1 /* 2 * Copyright (c) 2013, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 package org.graalvm.compiler.hotspot; 24 25 import static org.graalvm.compiler.lir.LIRInstruction.OperandFlag.STACK; 26 27 import java.util.Arrays; 28 29 import org.graalvm.compiler.core.common.LIRKind; 30 import org.graalvm.compiler.lir.LIRInstruction; 31 import org.graalvm.compiler.lir.LIRInstructionClass; 32 import org.graalvm.compiler.lir.VirtualStackSlot; 33 import org.graalvm.compiler.lir.asm.CompilationResultBuilder; 34 import org.graalvm.compiler.lir.framemap.FrameMapBuilder; 35 36 import jdk.vm.ci.meta.AllocatableValue; 37 38 /** 39 * Manages allocation and re-use of lock slots in a scoped manner. The slots are used in HotSpot's 40 * lightweight locking mechanism to store the mark word of an object being locked. 41 */ 42 public class HotSpotLockStack extends LIRInstruction { 43 public static final LIRInstructionClass<HotSpotLockStack> TYPE = LIRInstructionClass.create(HotSpotLockStack.class); 44 private static final AllocatableValue[] EMPTY = new AllocatableValue[0]; 45 46 @Def({STACK}) private AllocatableValue[] locks; 47 private final FrameMapBuilder frameMapBuilder; 48 private final LIRKind slotKind; 49 50 public HotSpotLockStack(FrameMapBuilder frameMapBuilder, LIRKind slotKind) { 51 super(TYPE); 52 this.frameMapBuilder = frameMapBuilder; 53 this.slotKind = slotKind; 54 this.locks = EMPTY; 55 } 56 57 /** 58 * Gets a stack slot for a lock at a given lock nesting depth, allocating it first if necessary. 59 */ 60 public VirtualStackSlot makeLockSlot(int lockDepth) { 61 if (locks == EMPTY) { 62 locks = new AllocatableValue[lockDepth + 1]; 63 } else if (locks.length < lockDepth + 1) { 64 locks = Arrays.copyOf(locks, lockDepth + 1); 65 } 66 if (locks[lockDepth] == null) { 67 locks[lockDepth] = frameMapBuilder.allocateSpillSlot(slotKind); 68 } 69 return (VirtualStackSlot) locks[lockDepth]; 70 } 71 72 @Override 73 public void emitCode(CompilationResultBuilder crb) { 74 // do nothing 75 } 76 }