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package jdk.internal.vm.compiler.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 LocationIdentity must use Object.equals(Object), not ==, when comparing two LocationIdentity values for equality. Likewise, they must not use IdentityHashMaps with LocationIdentity values as keys.

Since:19.0
/** * Marker interface for location identities. A different location identity of two memory accesses * guarantees that the two accesses do not interfere. * <p> * 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 19.0 */
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 Object.equals and Object.hashCode.
Since:19.0
/** * Creates a new location identity. Subclasses are responsible to provide proper implementations * of {@link #equals} and {@link #hashCode}. * * @since 19.0 */
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:19.0
/** * 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 19.0 */
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:19.0
/** * 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 19.0 */
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:19.0
/** * 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 19.0 */
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:19.0
/** * 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 19.0 */
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:19.0
/** * 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 19.0 */
public abstract boolean isImmutable();
The inversion of isImmutable.
Since:19.0
/** * The inversion of {@link #isImmutable}. * * @since 19.0 */
public final boolean isMutable() { return !isImmutable(); }
Returns true if this location identity is any.
Since:19.0
/** * Returns true if this location identity is {@link #any}. * * @since 19.0 */
public final boolean isAny() { return this == ANY_LOCATION; }
Returns true if this location identity is init.
Since:19.0
/** * Returns true if this location identity is {@link #init}. * * @since 19.0 */
public final boolean isInit() { return this == INIT_LOCATION; }
Returns true if this location identity is not any.
Since:19.0
/** * Returns true if this location identity is not {@link #any}. * * @since 19.0 */
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:19.0
/** * Returns true if the memory slice denoted by this location identity may overlap with the * provided other location identity. * * @since 19.0 */
public final boolean overlaps(LocationIdentity other) { return isAny() || other.isAny() || this.equals(other); } }