loopOpt.hpp

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/* Copyright 1996, LongView Technologies L.L.C. $Revision: 1.6 $ */
/* Copyright (c) 2006, Sun Microsystems, Inc.
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#ifdef DELTA_COMPILER

// Implementation of loop optimizations: moving type tests out of loops, finding candidates for register
// allocation within a loop, plus integer-specific optimizations (removing tag checks and bound checks).

// a candidate for register allocation within a loop
class LoopRegCandidate : public PrintableResourceObj {
  PReg* _preg;
  int _nuses, _ndefs;
public:
  LoopRegCandidate(PReg* r)     { _preg = r; _nuses = _ndefs = 0; }
  PReg* preg() const            { return _preg; }
  int   nuses() const           { return _nuses; }
  int   ndefs() const           { return _ndefs; }
  int   weight() const          { return _ndefs + _nuses; }
  void  incDUs(int u, int d)    { _nuses += u; _ndefs += d; }
  void  print();
};


// A CompiledLoop contains annotations for the compiler for integer loop optimizations.

class CompiledLoop : public PrintableResourceObj {
  InlinedScope* _scope;
  Node* _beforeLoop;                      // last node before loop (init. of loop var)
  LoopHeaderNode* _loopHeader;
  Node* _startOfLoop;
  Node* _endOfLoop;
  Node* _startOfBody;
  Node* _endOfBody;
  Node* _startOfCond;
  Node* _endOfCond;
  BranchNode* _loopBranch;                // branch ending loop condition  
  int _firstNodeID, _lastNodeID;          // all node IDs in loop are between these two

  // the instance variables below are set as a result of recognize()
  // and are valid only if isIntegerLoop()
  bool  _isIntegerLoop;                   // is this loop a recognized integer loop?
  PReg* _loopVar;                         // suspected loop variable
  PReg* _lowerBound;                      // lower bound of for-like loop (see comment in findLowerBound)
  PReg* _upperBound;                      // upper bound 
  PReg* _increment;                       // increment of loopVar
  bool  _isCountingUp;                    // true if loop is counting up, false if counting down
  NonTrivialNode* _incNode;               // node incrementing loop var
  PReg* _loopArray;                       // array whose size is upper bound (or NULL)
  LoadOffsetNode* _loopSizeLoad;          // node loading loopArray's size

  // instance variables for general loop optimizations
  GrowableArray<HoistedTypeTest*>* _hoistableTests;     // tests that can be hoisted out of the loop
  static GrowableArray<BB*>* _bbs;        // BBs in code generation order
 public:
  CompiledLoop();         
  
  // the routines below should be called with the appropriate nodes
  void set_startOfLoop(LoopHeaderNode* current);
  void set_startOfBody(Node* current);
  void set_endOfBody(Node* current);
  void set_startOfCond(Node* current);
  void set_endOfCond(Node* current);
  void set_endOfLoop(Node* end);

  bool isInLoop(Node* n) const;
  bool isInLoopCond(Node* n) const;
  bool isInLoopBody(Node* n) const;
  LoopHeaderNode* loopHeader() const      { return _loopHeader; }


  char* recognize();                      // does integer loop recognition; called after defs/uses built
                                          // returns NULL if successful, reason otherwise
  bool isIntegerLoop() const              { return _isIntegerLoop; }
  void optimize();                        // perform general loop optimization
  void optimizeIntegerLoop();             // perform integer loop optimization

  void print();

 protected:
   void  discoverLoopNesting();
   int   findStartOfSend(int bci);
   char* findLowerBound();
   char* findUpperBound();
   char* checkLoopVar();
   char* checkUpperBound();
   NonTrivialNode* findDefInLoop(PReg* r);        // find single definition of r in loop
   bool  isIncrement(PReg* r, ArithOpCode op);    // is r a suitable loop variable increment?
   void  removeTagChecks();
   void  removeLoopVarOverflow();
   void  checkForArraysDefinedInLoop();
   void  hoistTypeTests();
   void  removeBoundsChecks(PReg* array, PReg* var);
   void  findRegCandidates();
   bool  isEquivalentType(GrowableArray<klassOop>* klasses1, GrowableArray<klassOop>* klasses2);
 public:  // for iterators
   int   defsInLoop(PReg* r, NonTrivialNode** defNode = NULL);   // return number of definitions of r in loop and sets defNode if non-NULL
};

// holds the info associated with a single type test hoisted out of a loop
class HoistedTypeTest: public PrintableResourceObj {
public:
  NonTrivialNode* node;                     // node (within loop) doing the test
  PReg* testedPR;                           // PReg whose type is tested
  GrowableArray<klassOop>* klasses;         // klasses for which the PReg is tested
  bool  invalid;                            

  HoistedTypeTest(NonTrivialNode* node, PReg* testedPR, GrowableArray<klassOop>* klasses);
  void print();
  void print_test_on(outputStream* s);
};

#endif

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