Built-in functions

最新推荐文章于 2022-05-04 20:23:48 发布

raojun

最新推荐文章于 2022-05-04 20:23:48 发布

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原文链接：https://v8.dev/docs/builtin-functions

本文探讨了V8引擎中内置函数的不同实现方式，包括直接用JavaScript编写的函数、调用C++运行时函数的%-前缀函数以及平台依赖的汇编语言实现。还介绍了使用CodeStubAssembler进行平台独立抽象的函数，以及直接用C++实现的部分。

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Built-in functions in V8 come in different flavors w.r.t. implementation, depending on their functionality, performance requirements, and sometimes plain historical development.

Some are implemented in JavaScript directly, and are compiled into executable code at runtime just like any user JavaScript. Some of them resort to so-called runtime functions for part of their functionality. Runtime functions are written in C++ and called from JavaScript through a %-prefix. Usually, these runtime functions are limited to V8 internal JavaScript code. For debugging purposes, they can also be called from normal JavaScript code, if V8 is run with the flag --allow-natives-syntax. Some runtime functions are directly embedded by the compiler into generated code. For a list, see src/runtime/runtime.h.

Other functions are implemented as built-ins, which themselves can be implemented in a number of different ways. Some are implemented directly in platform-dependent assembly. Some are implemented in CodeStubAssembler, a platform-independent abstraction. Yet others are directly implemented in C++. Built-ins are sometimes also used to implement pieces of glue code, not necessarily entire functions. For a list, see src/builtins/builtins.h.