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/*
* Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package jdk.nashorn.internal.ir;
import static jdk.nashorn.internal.codegen.CompilerConstants.TEMP_PREFIX;
import static jdk.nashorn.internal.ir.Symbol.IS_TEMP;
import java.util.HashMap;
import java.util.Map;
import jdk.nashorn.internal.codegen.types.Type;
/**
* Class that holds reusable temporary symbols by type.
*
*/
public class TemporarySymbols {
private static final String prefix = TEMP_PREFIX.symbolName() + "$";
private int totalSymbolCount;
private final Map<Type, TypedTemporarySymbols> temporarySymbolsByType = new HashMap<>();
/**
* Associates a temporary symbol of a given type with a node, if the node doesn't already have any symbol.
* @param lc the current lexical context
* @param type the type of the temporary symbol
* @param node the node
* @return the node that is guaranteed to have a symbol.
*/
public Expression ensureSymbol(final LexicalContext lc, final Type type, final Expression node) {
final Symbol symbol = node.getSymbol();
if (symbol != null) {
return node;
}
return node.setSymbol(lc, getTypedTemporarySymbol(type));
}
/**
* Given a type, returns a temporary symbol of that type.
* @param type the required type of the symbol.
* @return a temporary symbol of the required type.
*/
public Symbol getTypedTemporarySymbol(final Type type) {
return getTypedTemporarySymbols(type).getTemporarySymbol(type);
}
private TypedTemporarySymbols getTypedTemporarySymbols(final Type type) {
TypedTemporarySymbols temporarySymbols = temporarySymbolsByType.get(type);
if(temporarySymbols == null) {
temporarySymbols = new TypedTemporarySymbols();
temporarySymbolsByType.put(type, temporarySymbols);
}
return temporarySymbols;
}
/**
* This method is called to signal to this object that all the symbols it holds can be reused now.
*/
public void reuse() {
for(TypedTemporarySymbols ts: temporarySymbolsByType.values()) {
ts.reuse();
}
}
/**
* Given a shared symbol, creates an unshared copy of it with a unique name.
* @param symbol the shared symbol
* @return the unshared, uniquely named copy of the symbol
*/
public Symbol createUnshared(Symbol symbol) {
return symbol.createUnshared(getUniqueName());
}
private String getUniqueName() {
return prefix + (++totalSymbolCount);
}
/**
* Returns the total number of symbols this object created during its lifetime.
* @return the total number of symbols this object created during its lifetime.
*/
public int getTotalSymbolCount() {
return totalSymbolCount;
}
private class TypedTemporarySymbols {
private Symbol[] symbols = new Symbol[16];
private int nextFreeSymbol = 0;
private int symbolCount = 0;
Symbol getTemporarySymbol(final Type type) {
while(nextFreeSymbol < symbolCount) {
final Symbol nextSymbol = symbols[nextFreeSymbol];
assert nextSymbol != null;
// If it has a slot, we can't reuse it.
if(!nextSymbol.hasSlot()) {
final Type symbolType = nextSymbol.getSymbolType();
if(symbolType == type) {
assert nextSymbol.isTemp();
assert !nextSymbol.isScope();
// If types match, we can reuse it.
nextSymbol.setIsShared();
nextFreeSymbol++;
return nextSymbol;
}
// If its type changed, but it doesn't have a slot then move it to its new home according to its
// new type.
getTypedTemporarySymbols(symbolType).addSymbol(nextSymbol);
}
// If we can move another symbol into its place, do that and repeat the analysis for this symbol.
--symbolCount;
if(symbolCount != nextFreeSymbol) {
final Symbol lastFreeSymbol = symbols[symbolCount];
symbols[nextFreeSymbol] = lastFreeSymbol;
}
symbols[symbolCount] = null;
}
return createNewSymbol(type);
}
private Symbol createNewSymbol(final Type type) {
ensureCapacity();
final Symbol symbol = symbols[nextFreeSymbol] = new Symbol(getUniqueName(), IS_TEMP, type);
nextFreeSymbol++;
symbolCount++;
return symbol;
}
private void addSymbol(Symbol symbol) {
ensureCapacity();
symbols[symbolCount++] = symbol;
}
void reuse() {
nextFreeSymbol = 0;
}
private void ensureCapacity() {
if(symbolCount == symbols.length) {
final Symbol[] newSymbols = new Symbol[symbolCount * 2];
System.arraycopy(symbols, 0, newSymbols, 0, symbolCount);
symbols = newSymbols;
}
}
}
}
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