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	/*
	* 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.
	*/

	/*
	* This file is available under and governed by the GNU General Public
	* License version 2 only, as published by the Free Software Foundation.
	* However, the following notice accompanied the original version of this
	* file:
	*
	* ASM: a very small and fast Java bytecode manipulation framework
	* Copyright (c) 2000-2011 INRIA, France Telecom
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. Neither the name of the copyright holders nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
	* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
	* THE POSSIBILITY OF SUCH DAMAGE.
	*/
	package jdk.internal.org.objectweb.asm;

	/**
	* A label represents a position in the bytecode of a method. Labels are used
	* for jump, goto, and switch instructions, and for try catch blocks. A label
	* designates the <i>instruction</i> that is just after. Note however that there
	* can be other elements between a label and the instruction it designates (such
	* as other labels, stack map frames, line numbers, etc.).
	*
	* @author Eric Bruneton
	*/
	public class Label {

	/**
	* Indicates if this label is only used for debug attributes. Such a label
	* is not the start of a basic block, the target of a jump instruction, or
	* an exception handler. It can be safely ignored in control flow graph
	* analysis algorithms (for optimization purposes).
	*/
	static final int DEBUG = 1;

	/**
	* Indicates if the position of this label is known.
	*/
	static final int RESOLVED = 2;

	/**
	* Indicates if this label has been updated, after instruction resizing.
	*/
	static final int RESIZED = 4;

	/**
	* Indicates if this basic block has been pushed in the basic block stack.
	* See {@link MethodWriter#visitMaxs visitMaxs}.
	*/
	static final int PUSHED = 8;

	/**
	* Indicates if this label is the target of a jump instruction, or the start
	* of an exception handler.
	*/
	static final int TARGET = 16;

	/**
	* Indicates if a stack map frame must be stored for this label.
	*/
	static final int STORE = 32;

	/**
	* Indicates if this label corresponds to a reachable basic block.
	*/
	static final int REACHABLE = 64;

	/**
	* Indicates if this basic block ends with a JSR instruction.
	*/
	static final int JSR = 128;

	/**
	* Indicates if this basic block ends with a RET instruction.
	*/
	static final int RET = 256;

	/**
	* Indicates if this basic block is the start of a subroutine.
	*/
	static final int SUBROUTINE = 512;

	/**
	* Indicates if this subroutine basic block has been visited by a
	* visitSubroutine(null, ...) call.
	*/
	static final int VISITED = 1024;

	/**
	* Indicates if this subroutine basic block has been visited by a
	* visitSubroutine(!null, ...) call.
	*/
	static final int VISITED2 = 2048;

	/**
	* Field used to associate user information to a label. Warning: this field
	* is used by the ASM tree package. In order to use it with the ASM tree
	* package you must override the
	* {@link jdk.internal.org.objectweb.asm.tree.MethodNode#getLabelNode} method.
	*/
	public Object info;

	/**
	* Flags that indicate the status of this label.
	*
	* @see #DEBUG
	* @see #RESOLVED
	* @see #RESIZED
	* @see #PUSHED
	* @see #TARGET
	* @see #STORE
	* @see #REACHABLE
	* @see #JSR
	* @see #RET
	*/
	int status;

	/**
	* The line number corresponding to this label, if known.
	*/
	int line;

	/**
	* The position of this label in the code, if known.
	*/
	int position;

	/**
	* Number of forward references to this label, times two.
	*/
	private int referenceCount;

	/**
	* Informations about forward references. Each forward reference is
	* described by two consecutive integers in this array: the first one is the
	* position of the first byte of the bytecode instruction that contains the
	* forward reference, while the second is the position of the first byte of
	* the forward reference itself. In fact the sign of the first integer
	* indicates if this reference uses 2 or 4 bytes, and its absolute value
	* gives the position of the bytecode instruction. This array is also used
	* as a bitset to store the subroutines to which a basic block belongs. This
	* information is needed in {@linked MethodWriter#visitMaxs}, after all
	* forward references have been resolved. Hence the same array can be used
	* for both purposes without problems.
	*/
	private int[] srcAndRefPositions;

	// ------------------------------------------------------------------------

	/*
	* Fields for the control flow and data flow graph analysis algorithms (used
	* to compute the maximum stack size or the stack map frames). A control
	* flow graph contains one node per "basic block", and one edge per "jump"
	* from one basic block to another. Each node (i.e., each basic block) is
	* represented by the Label object that corresponds to the first instruction
	* of this basic block. Each node also stores the list of its successors in
	* the graph, as a linked list of Edge objects.
	*
	* The control flow analysis algorithms used to compute the maximum stack
	* size or the stack map frames are similar and use two steps. The first
	* step, during the visit of each instruction, builds information about the
	* state of the local variables and the operand stack at the end of each
	* basic block, called the "output frame", <i>relatively</i> to the frame
	* state at the beginning of the basic block, which is called the "input
	* frame", and which is <i>unknown</i> during this step. The second step, in
	* {@link MethodWriter#visitMaxs}, is a fix point algorithm that computes
	* information about the input frame of each basic block, from the input
	* state of the first basic block (known from the method signature), and by
	* the using the previously computed relative output frames.
	*
	* The algorithm used to compute the maximum stack size only computes the
	* relative output and absolute input stack heights, while the algorithm
	* used to compute stack map frames computes relative output frames and
	* absolute input frames.
	*/

	/**
	* Start of the output stack relatively to the input stack. The exact
	* semantics of this field depends on the algorithm that is used.
	*
	* When only the maximum stack size is computed, this field is the number of
	* elements in the input stack.
	*
	* When the stack map frames are completely computed, this field is the
	* offset of the first output stack element relatively to the top of the
	* input stack. This offset is always negative or null. A null offset means
	* that the output stack must be appended to the input stack. A -n offset
	* means that the first n output stack elements must replace the top n input
	* stack elements, and that the other elements must be appended to the input
	* stack.
	*/
	int inputStackTop;

	/**
	* Maximum height reached by the output stack, relatively to the top of the
	* input stack. This maximum is always positive or null.
	*/
	int outputStackMax;

	/**
	* Information about the input and output stack map frames of this basic
	* block. This field is only used when {@link ClassWriter#COMPUTE_FRAMES}
	* option is used.
	*/
	Frame frame;

	/**
	* The successor of this label, in the order they are visited. This linked
	* list does not include labels used for debug info only. If
	* {@link ClassWriter#COMPUTE_FRAMES} option is used then, in addition, it
	* does not contain successive labels that denote the same bytecode position
	* (in this case only the first label appears in this list).
	*/
	Label successor;

	/**
	* The successors of this node in the control flow graph. These successors
	* are stored in a linked list of {@link Edge Edge} objects, linked to each
	* other by their {@link Edge#next} field.
	*/
	Edge successors;

	/**
	* The next basic block in the basic block stack. This stack is used in the
	* main loop of the fix point algorithm used in the second step of the
	* control flow analysis algorithms. It is also used in
	* {@link #visitSubroutine} to avoid using a recursive method.
	*
	* @see MethodWriter#visitMaxs
	*/
	Label next;

	// ------------------------------------------------------------------------
	// Constructor
	// ------------------------------------------------------------------------

	/**
	* Constructs a new label.
	*/
	public Label() {
	}

	// ------------------------------------------------------------------------
	// Methods to compute offsets and to manage forward references
	// ------------------------------------------------------------------------

	/**
	* Returns the offset corresponding to this label. This offset is computed
	* from the start of the method's bytecode. <i>This method is intended for
	* {@link Attribute} sub classes, and is normally not needed by class
	* generators or adapters.</i>
	*
	* @return the offset corresponding to this label.
	* @throws IllegalStateException
	* if this label is not resolved yet.
	*/
	public int getOffset() {
	if ((status & RESOLVED) == 0) {
	throw new IllegalStateException(
	"Label offset position has not been resolved yet");
	}
	return position;
	}

	/**
	* Puts a reference to this label in the bytecode of a method. If the
	* position of the label is known, the offset is computed and written
	* directly. Otherwise, a null offset is written and a new forward reference
	* is declared for this label.
	*
	* @param owner
	* the code writer that calls this method.
	* @param out
	* the bytecode of the method.
	* @param source
	* the position of first byte of the bytecode instruction that
	* contains this label.
	* @param wideOffset
	* <tt>true</tt> if the reference must be stored in 4 bytes, or
	* <tt>false</tt> if it must be stored with 2 bytes.
	* @throws IllegalArgumentException
	* if this label has not been created by the given code writer.
	*/
	void put(final MethodWriter owner, final ByteVector out, final int source,
	final boolean wideOffset) {
	if ((status & RESOLVED) == 0) {
	if (wideOffset) {
	addReference(-1 - source, out.length);
	out.putInt(-1);
	} else {
	addReference(source, out.length);
	out.putShort(-1);
	}
	} else {
	if (wideOffset) {
	out.putInt(position - source);
	} else {
	out.putShort(position - source);
	}
	}
	}

	/**
	* Adds a forward reference to this label. This method must be called only
	* for a true forward reference, i.e. only if this label is not resolved
	* yet. For backward references, the offset of the reference can be, and
	* must be, computed and stored directly.
	*
	* @param sourcePosition
	* the position of the referencing instruction. This position
	* will be used to compute the offset of this forward reference.
	* @param referencePosition
	* the position where the offset for this forward reference must
	* be stored.
	*/
	private void addReference(final int sourcePosition,
	final int referencePosition) {
	if (srcAndRefPositions == null) {
	srcAndRefPositions = new int[6];
	}
	if (referenceCount >= srcAndRefPositions.length) {
	int[] a = new int[srcAndRefPositions.length + 6];
	System.arraycopy(srcAndRefPositions, 0, a, 0,
	srcAndRefPositions.length);
	srcAndRefPositions = a;
	}
	srcAndRefPositions[referenceCount++] = sourcePosition;
	srcAndRefPositions[referenceCount++] = referencePosition;
	}

	/**
	* Resolves all forward references to this label. This method must be called
	* when this label is added to the bytecode of the method, i.e. when its
	* position becomes known. This method fills in the blanks that where left
	* in the bytecode by each forward reference previously added to this label.
	*
	* @param owner
	* the code writer that calls this method.
	* @param position
	* the position of this label in the bytecode.
	* @param data
	* the bytecode of the method.
	* @return <tt>true</tt> if a blank that was left for this label was to
	* small to store the offset. In such a case the corresponding jump
	* instruction is replaced with a pseudo instruction (using unused
	* opcodes) using an unsigned two bytes offset. These pseudo
	* instructions will need to be replaced with true instructions with
	* wider offsets (4 bytes instead of 2). This is done in
	* {@link MethodWriter#resizeInstructions}.
	* @throws IllegalArgumentException
	* if this label has already been resolved, or if it has not
	* been created by the given code writer.
	*/
	boolean resolve(final MethodWriter owner, final int position,
	final byte[] data) {
	boolean needUpdate = false;
	this.status \|= RESOLVED;
	this.position = position;
	int i = 0;
	while (i < referenceCount) {
	int source = srcAndRefPositions[i++];
	int reference = srcAndRefPositions[i++];
	int offset;
	if (source >= 0) {
	offset = position - source;
	if (offset < Short.MIN_VALUE \|\| offset > Short.MAX_VALUE) {
	/*
	* changes the opcode of the jump instruction, in order to
	* be able to find it later (see resizeInstructions in
	* MethodWriter). These temporary opcodes are similar to
	* jump instruction opcodes, except that the 2 bytes offset
	* is unsigned (and can therefore represent values from 0 to
	* 65535, which is sufficient since the size of a method is
	* limited to 65535 bytes).
	*/
	int opcode = data[reference - 1] & 0xFF;
	if (opcode <= Opcodes.JSR) {
	// changes IFEQ ... JSR to opcodes 202 to 217
	data[reference - 1] = (byte) (opcode + 49);
	} else {
	// changes IFNULL and IFNONNULL to opcodes 218 and 219
	data[reference - 1] = (byte) (opcode + 20);
	}
	needUpdate = true;
	}
	data[reference++] = (byte) (offset >>> 8);
	data[reference] = (byte) offset;
	} else {
	offset = position + source + 1;
	data[reference++] = (byte) (offset >>> 24);
	data[reference++] = (byte) (offset >>> 16);
	data[reference++] = (byte) (offset >>> 8);
	data[reference] = (byte) offset;
	}
	}
	return needUpdate;
	}

	/**
	* Returns the first label of the series to which this label belongs. For an
	* isolated label or for the first label in a series of successive labels,
	* this method returns the label itself. For other labels it returns the
	* first label of the series.
	*
	* @return the first label of the series to which this label belongs.
	*/
	Label getFirst() {
	return !ClassReader.FRAMES \|\| frame == null ? this : frame.owner;
	}

	// ------------------------------------------------------------------------
	// Methods related to subroutines
	// ------------------------------------------------------------------------

	/**
	* Returns true is this basic block belongs to the given subroutine.
	*
	* @param id
	* a subroutine id.
	* @return true is this basic block belongs to the given subroutine.
	*/
	boolean inSubroutine(final long id) {
	if ((status & Label.VISITED) != 0) {
	return (srcAndRefPositions[(int) (id >>> 32)] & (int) id) != 0;
	}
	return false;
	}

	/**
	* Returns true if this basic block and the given one belong to a common
	* subroutine.
	*
	* @param block
	* another basic block.
	* @return true if this basic block and the given one belong to a common
	* subroutine.
	*/
	boolean inSameSubroutine(final Label block) {
	if ((status & VISITED) == 0 \|\| (block.status & VISITED) == 0) {
	return false;
	}
	for (int i = 0; i < srcAndRefPositions.length; ++i) {
	if ((srcAndRefPositions[i] & block.srcAndRefPositions[i]) != 0) {
	return true;
	}
	}
	return false;
	}

	/**
	* Marks this basic block as belonging to the given subroutine.
	*
	* @param id
	* a subroutine id.
	* @param nbSubroutines
	* the total number of subroutines in the method.
	*/
	void addToSubroutine(final long id, final int nbSubroutines) {
	if ((status & VISITED) == 0) {
	status \|= VISITED;
	srcAndRefPositions = new int[nbSubroutines / 32 + 1];
	}
	srcAndRefPositions[(int) (id >>> 32)] \|= (int) id;
	}

	/**
	* Finds the basic blocks that belong to a given subroutine, and marks these
	* blocks as belonging to this subroutine. This method follows the control
	* flow graph to find all the blocks that are reachable from the current
	* block WITHOUT following any JSR target.
	*
	* @param JSR
	* a JSR block that jumps to this subroutine. If this JSR is not
	* null it is added to the successor of the RET blocks found in
	* the subroutine.
	* @param id
	* the id of this subroutine.
	* @param nbSubroutines
	* the total number of subroutines in the method.
	*/
	void visitSubroutine(final Label JSR, final long id, final int nbSubroutines) {
	// user managed stack of labels, to avoid using a recursive method
	// (recursivity can lead to stack overflow with very large methods)
	Label stack = this;
	while (stack != null) {
	// removes a label l from the stack
	Label l = stack;
	stack = l.next;
	l.next = null;

	if (JSR != null) {
	if ((l.status & VISITED2) != 0) {
	continue;
	}
	l.status \|= VISITED2;
	// adds JSR to the successors of l, if it is a RET block
	if ((l.status & RET) != 0) {
	if (!l.inSameSubroutine(JSR)) {
	Edge e = new Edge();
	e.info = l.inputStackTop;
	e.successor = JSR.successors.successor;
	e.next = l.successors;
	l.successors = e;
	}
	}
	} else {
	// if the l block already belongs to subroutine 'id', continue
	if (l.inSubroutine(id)) {
	continue;
	}
	// marks the l block as belonging to subroutine 'id'
	l.addToSubroutine(id, nbSubroutines);
	}
	// pushes each successor of l on the stack, except JSR targets
	Edge e = l.successors;
	while (e != null) {
	// if the l block is a JSR block, then 'l.successors.next' leads
	// to the JSR target (see {@link #visitJumpInsn}) and must
	// therefore not be followed
	if ((l.status & Label.JSR) == 0 \|\| e != l.successors.next) {
	// pushes e.successor on the stack if it not already added
	if (e.successor.next == null) {
	e.successor.next = stack;
	stack = e.successor;
	}
	}
	e = e.next;
	}
	}
	}

	// ------------------------------------------------------------------------
	// Overriden Object methods
	// ------------------------------------------------------------------------

	/**
	* Returns a string representation of this label.
	*
	* @return a string representation of this label.
	*/
	@Override
	public String toString() {
	return "L" + System.identityHashCode(this);
	}
	}

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