xref: /openjdk9/hotspot/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/extended/SwitchNode.java

/*
 * Copyright (c) 2009, 2015, 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.
 *
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package org.graalvm.compiler.nodes.extended;

import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_UNKNOWN;
import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_UNKNOWN;

import java.util.Arrays;

import org.graalvm.compiler.core.common.type.AbstractPointerStamp;
import org.graalvm.compiler.core.common.type.StampFactory;
import org.graalvm.compiler.debug.GraalError;
import org.graalvm.compiler.graph.Node;
import org.graalvm.compiler.graph.NodeClass;
import org.graalvm.compiler.graph.NodeSuccessorList;
import org.graalvm.compiler.graph.spi.SimplifierTool;
import org.graalvm.compiler.nodeinfo.NodeInfo;
import org.graalvm.compiler.nodes.AbstractBeginNode;
import org.graalvm.compiler.nodes.ControlSplitNode;
import org.graalvm.compiler.nodes.ValueNode;

import jdk.vm.ci.meta.Constant;

/**
 * The {@code SwitchNode} class is the base of both lookup and table switches.
 */
// @formatter:off
@NodeInfo(cycles = CYCLES_UNKNOWN,
          cyclesRationale = "We cannot estimate the runtime cost of a switch statement without knowing the number" +
                            "of case statements and the involved keys.",
          size = SIZE_UNKNOWN,
          sizeRationale = "We cannot estimate the code size of a switch statement without knowing the number" +
                          "of case statements.")
// @formatter:on
public abstract class SwitchNode extends ControlSplitNode {

    public static final NodeClass<SwitchNode> TYPE = NodeClass.create(SwitchNode.class);
    @Successor protected NodeSuccessorList<AbstractBeginNode> successors;
    @Input protected ValueNode value;

    // do not change the contents of these arrays:
    protected final double[] keyProbabilities;
    protected final int[] keySuccessors;

    /**
     * Constructs a new Switch.
     *
     * @param value the instruction that provides the value to be switched over
     * @param successors the list of successors of this switch
     */
    protected SwitchNode(NodeClass<? extends SwitchNode> c, ValueNode value, AbstractBeginNode[] successors, int[] keySuccessors, double[] keyProbabilities) {
        super(c, StampFactory.forVoid());
        assert value.stamp().getStackKind().isNumericInteger() || value.stamp() instanceof AbstractPointerStamp : value.stamp() + " key not supported by SwitchNode";
        assert keySuccessors.length == keyProbabilities.length;
        this.successors = new NodeSuccessorList<>(this, successors);
        this.value = value;
        this.keySuccessors = keySuccessors;
        this.keyProbabilities = keyProbabilities;
        assert assertProbabilities();
    }

    private boolean assertProbabilities() {
        double total = 0;
        for (double d : keyProbabilities) {
            total += d;
            assert d >= 0.0 : "Cannot have negative probabilities in switch node: " + d;
        }
        assert total > 0.999 && total < 1.001 : "Total " + total;
        return true;
    }

    @Override
    public double probability(AbstractBeginNode successor) {
        double sum = 0;
        for (int i = 0; i < keySuccessors.length; i++) {
            if (successors.get(keySuccessors[i]) == successor) {
                sum += keyProbabilities[i];
            }
        }
        return sum;
    }

    public ValueNode value() {
        return value;
    }

    public abstract boolean isSorted();

    /**
     * The number of distinct keys in this switch.
     */
    public abstract int keyCount();

    /**
     * The key at the specified position, encoded in a Constant.
     */
    public abstract Constant keyAt(int i);

    public boolean structureEquals(SwitchNode switchNode) {
        return Arrays.equals(keySuccessors, switchNode.keySuccessors) && equalKeys(switchNode);
    }

    /**
     * Returns true if the switch has the same keys in the same order as this switch.
     */
    public abstract boolean equalKeys(SwitchNode switchNode);

    /**
     * Returns the index of the successor belonging to the key at the specified index.
     */
    public int keySuccessorIndex(int i) {
        return keySuccessors[i];
    }

    /**
     * Returns the successor for the key at the given index.
     */
    public AbstractBeginNode keySuccessor(int i) {
        return successors.get(keySuccessors[i]);
    }

    /**
     * Returns the probability of the key at the given index.
     */
    public double keyProbability(int i) {
        return keyProbabilities[i];
    }

    /**
     * Returns the index of the default (fall through) successor of this switch.
     */
    public int defaultSuccessorIndex() {
        return keySuccessors[keySuccessors.length - 1];
    }

    public AbstractBeginNode blockSuccessor(int i) {
        return successors.get(i);
    }

    public void setBlockSuccessor(int i, AbstractBeginNode s) {
        successors.set(i, s);
    }

    public int blockSuccessorCount() {
        return successors.count();
    }

    /**
     * Gets the successor corresponding to the default (fall through) case.
     *
     * @return the default successor
     */
    public AbstractBeginNode defaultSuccessor() {
        if (defaultSuccessorIndex() == -1) {
            throw new GraalError("unexpected");
        }
        return successors.get(defaultSuccessorIndex());
    }

    @Override
    public AbstractBeginNode getPrimarySuccessor() {
        return this.defaultSuccessor();
    }

    /**
     * Delete all other successors except for the one reached by {@code survivingEdge}.
     *
     * @param tool
     * @param survivingEdge index of the edge in the {@link SwitchNode#successors} list
     */
    protected void killOtherSuccessors(SimplifierTool tool, int survivingEdge) {
        for (Node successor : successors()) {
            /*
             * Deleting a branch change change the successors so reload the surviving successor each
             * time.
             */
            if (successor != blockSuccessor(survivingEdge)) {
                tool.deleteBranch(successor);
            }
        }
        tool.addToWorkList(blockSuccessor(survivingEdge));
        graph().removeSplit(this, blockSuccessor(survivingEdge));
    }
}