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Performance improvements for TCO.

Browse Source 
http://jsperf.com/tco/17
This commit is contained in:
Ingvar Stepanyan
2015-02-09 18:00:07 +02:00
parent 5a842ab623
commit 0d542b61d3
12 changed files with 253 additions and 158 deletions
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14
lib/6to5/transformation/templates/tail-call-body.js
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@@ -1,15 +1,3 @@
{
var ARGUMENTS_ID = arguments,
THIS_ID = this,
SHOULD_CONTINUE_ID,
RESULT_ID;
var CALLEE_ID = FUNCTION;
do {
SHOULD_CONTINUE_ID = false;
RESULT_ID = CALLEE_ID.apply(THIS_ID, ARGUMENTS_ID);
} while(SHOULD_CONTINUE_ID);
return RESULT_ID;
FUNCTION_ID:while (true) BLOCK
}

4
lib/6to5/transformation/transformers/es6/parameters.default.js
View File

@@ -73,7 +73,9 @@ exports.Function = function (node, parent, scope, file) {
var left = param.left;
var right = param.right;
node.params[i] = scope.generateUidIdentifier("x");
var placeholder = scope.generateUidIdentifier("x");
placeholder._isDefaultPlaceholder = true;
node.params[i] = placeholder;
if (!state.iife) {
if (t.isIdentifier(right) && scope.hasOwnReference(right.name)) {

214
lib/6to5/transformation/transformers/es6/tail-call.js
View File

@@ -1,5 +1,6 @@
"use strict";
var _ = require("lodash");
var util = require("../../../util");
var t = require("../../../types");
@@ -27,7 +28,7 @@ function transformExpression(node, scope, state) {
} else {
node.alternate = returnBlock(node.alternate);
}
return node;
return [node];
case "LogicalExpression":
// only call in right-value of can be optimized
@@ -96,71 +97,137 @@ function transformExpression(node, scope, state) {
state.hasTailRecursion = true;
return [
t.expressionStatement(t.assignmentExpression(
"=",
state.getArgumentsId(),
args || t.arrayExpression(node.arguments)
)),
var body = [];
t.expressionStatement(t.assignmentExpression(
if (!t.isThisExpression(thisBinding)) {
body.push(t.expressionStatement(t.assignmentExpression(
"=",
state.getThisId(),
thisBinding || t.identifier("undefined")
)),
)));
}
t.returnStatement(t.assignmentExpression(
"=",
state.getShouldContinueId(),
t.literal(true)
))
];
if (!args) {
args = t.arrayExpression(node.arguments);
}
var argumentsId = state.getArgumentsId();
var params = state.getParams();
body.push(t.expressionStatement(t.assignmentExpression(
"=",
argumentsId,
args
)));
var i, param;
if (t.isArrayExpression(args)) {
var elems = args.elements;
for (i = 0; i < elems.length && i < params.length; i++) {
param = params[i];
var elem = elems[i] || (elems[i] = t.identifier("undefined"));
if (!param._isDefaultPlaceholder) {
elems[i] = t.assignmentExpression("=", param, elem);
}
}
} else {
state.setsArguments = true;
for (i = 0; i < params.length; i++) {
param = params[i];
if (!param._isDefaultPlaceholder) {
body.push(t.expressionStatement(t.assignmentExpression(
"=",
param,
t.memberExpression(argumentsId, t.literal(i), true)
)));
}
}
}
body.push(t.continueStatement(state.getFunctionId()));
return body;
}
})(node);
}
var functionChildrenVisitor = {
// Looks for and replaces tail recursion calls.
var firstPass = {
enter: function (node, parent, scope, state) {
if (t.isReturnStatement(node)) {
// prevent entrance by current visitor
this.skip();
// transform return argument into statement if
// it contains tail recursion
return transformExpression(node.argument, scope, state);
} else if (t.isFunction(node)) {
this.skip();
} else if (t.isTryStatement(parent)) {
if (node === parent.block) {
this.skip();
} else if (parent.finalizer && node !== parent.finalizer) {
this.skip();
}
} else if (t.isFunction(node)) {
this.skip();
} else if (t.isVariableDeclaration(node)) {
this.skip();
state.vars.push(node);
}
}
};
var functionVisitor = {
// Hoists up function declarations, replaces `this` and `arguments` and
// marks them as needed.
var secondPass = {
enter: function (node, parent, scope, state) {
// traverse all child nodes of this function and find `arguments` and `this`
scope.traverse(node, functionChildrenVisitor, state);
return this.skip();
if (t.isThisExpression(node)) {
state.needsThis = true;
return state.getThisId();
} else if (t.isReferencedIdentifier(node, parent, { name: "arguments" })) {
state.needsArguments = true;
return state.getArgumentsId();
} else if (t.isFunction(node)) {
this.skip();
if (t.isFunctionDeclaration(node)) {
node = t.variableDeclaration("var", [
t.variableDeclarator(node.id, t.toExpression(node))
]);
node._blockHoist = 2;
return node;
}
}
}
};
exports.FunctionDeclaration =
exports.FunctionExpression = function (node, parent, scope) {
// Optimizes recursion by removing `this` and `arguments`
// if they are not used.
var thirdPass = {
enter: function (node, parent, scope, state) {
if (!t.isExpressionStatement(node)) return;
var expr = node.expression;
if (!t.isAssignmentExpression(expr)) return;
if (!state.needsThis && expr.left === state.getThisId()) {
this.remove();
} else if (!state.needsArguments && expr.left === state.getArgumentsId() && t.isArrayExpression(expr.right)) {
return _.map(expr.right.elements, function (elem) {
return t.expressionStatement(elem);
});
}
}
};
exports.Function = function (node, parent, scope) {
// only tail recursion can be optimized as for now,
// so we can skip anonymous functions entirely
var ownerId = node.id;
if (!ownerId) return;
var argumentsId, thisId, shouldContinueId, leftId;
var argumentsId, thisId, leftId, functionId, params, paramDecls;
var state = {
hasTailRecursion: false,
needsThis: false,
needsArguments: false,
setsArguments: false,
ownerId: ownerId,
vars: [],
getArgumentsId: function () {
return argumentsId = argumentsId || scope.generateUidIdentifier("arguments");
@@ -170,37 +237,88 @@ exports.FunctionExpression = function (node, parent, scope) {
return thisId = thisId || scope.generateUidIdentifier("this");
},
getShouldContinueId: function () {
return shouldContinueId = shouldContinueId || scope.generateUidIdentifier("shouldContinue");
},
getLeftId: function () {
return leftId = leftId || scope.generateUidIdentifier("left");
},
getFunctionId: function () {
return functionId = functionId || scope.generateUidIdentifier("function");
},
getParams: function () {
if (!params) {
params = node.params;
paramDecls = [];
for (var i = 0; i < params.length; i++) {
var param = params[i];
if (!param._isDefaultPlaceholder) {
paramDecls.push(t.variableDeclarator(
param,
params[i] = scope.generateUidIdentifier("x")
));
}
}
}
return params;
}
};
// traverse the function and look for tail recursion
scope.traverse(node, functionVisitor, state);
scope.traverse(node, firstPass, state);
if (!state.hasTailRecursion) return;
var block = t.ensureBlock(node);
scope.traverse(node, secondPass, state);
if (leftId) {
block.body.unshift(t.variableDeclaration("var", [
t.variableDeclarator(leftId)
]));
if (!state.needsThis || !state.needsArguments) {
scope.traverse(node, thirdPass, state);
}
var resultId = scope.generateUidIdentifier("result");
state.getShouldContinueId();
var body = t.ensureBlock(node).body;
if (state.vars.length > 0) {
body.unshift(t.expressionStatement(
_(state.vars)
.map(function (decl) {
return decl.declarations;
})
.flatten()
.reduceRight(function (expr, decl) {
return t.assignmentExpression("=", decl.id, expr);
}, t.identifier("undefined"))
));
}
if (paramDecls.length > 0) {
body.unshift(t.variableDeclaration("var", paramDecls));
}
node.body = util.template("tail-call-body", {
SHOULD_CONTINUE_ID: shouldContinueId,
ARGUMENTS_ID: argumentsId,
RESULT_ID: resultId,
CALLEE_ID: scope.generateUidIdentifier("callee"),
FUNCTION: t.functionExpression(null, node.params, block),
THIS_ID: thisId,
THIS_ID: thisId,
ARGUMENTS_ID: argumentsId,
FUNCTION_ID: state.getFunctionId(),
BLOCK: node.body
});
var topVars = [];
if (state.needsThis) {
topVars.push(t.variableDeclarator(state.getThisId(), t.thisExpression()));
}
if (state.needsArguments || state.setsArguments) {
var decl = t.variableDeclarator(state.getArgumentsId());
if (state.needsArguments) {
decl.init = t.identifier("arguments");
}
topVars.push(decl);
}
if (leftId) {
topVars.push(t.variableDeclarator(leftId));
}
if (topVars.length > 0) {
node.body.body.unshift(t.variableDeclaration("var", topVars));
}
};

2
lib/6to5/transformation/transformers/index.js
View File

@@ -63,6 +63,8 @@ module.exports = {
// needs to be after `es6.blockScoping` due to needing `letReferences` set on blocks
"es6.blockScopingTDZ": require("./es6/block-scoping-tdz"),
// needs to be after `es6.parameters.*` and `es6.blockScoping` due to needing pure
// identifiers in parameters and variable declarators
"es6.tailCall": require("./es6/tail-call"),
regenerator: require("./other/regenerator"),

2
lib/6to5/traversal/scope.js
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@@ -408,7 +408,7 @@ Scope.prototype.addBindingToFunctionScope = function (node, kind) {
extend(scope.bindings, ids);
extend(scope.references, ids);
if (kind) extend(scope.bindingKinds[kind], ids)
if (kind) extend(scope.bindingKinds[kind], ids);
};
/**