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 * Copyright (c) 2011, 2019, 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.nodes.calc;

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

import org.graalvm.compiler.core.common.type.ArithmeticOpTable.ShiftOp.UShr;

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

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

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.NodeView;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;

import jdk.vm.ci.meta.JavaKind;

@NodeInfo(shortName = ">>>")

public final class UnsignedRightShiftNode extends ShiftNode<UShr> {

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

    public UnsignedRightShiftNode(ValueNode x, ValueNode y) {

    }

    public static ValueNode create(ValueNode x, ValueNode y, NodeView view) {

        ArithmeticOpTable.ShiftOp<UShr> op = ArithmeticOpTable.forStamp(x.stamp(view)).getUShr();

        Stamp stamp = op.foldStamp(x.stamp(view), (IntegerStamp) y.stamp(view));

        ValueNode value = ShiftNode.canonical(op, stamp, x, y, view);

        if (value != null) {

            return value;

        }

        return canonical(null, op, stamp, x, y, view);

    }

    @Override

    public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {

        NodeView view = NodeView.from(tool);

        ValueNode ret = super.canonical(tool, forX, forY);

        if (ret != this) {

            return ret;

        }

        return canonical(this, this.getArithmeticOp(), this.stamp(view), forX, forY, view);

    }

    @SuppressWarnings("unused")

    private static ValueNode canonical(UnsignedRightShiftNode node, ArithmeticOpTable.ShiftOp<UShr> op, Stamp stamp, ValueNode forX, ValueNode forY, NodeView view) {

        if (forY.isConstant()) {

            int amount = forY.asJavaConstant().asInt();

            int originalAmout = amount;

            int mask = op.getShiftAmountMask(stamp);

            amount &= mask;

            if (amount == 0) {

                return forX;

            }

            Stamp xStampGeneric = forX.stamp(view);

            if (xStampGeneric instanceof IntegerStamp) {

                IntegerStamp xStamp = (IntegerStamp) xStampGeneric;

                long xMask = CodeUtil.mask(xStamp.getBits());

                long xLowerBound = xStamp.lowerBound() & xMask;

                long xUpperBound = xStamp.upperBound() & xMask;

                if (xLowerBound >>> amount == xUpperBound >>> amount) {

                    // The result of the shift is constant.

                    return ConstantNode.forIntegerKind(stamp.getStackKind(), xLowerBound >>> amount);

                }

                if (amount == xStamp.getBits() - 1 && xStamp.lowerBound() == -1 && xStamp.upperBound() == 0) {

                    // Shift is equivalent to a negation, i.e., turns -1 into 1 and keeps 0 at 0.

                    return NegateNode.create(forX, view);

                }

            }

            if (forX instanceof ShiftNode) {

                ShiftNode<?> other = (ShiftNode<?>) forX;

                if (other.getY().isConstant()) {

                    int otherAmount = other.getY().asJavaConstant().asInt() & mask;

                    if (other instanceof UnsignedRightShiftNode) {

                        int total = amount + otherAmount;

                        if (total != (total & mask)) {

                            return ConstantNode.forIntegerKind(stamp.getStackKind(), 0);

                        }

                        return new UnsignedRightShiftNode(other.getX(), ConstantNode.forInt(total));

                    } else if (other instanceof LeftShiftNode && otherAmount == amount) {

                        if (stamp.getStackKind() == JavaKind.Long) {

                            return new AndNode(other.getX(), ConstantNode.forLong(-1L >>> amount));

                        } else {

                            assert stamp.getStackKind() == JavaKind.Int;

                            return new AndNode(other.getX(), ConstantNode.forInt(-1 >>> amount));

                        }

                    }

                }

            }

            if (originalAmout != amount) {

                return new UnsignedRightShiftNode(forX, ConstantNode.forInt(amount));

            }

        }

        if (node != null) {

            return node;

        }

        return new UnsignedRightShiftNode(forX, forY);

    }

    @Override

    public void generate(NodeLIRBuilderTool nodeValueMap, ArithmeticLIRGeneratorTool gen) {

        nodeValueMap.setResult(this, gen.emitUShr(nodeValueMap.operand(getX()), nodeValueMap.operand(getY())));

    }

    @Override

    public boolean isNarrowable(int resultBits) {

        if (super.isNarrowable(resultBits)) {

            /*

             * For unsigned right shifts, the narrow can be done before the shift if the cut off

             * bits are all zero.

             */

            IntegerStamp inputStamp = (IntegerStamp) getX().stamp(NodeView.DEFAULT);

            return (inputStamp.upMask() & ~(resultBits - 1)) == 0;

        } else {

            return false;

        }

    }

}