What is %GetOptimizationStatus function in js file running in node.js

Question

I'm reading this article on optimization techniques and there's the following code:

//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);

I have two questions:

The functions %GetOptimizationStatus and %OptimizeFunctionOnNextCall are never defined, where do they come from?
What does this phrase mean 2 calls are needed to go from uninitialized -> pre-monomorphic -> monomorphic ?

It kind of doesn't make any sense if your not running it in node.. The %GetOptimizationStatus, %OptimizeFunctionOnNextCall are of course injected by node when said flags are active. — Keith, Oct 07 '16 at 12:33
And the monomorphic part is basically saying the optimiser won't kick in until it detects multi-use,.. After this TurboFan is activated. — Keith, Oct 07 '16 at 12:39
For your second question (please ask only one per post), see [Why do monomorphic and polymorphic matter in JavaScript?](http://stackoverflow.com/q/37058643/1048572) — Bergi, Oct 07 '16 at 12:49

score 2 · Accepted Answer · edited Oct 18 '17 at 19:38

%GetOptimizationStatus and %OptimizeFunctionOnNextCall are injected into Node, when the specified optimization flags are set.

And the monomorphic part is basically saying the optimiser won't kick in until it detects multi-use,.. After this TurboFan is activated.

IOW: if you look at the output you will notice it call's exampleFunction twice (with optimisation disabled), and it's only on the third try does the TurboFan kick in.

What is %GetOptimizationStatus function in js file running in node.js

1 Answers1