001/*
002 * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.
008 *
009 * This code is distributed in the hope that it will be useful, but WITHOUT
010 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
011 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
012 * version 2 for more details (a copy is included in the LICENSE file that
013 * accompanied this code).
014 *
015 * You should have received a copy of the GNU General Public License version
016 * 2 along with this work; if not, write to the Free Software Foundation,
017 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
018 *
019 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
020 * or visit www.oracle.com if you need additional information or have any
021 * questions.
022 */
023package com.oracle.graal.hotspot;
024
025import static com.oracle.graal.lir.LIRInstruction.OperandFlag.*;
026
027import java.util.*;
028
029import jdk.internal.jvmci.code.*;
030import jdk.internal.jvmci.meta.*;
031
032import com.oracle.graal.lir.*;
033import com.oracle.graal.lir.asm.*;
034import com.oracle.graal.lir.framemap.*;
035
036/**
037 * Manages allocation and re-use of lock slots in a scoped manner. The slots are used in HotSpot's
038 * lightweight locking mechanism to store the mark word of an object being locked.
039 */
040public class HotSpotLockStack extends LIRInstruction {
041    public static final LIRInstructionClass<HotSpotLockStack> TYPE = LIRInstructionClass.create(HotSpotLockStack.class);
042    private static final StackSlotValue[] EMPTY = new StackSlotValue[0];
043
044    @Def({STACK}) private StackSlotValue[] locks;
045    private final FrameMapBuilder frameMapBuilder;
046    private final LIRKind slotKind;
047
048    public HotSpotLockStack(FrameMapBuilder frameMapBuilder, LIRKind slotKind) {
049        super(TYPE);
050        this.frameMapBuilder = frameMapBuilder;
051        this.slotKind = slotKind;
052        this.locks = EMPTY;
053    }
054
055    /**
056     * Gets a stack slot for a lock at a given lock nesting depth, allocating it first if necessary.
057     */
058    public StackSlotValue makeLockSlot(int lockDepth) {
059        if (locks == EMPTY) {
060            locks = new StackSlotValue[lockDepth + 1];
061        } else if (locks.length < lockDepth + 1) {
062            locks = Arrays.copyOf(locks, lockDepth + 1);
063        }
064        if (locks[lockDepth] == null) {
065            locks[lockDepth] = frameMapBuilder.allocateSpillSlot(slotKind);
066        }
067        return locks[lockDepth];
068    }
069
070    @Override
071    public void emitCode(CompilationResultBuilder crb) {
072        // do nothing
073    }
074}