/*
* Copyright 2014 Google Inc.
*
* 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.gwt.dev.jjs.impl;
import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.JCastOperation;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JField;
import com.google.gwt.dev.jjs.ast.JFieldRef;
import com.google.gwt.dev.jjs.ast.JModVisitor;
import com.google.gwt.dev.jjs.ast.JPrimitiveType;
import com.google.gwt.dev.jjs.ast.JProgram;
import com.google.gwt.dev.jjs.ast.JType;
import com.google.gwt.thirdparty.guava.common.collect.Maps;
import java.util.Map;
/**
* Replaces compile time constants by their values.
* <p>
* This pass is necessary, even in unoptimized compiles, to allow forward references to compile
* time values in bootstrap code.
**/
public class CompileTimeConstantsReplacer {
private static class CompileTimeConstantsReplacingVisitor extends JModVisitor {
private final Map<JField, JExpression> resolveValuesByField = Maps.newIdentityHashMap();
private final JProgram program;
@Override
public void endVisit(JFieldRef x, Context ctx) {
JField field = x.getField();
if (field.isCompileTimeConstant() && !ctx.isLvalue()) {
ctx.replaceMe(resolveFieldValue(field));
}
}
private JExpression resolveFieldValue(JField field) {
JExpression value = resolveValuesByField.get(field);
if (value != null) {
return new CloneExpressionVisitor().cloneExpression(value);
} else {
// TODO(rluble): Simplify the expression to a literal here after refactoring Simplifier.
// The initializer is guaranteed to be constant but it may be a non literal expression, so
// clone it and recursively remove field references, and finally cache the results.
value = accept(new CloneExpressionVisitor().cloneExpression(field.getInitializer()));
JType fieldType = field.getType().getUnderlyingType();
assert fieldType instanceof JPrimitiveType || fieldType == program.getTypeJavaLangString()
: fieldType.getName() + " is not a primitive nor String ";
if (fieldType != value.getType()) {
value = new JCastOperation(value.getSourceInfo(), fieldType, value);
}
resolveValuesByField.put(field, value);
}
return value;
}
public CompileTimeConstantsReplacingVisitor(JProgram program) {
this.program = program;
}
}
public static void exec(JProgram program) {
new CompileTimeConstantsReplacingVisitor(program).accept(program);
}
}