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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

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 * 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.

 *

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package org.graalvm.compiler.nodes.calc;

import org.graalvm.compiler.core.common.calc.Condition;

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

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.debug.GraalError;

import org.graalvm.compiler.graph.IterableNodeType;

import org.graalvm.compiler.graph.NodeClass;

import org.graalvm.compiler.graph.spi.CanonicalizerTool;

import org.graalvm.compiler.nodeinfo.NodeInfo;

import org.graalvm.compiler.nodes.LogicConstantNode;

import org.graalvm.compiler.nodes.LogicNode;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.util.GraphUtil;

import jdk.vm.ci.code.CodeUtil;

import jdk.vm.ci.meta.Constant;

import jdk.vm.ci.meta.ConstantReflectionProvider;

import jdk.vm.ci.meta.JavaKind;

import jdk.vm.ci.meta.PrimitiveConstant;

import jdk.vm.ci.meta.TriState;

@NodeInfo(shortName = "<")

public final class IntegerLessThanNode extends CompareNode implements IterableNodeType {

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

    public IntegerLessThanNode(ValueNode x, ValueNode y) {

        super(TYPE, Condition.LT, false, x, y);

        assert !x.getStackKind().isNumericFloat() && x.getStackKind() != JavaKind.Object;

        assert !y.getStackKind().isNumericFloat() && y.getStackKind() != JavaKind.Object;

    }

    public static LogicNode create(ValueNode x, ValueNode y, ConstantReflectionProvider constantReflection) {

        LogicNode result = CompareNode.tryConstantFold(Condition.LT, x, y, constantReflection, false);

        if (result != null) {

            return result;

        } else {

            result = findSynonym(x, y);

            if (result != null) {

                return result;

            }

            return new IntegerLessThanNode(x, y);

        }

    }

    @Override

    protected ValueNode optimizeNormalizeCmp(Constant constant, NormalizeCompareNode normalizeNode, boolean mirrored) {

        PrimitiveConstant primitive = (PrimitiveConstant) constant;

        assert condition() == Condition.LT;

        if (primitive.getJavaKind() == JavaKind.Int && primitive.asInt() == 0) {

            ValueNode a = mirrored ? normalizeNode.getY() : normalizeNode.getX();

            ValueNode b = mirrored ? normalizeNode.getX() : normalizeNode.getY();

            if (normalizeNode.getX().getStackKind() == JavaKind.Double || normalizeNode.getX().getStackKind() == JavaKind.Float) {

                return new FloatLessThanNode(a, b, mirrored ^ normalizeNode.isUnorderedLess);

            } else {

                return new IntegerLessThanNode(a, b);

            }

        }

        return this;

    }

    public static boolean subtractMayUnderflow(long x, long y, long minValue) {

        long r = x - y;

        // HD 2-12 Overflow iff the arguments have different signs and

        // the sign of the result is different than the sign of x

        return (((x ^ y) & (x ^ r)) < 0) || r <= minValue;

    }

    public static boolean subtractMayOverflow(long x, long y, long maxValue) {

        long r = x - y;

        // HD 2-12 Overflow iff the arguments have different signs and

        // the sign of the result is different than the sign of x

        return (((x ^ y) & (x ^ r)) < 0) || r > maxValue;

    }

    @Override

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

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

        if (result != this) {

            return result;

        }

        ValueNode synonym = findSynonym(forX, forY);

        if (synonym != null) {

            return synonym;

        }

        if (forX.stamp() instanceof IntegerStamp && forY.stamp() instanceof IntegerStamp) {

            if (IntegerStamp.sameSign((IntegerStamp) forX.stamp(), (IntegerStamp) forY.stamp())) {

                return new IntegerBelowNode(forX, forY);

            }

        }

        if (forY.isConstant() && forY.asConstant().isDefaultForKind() && forX instanceof SubNode) {

            // (x - y) < 0 when x - y is known not to underflow == x < y

            SubNode sub = (SubNode) forX;

            IntegerStamp xStamp = (IntegerStamp) sub.getX().stamp();

            IntegerStamp yStamp = (IntegerStamp) sub.getY().stamp();

            long minValue = CodeUtil.minValue(xStamp.getBits());

            long maxValue = CodeUtil.maxValue(xStamp.getBits());

            if (!subtractMayUnderflow(xStamp.lowerBound(), yStamp.upperBound(), minValue) && !subtractMayOverflow(xStamp.upperBound(), yStamp.lowerBound(), maxValue)) {

                return new IntegerLessThanNode(sub.getX(), sub.getY());

            }

        }

        return this;

    }

    private static LogicNode findSynonym(ValueNode forX, ValueNode forY) {

        if (GraphUtil.unproxify(forX) == GraphUtil.unproxify(forY)) {

            return LogicConstantNode.contradiction();

        } else if (forX.stamp() instanceof IntegerStamp && forY.stamp() instanceof IntegerStamp) {

            IntegerStamp xStamp = (IntegerStamp) forX.stamp();

            IntegerStamp yStamp = (IntegerStamp) forY.stamp();

            if (xStamp.upperBound() < yStamp.lowerBound()) {

                return LogicConstantNode.tautology();

            } else if (xStamp.lowerBound() >= yStamp.upperBound()) {

                return LogicConstantNode.contradiction();

            }

        }

        return null;

    }

    @Override

    protected CompareNode duplicateModified(ValueNode newX, ValueNode newY) {

        if (newX.stamp() instanceof FloatStamp && newY.stamp() instanceof FloatStamp) {

            return new FloatLessThanNode(newX, newY, true);

        } else if (newX.stamp() instanceof IntegerStamp && newY.stamp() instanceof IntegerStamp) {

            return new IntegerLessThanNode(newX, newY);

        }

        throw GraalError.shouldNotReachHere();

    }

    @Override

    public Stamp getSucceedingStampForX(boolean negated) {

        Stamp xStampGeneric = getX().stamp();

        Stamp yStampGeneric = getY().stamp();

        if (xStampGeneric instanceof IntegerStamp) {

            IntegerStamp xStamp = (IntegerStamp) xStampGeneric;

            int bits = xStamp.getBits();

            if (yStampGeneric instanceof IntegerStamp) {

                IntegerStamp yStamp = (IntegerStamp) yStampGeneric;

                assert yStamp.getBits() == bits;

                if (negated) {

                    // x >= y

                    long xLowerBound = xStamp.lowerBound();

                    long yLowerBound = yStamp.lowerBound();

                    if (yLowerBound > xLowerBound) {

                        return StampFactory.forIntegerWithMask(bits, yLowerBound, xStamp.upperBound(), xStamp);

                    }

                } else {

                    // x < y

                    long xUpperBound = xStamp.upperBound();

                    long yUpperBound = yStamp.upperBound();

                    if (yUpperBound == CodeUtil.minValue(bits)) {

                        return null;

                    } else if (yUpperBound <= xUpperBound) {

                        assert yUpperBound != CodeUtil.minValue(bits);

                        return StampFactory.forIntegerWithMask(bits, xStamp.lowerBound(), yUpperBound - 1, xStamp);

                    }

                }

            }

        }

        return null;

    }

    @Override

    public Stamp getSucceedingStampForY(boolean negated) {

        Stamp xStampGeneric = getX().stamp();

        Stamp yStampGeneric = getY().stamp();

        if (xStampGeneric instanceof IntegerStamp) {

            IntegerStamp xStamp = (IntegerStamp) xStampGeneric;

            int bits = xStamp.getBits();

            if (yStampGeneric instanceof IntegerStamp) {

                IntegerStamp yStamp = (IntegerStamp) yStampGeneric;

                assert yStamp.getBits() == bits;

                if (negated) {

                    // y <= x

                    long xUpperBound = xStamp.upperBound();

                    long yUpperBound = yStamp.upperBound();

                    if (xUpperBound < yUpperBound) {

                        return StampFactory.forIntegerWithMask(bits, yStamp.lowerBound(), xUpperBound, yStamp);

                    }

                } else {

                    // y > x

                    long xLowerBound = xStamp.lowerBound();

                    long yLowerBound = yStamp.lowerBound();

                    if (xLowerBound == CodeUtil.maxValue(bits)) {

                        return null;

                    } else if (xLowerBound >= yLowerBound) {

                        assert xLowerBound != CodeUtil.maxValue(bits);

                        return StampFactory.forIntegerWithMask(bits, xLowerBound + 1, yStamp.upperBound(), yStamp);

                    }

                }

            }

        }

        return null;

    }

    @Override

    public TriState tryFold(Stamp xStampGeneric, Stamp yStampGeneric) {

        if (xStampGeneric instanceof IntegerStamp && yStampGeneric instanceof IntegerStamp) {

            IntegerStamp xStamp = (IntegerStamp) xStampGeneric;

            IntegerStamp yStamp = (IntegerStamp) yStampGeneric;

            if (xStamp.upperBound() < yStamp.lowerBound()) {

                return TriState.TRUE;

            }

            if (xStamp.lowerBound() >= yStamp.upperBound()) {

                return TriState.FALSE;

            }

        }

        return TriState.UNKNOWN;

    }

}