x86指令前缀字节的编码顺序 [英] order for encoding x86 instruction prefix bytes

问题描述

我知道x86指令最多可以有4个字节的前缀，例如Lock，rep，段覆盖等.

I know that x86 instructions can have a maximum of 4 bytes of prefixes, e.g Lock, rep, segment overrides etc.

在使用多个前缀的情况下，它们的显示顺序是否有任何特定的顺序?

Is there any particular order in which they should appear, in case multiple prefixes are used?

推荐答案

可以在《英特尔软件开发人员手册》第2A卷中找到该顺序.

the order can be found in volume 2A of the Intel Software Developer's Manual.

简而言之:

• F2和F3前缀彼此抵消.以后的优先级高.
如果使用F2或F3(作为长指令中的强制性前缀)，则
• 66前缀将被忽略.当然，这不适用于rep movsw，因为这两个前缀都是简单的前缀，而不是操作码的一部分.
• REX转义符不得后面带有任何其他前缀.
• 在VEX转义符之前不能添加REX，66，F2或F3

• the F2 and F3 prefixes cancel each other out. The one that comes later has precedence.
• the 66 prefix is ignored if either F2 or F3 are used (as mandatory prefixes in a long instruction). This of course doesn't apply to rep movsw where both those prefixes are simply prefixes, not part of the opcode.
• the REX escape may not be followed by any other prefixes.
• the VEX escape may not be preceded by REX, 66, F2 or F3

其余的顺序无关紧要.

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