x86-64 操作数的汇编顺序 [英] x86-64 assembly order of operands

问题描述

x86-64 汇编中操作数的顺序是什么?:指令目的地，来源或者:指令源、目的地

What is the order of operands in x86-64 assembly?: instruction destination, source Or: instruction source, destination

我有三本书和两种不同的方法！

I have three books and two different approaches!

推荐答案

这取决于汇编程序的语法.大多数情况下，我们有两种选择:Intel 和 AT&T 语法.

It depends on the syntax of an assembler. Mostly we have two choices: Intel and AT&T syntaxes.

Intel 语法有多种风格，主要是 NASM (mov dword [symbol_name], 1) 和 MASM(包括 GAS 的 .intel_syntax noprefix 模式，其中许多GNU 和 Unix 工具都可以使用.)参见 https://stackoverflow.com/tags/intel-syntax/info有关差异的详细信息并区分它们.

There are multiple flavours of Intel syntax, the major ones being NASM (mov dword [symbol_name], 1) and MASM (including GAS's .intel_syntax noprefix mode which many GNU and Unix tools can use.) See https://stackoverflow.com/tags/intel-syntax/info for details on the differences and telling them apart.

Intel 语法示例(来自 objdump 反汇编，所以这是 GNU .intel_syntax，并添加了几个示例):

Intel syntax example (from objdump disassembly, so this is GNU .intel_syntax, with a couple examples added in):

push   rbp         # comment character can be # (GAS) or ; MASM/NASM
mov    rbp,rsp
mov    DWORD PTR [rbp-0x4],edi
mov    DWORD PTR [rbp-0x8],esi
mov    edx,DWORD PTR [rbp-0x4]
mov    eax,DWORD PTR [rbp-0x8]
add    eax,edx
pop    rbp
ret

add    dword ptr [rdi], 1    # size specifier mandatory if neither operand is a reg
imul   ecx, [rdi + rax*4 + 20], 12345

AT&T 语法只有一种风格 (https://stackoverflow.com/tags/att/info):

There's only one flavour of AT&T syntax (https://stackoverflow.com/tags/att/info):

push   %rbp                 # comment character is always #
mov    %rsp,%rbp
mov    %edi,-0x4(%rbp)
mov    %esi,-0x8(%rbp)
mov    -0x4(%rbp),%edx
mov    -0x8(%rbp),%eax
add    %edx,%eax
pop    %rbp
retq

addl  $1, (%rdi)      # size suffix b/w/l/q used to indicate operand-size if neither operand is a register

# with more than 2 operands, reverse the whole list
imul   $12345, 20(%rdi, %rax, 4), %ecx 

AT&T 语法是 Unix 系统固有的.通常，反编译器具有控制输出语法类型的标志.例如 objdump 有 -Mintel 标志，gdb 有 set disassembly-flavor intel 选项.

AT&T syntax is native to Unix systems. Usually, decompilers have flags to control a type of output syntax. For example objdump has -Mintel flag, gdb has set disassembly-flavor intel option.

另外，看看这个有用的站点，您可以在该站点上快速查看无噪音的汇编器输出编译器资源管理器

Also, take a look at this useful site on which you can quickly see assembler output without noise Compiler Explorer

请注意 AT&T 语法对于 x87 非可交换 FP 指令(如带有寄存器操作数的 fsub 和 fsubr)存在设计错误:请参阅手册:https://sourceware.org/binutils/docs/as/i386_002dBugs.html

Beware that AT&T syntax has a design bug for x87 non-commutative FP instructions like fsub and fsubr with register operands: see the manual: https://sourceware.org/binutils/docs/as/i386_002dBugs.html

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