/*
 * Copyright (c) 2009, 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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 * questions.
 */


package org.graalvm.compiler.nodes.calc;

import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_1;
import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_2;
import static org.graalvm.compiler.nodes.calc.CompareNode.createCompareNode;

import org.graalvm.compiler.core.common.calc.CanonicalCondition;
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.Canonicalizable;
import org.graalvm.compiler.graph.spi.CanonicalizerTool;
import org.graalvm.compiler.nodeinfo.InputType;
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.StructuredGraph;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.spi.LIRLowerable;
import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;

import jdk.vm.ci.meta.JavaConstant;

/**
 * The {@code ConditionalNode} class represents a comparison that yields one of two (eagerly
 * evaluated) values.
 */
@NodeInfo(cycles = CYCLES_1, size = SIZE_2)
public final class ConditionalNode extends FloatingNode implements Canonicalizable, LIRLowerable {

    public static final NodeClass<ConditionalNode> TYPE = NodeClass.create(ConditionalNode.class);
    @Input(InputType.Condition) LogicNode condition;
    @Input(InputType.Value) ValueNode trueValue;
    @Input(InputType.Value) ValueNode falseValue;

    public LogicNode condition() {
        return condition;
    }

    public ConditionalNode(LogicNode condition) {
        this(condition, ConstantNode.forInt(1, condition.graph()), ConstantNode.forInt(0, condition.graph()));
    }

    public ConditionalNode(LogicNode condition, ValueNode trueValue, ValueNode falseValue) {
        super(TYPE, trueValue.stamp(NodeView.DEFAULT).meet(falseValue.stamp(NodeView.DEFAULT)));
        assert trueValue.stamp(NodeView.DEFAULT).isCompatible(falseValue.stamp(NodeView.DEFAULT));
        this.condition = condition;
        this.trueValue = trueValue;
        this.falseValue = falseValue;
    }

    public static ValueNode create(LogicNode condition, NodeView view) {
        return create(condition, ConstantNode.forInt(1, condition.graph()), ConstantNode.forInt(0, condition.graph()), view);
    }

    public static ValueNode create(LogicNode condition, ValueNode trueValue, ValueNode falseValue, NodeView view) {
        ValueNode synonym = findSynonym(condition, trueValue, falseValue, view);
        if (synonym != null) {
            return synonym;
        }
        ValueNode result = canonicalizeConditional(condition, trueValue, falseValue, trueValue.stamp(view).meet(falseValue.stamp(view)), view);
        if (result != null) {
            return result;
        }
        return new ConditionalNode(condition, trueValue, falseValue);
    }

    @Override
    public boolean inferStamp() {
        Stamp valueStamp = trueValue.stamp(NodeView.DEFAULT).meet(falseValue.stamp(NodeView.DEFAULT));
        if (condition instanceof IntegerLessThanNode) {
            IntegerLessThanNode lessThan = (IntegerLessThanNode) condition;
            if (lessThan.getX() == trueValue && lessThan.getY() == falseValue) {
                // this encodes a min operation
                JavaConstant constant = lessThan.getX().asJavaConstant();
                if (constant == null) {
                    constant = lessThan.getY().asJavaConstant();
                }
                if (constant != null) {
                    IntegerStamp bounds = StampFactory.forInteger(constant.getJavaKind(), constant.getJavaKind().getMinValue(), constant.asLong());
                    valueStamp = valueStamp.join(bounds);
                }
            } else if (lessThan.getX() == falseValue && lessThan.getY() == trueValue) {
                // this encodes a max operation
                JavaConstant constant = lessThan.getX().asJavaConstant();
                if (constant == null) {
                    constant = lessThan.getY().asJavaConstant();
                }
                if (constant != null) {
                    IntegerStamp bounds = StampFactory.forInteger(constant.getJavaKind(), constant.asLong(), constant.getJavaKind().getMaxValue());
                    valueStamp = valueStamp.join(bounds);
                }
            }
        }
        return updateStamp(valueStamp);
    }

    public ValueNode trueValue() {
        return trueValue;
    }

    public ValueNode falseValue() {
        return falseValue;
    }

    @Override
    public ValueNode canonical(CanonicalizerTool tool) {
        NodeView view = NodeView.from(tool);
        ValueNode synonym = findSynonym(condition, trueValue(), falseValue(), view);
        if (synonym != null) {
            return synonym;
        }

        ValueNode result = canonicalizeConditional(condition, trueValue(), falseValue(), stamp, view);
        if (result != null) {
            return result;
        }

        return this;
    }

    public static ValueNode canonicalizeConditional(LogicNode condition, ValueNode trueValue, ValueNode falseValue, Stamp stamp, NodeView view) {
        if (trueValue == falseValue) {
            return trueValue;
        }

        if (condition instanceof CompareNode && ((CompareNode) condition).isIdentityComparison()) {
            // optimize the pattern (x == y) ? x : y
            CompareNode compare = (CompareNode) condition;
            if ((compare.getX() == trueValue && compare.getY() == falseValue) || (compare.getX() == falseValue && compare.getY() == trueValue)) {
                return falseValue;
            }
        }

        if (trueValue.stamp(view) instanceof IntegerStamp) {
            // check if the conditional is redundant
            if (condition instanceof IntegerLessThanNode) {
                IntegerLessThanNode lessThan = (IntegerLessThanNode) condition;
                IntegerStamp falseValueStamp = (IntegerStamp) falseValue.stamp(view);
                IntegerStamp trueValueStamp = (IntegerStamp) trueValue.stamp(view);
                if (lessThan.getX() == trueValue && lessThan.getY() == falseValue) {
                    // return "x" for "x < y ? x : y" in case that we know "x <= y"
                    if (trueValueStamp.upperBound() <= falseValueStamp.lowerBound()) {
                        return trueValue;
                    }
                } else if (lessThan.getX() == falseValue && lessThan.getY() == trueValue) {
                    // return "y" for "x < y ? y : x" in case that we know "x <= y"
                    if (falseValueStamp.upperBound() <= trueValueStamp.lowerBound()) {
                        return trueValue;
                    }
                }
            }

            // this optimizes the case where a value from the range 0 - 1 is mapped to the
            // range 0 - 1
            if (trueValue.isConstant() && falseValue.isConstant()) {
                long constTrueValue = trueValue.asJavaConstant().asLong();
                long constFalseValue = falseValue.asJavaConstant().asLong();
                if (condition instanceof IntegerEqualsNode) {
                    IntegerEqualsNode equals = (IntegerEqualsNode) condition;
                    if (equals.getY().isConstant() && equals.getX().stamp(view) instanceof IntegerStamp) {
                        IntegerStamp equalsXStamp = (IntegerStamp) equals.getX().stamp(view);
                        if (equalsXStamp.upMask() == 1) {
                            long equalsY = equals.getY().asJavaConstant().asLong();
                            if (equalsY == 0) {
                                if (constTrueValue == 0 && constFalseValue == 1) {
                                    // return x when: x == 0 ? 0 : 1;
                                    return IntegerConvertNode.convertUnsigned(equals.getX(), stamp, view);
                                } else if (constTrueValue == 1 && constFalseValue == 0) {
                                    // negate a boolean value via xor
                                    return IntegerConvertNode.convertUnsigned(XorNode.create(equals.getX(), ConstantNode.forIntegerStamp(equals.getX().stamp(view), 1), view), stamp, view);
                                }
                            } else if (equalsY == 1) {
                                if (constTrueValue == 1 && constFalseValue == 0) {
                                    // return x when: x == 1 ? 1 : 0;
                                    return IntegerConvertNode.convertUnsigned(equals.getX(), stamp, view);
                                } else if (constTrueValue == 0 && constFalseValue == 1) {
                                    // negate a boolean value via xor
                                    return IntegerConvertNode.convertUnsigned(XorNode.create(equals.getX(), ConstantNode.forIntegerStamp(equals.getX().stamp(view), 1), view), stamp, view);
                                }
                            }
                        }
                    }
                } else if (condition instanceof IntegerTestNode) {
                    // replace IntegerTestNode with AndNode for the following patterns:
                    // (value & 1) == 0 ? 0 : 1
                    // (value & 1) == 1 ? 1 : 0
                    IntegerTestNode integerTestNode = (IntegerTestNode) condition;
                    if (integerTestNode.getY().isConstant()) {
                        assert integerTestNode.getX().stamp(view) instanceof IntegerStamp;
                        long testY = integerTestNode.getY().asJavaConstant().asLong();
                        if (testY == 1 && constTrueValue == 0 && constFalseValue == 1) {
                            return IntegerConvertNode.convertUnsigned(AndNode.create(integerTestNode.getX(), integerTestNode.getY(), view), stamp, view);
                        }
                    }
                }
            }

            if (condition instanceof IntegerLessThanNode) {
                /*
                 * Convert a conditional add ((x < 0) ? (x + y) : x) into (x + (y & (x >> (bits -
                 * 1)))) to avoid the test.
                 */
                IntegerLessThanNode lt = (IntegerLessThanNode) condition;
                if (lt.getY().isDefaultConstant()) {
                    if (falseValue == lt.getX()) {
                        if (trueValue instanceof AddNode) {
                            AddNode add = (AddNode) trueValue;
                            if (add.getX() == falseValue) {
                                int bits = ((IntegerStamp) trueValue.stamp(NodeView.DEFAULT)).getBits();
                                ValueNode shift = new RightShiftNode(lt.getX(), ConstantNode.forIntegerBits(32, bits - 1));
                                ValueNode and = new AndNode(shift, add.getY());
                                return new AddNode(add.getX(), and);
                            }
                        }
                    }
                }
            }
        }

        return null;
    }

    private static ValueNode findSynonym(ValueNode condition, ValueNode trueValue, ValueNode falseValue, NodeView view) {
        if (condition instanceof LogicNegationNode) {
            LogicNegationNode negated = (LogicNegationNode) condition;
            return ConditionalNode.create(negated.getValue(), falseValue, trueValue, view);
        }
        if (condition instanceof LogicConstantNode) {
            LogicConstantNode c = (LogicConstantNode) condition;
            if (c.getValue()) {
                return trueValue;
            } else {
                return falseValue;
            }
        }
        return null;
    }

    @Override
    public void generate(NodeLIRBuilderTool generator) {
        generator.emitConditional(this);
    }

    public ConditionalNode(StructuredGraph graph, CanonicalCondition condition, ValueNode x, ValueNode y) {
        this(createCompareNode(graph, condition, x, y, null, NodeView.DEFAULT));
    }
}
