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 * Copyright (c) 2011, 2018, 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 static org.graalvm.compiler.core.common.calc.CanonicalCondition.LT;

import org.graalvm.compiler.core.common.NumUtil;

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

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

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

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.spi.CanonicalizerTool;

import org.graalvm.compiler.nodeinfo.NodeInfo;

import org.graalvm.compiler.nodes.ConstantNode;

import org.graalvm.compiler.nodes.LogicConstantNode;

import org.graalvm.compiler.nodes.LogicNegationNode;

import org.graalvm.compiler.nodes.LogicNode;

import org.graalvm.compiler.nodes.NodeView;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.options.OptionValues;

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.MetaAccessProvider;

import jdk.vm.ci.meta.PrimitiveConstant;

import jdk.vm.ci.meta.TriState;

@NodeInfo(shortName = "<")

public final class IntegerLessThanNode extends IntegerLowerThanNode {

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

    private static final LessThanOp OP = new LessThanOp();

    public IntegerLessThanNode(ValueNode x, ValueNode y) {

        super(TYPE, x, y, OP);

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

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

    }

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

        return OP.create(x, y, view);

    }

    public static LogicNode create(ConstantReflectionProvider constantReflection, MetaAccessProvider metaAccess, OptionValues options, Integer smallestCompareWidth,

                    ValueNode x, ValueNode y, NodeView view) {

        LogicNode value = OP.canonical(constantReflection, metaAccess, options, smallestCompareWidth, OP.getCondition(), false, x, y, view);

        if (value != null) {

            return value;

        }

        return create(x, y, view);

    }

    @Override

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

        NodeView view = NodeView.from(tool);

        ValueNode value = OP.canonical(tool.getConstantReflection(), tool.getMetaAccess(), tool.getOptions(), tool.smallestCompareWidth(), OP.getCondition(), false, forX, forY, view);

        if (value != null) {

            return value;

        }

        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;

    }

    public static class LessThanOp extends LowerOp {

        @Override

        protected CompareNode duplicateModified(ValueNode newX, ValueNode newY, boolean unorderedIsTrue, NodeView view) {

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

                return new FloatLessThanNode(newX, newY, unorderedIsTrue); // TODO: Is the last arg

                                                                           // supposed to be true?

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

                return new IntegerLessThanNode(newX, newY);

            }

            throw GraalError.shouldNotReachHere();

        }

        @Override

        protected LogicNode optimizeNormalizeCompare(ConstantReflectionProvider constantReflection, MetaAccessProvider metaAccess, OptionValues options, Integer smallestCompareWidth,

            PrimitiveConstant primitive = (PrimitiveConstant) constant;

            /* @formatter:off

             * a NC b < c  (not mirrored)

             * cases for c:

             *  0         -> a < b

             *  [MIN, -1] -> false

             *  1         -> a <= b

             *  [2, MAX]  -> true

             * unordered-is-less means unordered-is-true.

             *

             * c < a NC b  (mirrored)

             * cases for c:

             *  0         -> a > b

             *  [1, MAX]  -> false

             *  -1        -> a >= b

             *  [MIN, -2] -> true

             * unordered-is-less means unordered-is-false.

             *

             *  We can handle mirroring by swapping a & b and negating the constant.

             *  @formatter:on

             */

            long cst = mirrored ? -primitive.asLong() : primitive.asLong();

            if (cst == 0) {

            } else if (cst == 1) {

                // a <= b <=> !(a > b)

                return LogicNegationNode.create(compare);

            } else if (cst <= -1) {

                return LogicConstantNode.contradiction();

            } else {

                assert cst >= 2;

                return LogicConstantNode.tautology();

            }

        }

        @Override

        protected LogicNode findSynonym(ValueNode forX, ValueNode forY, NodeView view) {

            LogicNode result = super.findSynonym(forX, forY, view);

            if (result != null) {

                return result;

            }

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

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

                    return new IntegerBelowNode(forX, forY);

                }

            }

            // Attempt to optimize the case where we can fold a constant from the left side (either

            // from an add or sub) into the constant on the right side.

            if (forY.isConstant()) {

                if (forX instanceof SubNode) {

                    SubNode sub = (SubNode) forX;

                    ValueNode xx = null;

                    ValueNode yy = null;

                    boolean negate = false;

                    if (forY.asConstant().isDefaultForKind()) {

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

                        xx = sub.getX();

                        yy = sub.getY();

                    } else if (forY.isJavaConstant() && forY.asJavaConstant().asLong() == 1) {

                        // (x - y) < 1 when x - y is known not to underflow <=> !(y < x)

                        xx = sub.getY();

                        yy = sub.getX();

                        negate = true;

                    }

                    if (xx != null) {

                        assert yy != null;

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

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

                        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)) {

                            LogicNode logic = new IntegerLessThanNode(xx, yy);

                            if (negate) {

                                logic = LogicNegationNode.create(logic);

                            }

                            return logic;

                        }

                    }

                } else if (forX instanceof AddNode) {

                    // (x + xConstant) < forY => x < (forY - xConstant)

                    AddNode addNode = (AddNode) forX;

                    if (addNode.getY().isJavaConstant()) {

                        IntegerStamp xStamp = (IntegerStamp) addNode.getX().stamp(view);

                        if (!IntegerStamp.addCanOverflow(xStamp, (IntegerStamp) addNode.getY().stamp(view))) {

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

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

                            long yConstant = forY.asJavaConstant().asLong();

                            long xConstant = addNode.getY().asJavaConstant().asLong();

                            if (!subtractMayUnderflow(yConstant, xConstant, minValue) && !subtractMayOverflow(yConstant, xConstant, maxValue)) {

                                long newConstant = yConstant - xConstant;

                                return IntegerLessThanNode.create(addNode.getX(), ConstantNode.forIntegerStamp(xStamp, newConstant), view);

                            }

                        }

                    }

                }

            }

            if (forX.stamp(view) instanceof IntegerStamp) {

                assert forY.stamp(view) instanceof IntegerStamp;

                int bits = ((IntegerStamp) forX.stamp(view)).getBits();

                assert ((IntegerStamp) forY.stamp(view)).getBits() == bits;

                LogicNode logic = canonicalizeRangeFlip(forX, forY, bits, true, view);

                if (logic != null) {

                    return logic;

                }

            }

            return null;

        }

        @Override

        protected CanonicalCondition getCondition() {

            return LT;

        }

        @Override

        protected IntegerLowerThanNode createNode(ValueNode x, ValueNode y) {

            return new IntegerLessThanNode(x, y);

        }

        @Override

        protected long upperBound(IntegerStamp stamp) {

            return stamp.upperBound();

        }

        @Override

        protected long lowerBound(IntegerStamp stamp) {

            return stamp.lowerBound();

        }

        @Override

        protected int compare(long a, long b) {

            return Long.compare(a, b);

        }

        @Override

        protected long min(long a, long b) {

            return Math.min(a, b);

        }

        @Override

        protected long max(long a, long b) {

            return Math.max(a, b);

        }

        @Override

        protected long cast(long a, int bits) {

            return CodeUtil.signExtend(a, bits);

        }

        @Override

        protected long minValue(int bits) {

            return NumUtil.minValue(bits);

        }

        @Override

        protected long maxValue(int bits) {

            return NumUtil.maxValue(bits);

        }

        @Override

        protected IntegerStamp forInteger(int bits, long min, long max) {

            return StampFactory.forInteger(bits, cast(min, bits), cast(max, bits));

        }

    }

    @Override

    public TriState implies(boolean thisNegated, LogicNode other) {

        if (!thisNegated) {

            if (other instanceof IntegerLessThanNode) {

                ValueNode otherX = ((IntegerLessThanNode) other).getX();

                ValueNode otherY = ((IntegerLessThanNode) other).getY();

                // x < y => !y < x

                if (getX() == otherY && getY() == otherX) {

                    return TriState.FALSE;

                }

            }

            // x < y => !x == y

            // x < y => !y == x

            if (other instanceof IntegerEqualsNode) {

                ValueNode otherX = ((IntegerEqualsNode) other).getX();

                ValueNode otherY = ((IntegerEqualsNode) other).getY();

                if ((getX() == otherX && getY() == otherY) || (getX() == otherY && getY() == otherX)) {

                    return TriState.FALSE;

                }

            }

        }

        return super.implies(thisNegated, other);

    }

}