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 * 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,
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package org.graalvm.compiler.loop;

import org.graalvm.compiler.core.common.type.Stamp;
import org.graalvm.compiler.debug.GraalError;
import org.graalvm.compiler.nodes.NodeView;
import org.graalvm.compiler.nodes.StructuredGraph;
import org.graalvm.compiler.nodes.ValueNode;

This class describes a value node that is an induction variable in a counted loop.
/**
 * This class describes a value node that is an induction variable in a counted loop.
 */
public abstract class InductionVariable {

    public enum Direction {
        Up,
        Down;

        public Direction opposite() {
            switch (this) {
                case Up:
                    return Down;
                case Down:
                    return Up;
                default:
                    throw GraalError.shouldNotReachHere();
            }
        }
    }

    public abstract StructuredGraph graph();

    protected final LoopEx loop;

    public InductionVariable(LoopEx loop) {
        this.loop = loop;
    }

    public LoopEx getLoop() {
        return loop;
    }

    public abstract Direction direction();

    
Returns the value node that is described by this induction variable.
/**
     * Returns the value node that is described by this induction variable.
     */
    public abstract ValueNode valueNode();

    
Returns the node that gives the initial value of this induction variable.
/**
     * Returns the node that gives the initial value of this induction variable.
     */
    public abstract ValueNode initNode();

    
Returns the stride of the induction variable. The stride is the value that is added to the
induction variable at each iteration.
/**
     * Returns the stride of the induction variable. The stride is the value that is added to the
     * induction variable at each iteration.
     */
    public abstract ValueNode strideNode();

    public abstract boolean isConstantInit();

    public abstract boolean isConstantStride();

    public abstract long constantInit();

    public abstract long constantStride();

    
Returns the extremum value of the induction variable. The extremum value is the value of the induction variable in the loop body of the last iteration, only taking into account the main loop limit test. It's possible for the loop to exit before this value if CountedLoopInfo.isExactTripCount() returns false for the containing loop. /**
     * Returns the extremum value of the induction variable. The extremum value is the value of the
     * induction variable in the loop body of the last iteration, only taking into account the main
     * loop limit test. It's possible for the loop to exit before this value if
     * {@link CountedLoopInfo#isExactTripCount()} returns false for the containing loop.
     */
    public ValueNode extremumNode() {
        return extremumNode(false, valueNode().stamp(NodeView.DEFAULT));
    }

    public abstract ValueNode extremumNode(boolean assumePositiveTripCount, Stamp stamp);

    public abstract boolean isConstantExtremum();

    public abstract long constantExtremum();

    
Returns the exit value of the induction variable. The exit value is the value of the
induction variable at the loop exit.
/**
     * Returns the exit value of the induction variable. The exit value is the value of the
     * induction variable at the loop exit.
     */
    public abstract ValueNode exitValueNode();

    
Deletes any nodes created within the scope of this object that have no usages.
/**
     * Deletes any nodes created within the scope of this object that have no usages.
     */
    public abstract void deleteUnusedNodes();
}