package org.checkerframework.dataflow.analysis;
/**
* A store is used to keep track of the information that the org.checkerframework.dataflow analysis
* has accumulated at any given point in time.
*
* @author Stefan Heule
*
* @param <S>
* The type of the store returned by {@code copy} and that is used in
* {@code leastUpperBound}. Usually it is the implementing class
* itself, e.g. in {@code T extends Store<T>}.
*/
public interface Store<S extends Store<S>> {
// We maintain a then store and an else store before each basic block.
// When they are identical (by reference equality), they can be treated
// as a regular unconditional store.
// Once we have some information for both the then and else store, we
// create a TransferInput for the block and allow it to be analyzed.
public static enum Kind {
THEN,
ELSE,
BOTH
}
// A flow rule describes how stores flow along one edge between basic blocks.
public static enum FlowRule {
EACH_TO_EACH, // The normal case, then store flows to the then store
// and else store flows to the else store.
THEN_TO_BOTH, // Then store flows to both then and else of successor.
ELSE_TO_BOTH, // Else store flows to both then and else of successor.
THEN_TO_THEN, // Then store flows to the then of successor. Else store is ignored.
ELSE_TO_ELSE, // Else store flows to the else of successor. Then store is ignored.
}
/** @return An exact copy of this store. */
S copy();
/**
* Compute the least upper bound of two stores.
*
* <p>
*
* <em>Important</em>: This method must fulfill the following contract:
* <ul>
* <li>Does not change {@code this}.</li>
* <li>Does not change {@code other}.</li>
* <li>Returns a fresh object which is not aliased yet.</li>
* <li>Returns an object of the same (dynamic) type as {@code this}, even if
* the signature is more permissive.</li>
* <li>Is commutative.</li>
* </ul>
*/
S leastUpperBound(S other);
/**
* Can the objects {@code a} and {@code b} be aliases? Returns a
* conservative answer (i.e., returns {@code true} if not enough information
* is available to determine aliasing).
*/
boolean canAlias(FlowExpressions.Receiver a,
FlowExpressions.Receiver b);
/** @return Whether the Store supports DOT graph output. */
boolean hasDOToutput();
/** @return The store encoded as a DOT graph for visualization. */
String toDOToutput();
}