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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 jdk.nashorn.internal.codegen.types.Type;
/**
* Class describing one or more local variable conversions that needs to be performed on entry to a control flow join
* point. Note that the class is named as a singular "Conversion" and not a plural "Conversions", but instances of the
* class have a reference to the next conversion, so multiple conversions are always represented with a single instance
* that is a head of a linked list of instances.
* @see JoinPredecessor
*/
public final class LocalVariableConversion {
private final Symbol symbol;
// TODO: maybe introduce a type pair class? These will often be repeated.
private final Type from;
private final Type to;
private final LocalVariableConversion next;
/**
* Creates a new object representing a local variable conversion.
* @param symbol the symbol representing the local variable whose value is being converted.
* @param from the type value is being converted from.
* @param to the type value is being converted to.
* @param next next conversion at the same join point, if any (the conversion object implements a singly-linked
* list of conversions).
*/
public LocalVariableConversion(final Symbol symbol, final Type from, final Type to, final LocalVariableConversion next) {
this.symbol = symbol;
this.from = from;
this.to = to;
this.next = next;
}
/**
* Returns the type being converted from.
* @return the type being converted from.
*/
public Type getFrom() {
return from;
}
/**
* Returns the type being converted to.
* @return the type being converted to.
*/
public Type getTo() {
return to;
}
/**
* Returns the next conversion at the same join point, or null if this is the last one.
* @return the next conversion at the same join point.
*/
public LocalVariableConversion getNext() {
return next;
}
/**
* Returns the symbol representing the local variable whose value is being converted.
* @return the symbol representing the local variable whose value is being converted.
*/
public Symbol getSymbol() {
return symbol;
}
/**
* Returns true if this conversion is live. A conversion is live if the symbol has a slot for the conversion's
* {@link #getTo() to} type. If a conversion is dead, it can be omitted in code generator.
* @return true if this conversion is live.
*/
public boolean isLive() {
return symbol.hasSlotFor(to);
}
/**
* Returns true if this conversion {@link #isLive()}, or if any of its {@link #getNext()} conversions are live.
* @return true if this conversion, or any conversion following it, are live.
*/
public boolean isAnyLive() {
return isLive() || isAnyLive(next);
}
/**
* Returns true if the passed join predecessor has {@link #isAnyLive()} conversion.
* @param jp the join predecessor being examined.
* @return true if the join predecessor conversion is not null and {@link #isAnyLive()}.
*/
public static boolean hasLiveConversion(final JoinPredecessor jp) {
return isAnyLive(jp.getLocalVariableConversion());
}
/**
* Returns true if the passed conversion is not null, and it {@link #isAnyLive()}.
* @parameter conv the conversion being tested for liveness.
* @return true if the conversion is not null and {@link #isAnyLive()}.
*/
private static boolean isAnyLive(final LocalVariableConversion conv) {
return conv != null && conv.isAnyLive();
}
@Override
public String toString() {
return toString(new StringBuilder()).toString();
}
/**
* Generates a string representation of this conversion in the passed string builder.
* @param sb the string builder in which to generate a string representation of this conversion.
* @return the passed in string builder.
*/
public StringBuilder toString(final StringBuilder sb) {
if(isLive()) {
return toStringNext(sb.append('\u27e6'), true).append("\u27e7 ");
}
return next == null ? sb : next.toString(sb);
}
/**
* Generates a string representation of the passed conversion in the passed string builder.
* @param conv the conversion to render in the string builder.
* @param sb the string builder in which to generate a string representation of this conversion.
* @return the passed in string builder.
*/
public static StringBuilder toString(final LocalVariableConversion conv, final StringBuilder sb) {
return conv == null ? sb : conv.toString(sb);
}
private StringBuilder toStringNext(final StringBuilder sb, final boolean first) {
if(isLive()) {
if(!first) {
sb.append(", ");
}
sb.append(symbol.getName()).append(':').append(getTypeChar(from)).append('\u2192').append(getTypeChar(to));
return next == null ? sb : next.toStringNext(sb, false);
}
return next == null ? sb : next.toStringNext(sb, first);
}
private static char getTypeChar(final Type type) {
if(type == Type.UNDEFINED) {
return 'U';
} else if(type.isObject()) {
return 'O';
} else if(type == Type.BOOLEAN) {
return 'Z';
}
return type.getBytecodeStackType();
}
}
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