志。这些通常是设定测试或CMP（或其他许多指令的副作用）。

  CMP EBX，10
JLE有
 

• CMP对应于计算所述操作数的差异，更新标志和废弃的结果。通常用于大于/小检查


• 测试对应的操作数和计算的二进制文件，更新标记和丢弃的结果。通常用于相等检查。

参见：<一href=\"http://books.google.com/books?id=094tYob7ipQC&pg=PA378&lpg=PA378&dq=CMP+instruction&source=bl&ots=e687FSncG9&sig=jVzoRmeztIOsniN9wfQQLYhVI1E&hl=en&ei=ZJEbTY6gG8Ttsga82e3YDA&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBYQ6AEwATgK#v=onepage&q=CMP%20instruction&f=false\">The在CMP 汇编语言的艺术

一点题外话：你应该得到英特尔的参考手册的。尤其是两部分的英特尔®64和IA-32架构软件开发人员手册卷2：指令集。这说明了所有的x86指令

How do you use the jump family of instructions?

This is what they've got:

JL label
"It" jumps if it is less than or if it is not larger than or equal to.

My question is what is it in this sentence? Say I have a variable in ebx and I want to jump to label there: if ebx is <= 10.

Specifically I'm interested in using the x86 jump family of instructions

解决方案

The jump itself checks the flags in the EFL register. These are usually set with TEST or CMP(or as a side effect of many other instructions).

CMP ebx,10
JLE there

• CMP corresponds to calculating the difference of the operands, updating the flags and discarding the result. Typically used for greater/smaller checks
• TEST corresponds to calculating the binary AND of the operands, updating the flags and discarding the result. Typically used for equality checks.

See also: The art of assembly language on CMP

As a sidenote: You should get the Intel reference manuals. In particular the two part "Intel® 64 and IA-32 Architectures Software Developer's Manual Volume 2: Instruction Set Reference" which describes all x86 instructions.

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