/*

 * Copyright (c) 2013, 2015, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package org.graalvm.compiler.nodes.calc;

import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_1;

import java.nio.ByteBuffer;

import java.nio.ByteOrder;

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

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

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.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.ValueNode;

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

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

import jdk.vm.ci.code.CodeUtil;

import jdk.vm.ci.meta.JavaKind;

import jdk.vm.ci.meta.SerializableConstant;

/**

 * The {@code ReinterpretNode} class represents a reinterpreting conversion that changes the stamp

 * of a primitive value to some other incompatible stamp. The new stamp must have the same width as

 * the old stamp.

 */

@NodeInfo(cycles = CYCLES_1)

public final class ReinterpretNode extends UnaryNode implements ArithmeticLIRLowerable {

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

    public ReinterpretNode(JavaKind to, ValueNode value) {

        this(StampFactory.forKind(to), value);

    }

    public ReinterpretNode(Stamp to, ValueNode value) {

        super(TYPE, getReinterpretStamp(to, value.stamp()), value);

        assert to instanceof ArithmeticStamp;

    }

    private SerializableConstant evalConst(SerializableConstant c) {

        /*

         * We don't care about byte order here. Either would produce the correct result.

         */

        ByteBuffer buffer = ByteBuffer.wrap(new byte[c.getSerializedSize()]).order(ByteOrder.nativeOrder());

        c.serialize(buffer);

        buffer.rewind();

        SerializableConstant ret = ((ArithmeticStamp) stamp()).deserialize(buffer);

        assert !buffer.hasRemaining();

        return ret;

    }

    @Override

    public ValueNode canonical(CanonicalizerTool tool, ValueNode forValue) {

        if (forValue.isConstant()) {

            return ConstantNode.forConstant(stamp(), evalConst((SerializableConstant) forValue.asConstant()), null);

        }

        if (stamp().isCompatible(forValue.stamp())) {

            return forValue;

        }

        if (forValue instanceof ReinterpretNode) {

            ReinterpretNode reinterpret = (ReinterpretNode) forValue;

            return new ReinterpretNode(stamp(), reinterpret.getValue());

        }

        return this;

    }

    /**

     * Compute the {@link IntegerStamp} from a {@link FloatStamp}, losing as little information as

     * possible.

     *

     * Sorting by their bit pattern reinterpreted as signed integers gives the following order of

     * floating point numbers:

     *

     * -0 | negative numbers | -Inf | NaNs | 0 | positive numbers | +Inf | NaNs

     *

     * So we can compute a better integer range if we know that the input is positive, negative,

     * finite, non-zero and/or not NaN.

     */

    private static IntegerStamp floatToInt(FloatStamp stamp) {

        int bits = stamp.getBits();

        long signBit = 1L << (bits - 1);

        long exponentMask;

        if (bits == 64) {

            exponentMask = Double.doubleToRawLongBits(Double.POSITIVE_INFINITY);

        } else {

            assert bits == 32;

            exponentMask = Float.floatToRawIntBits(Float.POSITIVE_INFINITY);

        }

        long positiveInfinity = exponentMask;

        long negativeInfinity = CodeUtil.signExtend(signBit | positiveInfinity, bits);

        long negativeZero = CodeUtil.signExtend(signBit | 0, bits);

        if (stamp.isNaN()) {

            // special case: in addition to the range, we know NaN has all exponent bits set

            return IntegerStamp.create(bits, negativeInfinity + 1, CodeUtil.maxValue(bits), exponentMask, CodeUtil.mask(bits));

        }

        long upperBound;

        if (stamp.isNonNaN()) {

            if (stamp.upperBound() < 0.0) {

                if (stamp.lowerBound() > Double.NEGATIVE_INFINITY) {

                    upperBound = negativeInfinity - 1;

                } else {

                    upperBound = negativeInfinity;

                }

            } else if (stamp.upperBound() == 0.0) {

                upperBound = 0;

            } else if (stamp.upperBound() < Double.POSITIVE_INFINITY) {

                upperBound = positiveInfinity - 1;

            } else {

                upperBound = positiveInfinity;

            }

        } else {

            upperBound = CodeUtil.maxValue(bits);

        }

        long lowerBound;

        if (stamp.lowerBound() > 0.0) {

            if (stamp.isNonNaN()) {

                lowerBound = 1;

            } else {

                lowerBound = negativeInfinity + 1;

            }

        } else if (stamp.upperBound() == Double.NEGATIVE_INFINITY) {

            lowerBound = negativeInfinity;

        } else if (stamp.upperBound() < 0.0) {

            lowerBound = negativeZero + 1;

        } else {

            lowerBound = negativeZero;

        }

        return StampFactory.forInteger(bits, lowerBound, upperBound);

    }

    /**

     * Compute the {@link IntegerStamp} from a {@link FloatStamp}, losing as little information as

     * possible.

     *

     * Sorting by their bit pattern reinterpreted as signed integers gives the following order of

     * floating point numbers:

     *

     * -0 | negative numbers | -Inf | NaNs | 0 | positive numbers | +Inf | NaNs

     *

     * So from certain integer ranges we may be able to infer something about the sign, finiteness

     * or NaN-ness of the result.

     */

    private static FloatStamp intToFloat(IntegerStamp stamp) {

        int bits = stamp.getBits();

        double minPositive;

        double maxPositive;

        long signBit = 1L << (bits - 1);

        long exponentMask;

        if (bits == 64) {

            exponentMask = Double.doubleToRawLongBits(Double.POSITIVE_INFINITY);

            minPositive = Double.MIN_VALUE;

            maxPositive = Double.MAX_VALUE;

        } else {

            assert bits == 32;

            exponentMask = Float.floatToRawIntBits(Float.POSITIVE_INFINITY);

            minPositive = Float.MIN_VALUE;

            maxPositive = Float.MAX_VALUE;

        }

        long significandMask = CodeUtil.mask(bits) & ~(signBit | exponentMask);

        long positiveInfinity = exponentMask;

        long negativeInfinity = CodeUtil.signExtend(signBit | positiveInfinity, bits);

        long negativeZero = CodeUtil.signExtend(signBit | 0, bits);

        if ((stamp.downMask() & exponentMask) == exponentMask && (stamp.downMask() & significandMask) != 0) {

            // if all exponent bits and at least one significand bit are set, the result is NaN

            return new FloatStamp(bits, Double.NaN, Double.NaN, false);

        }

        double upperBound;

        if (stamp.upperBound() < negativeInfinity) {

            if (stamp.lowerBound() > negativeZero) {

                upperBound = -minPositive;

            } else {

                upperBound = -0.0;

            }

        } else if (stamp.upperBound() < 0) {

            if (stamp.lowerBound() > negativeInfinity) {

                return new FloatStamp(bits, Double.NaN, Double.NaN, false);

            } else if (stamp.lowerBound() == negativeInfinity) {

                upperBound = Double.NEGATIVE_INFINITY;

            } else if (stamp.lowerBound() > negativeZero) {

                upperBound = -minPositive;

            } else {

                upperBound = -0.0;

            }

        } else if (stamp.upperBound() == 0) {

            upperBound = 0.0;

        } else if (stamp.upperBound() < positiveInfinity) {

            upperBound = maxPositive;

        } else {

            upperBound = Double.POSITIVE_INFINITY;

        }

        double lowerBound;

        if (stamp.lowerBound() > positiveInfinity) {

            return new FloatStamp(bits, Double.NaN, Double.NaN, false);

        } else if (stamp.lowerBound() == positiveInfinity) {

            lowerBound = Double.POSITIVE_INFINITY;

        } else if (stamp.lowerBound() > 0) {

            lowerBound = minPositive;

        } else if (stamp.lowerBound() > negativeInfinity) {

            lowerBound = 0.0;

        } else {

            lowerBound = Double.NEGATIVE_INFINITY;

        }

        boolean nonNaN;

        if ((stamp.upMask() & exponentMask) != exponentMask) {

            // NaN has all exponent bits set

            nonNaN = true;

        } else {

            boolean negativeNaNBlock = stamp.lowerBound() < 0 && stamp.upperBound() > negativeInfinity;

            boolean positiveNaNBlock = stamp.upperBound() > positiveInfinity;

            nonNaN = !negativeNaNBlock && !positiveNaNBlock;

        }

        return new FloatStamp(bits, lowerBound, upperBound, nonNaN);

    }

    private static Stamp getReinterpretStamp(Stamp toStamp, Stamp fromStamp) {

        if (toStamp instanceof IntegerStamp && fromStamp instanceof FloatStamp) {

            return floatToInt((FloatStamp) fromStamp);

        } else if (toStamp instanceof FloatStamp && fromStamp instanceof IntegerStamp) {

            return intToFloat((IntegerStamp) fromStamp);

        } else {

            return toStamp;

        }

    }

    @Override

    public boolean inferStamp() {

        return updateStamp(getReinterpretStamp(stamp(), getValue().stamp()));

    }

    @Override

    public void generate(NodeLIRBuilderTool builder, ArithmeticLIRGeneratorTool gen) {

        LIRKind kind = builder.getLIRGeneratorTool().getLIRKind(stamp());

        builder.setResult(this, gen.emitReinterpret(kind, builder.operand(getValue())));

    }

    public static ValueNode reinterpret(JavaKind toKind, ValueNode value) {

        return value.graph().unique(new ReinterpretNode(toKind, value));

    }

}