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 * Copyright (c) 2015, 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
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package org.graalvm.compiler.lir.alloc.trace.lsra;

import static jdk.vm.ci.code.ValueUtil.asRegister;
import static jdk.vm.ci.code.ValueUtil.isRegister;

import org.graalvm.compiler.lir.LIRInstruction;

import jdk.vm.ci.meta.AllocatableValue;
import jdk.vm.ci.meta.Value;

/**
 * Represents a fixed interval.
 */
final class FixedInterval extends IntervalHint {

    static final class FixedList {

        public FixedInterval fixed;

        FixedList(FixedInterval fixed) {
            this.fixed = fixed;
        }

        /**
         * Gets the fixed list.
         */
        public FixedInterval getFixed() {
            return fixed;
        }

        /**
         * Sets the fixed list.
         */
        public void setFixed(FixedInterval list) {
            fixed = list;
        }

        /**
         * Adds an interval to a list sorted by {@linkplain FixedInterval#currentFrom() current
         * from} positions.
         *
         * @param interval the interval to add
         */
        public void addToListSortedByCurrentFromPositions(FixedInterval interval) {
            FixedInterval list = getFixed();
            FixedInterval prev = null;
            FixedInterval cur = list;
            while (cur.currentFrom() < interval.currentFrom()) {
                prev = cur;
                cur = cur.next;
            }
            FixedInterval result = list;
            if (prev == null) {
                // add to head of list
                result = interval;
            } else {
                // add before 'cur'
                prev.next = interval;
            }
            interval.next = cur;
            setFixed(result);
        }

    }

    /**
     * The fixed operand of this interval.
     */
    public final AllocatableValue operand;

    /**
     * The head of the list of ranges describing this interval. This list is sorted by
     * {@linkplain LIRInstruction#id instruction ids}.
     */
    private FixedRange first;

    /**
     * Iterator used to traverse the ranges of an interval.
     */
    private FixedRange current;

    /**
     * Link to next interval in a sorted list of intervals that ends with {@link #EndMarker}.
     */
    FixedInterval next;

    private int cachedTo; // cached value: to of last range (-1: not cached)

    public FixedRange first() {
        return first;
    }

    @Override
    public int from() {
        return first.from;
    }

    public int to() {
        if (cachedTo == -1) {
            cachedTo = calcTo();
        }
        assert cachedTo == calcTo() : "invalid cached value";
        return cachedTo;
    }

    // test intersection
    boolean intersects(TraceInterval i) {
        return first.intersects(i);
    }

    int intersectsAt(TraceInterval i) {
        return first.intersectsAt(i);
    }

    // range iteration
    void rewindRange() {
        current = first;
    }

    void nextRange() {
        assert this != EndMarker : "not allowed on sentinel";
        current = current.next;
    }

    int currentFrom() {
        return current.from;
    }

    int currentTo() {
        return current.to;
    }

    boolean currentAtEnd() {
        return current == FixedRange.EndMarker;
    }

    boolean currentIntersects(TraceInterval it) {
        return current.intersects(it);
    }

    int currentIntersectsAt(TraceInterval it) {
        return current.intersectsAt(it);
    }

    // range creation
    public void setFrom(int from) {
        assert !isEmpty();
        first().from = from;
    }

    private boolean isEmpty() {
        return first() == FixedRange.EndMarker;
    }

    public void addRange(int from, int to) {
        if (isEmpty()) {
            first = new FixedRange(from, to, first());
            return;
        }
        if (to <= to() && from >= from()) {
            return;
        }
        if (from() == to) {
            first().from = from;
        } else {
            first = new FixedRange(from, to, first());
        }
    }

    @Override
    public AllocatableValue location() {
        return operand;
    }

    /**
     * Sentinel interval to denote the end of an interval list.
     */
    static final FixedInterval EndMarker = new FixedInterval(Value.ILLEGAL);

    FixedInterval(AllocatableValue operand) {
        assert operand != null;
        this.operand = operand;
        this.first = FixedRange.EndMarker;
        this.current = FixedRange.EndMarker;
        this.next = FixedInterval.EndMarker;
        this.cachedTo = -1;
    }

    int calcTo() {
        assert first != FixedRange.EndMarker : "interval has no range";

        FixedRange r = first;
        while (r.next != FixedRange.EndMarker) {
            r = r.next;
        }
        return r.to;
    }

    // returns true if the opId is inside the interval
    boolean covers(int opId, LIRInstruction.OperandMode mode) {
        FixedRange cur = first;

        while (cur != FixedRange.EndMarker && cur.to < opId) {
            cur = cur.next;
        }
        if (cur != FixedRange.EndMarker) {
            assert cur.to != cur.next.from : "ranges not separated";

            if (mode == LIRInstruction.OperandMode.DEF) {
                return cur.from <= opId && opId < cur.to;
            } else {
                return cur.from <= opId && opId <= cur.to;
            }
        }
        return false;
    }

    // returns true if the interval has any hole between holeFrom and holeTo
    // (even if the hole has only the length 1)
    boolean hasHoleBetween(int holeFrom, int holeTo) {
        assert holeFrom < holeTo : "check";
        assert from() <= holeFrom && holeTo <= to() : "index out of interval";

        FixedRange cur = first;
        while (cur != FixedRange.EndMarker) {
            assert cur.to < cur.next.from : "no space between ranges";

            // hole-range starts before this range . hole
            if (holeFrom < cur.from) {
                return true;

                // hole-range completely inside this range . no hole
            } else {
                if (holeTo <= cur.to) {
                    return false;

                    // overlapping of hole-range with this range . hole
                } else {
                    if (holeFrom <= cur.to) {
                        return true;
                    }
                }
            }

            cur = cur.next;
        }

        return false;
    }

    @Override
    public String toString() {
        if (this == EndMarker) {
            return "EndMarker [?,?]";
        }
        String from = "?";
        String to = "?";
        if (first != null && first != FixedRange.EndMarker) {
            from = String.valueOf(from());
            // to() may cache a computed value, modifying the current object, which is a bad idea
            // for a printing function. Compute it directly instead.
            to = String.valueOf(calcTo());
        }
        String locationString = "@" + this.operand;
        return asRegister(operand).number + ":" + operand + (isRegister(operand) ? "" : locationString) + "[" + from + "," + to + "]";
    }

    /**
     * Gets a single line string for logging the details of this interval to a log stream.
     */
    @Override
    public String logString() {
        StringBuilder buf = new StringBuilder(100);
        buf.append("fix ").append(asRegister(operand).number).append(':').append(operand).append(' ');

        buf.append(" ranges{");

        // print ranges
        FixedRange cur = first;
        while (cur != FixedRange.EndMarker) {
            if (cur != first) {
                buf.append(", ");
            }
            buf.append(cur);
            cur = cur.next;
            assert cur != null : "range list not closed with range sentinel";
        }
        buf.append("}");
        return buf.toString();
    }

}