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 * Copyright (c) 2014, 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
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package org.graalvm.compiler.replacements.nodes.arithmetic;

import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_4;
import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_4;

import java.util.function.BiFunction;

import org.graalvm.compiler.core.common.type.IntegerStamp;
import org.graalvm.compiler.core.common.type.Stamp;
import org.graalvm.compiler.core.common.type.StampFactory;
import org.graalvm.compiler.graph.NodeClass;
import org.graalvm.compiler.graph.spi.CanonicalizerTool;
import org.graalvm.compiler.lir.gen.ArithmeticLIRGeneratorTool;
import org.graalvm.compiler.nodeinfo.NodeInfo;
import org.graalvm.compiler.nodes.ConstantNode;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.calc.BinaryNode;
import org.graalvm.compiler.nodes.spi.ArithmeticLIRLowerable;
import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;

import jdk.vm.ci.meta.JavaKind;
import jdk.vm.ci.meta.Value;

@NodeInfo(shortName = "|*H|", cycles = CYCLES_4, cyclesRationale = "mul + mov", size = SIZE_4)
public final class UnsignedMulHighNode extends BinaryNode implements ArithmeticLIRLowerable {

    public static final NodeClass<UnsignedMulHighNode> TYPE = NodeClass.create(UnsignedMulHighNode.class);

    public UnsignedMulHighNode(ValueNode x, ValueNode y) {
        this((IntegerStamp) x.stamp().unrestricted(), x, y);
    }

    public UnsignedMulHighNode(IntegerStamp stamp, ValueNode x, ValueNode y) {
        super(TYPE, stamp, x, y);
    }

    private static long[] getUnsignedExtremes(IntegerStamp stamp) {
        if (stamp.lowerBound() < 0 && stamp.upperBound() >= 0) {
            /*
             * If -1 and 0 are both in the signed range, then we can't say anything about the
             * unsigned range, so we have to return [0, MAX_UNSIGNED].
             */
            return new long[]{0, -1L};
        } else {
            return new long[]{stamp.lowerBound(), stamp.upperBound()};
        }
    }

    
Determines the minimum and maximum result of this node for the given inputs and returns the
result of the given BiFunction on the minimum and maximum values. Note that the minima and
maxima are calculated using signed min/max functions, while the values themselves are
unsigned.
/**
     * Determines the minimum and maximum result of this node for the given inputs and returns the
     * result of the given BiFunction on the minimum and maximum values. Note that the minima and
     * maxima are calculated using signed min/max functions, while the values themselves are
     * unsigned.
     */
    private <T> T processExtremes(Stamp forX, Stamp forY, BiFunction<Long, Long, T> op) {
        IntegerStamp xStamp = (IntegerStamp) forX;
        IntegerStamp yStamp = (IntegerStamp) forY;

        JavaKind kind = getStackKind();
        assert kind == JavaKind.Int || kind == JavaKind.Long;
        long[] xExtremes = getUnsignedExtremes(xStamp);
        long[] yExtremes = getUnsignedExtremes(yStamp);
        long min = Long.MAX_VALUE;
        long max = Long.MIN_VALUE;
        for (long a : xExtremes) {
            for (long b : yExtremes) {
                long result = kind == JavaKind.Int ? multiplyHighUnsigned((int) a, (int) b) : multiplyHighUnsigned(a, b);
                min = Math.min(min, result);
                max = Math.max(max, result);
            }
        }
        return op.apply(min, max);
    }

    @SuppressWarnings("cast")
    @Override
    public Stamp foldStamp(Stamp stampX, Stamp stampY) {
        // if min is negative, then the value can reach into the unsigned range
        return processExtremes(stampX, stampY, (min, max) -> (min == (long) max || min >= 0) ? StampFactory.forInteger(getStackKind(), min, max) : StampFactory.forKind(getStackKind()));
    }

    @SuppressWarnings("cast")
    @Override
    public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {
        return processExtremes(forX.stamp(), forY.stamp(), (min, max) -> min == (long) max ? ConstantNode.forIntegerKind(getStackKind(), min) : this);
    }

    @Override
    public void generate(NodeLIRBuilderTool nodeValueMap, ArithmeticLIRGeneratorTool gen) {
        Value a = nodeValueMap.operand(getX());
        Value b = nodeValueMap.operand(getY());
        nodeValueMap.setResult(this, gen.emitUMulHigh(a, b));
    }

    public static int multiplyHighUnsigned(int x, int y) {
        long xl = x & 0xFFFFFFFFL;
        long yl = y & 0xFFFFFFFFL;
        long r = xl * yl;
        return (int) (r >> 32);
    }

    public static long multiplyHighUnsigned(long x, long y) {
        // Checkstyle: stop
        long x0, y0, z0;
        long x1, y1, z1, z2, t;
        // Checkstyle: resume

        x0 = x & 0xFFFFFFFFL;
        x1 = x >>> 32;

        y0 = y & 0xFFFFFFFFL;
        y1 = y >>> 32;

        z0 = x0 * y0;
        t = x1 * y0 + (z0 >>> 32);
        z1 = t & 0xFFFFFFFFL;
        z2 = t >>> 32;
        z1 += x0 * y1;

        return x1 * y1 + z2 + (z1 >>> 32);
    }
}