path: root/tools/js-optimizer.js

//==============================================================================
//  Optimizer tool. This is meant to be run after the emscripten compiler has
//  finished generating code. These optimizations are done on the generated
//  code to further improve it. Some of the modifications also work in
//  conjunction with closure compiler.
//==============================================================================

var uglify = require('../tools/eliminator/node_modules/uglify-js');
var fs = require('fs');

// Make node environment compatible with JS shells

function print(text) {
  process.stdout.write(text + '\n');
}
function printErr(text) {
  process.stderr.write(text + '\n');
}
function read(filename) {
  if (filename[0] != '/') filename = __dirname.split('/').slice(0, -1).join('/') + '/src/' + filename;
  return fs.readFileSync(filename).toString();
}
var arguments = process.argv.slice(2);

// Load some modules

eval(read('utility.js'));

// Utilities

var FUNCTION = set('defun', 'function');
var LOOP = set('do', 'while', 'for');
var LOOP_FLOW = set('break', 'continue');

var NULL_NODE = ['name', 'null'];
var UNDEFINED_NODE = ['unary-prefix', 'void', ['num', 0]];
var TRUE_NODE = ['unary-prefix', '!', ['num', 0]];
var FALSE_NODE = ['unary-prefix', '!', ['num', 1]];

var GENERATED_FUNCTIONS_MARKER = '// EMSCRIPTEN_GENERATED_FUNCTIONS:';
var generatedFunctions = null;
function setGeneratedFunctions(metadata) {
  generatedFunctions = set(eval(metadata.replace(GENERATED_FUNCTIONS_MARKER, '')));
}
function isGenerated(ident) {
  return ident in generatedFunctions;
}

function srcToAst(src) {
  return uglify.parser.parse(src);
}

function astToSrc(ast) {
    return uglify.uglify.gen_code(ast, {
    ascii_only: true,
    beautify: true,
    indent_level: 2
  });
}

// Traverses a JavaScript syntax tree rooted at the given node calling the given
// callback for each node.
//   @arg node: The root of the AST.
//   @arg pre: The pre to call for each node. This will be called with
//     the node as the first argument and its type as the second. If true is
//     returned, the traversal is stopped. If an object is returned,
//     it replaces the passed node in the tree.
//   @arg post: A callback to call after traversing all children.
//   @arg stack: If true, a stack will be implemented: If pre does not push on
//               the stack, we push a 0. We pop when we leave the node. The
//               stack is passed as a third parameter to the callbacks.
//   @returns: If the root node was replaced, the new root node. If the traversal
//     was stopped, true. Otherwise undefined.
function traverse(node, pre, post, stack) {
  var type = node[0], result, len;
  var relevant = typeof type == 'string';
  if (relevant) {
    if (stack) len = stack.length;
    var result = pre(node, type, stack);
    if (result == true) return true;
    if (typeof result == 'object') node = result; // Continue processing on this node
    if (stack && len == stack.length) stack.push(0);
  }
  for (var i = 0; i < node.length; i++) {
    var subnode = node[i];
    if (typeof subnode == 'object' && subnode && subnode.length) {
      var subresult = traverse(subnode, pre, post, stack);
      if (subresult == true) return true;
      if (typeof subresult == 'object') node[i] = subresult;
    }
  }
  if (relevant) {
    if (post) {
      var postResult = post(node, type, stack);
      result = result || postResult;
    }
    if (stack) stack.pop();
  }
  return result;
}

// Only walk through the generated functions
function traverseGenerated(ast, pre, post, stack) {
  ast[1].forEach(function(node, i) {
    if (node[0] == 'defun' && isGenerated(node[1])) {
      traverse(node, pre, post, stack);
    }
  });
}

function traverseGeneratedFunctions(ast, callback) {
  ast[1].forEach(function(node, i) {
    if (node[0] == 'defun' && isGenerated(node[1])) {
      callback(node);
    }
  });
}

// Walk the ast in a simple way, with an understanding of which JS variables are defined)
function traverseWithVariables(ast, callback) {
  traverse(ast, function(node, type, stack) {
    if (type in FUNCTION) {
      stack.push({ type: 'function', vars: node[2] });
    } else if (type ==