drlvm/vm/jitrino/src/optimizer/deadcodeeliminator.h

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

/**
 * @author Intel, Pavel A. Ozhdikhin
 *
 */

#ifndef _DEADCODEELIMINATOR_H_
#define _DEADCODEELIMINATOR_H_

#include "Stl.h"
#include "optpass.h"
#include "LoopTree.h"

namespace Jitrino {

class IRManager;
class Inst;
class Opnd;
class ControlFlowGraph;
class Node;
class BitSet;

///the structure that holds info to fix infinite loops.
class InfiniteLoopsInfo {
public:
    InfiniteLoopsInfo(MemoryManager& mm) : map(mm), hasLoops(false) {}
    
    ///loop header to dispatch node mapping
    StlMap<Node*, Node*> map;
    
    ////caches if cfg has loops
    bool hasLoops;
};

class DeadCodeEliminator {
public:
    DeadCodeEliminator(IRManager& irm);
    void eliminateDeadCode(bool keepEmptyNodes);
    static void copyPropagate(Inst*);
    static Opnd* copyPropagate(Opnd*);
    bool eliminateUnreachableCode(); // returns true if any node is eliminated
    void removeExtraPseudoThrow();
    
    ///creates a mapping of loop-header to dispatch nodes that can be used later to fix infinite loops
    static void createLoop2DispatchMapping(ControlFlowGraph& cfg, InfiniteLoopsInfo& info);

    ///looks for infinite loops in code and adds pseudothrow inst using dispatch node provided by 'info' 
    static void fixInfiniteLoops(IRManager& irm, const InfiniteLoopsInfo& info);

private:
    void sweepInst(Node* node, Inst* inst, BitSet& usefulInstSet, BitSet& usefulVarSet, U_8 *usedInstWidth, U_32 minInstId, U_32 maxInstId, bool canRemoveStvars);
    void sweepInst1(Node* node, Inst* inst, BitSet& usefulInstSet, BitSet& usefulVarSet,
                    U_32 minInstId, U_32 maxInstId, bool canRemoveStvars); // if we're skipping instWidth
    static Opnd* findDefiningTemp(Opnd* var);
    void markEssentialPseudoThrows(LoopNode* loopNode, BitSet& essentialNodes);

    IRManager& irManager;
    ControlFlowGraph& flowGraph;
    Opnd* returnOpnd;
    bool preserveCriticalEdges;
};

} //namespace Jitrino 

#endif // _DEADCODEELIMINATOR_H_