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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;
	import sun.tools.asm.Label;
	import java.util.Hashtable;

	/**
	* 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 NotExpression extends UnaryExpression {
	/**
	* Constructor
	*/
	public NotExpression(long where, Expression right) {
	super(NOT, where, Type.tBoolean, right);
	}

	/**
	* Select the type of the expression
	*/
	void selectType(Environment env, Context ctx, int tm) {
	right = convert(env, ctx, Type.tBoolean, right);
	}

	/*
	* Check a "not" expression.
	*
	* cvars is modified so that
	* cvar.vsTrue indicates variables with a known value if
	* the expression is true.
	* cvars.vsFalse indicates variables with a known value if
	* the expression is false
	*
	* For "not" expressions, we look at the inside expression, and then
	* swap true and false.
	*/

	public void checkCondition(Environment env, Context ctx, Vset vset,
	Hashtable exp, ConditionVars cvars) {
	right.checkCondition(env, ctx, vset, exp, cvars);
	right = convert(env, ctx, Type.tBoolean, right);
	// swap true and false
	Vset temp = cvars.vsFalse;
	cvars.vsFalse = cvars.vsTrue;
	cvars.vsTrue = temp;
	}

	/**
	* Evaluate
	*/
	Expression eval(boolean a) {
	return new BooleanExpression(where, !a);
	}

	/**
	* Simplify
	*/
	Expression simplify() {
	// Check if the expression can be optimized
	switch (right.op) {
	case NOT:
	return ((NotExpression)right).right;

	case EQ:
	case NE:
	case LT:
	case LE:
	case GT:
	case GE:
	break;

	default:
	return this;
	}

	// Can't negate real comparisons
	BinaryExpression bin = (BinaryExpression)right;
	if (bin.left.type.inMask(TM_REAL)) {
	return this;
	}

	// Negate comparison
	switch (right.op) {
	case EQ:
	return new NotEqualExpression(where, bin.left, bin.right);
	case NE:
	return new EqualExpression(where, bin.left, bin.right);
	case LT:
	return new GreaterOrEqualExpression(where, bin.left, bin.right);
	case LE:
	return new GreaterExpression(where, bin.left, bin.right);
	case GT:
	return new LessOrEqualExpression(where, bin.left, bin.right);
	case GE:
	return new LessExpression(where, bin.left, bin.right);
	}
	return this;
	}

	/**
	* Code
	*/
	void codeBranch(Environment env, Context ctx, Assembler asm, Label lbl, boolean whenTrue) {
	right.codeBranch(env, ctx, asm, lbl, !whenTrue);
	}

	/**
	* Instead of relying on the default code generation which uses
	* conditional branching, generate a simpler stream using XOR.
	*/
	public void codeValue(Environment env, Context ctx, Assembler asm) {
	right.codeValue(env, ctx, asm);
	asm.add(where, opc_ldc, new Integer(1));
	asm.add(where, opc_ixor);
	}

	}

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