/*
* Copyright 2010 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.javascript.jscomp;
import com.google.javascript.jscomp.NodeTraversal.AbstractShallowCallback;
import com.google.javascript.jscomp.NodeTraversal.FunctionCallback;
import com.google.javascript.rhino.Node;
/**
* A compiler pass to run various peephole optimizations (e.g. constant folding,
* some useless code removal, some minimizations).
*
* @author dcc@google.com (Devin Coughlin)
*/
class PeepholeOptimizationsPass implements CompilerPass {
private AbstractCompiler compiler;
// Use an array here for faster iteration compared to ImmutableSet
private final AbstractPeepholeOptimization[] peepholeOptimizations;
private boolean retraverseOnChange;
private RecentChange handler;
/**
* Creates a peephole optimization pass that runs the given
* optimizations.
*/
PeepholeOptimizationsPass(AbstractCompiler compiler,
AbstractPeepholeOptimization... optimizations) {
this.compiler = compiler;
this.peepholeOptimizations = optimizations;
this.retraverseOnChange = true;
this.handler = new RecentChange();
}
void setRetraverseOnChange(boolean retraverse) {
this.retraverseOnChange = retraverse;
}
public AbstractCompiler getCompiler() {
return compiler;
}
@Override
public void process(Node externs, Node root) {
compiler.addChangeHandler(handler);
beginTraversal();
NodeTraversal.traverseChangedFunctions(compiler, new FunctionCallback() {
@Override
public void visit(AbstractCompiler compiler, Node root) {
if (root.isFunction()) {
root = root.getLastChild();
}
do {
handler.reset();
NodeTraversal.traverse(compiler, root, new PeepCallback());
} while (retraverseOnChange && handler.hasCodeChanged());
}
});
endTraversal();
compiler.removeChangeHandler(handler);
}
private class PeepCallback extends AbstractShallowCallback {
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
Node currentNode = n, newNode;
boolean codeChanged = false;
do {
codeChanged = false;
for (AbstractPeepholeOptimization optim : peepholeOptimizations) {
newNode = optim.optimizeSubtree(currentNode);
if (newNode != currentNode) {
codeChanged = true;
currentNode = newNode;
}
if (currentNode == null) {
return;
}
}
} while(codeChanged);
}
}
/**
* Make sure that all the optimizations have the current traversal so they
* can report errors.
*/
private void beginTraversal() {
for (AbstractPeepholeOptimization optimization : peepholeOptimizations) {
optimization.beginTraversal(compiler);
}
}
private void endTraversal() {
for (AbstractPeepholeOptimization optimization : peepholeOptimizations) {
optimization.endTraversal(compiler);
}
}
}