/*

 * 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.loop;

import org.graalvm.compiler.core.common.type.IntegerStamp;

import org.graalvm.compiler.nodes.FixedNode;

import org.graalvm.compiler.nodes.NodeView;

import org.graalvm.compiler.nodes.StructuredGraph;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.calc.BinaryArithmeticNode;

import org.graalvm.compiler.nodes.calc.FixedBinaryNode;

import org.graalvm.compiler.nodes.calc.SignedDivNode;

import org.graalvm.compiler.nodes.calc.UnsignedDivNode;

import org.graalvm.compiler.nodes.extended.GuardingNode;

import java.util.function.BiFunction;

/**

 * Utility methods to perform integer math with some obvious constant folding first.

 */

public class MathUtil {

    private static boolean isConstantOne(ValueNode v1) {

        return v1.isConstant() && v1.stamp(NodeView.DEFAULT) instanceof IntegerStamp && v1.asJavaConstant().asLong() == 1;

    }

    private static boolean isConstantZero(ValueNode v1) {

        return v1.isConstant() && v1.stamp(NodeView.DEFAULT) instanceof IntegerStamp && v1.asJavaConstant().asLong() == 0;

    }

    public static ValueNode add(StructuredGraph graph, ValueNode v1, ValueNode v2) {

        if (isConstantZero(v1)) {

            return v2;

        }

        if (isConstantZero(v2)) {

            return v1;

        }

        return BinaryArithmeticNode.add(graph, v1, v2, NodeView.DEFAULT);

    }

    public static ValueNode mul(StructuredGraph graph, ValueNode v1, ValueNode v2) {

        if (isConstantOne(v1)) {

            return v2;

        }

        if (isConstantOne(v2)) {

            return v1;

        }

        return BinaryArithmeticNode.mul(graph, v1, v2, NodeView.DEFAULT);

    }

    public static ValueNode sub(StructuredGraph graph, ValueNode v1, ValueNode v2) {

        if (isConstantZero(v2)) {

            return v1;

        }

        return BinaryArithmeticNode.sub(graph, v1, v2, NodeView.DEFAULT);

    }

    public static ValueNode divBefore(StructuredGraph graph, FixedNode before, ValueNode dividend, ValueNode divisor, GuardingNode zeroCheck) {

        return fixedDivBefore(graph, before, dividend, divisor, (dend, sor) -> SignedDivNode.create(dend, sor, zeroCheck, NodeView.DEFAULT));

    }

    public static ValueNode unsignedDivBefore(StructuredGraph graph, FixedNode before, ValueNode dividend, ValueNode divisor, GuardingNode zeroCheck) {

        return fixedDivBefore(graph, before, dividend, divisor, (dend, sor) -> UnsignedDivNode.create(dend, sor, zeroCheck, NodeView.DEFAULT));

    }

    private static ValueNode fixedDivBefore(StructuredGraph graph, FixedNode before, ValueNode dividend, ValueNode divisor, BiFunction<ValueNode, ValueNode, ValueNode> createDiv) {

        if (isConstantOne(divisor)) {

            return dividend;

        }

        ValueNode div = createDiv.apply(dividend, divisor);

        if (div instanceof FixedBinaryNode) {

            FixedBinaryNode fixedDiv = (FixedBinaryNode) div;

            if (before.predecessor() instanceof FixedBinaryNode) {

                FixedBinaryNode binaryPredecessor = (FixedBinaryNode) before.predecessor();

                if (fixedDiv.dataFlowEquals(binaryPredecessor)) {

                    return binaryPredecessor;

                }

            }

            graph.addBeforeFixed(before, graph.addOrUniqueWithInputs(fixedDiv));

        }

        return div;

    }

}