asm.js

A Mozilla Research project to specify and develop the extremely optimizable subset of JS targeted by compilers like Emscripten, Mandreel, and LLJS.

Example

``javascript
function mymodule(stdlib, foreign, heap) {
"use asm";

// -------------------------------------------------------------------------
// SECTION 1: globals

var H32 = new stdlib.Int32Array(heap);
var HU32 = new stdlib.Uint32Array(heap);
var log = foreign.consoleDotLog;

var g_i = 0; // int global
var g_f = 0.0; // double global

// -------------------------------------------------------------------------
// SECTION 2: functions

function f(x, y) {
// SECTION A: parameter type declarations
x = x|0; // int parameter
y = +y; // double parameter

// SECTION B: function body
log(x|0); // call into FFI -- must force the sign
log(y); // call into FFI -- already know it's a double
x = (x+3)|0; // signed addition

// SECTION C: unconditional return
return ((((x+1)|0)>>>0)/(x|0))>>>0; // compound expression
}

function g() {
g_f = +g_i; // read/write globals
return;
}

function g2() {
return;
}

function h(i, x) {
i = i|0;
x = x|0;
H32[i>>2] = x; // shifted by log2(byte count)
ftable_2[(x-2)&2](); // dynamic call of functions in table 2

// no return necessary when return type is void
}

// -------------------------------------------------------------------------
// SECTION 3: function tables

var ftable_1 = [f];
var ftable_2 = [g, g2]; // all of the same type

// -------------------------------------------------------------------------
// SECTION 4: exports

return { f_export: f, goop: g };
}
``