javascript - 在node.js中运行的js文件中的%GetOptimizationStatus函数是什么

Question

我正在阅读this article关于优化技术，有以下代码:

//Function that contains the pattern to be inspected (using an `eval` statement)
function exampleFunction() {
    return 3;
    eval('');
}

function printStatus(fn) {
    switch(%GetOptimizationStatus(fn)) {
        case 1: console.log("Function is optimized"); break;
        case 2: console.log("Function is not optimized"); break;
        case 3: console.log("Function is always optimized"); break;
        case 4: console.log("Function is never optimized"); break;
        case 6: console.log("Function is maybe deoptimized"); break;
        case 7: console.log("Function is optimized by TurboFan"); break;
        default: console.log("Unknown optimization status"); break;
    }
}

//Fill type-info
exampleFunction();
// 2 calls are needed to go from uninitialized -> pre-monomorphic -> monomorphic
exampleFunction();

%OptimizeFunctionOnNextCall(exampleFunction);
//The next call
exampleFunction();

//Check
printStatus(exampleFunction);

我有两个问题:

• 函数%GetOptimizationStatus和%OptimizeFunctionOnNextCall从未被定义，它们从何而来？

• 这句话是什么意思2 calls are needed to go from uninitialized -> pre-monomorphic -> monomorphic ？

Answer 1

当设置指定的优化标志时，

%GetOptimizationStatus 和 %OptimizeFunctionOnNextCall 被注入(inject)到 Node 中。

单态部分基本上是说优化器在检测到多用途之前不会启动，.. 在激活 TurboFan 后。

IOW:如果您查看输出，您会注意到它调用了 exampleFunction 两次(禁用优化)，并且只有在第三次尝试时 TurboFan 才会启动。