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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package org.graalvm.compiler.asm;

import java.util.ArrayList;

import org.graalvm.compiler.debug.GraalError;

This class represents a label within assembly code.
/** * This class represents a label within assembly code. */
public final class Label { private int position = -1; private int blockId = -1;
Positions of instructions that jump to this unresolved label. These instructions are patched when the label is bound.
/** * Positions of instructions that jump to this unresolved label. These instructions are patched * when the label is bound. */
ArrayList<Integer> patchPositions;
Link in list of labels with instructions to be patched.
/** * Link in list of labels with instructions to be patched. */
Label nextWithPatches;
Returns the position of this label in the code buffer.
Returns:the position
/** * Returns the position of this label in the code buffer. * * @return the position */
public int position() { assert position >= 0 : "Unbound label is being referenced"; return position; } public Label() { } public Label(int id) { blockId = id; } public int getBlockId() { return blockId; }
Binds the label to pos and patches all instructions added by addPatchAt(int, Assembler).
/** * Binds the label to {@code pos} and patches all instructions added by * {@link #addPatchAt(int, Assembler)}. */
protected void bind(int pos, Assembler asm) { if (pos < 0) { throw new GraalError("Cannot bind label to negative position %d", pos); } this.position = pos; if (patchPositions != null) { for (int i = 0; i < patchPositions.size(); ++i) { asm.patchJumpTarget(patchPositions.get(i), position); } patchPositions = null; } } public boolean isBound() { return position >= 0; } public void addPatchAt(int branchLocation, Assembler asm) { assert !isBound() : "Label is already bound " + this + " " + branchLocation + " at position " + position; if (patchPositions == null) { patchPositions = new ArrayList<>(2); nextWithPatches = asm.labelsWithPatches; asm.labelsWithPatches = this; } patchPositions.add(branchLocation); } public void reset() { if (this.patchPositions != null) { this.patchPositions.clear(); } this.position = -1; } @Override public String toString() { return isBound() ? String.valueOf(position()) : "?"; } }