/*******************************************************************************
* Copyright (c) 2000, 2007 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.wst.jsdt.internal.compiler.flow;
import org.eclipse.wst.jsdt.internal.compiler.lookup.FieldBinding;
import org.eclipse.wst.jsdt.internal.compiler.lookup.LocalVariableBinding;
public abstract class FlowInfo {
public int tagBits; // REACHABLE by default
public final static int REACHABLE = 0;
public final static int UNREACHABLE = 1;
public final static int NULL_FLAG_MASK = 2;
public final static int UNKNOWN = 0;
public final static int NULL = 1;
public final static int NON_NULL = -1;
public static final UnconditionalFlowInfo DEAD_END; // Represents a dead branch status of initialization
static {
DEAD_END = new UnconditionalFlowInfo();
DEAD_END.tagBits = UNREACHABLE;
}
/**
* Add other inits to this flow info, then return this. The operation semantics
* are to match as closely as possible the application to this flow info of all
* the operations that resulted into otherInits.
* @param otherInits other inits to add to this
* @return this, modified according to otherInits information
*/
abstract public FlowInfo addInitializationsFrom(FlowInfo otherInits);
/**
* Compose other inits over this flow info, then return this. The operation
* semantics are to wave into this flow info the consequences of a possible
* path into the operations that resulted into otherInits. The fact that this
* path may be left unexecuted under peculiar conditions results into less
* specific results than {@link #addInitializationsFrom(FlowInfo)
* addInitializationsFrom}.
* @param otherInits other inits to compose over this
* @return this, modified according to otherInits information
*/
abstract public FlowInfo addPotentialInitializationsFrom(FlowInfo otherInits);
public FlowInfo asNegatedCondition() {
return this;
}
public static FlowInfo conditional(FlowInfo initsWhenTrue, FlowInfo initsWhenFalse){
// if (initsWhenTrue.equals(initsWhenFalse)) return initsWhenTrue; -- could optimize if #equals is defined
return new ConditionalFlowInfo(initsWhenTrue, initsWhenFalse);
}
/**
* Check whether a given local variable is known to be unable to gain a definite
* non null or definite null status by the use of an enclosing flow info. The
* semantics are that if the current flow info marks the variable as potentially
* unknown or else as being both potentially null and potentially non null,
* then it won't ever be promoted as definitely null or definitely non null. (It
* could still get promoted to definite unknown).
* @param local the variable to ckeck
* @return true iff this flow info prevents local from being promoted to
* definite non null or definite null against an enclosing flow info
*/
public boolean cannotBeDefinitelyNullOrNonNull(LocalVariableBinding local) {
return isPotentiallyUnknown(local) ||
isPotentiallyNonNull(local) && isPotentiallyNull(local);
}
/**
* Check whether a given local variable is known to be non null, either because
* it is definitely non null, or because is has been tested against non null.
* @param local the variable to ckeck
* @return true iff local cannot be null for this flow info
*/
public boolean cannotBeNull(LocalVariableBinding local) {
return isDefinitelyNonNull(local) || isProtectedNonNull(local);
}
/**
* Check whether a given local variable is known to be null, either because it
* is definitely null, or because is has been tested against null.
* @param local the variable to ckeck
* @return true iff local can only be null for this flow info
*/
public boolean canOnlyBeNull(LocalVariableBinding local) {
return isDefinitelyNull(local) || isProtectedNull(local);
}
/**
* Return a deep copy of the current instance.
* @return a deep copy of this flow info
*/
abstract public FlowInfo copy();
public static UnconditionalFlowInfo initial(int maxFieldCount) {
UnconditionalFlowInfo info = new UnconditionalFlowInfo();
info.maxFieldCount = maxFieldCount;
return info;
}
/**
* Return the flow info that would result from the path associated to the
* value false for the condition expression that generated this flow info.
* May be this flow info if it is not an instance of {@link
* ConditionalFlowInfo}. May have a side effect on subparts of this flow
* info (subtrees get merged).
* @return the flow info associated to the false branch of the condition
* that generated this flow info
*/
abstract public FlowInfo initsWhenFalse();
/**
* Return the flow info that would result from the path associated to the
* value true for the condition expression that generated this flow info.
* May be this flow info if it is not an instance of {@link
* ConditionalFlowInfo}. May have a side effect on subparts of this flow
* info (subtrees get merged).
* @return the flow info associated to the true branch of the condition
* that generated this flow info
*/
abstract public FlowInfo initsWhenTrue();
/**
* Check status of definite assignment for a field.
*/
abstract public boolean isDefinitelyAssigned(FieldBinding field);
/**
* Check status of definite assignment for a local.
*/
public abstract boolean isDefinitelyAssigned(LocalVariableBinding local);
/**
* Check status of definite non-null value for a given local variable.
* @param local the variable to ckeck
* @return true iff local is definitely non null for this flow info
*/
public abstract boolean isDefinitelyNonNull(LocalVariableBinding local);
/**
* Check status of definite null value for a given local variable.
* @param local the variable to ckeck
* @return true iff local is definitely null for this flow info
*/
public abstract boolean isDefinitelyNull(LocalVariableBinding local);
/**
* Check status of definite unknown value for a given local variable.
* @param local the variable to ckeck
* @return true iff local is definitely unknown for this flow info
*/
public abstract boolean isDefinitelyUnknown(LocalVariableBinding local);
/**
* Check status of potential assignment for a field.
*/
abstract public boolean isPotentiallyAssigned(FieldBinding field);
/**
* Check status of potential assignment for a local variable.
*/
abstract public boolean isPotentiallyAssigned(LocalVariableBinding field);
/**
* Check status of potential null assignment for a local. Return true if there
* is a reasonable expectation that the variable be non null at this point.
* @param local LocalVariableBinding - the binding for the checked local
* @return true if there is a reasonable expectation that local be non null at
* this point
*/
public abstract boolean isPotentiallyNonNull(LocalVariableBinding local);
/**
* Check status of potential null assignment for a local. Return true if there
* is a reasonable expectation that the variable be null at this point. This
* includes the protected null case, so as to augment diagnostics, but does not
* really check that someone deliberately assigned to null on any specific
* path
* @param local LocalVariableBinding - the binding for the checked local
* @return true if there is a reasonable expectation that local be null at
* this point
*/
public abstract boolean isPotentiallyNull(LocalVariableBinding local);
/**
* Return true if the given local may have been assigned to an unknown value.
* @param local the local to check
* @return true if the given local may have been assigned to an unknown value
*/
public abstract boolean isPotentiallyUnknown(LocalVariableBinding local);
/**
* Return true if the given local is protected by a test against a non null
* value.
* @param local the local to check
* @return true if the given local is protected by a test against a non null
*/
public abstract boolean isProtectedNonNull(LocalVariableBinding local);
/**
* Return true if the given local is protected by a test against null.
* @param local the local to check
* @return true if the given local is protected by a test against null
*/
public abstract boolean isProtectedNull(LocalVariableBinding local);
/**
* Record that a local variable got checked to be non null.
* @param local the checked local variable
*/
abstract public void markAsComparedEqualToNonNull(LocalVariableBinding local);
/**
* Record that a local variable got checked to be null.
* @param local the checked local variable
*/
abstract public void markAsComparedEqualToNull(LocalVariableBinding local);
/**
* Record a field got definitely assigned.
*/
abstract public void markAsDefinitelyAssigned(FieldBinding field);
/**
* Record a local got definitely assigned to a non-null value.
*/
abstract public void markAsDefinitelyNonNull(LocalVariableBinding local);
/**
* Record a local got definitely assigned to null.
*/
abstract public void markAsDefinitelyNull(LocalVariableBinding local);
/**
* Record a local got definitely assigned.
*/
abstract public void markAsDefinitelyAssigned(LocalVariableBinding local);
/**
* Record a local got definitely assigned to an unknown value.
*/
abstract public void markAsDefinitelyUnknown(LocalVariableBinding local);
/**
* Merge branches using optimized boolean conditions
*/
public static UnconditionalFlowInfo mergedOptimizedBranches(
FlowInfo initsWhenTrue, boolean isOptimizedTrue,
FlowInfo initsWhenFalse, boolean isOptimizedFalse,
boolean allowFakeDeadBranch) {
UnconditionalFlowInfo mergedInfo;
if (isOptimizedTrue){
if (initsWhenTrue == FlowInfo.DEAD_END && allowFakeDeadBranch) {
mergedInfo = initsWhenFalse.setReachMode(FlowInfo.UNREACHABLE).
unconditionalInits();
}
else {
mergedInfo =
initsWhenTrue.addPotentialInitializationsFrom(initsWhenFalse.
nullInfoLessUnconditionalCopy()).
unconditionalInits();
}
}
else if (isOptimizedFalse) {
if (initsWhenFalse == FlowInfo.DEAD_END && allowFakeDeadBranch) {
mergedInfo = initsWhenTrue.setReachMode(FlowInfo.UNREACHABLE).
unconditionalInits();
}
else {
mergedInfo =
initsWhenFalse.addPotentialInitializationsFrom(initsWhenTrue.
nullInfoLessUnconditionalCopy()).
unconditionalInits();
}
}
else {
mergedInfo = initsWhenTrue.
mergedWith(initsWhenFalse.unconditionalInits());
}
return mergedInfo;
}
/**
* Return REACHABLE if this flow info is reachable, UNREACHABLE
* else.
* @return REACHABLE if this flow info is reachable, UNREACHABLE
* else
*/
public int reachMode() {
return this.tagBits & UNREACHABLE;
}
/**
* Return a flow info that carries the same information as the result of
* {@link #initsWhenTrue() initsWhenTrue}, but warrantied to be different
* from this.<br>
* Caveat: side effects on the result may affect components of this.
* @return the result of initsWhenTrue or a copy of it
*/
abstract public FlowInfo safeInitsWhenTrue();
/**
* Set this flow info reach mode and return this.
* @param reachMode one of {@link #REACHABLE REACHABLE} or {@link #UNREACHABLE UNREACHABLE}
* @return this, with the reach mode set to reachMode
*/
abstract public FlowInfo setReachMode(int reachMode);
/**
* Return the intersection of this and otherInits, that is
* one of:<ul>
* <li>the receiver updated in the following way:<ul>
* <li>intersection of definitely assigned variables,
* <li>union of potentially assigned variables,
* <li>similar operations for null,</ul>
* <li>or the receiver or otherInits if the other one is non
* reachable.</ul>
* otherInits is not affected, and is not returned either (no
* need to protect the result).
* @param otherInits the flow info to merge with this
* @return the intersection of this and otherInits.
*/
abstract public UnconditionalFlowInfo mergedWith(
UnconditionalFlowInfo otherInits);
/**
* Return a copy of this unconditional flow info, deprived from its null
* info. {@link #DEAD_END DEAD_END} is returned unmodified.
* @return a copy of this unconditional flow info deprived from its null info
*/
abstract public UnconditionalFlowInfo nullInfoLessUnconditionalCopy();
public String toString(){
if (this == DEAD_END){
return "FlowInfo.DEAD_END"; //$NON-NLS-1$
}
return super.toString();
}
/**
* Return a new flow info that holds the same information as this would after
* a call to unconditionalInits, but leaving this info unaffected. Moreover,
* the result can be modified without affecting this.
* @return a new flow info carrying this unconditional flow info
*/
abstract public UnconditionalFlowInfo unconditionalCopy();
/**
* Return a new flow info that holds the same information as this would after
* a call to {@link #unconditionalInits() unconditionalInits} followed by the
* erasure of fields specific information, but leaving this flow info unaffected.
* @return a new flow info carrying the unconditional flow info for local variables
*/
abstract public UnconditionalFlowInfo unconditionalFieldLessCopy();
/**
* Return a flow info that merges the possible paths of execution described by
* this flow info. In case of an unconditional flow info, return this. In case
* of a conditional flow info, merge branches recursively. Caveat: this may
* be affected, and modifying the result may affect this.
* @return a flow info that merges the possible paths of execution described by
* this
*/
abstract public UnconditionalFlowInfo unconditionalInits();
/**
* Return a new flow info that holds the same information as this would after
* a call to {@link #unconditionalInits() unconditionalInits}, but leaving
* this info unaffected. Side effects on the result might affect this though
* (consider it as read only).
* @return a flow info carrying this unconditional flow info
*/
abstract public UnconditionalFlowInfo unconditionalInitsWithoutSideEffect();
}
