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package org.graalvm.compiler.hotspot;

import static org.graalvm.compiler.lir.LIRInstruction.OperandFlag.STACK;

import java.util.Arrays;

import org.graalvm.compiler.core.common.LIRKind;
import org.graalvm.compiler.lir.LIRInstruction;
import org.graalvm.compiler.lir.LIRInstructionClass;
import org.graalvm.compiler.lir.VirtualStackSlot;
import org.graalvm.compiler.lir.asm.CompilationResultBuilder;
import org.graalvm.compiler.lir.framemap.FrameMapBuilder;

import jdk.vm.ci.meta.AllocatableValue;

Manages allocation and re-use of lock slots in a scoped manner. The slots are used in HotSpot's lightweight locking mechanism to store the mark word of an object being locked.
/** * Manages allocation and re-use of lock slots in a scoped manner. The slots are used in HotSpot's * lightweight locking mechanism to store the mark word of an object being locked. */
public class HotSpotLockStack extends LIRInstruction { public static final LIRInstructionClass<HotSpotLockStack> TYPE = LIRInstructionClass.create(HotSpotLockStack.class); private static final AllocatableValue[] EMPTY = new AllocatableValue[0]; @Def({STACK}) private AllocatableValue[] locks; private final FrameMapBuilder frameMapBuilder; private final LIRKind slotKind; public HotSpotLockStack(FrameMapBuilder frameMapBuilder, LIRKind slotKind) { super(TYPE); this.frameMapBuilder = frameMapBuilder; this.slotKind = slotKind; this.locks = EMPTY; }
Gets a stack slot for a lock at a given lock nesting depth, allocating it first if necessary.
/** * Gets a stack slot for a lock at a given lock nesting depth, allocating it first if necessary. */
public VirtualStackSlot makeLockSlot(int lockDepth) { if (locks == EMPTY) { locks = new AllocatableValue[lockDepth + 1]; } else if (locks.length < lockDepth + 1) { locks = Arrays.copyOf(locks, lockDepth + 1); } if (locks[lockDepth] == null) { locks[lockDepth] = frameMapBuilder.allocateSpillSlot(slotKind); } return (VirtualStackSlot) locks[lockDepth]; } @Override public void emitCode(CompilationResultBuilder crb) { // do nothing } }