/*

 * Copyright (c) 2009, 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.lir.alloc.trace.lsra;

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

import static jdk.vm.ci.code.ValueUtil.asStackSlot;

import static jdk.vm.ci.code.ValueUtil.isIllegal;

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

import static jdk.vm.ci.code.ValueUtil.isStackSlot;

import static org.graalvm.compiler.lir.LIRValueUtil.asVirtualStackSlot;

import static org.graalvm.compiler.lir.LIRValueUtil.isStackSlotValue;

import static org.graalvm.compiler.lir.LIRValueUtil.isVirtualStackSlot;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.HashSet;

import java.util.List;

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

import org.graalvm.compiler.debug.Debug;

import org.graalvm.compiler.debug.DebugCounter;

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.debug.Indent;

import org.graalvm.compiler.lir.LIRInsertionBuffer;

import org.graalvm.compiler.lir.LIRInstruction;

import org.graalvm.compiler.lir.VirtualStackSlot;

import org.graalvm.compiler.lir.alloc.trace.lsra.TraceLinearScanPhase.TraceLinearScan;

import org.graalvm.compiler.lir.framemap.FrameMap;

import org.graalvm.compiler.lir.framemap.FrameMapBuilderTool;

import jdk.vm.ci.code.StackSlot;

import jdk.vm.ci.meta.AllocatableValue;

import jdk.vm.ci.meta.Constant;

import jdk.vm.ci.meta.JavaConstant;

import jdk.vm.ci.meta.Value;

/**

 */

final class TraceLocalMoveResolver {

    private static final DebugCounter cycleBreakingSlotsAllocated = Debug.counter("TraceRA[cycleBreakingSlotsAllocated(local)]");

    private static final int STACK_SLOT_IN_CALLER_FRAME_IDX = -1;

    private final TraceLinearScan allocator;

    private int insertIdx;

    private LIRInsertionBuffer insertionBuffer; // buffer where moves are inserted

    private final ArrayList<TraceInterval> mappingFrom;

    private final ArrayList<Constant> mappingFromOpr;

    private final ArrayList<TraceInterval> mappingTo;

    private final int[] registerBlocked;

    private int[] stackBlocked;

    private final int firstVirtualStackIndex;

    private int getStackArrayIndex(Value stackSlotValue) {

        if (isStackSlot(stackSlotValue)) {

            return getStackArrayIndex(asStackSlot(stackSlotValue));

        }

        if (isVirtualStackSlot(stackSlotValue)) {

            return getStackArrayIndex(asVirtualStackSlot(stackSlotValue));

        }

        throw GraalError.shouldNotReachHere("value is not a stack slot: " + stackSlotValue);

    }

    private int getStackArrayIndex(StackSlot stackSlot) {

        int stackIdx;

        if (stackSlot.isInCallerFrame()) {

            // incoming stack arguments can be ignored

            stackIdx = STACK_SLOT_IN_CALLER_FRAME_IDX;

        } else {

            assert stackSlot.getRawAddFrameSize() : "Unexpected stack slot: " + stackSlot;

            int offset = -stackSlot.getRawOffset();

            assert 0 <= offset && offset < firstVirtualStackIndex : String.format("Wrong stack slot offset: %d (first virtual stack slot index: %d", offset, firstVirtualStackIndex);

            stackIdx = offset;

        }

        return stackIdx;

    }

    private int getStackArrayIndex(VirtualStackSlot virtualStackSlot) {

        return firstVirtualStackIndex + virtualStackSlot.getId();

    }

    protected void setValueBlocked(Value location, int direction) {

        assert direction == 1 || direction == -1 : "out of bounds";

        if (isStackSlotValue(location)) {

            int stackIdx = getStackArrayIndex(location);

            if (stackIdx == STACK_SLOT_IN_CALLER_FRAME_IDX) {

                // incoming stack arguments can be ignored

                return;

            }

            if (stackIdx >= stackBlocked.length) {

                stackBlocked = Arrays.copyOf(stackBlocked, stackIdx + 1);

            }

            stackBlocked[stackIdx] += direction;

        } else {

            assert direction == 1 || direction == -1 : "out of bounds";

            if (isRegister(location)) {

                registerBlocked[asRegister(location).number] += direction;

            } else {

                throw GraalError.shouldNotReachHere("unhandled value " + location);

            }

        }

    }

    protected TraceInterval getMappingFrom(int i) {

        return mappingFrom.get(i);

    }

    protected int mappingFromSize() {

        return mappingFrom.size();

    }

    protected int valueBlocked(Value location) {

        if (isStackSlotValue(location)) {

            int stackIdx = getStackArrayIndex(location);

            if (stackIdx == STACK_SLOT_IN_CALLER_FRAME_IDX) {

                // incoming stack arguments are always blocked (aka they can not be written)

                return 1;

            }

            if (stackIdx >= stackBlocked.length) {

                return 0;

            }

            return stackBlocked[stackIdx];

        }

        if (isRegister(location)) {

            return registerBlocked[asRegister(location).number];

        }

        throw GraalError.shouldNotReachHere("unhandled value " + location);

    }

    /*

     * TODO (je) remove?

     */

    protected static boolean areMultipleReadsAllowed() {

        return true;

    }

    boolean hasMappings() {

        return mappingFrom.size() > 0;

    }

    protected TraceLinearScan getAllocator() {

        return allocator;

    }

    protected TraceLocalMoveResolver(TraceLinearScan allocator) {

        this.allocator = allocator;

        this.mappingFrom = new ArrayList<>(8);

        this.mappingFromOpr = new ArrayList<>(8);

        this.mappingTo = new ArrayList<>(8);

        this.insertIdx = -1;

        this.insertionBuffer = new LIRInsertionBuffer();

        this.registerBlocked = new int[allocator.getRegisters().size()];

        FrameMapBuilderTool frameMapBuilderTool = (FrameMapBuilderTool) allocator.getFrameMapBuilder();

        FrameMap frameMap = frameMapBuilderTool.getFrameMap();

        this.stackBlocked = new int[frameMapBuilderTool.getNumberOfStackSlots()];

        this.firstVirtualStackIndex = !frameMap.frameNeedsAllocating() ? 0 : frameMap.currentFrameSize() + 1;

    }

    protected boolean checkEmpty() {

        assert mappingFrom.size() == 0 && mappingFromOpr.size() == 0 && mappingTo.size() == 0 : "list must be empty before and after processing";

        for (int i = 0; i < stackBlocked.length; i++) {

            assert stackBlocked[i] == 0 : "stack map must be empty before and after processing";

        }

        for (int i = 0; i < getAllocator().getRegisters().size(); i++) {

            assert registerBlocked[i] == 0 : "register map must be empty before and after processing";

        }

        checkMultipleReads();

        return true;

    }

    protected void checkMultipleReads() {

        // multiple reads are allowed in SSA LSRA

    }

    private boolean verifyBeforeResolve() {

        assert mappingFrom.size() == mappingFromOpr.size() : "length must be equal";

        assert mappingFrom.size() == mappingTo.size() : "length must be equal";

        assert insertIdx != -1 : "insert position not set";

        int i;

        int j;

        if (!areMultipleReadsAllowed()) {

            for (i = 0; i < mappingFrom.size(); i++) {

                for (j = i + 1; j < mappingFrom.size(); j++) {

                    assert mappingFrom.get(i) == null || mappingFrom.get(i) != mappingFrom.get(j) : "cannot read from same interval twice";

                }

            }

        }

        for (i = 0; i < mappingTo.size(); i++) {

            for (j = i + 1; j < mappingTo.size(); j++) {

                assert mappingTo.get(i) != mappingTo.get(j) : "cannot write to same interval twice";

            }

        }

        HashSet<Value> usedRegs = new HashSet<>();

        if (!areMultipleReadsAllowed()) {

            for (i = 0; i < mappingFrom.size(); i++) {

                TraceInterval interval = mappingFrom.get(i);

                if (interval != null && !isIllegal(interval.location())) {

                    boolean unique = usedRegs.add(interval.location());

                    assert unique : "cannot read from same register twice";

                }

            }

        }

        usedRegs.clear();

        for (i = 0; i < mappingTo.size(); i++) {

            TraceInterval interval = mappingTo.get(i);

            if (isIllegal(interval.location())) {

                // After insertion the location may become illegal, so don't check it since multiple

                // intervals might be illegal.

                continue;

            }

            boolean unique = usedRegs.add(interval.location());

            assert unique : "cannot write to same register twice";

        }

        verifyStackSlotMapping();

        return true;

    }

    protected void verifyStackSlotMapping() {

        // relax disjoint stack maps invariant

    }

    // mark assignedReg and assignedRegHi of the interval as blocked

    private void blockRegisters(TraceInterval interval) {

        Value location = interval.location();

        if (mightBeBlocked(location)) {

            assert areMultipleReadsAllowed() || valueBlocked(location) == 0 : "location already marked as used: " + location;

            int direction = 1;

            setValueBlocked(location, direction);

            Debug.log("block %s", location);

        }

    }

    // mark assignedReg and assignedRegHi of the interval as unblocked

    private void unblockRegisters(TraceInterval interval) {

        Value location = interval.location();

        if (mightBeBlocked(location)) {

            assert valueBlocked(location) > 0 : "location already marked as unused: " + location;

            setValueBlocked(location, -1);

            Debug.log("unblock %s", location);

        }

    }

    /**

     * Checks if the {@linkplain TraceInterval#location() location} of {@code to} is not blocked or

     * is only blocked by {@code from}.

     */

    private boolean safeToProcessMove(TraceInterval from, TraceInterval to) {

        Value fromReg = from != null ? from.location() : null;

        Value location = to.location();

        if (mightBeBlocked(location)) {

            if ((valueBlocked(location) > 1 || (valueBlocked(location) == 1 && !isMoveToSelf(fromReg, location)))) {

                return false;

            }

        }

        return true;

    }

    protected static boolean isMoveToSelf(Value from, Value to) {

        assert to != null;

        if (to.equals(from)) {

            return true;

        }

        if (from != null && isRegister(from) && isRegister(to) && asRegister(from).equals(asRegister(to))) {

            return true;

        }

        return false;

    }

    protected static boolean mightBeBlocked(Value location) {

        if (isRegister(location)) {

            return true;

        }

        if (isStackSlotValue(location)) {

            return true;

        }

        return false;

    }

    private void createInsertionBuffer(List<LIRInstruction> list) {

        assert !insertionBuffer.initialized() : "overwriting existing buffer";

        insertionBuffer.init(list);

    }

    private void appendInsertionBuffer() {

        if (insertionBuffer.initialized()) {

            insertionBuffer.finish();

        }

        assert !insertionBuffer.initialized() : "must be uninitialized now";

        insertIdx = -1;

    }

    private void insertMove(TraceInterval fromInterval, TraceInterval toInterval) {

        assert !fromInterval.operand.equals(toInterval.operand) : "from and to interval equal: " + fromInterval;

        assert insertIdx != -1 : "must setup insert position first";

        insertionBuffer.append(insertIdx, createMove(fromInterval.operand, toInterval.operand, fromInterval.location(), toInterval.location()));

        if (Debug.isLogEnabled()) {

            Debug.log("insert move from %s to %s at %d", fromInterval, toInterval, insertIdx);

        }

    }

    /**

     * @param fromOpr {@link TraceInterval#operand operand} of the {@code from} interval

     * @param toOpr {@link TraceInterval#operand operand} of the {@code to} interval

     * @param fromLocation {@link TraceInterval#location() location} of the {@code to} interval

     * @param toLocation {@link TraceInterval#location() location} of the {@code to} interval

     */

    protected LIRInstruction createMove(AllocatableValue fromOpr, AllocatableValue toOpr, AllocatableValue fromLocation, AllocatableValue toLocation) {

        if (isStackSlotValue(toLocation) && isStackSlotValue(fromLocation)) {

            return getAllocator().getSpillMoveFactory().createStackMove(toOpr, fromOpr);

        }

        return getAllocator().getSpillMoveFactory().createMove(toOpr, fromOpr);

    }

    private void insertMove(Constant fromOpr, TraceInterval toInterval) {

        assert insertIdx != -1 : "must setup insert position first";

        AllocatableValue toOpr = toInterval.operand;

        LIRInstruction move = getAllocator().getSpillMoveFactory().createLoad(toOpr, fromOpr);

        insertionBuffer.append(insertIdx, move);

        if (Debug.isLogEnabled()) {

            Debug.log("insert move from value %s to %s at %d", fromOpr, toInterval, insertIdx);

        }

    }

    @SuppressWarnings("try")

    private void resolveMappings() {

        try (Indent indent = Debug.logAndIndent("resolveMapping")) {

            assert verifyBeforeResolve();

            if (Debug.isLogEnabled()) {

                printMapping();

            }

            // Block all registers that are used as input operands of a move.

            // When a register is blocked, no move to this register is emitted.

            // This is necessary for detecting cycles in moves.

            int i;

            for (i = mappingFrom.size() - 1; i >= 0; i--) {

                TraceInterval fromInterval = mappingFrom.get(i);

                if (fromInterval != null) {

                    blockRegisters(fromInterval);

                }

            }

            ArrayList<AllocatableValue> busySpillSlots = null;

            while (mappingFrom.size() > 0) {

                boolean processedInterval = false;

                int spillCandidate = -1;

                for (i = mappingFrom.size() - 1; i >= 0; i--) {

                    TraceInterval fromInterval = mappingFrom.get(i);

                    TraceInterval toInterval = mappingTo.get(i);

                    if (safeToProcessMove(fromInterval, toInterval)) {

                        // this interval can be processed because target is free

                        if (fromInterval != null) {

                            insertMove(fromInterval, toInterval);

                            unblockRegisters(fromInterval);

                        } else {

                            insertMove(mappingFromOpr.get(i), toInterval);

                        }

                        if (isStackSlotValue(toInterval.location())) {

                            if (busySpillSlots == null) {

                                busySpillSlots = new ArrayList<>(2);

                            }

                            busySpillSlots.add(toInterval.location());

                        }

                        mappingFrom.remove(i);

                        mappingFromOpr.remove(i);

                        mappingTo.remove(i);

                        processedInterval = true;

                    } else if (fromInterval != null && isRegister(fromInterval.location()) && (busySpillSlots == null || !busySpillSlots.contains(fromInterval.spillSlot()))) {

                        // this interval cannot be processed now because target is not free

                        // it starts in a register, so it is a possible candidate for spilling

                        spillCandidate = i;

                    }

                }

                if (!processedInterval) {

                    breakCycle(spillCandidate);

                }

            }

        }

        // check that all intervals have been processed

        assert checkEmpty();

    }

    protected void breakCycle(int spillCandidate) {

        if (spillCandidate != -1) {

            // no move could be processed because there is a cycle in the move list

            // (e.g. r1 . r2, r2 . r1), so one interval must be spilled to memory

            assert spillCandidate != -1 : "no interval in register for spilling found";

            // create a new spill interval and assign a stack slot to it

            TraceInterval fromInterval1 = mappingFrom.get(spillCandidate);

            // do not allocate a new spill slot for temporary interval, but

            // use spill slot assigned to fromInterval. Otherwise moves from

            // one stack slot to another can happen (not allowed by LIRAssembler

            AllocatableValue spillSlot1 = fromInterval1.spillSlot();

            if (spillSlot1 == null) {

                spillSlot1 = getAllocator().getFrameMapBuilder().allocateSpillSlot(fromInterval1.kind());

                fromInterval1.setSpillSlot(spillSlot1);

                cycleBreakingSlotsAllocated.increment();

            }

            spillInterval(spillCandidate, fromInterval1, spillSlot1);

            return;

        }

        assert mappingFromSize() > 1;

        // Arbitrarily select the first entry for spilling.

        int stackSpillCandidate = 0;

        TraceInterval fromInterval = getMappingFrom(stackSpillCandidate);

        // allocate new stack slot

        VirtualStackSlot spillSlot = getAllocator().getFrameMapBuilder().allocateSpillSlot(fromInterval.kind());

        spillInterval(stackSpillCandidate, fromInterval, spillSlot);

    }

    protected void spillInterval(int spillCandidate, TraceInterval fromInterval, AllocatableValue spillSlot) {

        assert mappingFrom.get(spillCandidate).equals(fromInterval);

        TraceInterval spillInterval = getAllocator().createDerivedInterval(fromInterval);

        // add a dummy range because real position is difficult to calculate

        // Note: this range is a special case when the integrity of the allocation is

        // checked

        spillInterval.addRange(1, 2);

        spillInterval.assignLocation(spillSlot);

        if (Debug.isLogEnabled()) {

            Debug.log("created new Interval for spilling: %s", spillInterval);

        }

        blockRegisters(spillInterval);

        // insert a move from register to stack and update the mapping

        insertMove(fromInterval, spillInterval);

        mappingFrom.set(spillCandidate, spillInterval);

        unblockRegisters(fromInterval);

    }

    @SuppressWarnings("try")

    private void printMapping() {

        try (Indent indent = Debug.logAndIndent("Mapping")) {

            for (int i = mappingFrom.size() - 1; i >= 0; i--) {

                TraceInterval fromInterval = mappingFrom.get(i);

                TraceInterval toInterval = mappingTo.get(i);

                String from;

                Value to = toInterval.location();

                if (fromInterval == null) {

                    from = mappingFromOpr.get(i).toString();

                } else {

                    from = fromInterval.location().toString();

                }

                Debug.log("move %s <- %s", from, to);

            }

        }

    }

    void setInsertPosition(List<LIRInstruction> insertList, int insertIdx) {

        assert this.insertIdx == -1 : "use moveInsertPosition instead of setInsertPosition when data already set";

        createInsertionBuffer(insertList);

        this.insertIdx = insertIdx;

    }

    void moveInsertPosition(List<LIRInstruction> newInsertList, int newInsertIdx) {

        if (insertionBuffer.lirList() != null && (insertionBuffer.lirList() != newInsertList || this.insertIdx != newInsertIdx)) {

            // insert position changed . resolve current mappings

            resolveMappings();

        }

        assert insertionBuffer.lirList() != newInsertList || newInsertIdx >= insertIdx : String.format("Decreasing insert index: old=%d new=%d", insertIdx, newInsertIdx);

        if (insertionBuffer.lirList() != newInsertList) {

            // block changed . append insertionBuffer because it is

            // bound to a specific block and create a new insertionBuffer

            appendInsertionBuffer();

            createInsertionBuffer(newInsertList);

        }

        this.insertIdx = newInsertIdx;

    }

    public void addMapping(TraceInterval fromInterval, TraceInterval toInterval) {

        if (isIllegal(toInterval.location()) && toInterval.canMaterialize()) {

            if (Debug.isLogEnabled()) {

                Debug.log("no store to rematerializable interval %s needed", toInterval);

            }

            return;

        }

        if (isIllegal(fromInterval.location()) && fromInterval.canMaterialize()) {