/*

 * Copyright (c) 2017, 2017, 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.IntegerStamp;

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

import org.graalvm.compiler.graph.NodeClass;

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.nodes.util.GraphUtil;

import jdk.vm.ci.meta.TriState;

/**

 * Common super-class for "a < b" comparisons both {@linkplain IntegerLowerThanNode signed} and

 * {@linkplain IntegerBelowNode unsigned}.

 */

@NodeInfo()

public abstract class IntegerLowerThanNode extends CompareNode {

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

    private final LowerOp op;

    protected IntegerLowerThanNode(NodeClass<? extends CompareNode> c, ValueNode x, ValueNode y, LowerOp op) {

        super(c, op.getCondition(), false, x, y);

        this.op = op;

    }

    protected LowerOp getOp() {

        return op;

    }

    @Override

    public Stamp getSucceedingStampForX(boolean negated, Stamp xStampGeneric, Stamp yStampGeneric) {

        return getSucceedingStampForX(negated, !negated, xStampGeneric, yStampGeneric, getX(), getY());

    }

    @Override

    public Stamp getSucceedingStampForY(boolean negated, Stamp xStampGeneric, Stamp yStampGeneric) {

        return getSucceedingStampForX(!negated, !negated, yStampGeneric, xStampGeneric, getY(), getX());

    }

    private Stamp getSucceedingStampForX(boolean mirror, boolean strict, Stamp xStampGeneric, Stamp yStampGeneric, ValueNode forX, ValueNode forY) {

        Stamp s = getSucceedingStampForX(mirror, strict, xStampGeneric, yStampGeneric);

        if (s != null) {

            return s;

        }

        if (forY instanceof AddNode && xStampGeneric instanceof IntegerStamp) {

            IntegerStamp xStamp = (IntegerStamp) xStampGeneric;

            AddNode addNode = (AddNode) forY;

            IntegerStamp aStamp = null;

            if (addNode.getX() == forX && addNode.getY().stamp(NodeView.DEFAULT) instanceof IntegerStamp) {

                // x < x + a

                aStamp = (IntegerStamp) addNode.getY().stamp(NodeView.DEFAULT);

            } else if (addNode.getY() == forX && addNode.getX().stamp(NodeView.DEFAULT) instanceof IntegerStamp) {

                // x < a + x

                aStamp = (IntegerStamp) addNode.getX().stamp(NodeView.DEFAULT);

            }

            if (aStamp != null) {

                IntegerStamp result = getOp().getSucceedingStampForXLowerXPlusA(mirror, strict, aStamp);

                result = (IntegerStamp) xStamp.tryImproveWith(result);

                if (result != null) {

                    return result;

                }

            }

        }

        return null;

    }

    private Stamp getSucceedingStampForX(boolean mirror, boolean strict, Stamp xStampGeneric, Stamp yStampGeneric) {

        if (xStampGeneric instanceof IntegerStamp) {

            IntegerStamp xStamp = (IntegerStamp) xStampGeneric;

            if (yStampGeneric instanceof IntegerStamp) {

                IntegerStamp yStamp = (IntegerStamp) yStampGeneric;

                assert yStamp.getBits() == xStamp.getBits();

                Stamp s = getOp().getSucceedingStampForX(xStamp, yStamp, mirror, strict);

                if (s != null) {

                    return s;

                }

            }

        }

        return null;

    }

    @Override

    public TriState tryFold(Stamp xStampGeneric, Stamp yStampGeneric) {

        return getOp().tryFold(xStampGeneric, yStampGeneric);

    }

    public abstract static class LowerOp extends CompareOp {

        @Override

                        boolean unorderedIsTrue, ValueNode forX, ValueNode forY, NodeView view) {

            LogicNode result = super.canonical(constantReflection, metaAccess, options, smallestCompareWidth, condition, unorderedIsTrue, forX, forY, view);

            if (result != null) {

                return result;

            }

            LogicNode synonym = findSynonym(forX, forY, view);

            if (synonym != null) {

                return synonym;

            }

            return null;

        }

        protected abstract long upperBound(IntegerStamp stamp);

        protected abstract long lowerBound(IntegerStamp stamp);

        protected abstract int compare(long a, long b);

        protected abstract long min(long a, long b);

        protected abstract long max(long a, long b);

        protected long min(long a, long b, int bits) {

            return min(cast(a, bits), cast(b, bits));

        }

        protected long max(long a, long b, int bits) {

            return max(cast(a, bits), cast(b, bits));

        }

        protected abstract long cast(long a, int bits);

        protected abstract long minValue(int bits);

        protected abstract long maxValue(int bits);

        protected abstract IntegerStamp forInteger(int bits, long min, long max);

        protected abstract IntegerLowerThanNode createNode(ValueNode x, ValueNode y);

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

            LogicNode result = CompareNode.tryConstantFoldPrimitive(getCondition(), x, y, false, view);

            if (result != null) {

                return result;

            } else {

                result = findSynonym(x, y, view);

                if (result != null) {

                    return result;

                }

                return createNode(x, y);

            }

        }

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

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

                return LogicConstantNode.contradiction();

            }

            TriState fold = tryFold(forX.stamp(view), forY.stamp(view));

            if (fold.isTrue()) {

                return LogicConstantNode.tautology();

            } else if (fold.isFalse()) {

                return LogicConstantNode.contradiction();

            }

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

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

                int bits = yStamp.getBits();

                if (forX.isJavaConstant() && !forY.isConstant()) {

                    // bring the constant on the right

                    long xValue = forX.asJavaConstant().asLong();

                    if (xValue != maxValue(bits)) {

                        // c < x <=> !(c >= x) <=> !(x <= c) <=> !(x < c + 1)

                        return LogicNegationNode.create(create(forY, ConstantNode.forIntegerStamp(yStamp, xValue + 1), view));

                    }

                }

                if (forY.isJavaConstant()) {

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

                    if (yValue == maxValue(bits)) {

                        // x < MAX <=> x != MAX

                        return LogicNegationNode.create(IntegerEqualsNode.create(forX, forY, view));

                    }

                    if (yValue == minValue(bits) + 1) {

                        // x < MIN + 1 <=> x <= MIN <=> x == MIN

                        return IntegerEqualsNode.create(forX, ConstantNode.forIntegerStamp(yStamp, minValue(bits)), view);

                    }

                } else if (forY instanceof AddNode) {

                    AddNode addNode = (AddNode) forY;

                    LogicNode canonical = canonicalizeXLowerXPlusA(forX, addNode, false, true, view);

                    if (canonical != null) {

                        return canonical;

                    }

                }

                if (forX instanceof AddNode) {

                    AddNode addNode = (AddNode) forX;

                    LogicNode canonical = canonicalizeXLowerXPlusA(forY, addNode, true, false, view);

                    if (canonical != null) {

                        return canonical;

                    }

                }

            }

            return null;

        }

        private LogicNode canonicalizeXLowerXPlusA(ValueNode forX, AddNode addNode, boolean mirrored, boolean strict, NodeView view) {

            // x < x + a

            IntegerStamp succeedingXStamp;

            boolean exact;

            if (addNode.getX() == forX && addNode.getY().stamp(view) instanceof IntegerStamp) {

                IntegerStamp aStamp = (IntegerStamp) addNode.getY().stamp(view);

                succeedingXStamp = getSucceedingStampForXLowerXPlusA(mirrored, strict, aStamp);

                exact = aStamp.lowerBound() == aStamp.upperBound();

            } else if (addNode.getY() == forX && addNode.getX().stamp(view) instanceof IntegerStamp) {

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

                succeedingXStamp = getSucceedingStampForXLowerXPlusA(mirrored, strict, aStamp);

                exact = aStamp.lowerBound() == aStamp.upperBound();

            } else {

                return null;

            }

            if (succeedingXStamp.join(forX.stamp(view)).isEmpty()) {

                return LogicConstantNode.contradiction();

            } else if (exact && !succeedingXStamp.isEmpty()) {

                int bits = succeedingXStamp.getBits();

                if (compare(lowerBound(succeedingXStamp), minValue(bits)) > 0) {

                    assert upperBound(succeedingXStamp) == maxValue(bits);

                    // x must be in [L..MAX] <=> x >= L <=> !(x < L)

                    return LogicNegationNode.create(create(forX, ConstantNode.forIntegerStamp(succeedingXStamp, lowerBound(succeedingXStamp)), view));

                } else if (compare(upperBound(succeedingXStamp), maxValue(bits)) < 0) {

                    // x must be in [MIN..H] <=> x <= H <=> !(H < x)

                    return LogicNegationNode.create(create(ConstantNode.forIntegerStamp(succeedingXStamp, upperBound(succeedingXStamp)), forX, view));

                }

            }

            return null;

        }

        protected TriState tryFold(Stamp xStampGeneric, Stamp yStampGeneric) {

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

                IntegerStamp xStamp = (IntegerStamp) xStampGeneric;

                IntegerStamp yStamp = (IntegerStamp) yStampGeneric;

                if (compare(upperBound(xStamp), lowerBound(yStamp)) < 0) {

                    return TriState.TRUE;

                }

                if (compare(lowerBound(xStamp), upperBound(yStamp)) >= 0) {

                    return TriState.FALSE;

                }

            }

            return TriState.UNKNOWN;

        }

        protected IntegerStamp getSucceedingStampForX(IntegerStamp xStamp, IntegerStamp yStamp, boolean mirror, boolean strict) {

            int bits = xStamp.getBits();

            assert yStamp.getBits() == bits;

            if (mirror) {

                long low = lowerBound(yStamp);

                if (strict) {

                    if (low == maxValue(bits)) {

                        return null;

                    }

                    low += 1;

                }

                if (compare(low, lowerBound(xStamp)) > 0) {

                    return forInteger(bits, low, upperBound(xStamp));

                }

            } else {

                // x < y, i.e., x < y <= Y_UPPER_BOUND so x <= Y_UPPER_BOUND - 1

                long low = upperBound(yStamp);

                if (strict) {

                    if (low == minValue(bits)) {

                        return null;

                    }

                    low -= 1;

                }

                if (compare(low, upperBound(xStamp)) < 0) {

                    return forInteger(bits, lowerBound(xStamp), low);

                }

            }

            return null;

        }

        protected IntegerStamp getSucceedingStampForXLowerXPlusA(boolean mirrored, boolean strict, IntegerStamp a) {

            int bits = a.getBits();

            long min = minValue(bits);

            long max = maxValue(bits);

            /*

             * if x < x + a <=> x + a didn't overflow:

             *

             * x is outside ]MAX - a, MAX], i.e., inside [MIN, MAX - a]

             *

             * if a is negative those bounds wrap around correctly.

             *

             * If a is exactly zero this gives an unbounded stamp (any integer) in the positive case

             * and an empty stamp in the negative case: if x |<| x is true, then either x has no

             * value or any value...

             *

             * This does not use upper/lowerBound from LowerOp because it's about the (signed)

             * addition not the comparison.

             */

            if (mirrored) {

                if (a.contains(0)) {

                    // a may be zero

                    return a.unrestricted();

                }

                return forInteger(bits, min(max - a.lowerBound() + 1, max - a.upperBound() + 1, bits), max);

            } else {

                long aLower = a.lowerBound();

                long aUpper = a.upperBound();

                if (strict) {

                    if (aLower == 0) {

                        aLower = 1;

                    }

                    if (aUpper == 0) {

                        aUpper = -1;

                    }

                    if (aLower > aUpper) {

                        // impossible

                        return a.empty();

                    }

                }

                if (aLower < 0 && aUpper > 0) {

                    // a may be zero

                    return a.unrestricted();

                }

                return forInteger(bits, min, max(max - aLower, max - aUpper, bits));

            }

        }

    }

}