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	/*
	* Copyright (c) 1994, 2003, 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 sun.tools.tree;

	import sun.tools.java.*;
	import sun.tools.asm.Assembler;

	/**
	* WARNING: The contents of this source file are not part of any
	* supported API. Code that depends on them does so at its own risk:
	* they are subject to change or removal without notice.
	*/
	public
	class AddExpression extends BinaryArithmeticExpression {
	/**
	* constructor
	*/
	public AddExpression(long where, Expression left, Expression right) {
	super(ADD, where, left, right);
	}

	/**
	* Select the type
	*/
	void selectType(Environment env, Context ctx, int tm) {
	if ((left.type == Type.tString) && !right.type.isType(TC_VOID)) {
	type = Type.tString;
	return;
	} else if ((right.type == Type.tString) && !left.type.isType(TC_VOID)) {
	type = Type.tString;
	return;
	}
	super.selectType(env, ctx, tm);
	}

	public boolean isNonNull() {
	// an addition expression cannot yield a null reference as a result
	return true;
	}

	/**
	* Evaluate
	*/
	Expression eval(int a, int b) {
	return new IntExpression(where, a + b);
	}
	Expression eval(long a, long b) {
	return new LongExpression(where, a + b);
	}
	Expression eval(float a, float b) {
	return new FloatExpression(where, a + b);
	}
	Expression eval(double a, double b) {
	return new DoubleExpression(where, a + b);
	}
	Expression eval(String a, String b) {
	return new StringExpression(where, a + b);
	}

	/**
	* Inline the value of an AddExpression. If this AddExpression
	* represents a concatenation of compile-time constant strings,
	* dispatch to the special method inlineValueSB, which handles
	* the inlining more efficiently.
	*/
	public Expression inlineValue(Environment env, Context ctx) {
	if (type == Type.tString && isConstant()) {
	StringBuffer buffer = inlineValueSB(env, ctx, new StringBuffer());
	if (buffer != null) {
	// We were able to evaluate the String concatenation.
	return new StringExpression(where, buffer.toString());
	}
	}
	// For some reason inlinValueSB() failed to produce a value.
	// Use the older, less efficient, inlining mechanism.
	return super.inlineValue(env, ctx);
	}

	/**
	* Attempt to evaluate this expression. If this expression
	* yields a value, append it to the StringBuffer `buffer'.
	* If this expression cannot be evaluated at this time (for
	* example if it contains a division by zero, a non-constant
	* subexpression, or a subexpression which "refuses" to evaluate)
	* then return `null' to indicate failure.
	*
	* It is anticipated that this method will be called to evaluate
	* concatenations of compile-time constant strings. The call
	* originates from AddExpression#inlineValue().
	*
	* This method does not use associativity to good effect in
	* folding string concatenations. This is room for improvement.
	*
	* -------------
	*
	* A bit of history: this method was added because an
	* expression like...
	*
	* "a" + "b" + "c" + "d"
	*
	* ...was evaluated at compile-time as...
	*
	* (new StringBuffer((new StringBuffer("a")).append("b").toString())).
	* append((new StringBuffer("c")).append("d").toString()).toString()
	*
	* Alex Garthwaite, in profiling the memory allocation of the
	* compiler, noticed this and suggested that the method inlineValueSB()
	* be added to evaluate constant string concatenations in a more
	* efficient manner. The compiler now builds the string in a
	* top-down fashion, by accumulating the result in a StringBuffer
	* which is allocated once and passed in as a parameter. The new
	* evaluation scheme is equivalent to...
	*
	* (new StringBuffer("a")).append("b").append("c").append("d")
	* .toString()
	*
	* ...which is more efficient. Since then, the code has been modified
	* to fix certain problems. Now, for example, it can return `null'
	* when it encounters a concatenation which it is not able to
	* evaluate.
	*
	* See also Expression#inlineValueSB() and ExprExpression#inlineValueSB().
	*/
	protected StringBuffer inlineValueSB(Environment env,
	Context ctx,
	StringBuffer buffer) {
	if (type != Type.tString) {
	// This isn't a concatenation. It is actually an addition
	// of some sort. Call the generic inlineValueSB()
	return super.inlineValueSB(env, ctx, buffer);
	}

	buffer = left.inlineValueSB(env, ctx, buffer);
	if (buffer != null) {
	buffer = right.inlineValueSB(env, ctx, buffer);
	}
	return buffer;
	}

	/**
	* Simplify
	*/
	Expression simplify() {
	if (!type.isType(TC_CLASS)) {
	// Can't simplify floating point add because of -0.0 strangeness
	if (type.inMask(TM_INTEGER)) {
	if (left.equals(0)) {
	return right;
	}
	if (right.equals(0)) {
	return left;
	}
	}
	} else if (right.type.isType(TC_NULL)) {
	right = new StringExpression(right.where, "null");
	} else if (left.type.isType(TC_NULL)) {
	left = new StringExpression(left.where, "null");
	}
	return this;
	}

	/**
	* The cost of inlining this expression
	*/
	public int costInline(int thresh, Environment env, Context ctx) {
	return (type.isType(TC_CLASS) ? 12 : 1)
	+ left.costInline(thresh, env, ctx)
	+ right.costInline(thresh, env, ctx);
	}

	/**
	* Code
	*/
	void codeOperation(Environment env, Context ctx, Assembler asm) {
	asm.add(where, opc_iadd + type.getTypeCodeOffset());
	}

	/**
	* Convert this expression to a string and append it to the string
	* buffer on the top of the stack.
	* If the needBuffer argument is true, the string buffer needs to be
	* created, initialized, and pushed on the stack, first.
	*/
	void codeAppend(Environment env, Context ctx, Assembler asm,
	ClassDeclaration sbClass, boolean needBuffer)
	throws ClassNotFound, AmbiguousMember {
	if (type.isType(TC_CLASS)) {
	left.codeAppend(env, ctx, asm, sbClass, needBuffer);
	right.codeAppend(env, ctx, asm, sbClass, false);
	} else {
	super.codeAppend(env, ctx, asm, sbClass, needBuffer);
	}
	}

	public void codeValue(Environment env, Context ctx, Assembler asm) {
	if (type.isType(TC_CLASS)) {
	try {
	// optimize (""+foo) or (foo+"") to String.valueOf(foo)
	if (left.equals("")) {
	right.codeValue(env, ctx, asm);
	right.ensureString(env, ctx, asm);
	return;
	}
	if (right.equals("")) {
	left.codeValue(env, ctx, asm);
	left.ensureString(env, ctx, asm);
	return;
	}

	ClassDeclaration sbClass =
	env.getClassDeclaration(idJavaLangStringBuffer);
	ClassDefinition sourceClass = ctx.field.getClassDefinition();
	// Create the string buffer and append to it.
	codeAppend(env, ctx, asm, sbClass, true);
	// Convert the string buffer to a string
	MemberDefinition f =
	sbClass.getClassDefinition(env).matchMethod(env,
	sourceClass,
	idToString);
	asm.add(where, opc_invokevirtual, f);
	} catch (ClassNotFound e) {
	throw new CompilerError(e);
	} catch (AmbiguousMember e) {
	throw new CompilerError(e);
	}
	} else {
	super.codeValue(env, ctx, asm);
	}
	}
	}

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