org.graalvm.word.LocationIdentity Maven / Gradle / Ivy
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/*
* Copyright (c) 2011, 2016, Oracle and/or its affiliates. All rights reserved.
* 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
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*/
package org.graalvm.word;
// JaCoCo Exclude
/**
* Marker interface for location identities. A different location identity of two memory accesses
* guarantees that the two accesses do not interfere.
*
* Clients of {@link LocationIdentity} must use {@link #equals(Object)}, not {@code ==}, when
* comparing two {@link LocationIdentity} values for equality. Likewise, they must not use
* {@link java.util.IdentityHashMap}s with {@link LocationIdentity} values as keys.
*
* @since 1.0
*/
public abstract class LocationIdentity {
private static final class AnyLocationIdentity extends LocationIdentity {
@Override
public boolean isImmutable() {
return false;
}
@Override
public String toString() {
return "ANY_LOCATION";
}
}
private static final class InitLocationIdentity extends LocationIdentity {
@Override
public boolean isImmutable() {
return true;
}
@Override
public String toString() {
return "INIT_LOCATION";
}
}
/**
* Creates a new location identity. Subclasses are responsible to provide proper implementations
* of {@link #equals} and {@link #hashCode}.
*
* @since 1.0
*/
protected LocationIdentity() {
}
/**
* Indicates that the given location is the union of all possible mutable locations. A write to
* such a location kill all reads from mutable locations and a read from this location is killed
* by any write (except for initialization writes).
*
* @since 1.0
*/
public static final LocationIdentity ANY_LOCATION = new AnyLocationIdentity();
/**
* Location only allowed to be used for writes. Indicates that a completely new memory location
* is written. Kills no read. The previous value at the given location must be either
* uninitialized or null. Writes to this location do not need a GC pre-barrier.
*
* @since 1.0
*/
public static final LocationIdentity INIT_LOCATION = new InitLocationIdentity();
/**
* Indicates that the given location is the union of all possible mutable locations. A write to
* such a location kill all reads from mutable locations and a read from this location is killed
* by any write (except for initialization writes).
*
* @since 1.0
*/
public static LocationIdentity any() {
return ANY_LOCATION;
}
/**
* Location only allowed to be used for writes. Indicates that a completely new memory location
* is written. Kills no read. The previous value at the given location must be either
* uninitialized or null. Writes to this location do not need a GC pre-barrier.
*
* @since 1.0
*/
public static LocationIdentity init() {
return INIT_LOCATION;
}
/**
* Denotes a location is unchanging in all cases. Not that this is different than the Java
* notion of final which only requires definite assignment.
*
* @since 1.0
*/
public abstract boolean isImmutable();
/**
* The inversion of {@link #isImmutable}.
*
* @since 1.0
*/
public final boolean isMutable() {
return !isImmutable();
}
/**
* Returns true if this location identity is {@link #any}.
*
* @since 1.0
*/
public final boolean isAny() {
return this == ANY_LOCATION;
}
/**
* Returns true if this location identity is {@link #init}.
*
* @since 1.0
*/
public final boolean isInit() {
return this == INIT_LOCATION;
}
/**
* Returns true if this location identity is not {@link #any}.
*
* @since 1.0
*/
public final boolean isSingle() {
return this != ANY_LOCATION;
}
/**
* Returns true if the memory slice denoted by this location identity may overlap with the
* provided other location identity.
*
* @since 1.0
*/
public final boolean overlaps(LocationIdentity other) {
return isAny() || other.isAny() || this.equals(other);
}
}