/*

 * Copyright (c) 2015, 2016, 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.stackslotalloc;

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

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

import java.util.ArrayDeque;

import java.util.ArrayList;

import java.util.BitSet;

import java.util.Deque;

import java.util.EnumSet;

import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;

import org.graalvm.compiler.core.common.cfg.BlockMap;

import org.graalvm.compiler.debug.CounterKey;

import org.graalvm.compiler.debug.DebugContext;

import org.graalvm.compiler.debug.Indent;

import org.graalvm.compiler.lir.InstructionValueConsumer;

import org.graalvm.compiler.lir.InstructionValueProcedure;

import org.graalvm.compiler.lir.LIR;

import org.graalvm.compiler.lir.LIRInstruction;

import org.graalvm.compiler.lir.LIRInstruction.OperandFlag;

import org.graalvm.compiler.lir.LIRInstruction.OperandMode;

import org.graalvm.compiler.lir.VirtualStackSlot;

import jdk.vm.ci.meta.Value;

/**

 * Calculates the stack intervals using a worklist-based backwards data-flow analysis.

 */

final class FixPointIntervalBuilder {

    private final BlockMap<BitSet> liveInMap;

    private final BlockMap<BitSet> liveOutMap;

    private final LIR lir;

    private final int maxOpId;

    private final StackInterval[] stackSlotMap;

    private final EconomicSet<LIRInstruction> usePos;

    /**

     * The number of allocated stack slots.

     */

    private static final CounterKey uninitializedSlots = DebugContext.counter("StackSlotAllocator[uninitializedSlots]");

    FixPointIntervalBuilder(LIR lir, StackInterval[] stackSlotMap, int maxOpId) {

        this.lir = lir;

        this.stackSlotMap = stackSlotMap;

        this.maxOpId = maxOpId;

        liveInMap = new BlockMap<>(lir.getControlFlowGraph());

        liveOutMap = new BlockMap<>(lir.getControlFlowGraph());

        this.usePos = EconomicSet.create(Equivalence.IDENTITY);

    }

    /**

     * Builds the lifetime intervals for {@link VirtualStackSlot virtual stack slots}, sets up

     * {@link #stackSlotMap} and returns a set of use positions, i.e. instructions that contain

     * virtual stack slots.

     */

    EconomicSet<LIRInstruction> build() {

        Deque<AbstractBlockBase<?>> worklist = new ArrayDeque<>();

        AbstractBlockBase<?>[] blocks = lir.getControlFlowGraph().getBlocks();

        for (int i = blocks.length - 1; i >= 0; i--) {

            worklist.add(blocks[i]);

        }

        for (AbstractBlockBase<?> block : lir.getControlFlowGraph().getBlocks()) {

            liveInMap.put(block, new BitSet(stackSlotMap.length));

        }

        while (!worklist.isEmpty()) {

            AbstractBlockBase<?> block = worklist.poll();

            processBlock(block, worklist);

        }

        return usePos;

    }

    /**

     * Merge outSet with in-set of successors.

     */

    private boolean updateOutBlock(AbstractBlockBase<?> block) {

        BitSet union = new BitSet(stackSlotMap.length);

        for (AbstractBlockBase<?> succ : block.getSuccessors()) {

            union.or(liveInMap.get(succ));

        }

        BitSet outSet = liveOutMap.get(block);

        // check if changed

        if (outSet == null || !union.equals(outSet)) {

            liveOutMap.put(block, union);

            return true;

        }

        return false;

    }

    @SuppressWarnings("try")

    private void processBlock(AbstractBlockBase<?> block, Deque<AbstractBlockBase<?>> worklist) {

        DebugContext debug = lir.getDebug();

        if (updateOutBlock(block)) {

            try (Indent indent = debug.logAndIndent("handle block %s", block)) {

                ArrayList<LIRInstruction> instructions = lir.getLIRforBlock(block);

                // get out set and mark intervals

                BitSet outSet = liveOutMap.get(block);

                markOutInterval(outSet, getBlockEnd(instructions));

                printLiveSet("liveOut", outSet);

                // process instructions

                BlockClosure closure = new BlockClosure((BitSet) outSet.clone());

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

                    LIRInstruction inst = instructions.get(i);

                    closure.processInstructionBottomUp(inst);

                }

                // add predecessors to work list

                for (AbstractBlockBase<?> b : block.getPredecessors()) {

                    worklist.add(b);

                }

                // set in set and mark intervals

                BitSet inSet = closure.getCurrentSet();

                liveInMap.put(block, inSet);

                markInInterval(inSet, getBlockBegin(instructions));

                printLiveSet("liveIn", inSet);

            }

        }

    }

    @SuppressWarnings("try")

    private void printLiveSet(String label, BitSet liveSet) {

        DebugContext debug = lir.getDebug();

        if (debug.isLogEnabled()) {

            try (Indent indent = debug.logAndIndent(label)) {

                debug.log("%s", liveSetToString(liveSet));

            }

        }

    }

    private String liveSetToString(BitSet liveSet) {

        StringBuilder sb = new StringBuilder();

        for (int i = liveSet.nextSetBit(0); i >= 0; i = liveSet.nextSetBit(i + 1)) {

            StackInterval interval = getIntervalFromStackId(i);

            sb.append(interval.getOperand()).append(" ");

        }

        return sb.toString();

    }

    private void markOutInterval(BitSet outSet, int blockEndOpId) {

        DebugContext debug = lir.getDebug();

        for (int i = outSet.nextSetBit(0); i >= 0; i = outSet.nextSetBit(i + 1)) {

            StackInterval interval = getIntervalFromStackId(i);

            debug.log("mark live operand: %s", interval.getOperand());

            interval.addTo(blockEndOpId);

        }

    }

    private void markInInterval(BitSet inSet, int blockFirstOpId) {

        DebugContext debug = lir.getDebug();

        for (int i = inSet.nextSetBit(0); i >= 0; i = inSet.nextSetBit(i + 1)) {

            StackInterval interval = getIntervalFromStackId(i);

            debug.log("mark live operand: %s", interval.getOperand());

            interval.addFrom(blockFirstOpId);

        }

    }

    private final class BlockClosure {

        private final BitSet currentSet;

        private BlockClosure(BitSet set) {

            currentSet = set;

        }

        private BitSet getCurrentSet() {

            return currentSet;

        }

        /**

         * Process all values of an instruction bottom-up, i.e. definitions before usages. Values

         * that start or end at the current operation are not included.

         */

        @SuppressWarnings("try")

        private void processInstructionBottomUp(LIRInstruction op) {

            DebugContext debug = lir.getDebug();

            try (Indent indent = debug.logAndIndent("handle op %d, %s", op.id(), op)) {

                // kills

                op.visitEachTemp(defConsumer);

                op.visitEachOutput(defConsumer);

                // gen - values that are considered alive for this state

                op.visitEachAlive(useConsumer);

                op.visitEachState(useConsumer);

                // mark locations

                // gen

                op.visitEachInput(useConsumer);

            }

        }

        InstructionValueConsumer useConsumer = new InstructionValueConsumer() {

            @Override

            public void visitValue(LIRInstruction inst, Value operand, OperandMode mode, EnumSet<OperandFlag> flags) {

                if (isVirtualStackSlot(operand)) {

                    DebugContext debug = lir.getDebug();

                    VirtualStackSlot vslot = asVirtualStackSlot(operand);

                    addUse(vslot, inst, flags);

                    addRegisterHint(inst, vslot, mode, flags, false);

                    usePos.add(inst);

                    debug.log("set operand: %s", operand);

                    currentSet.set(vslot.getId());

                }

            }

        };

        InstructionValueConsumer defConsumer = new InstructionValueConsumer() {

            @Override

            public void visitValue(LIRInstruction inst, Value operand, OperandMode mode, EnumSet<OperandFlag> flags) {

                if (isVirtualStackSlot(operand)) {

                    DebugContext debug = lir.getDebug();

                    VirtualStackSlot vslot = asVirtualStackSlot(operand);

                    addDef(vslot, inst);

                    addRegisterHint(inst, vslot, mode, flags, true);

                    usePos.add(inst);

                    debug.log("clear operand: %s", operand);

                    currentSet.clear(vslot.getId());

                }

            }

        };

        private void addUse(VirtualStackSlot stackSlot, LIRInstruction inst, EnumSet<OperandFlag> flags) {

            StackInterval interval = getOrCreateInterval(stackSlot);

            if (flags.contains(OperandFlag.UNINITIALIZED)) {

                // Stack slot is marked uninitialized so we have to assume it is live all

                // the time.

                DebugContext debug = lir.getDebug();

                if (debug.isCountEnabled() && !(interval.from() == 0 && interval.to() == maxOpId)) {

                    uninitializedSlots.increment(debug);

                }

                interval.addFrom(0);

                interval.addTo(maxOpId);

            } else {

                interval.addTo(inst.id());

            }

        }

        private void addDef(VirtualStackSlot stackSlot, LIRInstruction inst) {

            StackInterval interval = getOrCreateInterval(stackSlot);

            interval.addFrom(inst.id());

        }

        void addRegisterHint(final LIRInstruction op, VirtualStackSlot targetValue, OperandMode mode, EnumSet<OperandFlag> flags, final boolean hintAtDef) {

            if (flags.contains(OperandFlag.HINT)) {

                InstructionValueProcedure proc = new InstructionValueProcedure() {

                    @Override

                    public Value doValue(LIRInstruction instruction, Value registerHint, OperandMode vaueMode, EnumSet<OperandFlag> valueFlags) {

                        if (isVirtualStackSlot(registerHint)) {

                            StackInterval from = getOrCreateInterval((VirtualStackSlot) registerHint);

                            StackInterval to = getOrCreateInterval(targetValue);

                            // hints always point from def to use

                            if (hintAtDef) {

                                to.setLocationHint(from);

                            } else {

                                from.setLocationHint(to);

                            }

                            DebugContext debug = lir.getDebug();

                            if (debug.isLogEnabled()) {

                                debug.log("operation %s at opId %d: added hint from interval %s to %s", op, op.id(), from, to);

                            }

                            return registerHint;

                        }

                        return null;

                    }

                };

                op.forEachRegisterHint(targetValue, mode, proc);

            }

        }

    }

    private StackInterval get(VirtualStackSlot stackSlot) {

        return stackSlotMap[stackSlot.getId()];

    }

    private void put(VirtualStackSlot stackSlot, StackInterval interval) {

        stackSlotMap[stackSlot.getId()] = interval;

    }

    private StackInterval getOrCreateInterval(VirtualStackSlot stackSlot) {

        StackInterval interval = get(stackSlot);

        if (interval == null) {

            interval = new StackInterval(stackSlot, stackSlot.getValueKind());

            put(stackSlot, interval);

        }

        return interval;

    }

    private StackInterval getIntervalFromStackId(int id) {

        return stackSlotMap[id];

    }

    private static int getBlockBegin(ArrayList<LIRInstruction> instructions) {

        return instructions.get(0).id();

    }

    private static int getBlockEnd(ArrayList<LIRInstruction> instructions) {

        return instructions.get(instructions.size() - 1).id() + 1;

    }

}