> For the complete documentation index, see [llms.txt](https://u.naturaldao.io/solidity/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://u.naturaldao.io/solidity/1.6-solidity-yu-yan-jiao-cheng/assembly.md).

# 1.6.7 Solidity汇编语言

Solidity定义了一套汇编语言，这套语言可以独立于Solidity单独使用。这套汇编语言可以嵌在Solidity的源代码内作为内联汇编语言使用。

在编写库时，为了更好的控制和提高语言的效率，可以用虚拟机很容易解析的内联汇编语言和Solidity一起使用。虽然以太坊虚拟机是基于堆栈的，但要正确地处理堆栈并给操作码输入合适的参数也不容易。Solidity的内联汇编语言就很好地处理了这些问题。它有下列这些特性：

\- 类函数风格的操作码：mul(1, add(2, 3)) 而不是push1 3 push1 2 add push1 1 mul。

\- 局部汇编变量：let x := add(2, 3) let y := mload(0x40) x := add(x, y)。

\- 访问外部变量：function f(uint x) public { assembly { x := sub(x, 1) } }。

\- 标签（label）：let x := 10 repeat: x := sub(x, 1) jumpi(repeat, eq(x, 0))。

\- 循环：for { let i := 0 } lt(i, x) { i := add(i, 1) } { y := mul(2, y) }。

\- if语句：if slt(x, 0) { x := sub(0, x) }。

\- switch语句：switch x case 0 { y := mul(x, 2) } default { y := 0 }。

\- 函数调用：function f(x) -> y { switch x case 0 { y := 1 } default { y := mul(x, f(sub(x, 1))) } }。

注意：内联汇编语言是直接和以太坊虚拟机交互的低级语言，为了效率牺牲了部分安全性能。

实际上内联汇编语言也可以脱离Solidity单独作为Solidity编译器的汇编语言使用，而且这也是其原本的规划。这样做主要是希望达到下面三个目的：

\- 用汇编语言写的程序要有可读性，甚至对由用Solidity编写而经过编译器产生的汇编码都是如此。

\- 从汇编再转换为字节码（bytecode）的过程应该尽量平滑，变化尽量小。

\- 汇编语言写的代码其控制流程应该容易检查和审阅，以便对代码进行验证和优化。

关于Solidity汇编语言的细节可参考[https://solidity.readthedocs.io/en/v0.4.24/assembly.html#](https://solidity.readthedocs.io/en/v0.4.24/assembly.html) 。


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