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Java example source code file (ciTypeFlow.hpp)

This example Java source code file (ciTypeFlow.hpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

block, cell, createoption, finished, growablearray, jsrrecord, jsrset, localset, loop, null, product_return, resourceobj, statevector, succiter

The ciTypeFlow.hpp Java example source code

/*
 * Copyright (c) 2000, 2012, 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.
 *
 */

#ifndef SHARE_VM_CI_CITYPEFLOW_HPP
#define SHARE_VM_CI_CITYPEFLOW_HPP

#ifdef COMPILER2
#include "ci/ciEnv.hpp"
#include "ci/ciKlass.hpp"
#include "ci/ciMethodBlocks.hpp"
#endif
#ifdef SHARK
#include "ci/ciEnv.hpp"
#include "ci/ciKlass.hpp"
#include "ci/ciMethodBlocks.hpp"
#include "shark/shark_globals.hpp"
#endif


class ciTypeFlow : public ResourceObj {
private:
  ciEnv*    _env;
  ciMethod* _method;
  ciMethodBlocks* _methodBlocks;
  int       _osr_bci;

  // information cached from the method:
  int _max_locals;
  int _max_stack;
  int _code_size;
  bool      _has_irreducible_entry;

  const char* _failure_reason;

public:
  class StateVector;
  class Loop;
  class Block;

  // Build a type flow analyzer
  // Do an OSR analysis if osr_bci >= 0.
  ciTypeFlow(ciEnv* env, ciMethod* method, int osr_bci = InvocationEntryBci);

  // Accessors
  ciMethod* method() const     { return _method; }
  ciEnv*    env()              { return _env; }
  Arena*    arena()            { return _env->arena(); }
  bool      is_osr_flow() const{ return _osr_bci != InvocationEntryBci; }
  int       start_bci() const  { return is_osr_flow()? _osr_bci: 0; }
  int       max_locals() const { return _max_locals; }
  int       max_stack() const  { return _max_stack; }
  int       max_cells() const  { return _max_locals + _max_stack; }
  int       code_size() const  { return _code_size; }
  bool      has_irreducible_entry() const { return _has_irreducible_entry; }

  // Represents information about an "active" jsr call.  This
  // class represents a call to the routine at some entry address
  // with some distinct return address.
  class JsrRecord : public ResourceObj {
  private:
    int _entry_address;
    int _return_address;
  public:
    JsrRecord(int entry_address, int return_address) {
      _entry_address = entry_address;
      _return_address = return_address;
    }

    int entry_address() const  { return _entry_address; }
    int return_address() const { return _return_address; }

    void print_on(outputStream* st) const {
#ifndef PRODUCT
      st->print("%d->%d", entry_address(), return_address());
#endif
    }
  };

  // A JsrSet represents some set of JsrRecords.  This class
  // is used to record a set of all jsr routines which we permit
  // execution to return (ret) from.
  //
  // During abstract interpretation, JsrSets are used to determine
  // whether two paths which reach a given block are unique, and
  // should be cloned apart, or are compatible, and should merge
  // together.
  //
  // Note that different amounts of effort can be expended determining
  // if paths are compatible.  <DISCUSSION>
  class JsrSet : public ResourceObj {
  private:
    GrowableArray<JsrRecord*>* _set;

    JsrRecord* record_at(int i) {
      return _set->at(i);
    }

    // Insert the given JsrRecord into the JsrSet, maintaining the order
    // of the set and replacing any element with the same entry address.
    void insert_jsr_record(JsrRecord* record);

    // Remove the JsrRecord with the given return address from the JsrSet.
    void remove_jsr_record(int return_address);

  public:
    JsrSet(Arena* arena, int default_len = 4);

    // Copy this JsrSet.
    void copy_into(JsrSet* jsrs);

    // Is this JsrSet compatible with some other JsrSet?
    bool is_compatible_with(JsrSet* other);

    // Apply the effect of a single bytecode to the JsrSet.
    void apply_control(ciTypeFlow* analyzer,
                       ciBytecodeStream* str,
                       StateVector* state);

    // What is the cardinality of this set?
    int size() const { return _set->length(); }

    void print_on(outputStream* st) const PRODUCT_RETURN;
  };

  class LocalSet VALUE_OBJ_CLASS_SPEC {
  private:
    enum Constants { max = 63 };
    uint64_t _bits;
  public:
    LocalSet() : _bits(0) {}
    void add(uint32_t i)        { if (i < (uint32_t)max) _bits |=  (1LL << i); }
    void add(LocalSet* ls)      { _bits |= ls->_bits; }
    bool test(uint32_t i) const { return i < (uint32_t)max ? (_bits>>i)&1U : true; }
    void clear()                { _bits = 0; }
    void print_on(outputStream* st, int limit) const  PRODUCT_RETURN;
  };

  // Used as a combined index for locals and temps
  enum Cell {
    Cell_0, Cell_max = INT_MAX
  };

  // A StateVector summarizes the type information at some
  // point in the program
  class StateVector : public ResourceObj {
  private:
    ciType**    _types;
    int         _stack_size;
    int         _monitor_count;
    ciTypeFlow* _outer;

    int         _trap_bci;
    int         _trap_index;

    LocalSet    _def_locals;  // For entire block

    static ciType* type_meet_internal(ciType* t1, ciType* t2, ciTypeFlow* analyzer);

  public:
    // Special elements in our type lattice.
    enum {
      T_TOP     = T_VOID,      // why not?
      T_BOTTOM  = T_CONFLICT,
      T_LONG2   = T_SHORT,     // 2nd word of T_LONG
      T_DOUBLE2 = T_CHAR,      // 2nd word of T_DOUBLE
      T_NULL    = T_BYTE       // for now.
    };
    static ciType* top_type()    { return ciType::make((BasicType)T_TOP); }
    static ciType* bottom_type() { return ciType::make((BasicType)T_BOTTOM); }
    static ciType* long2_type()  { return ciType::make((BasicType)T_LONG2); }
    static ciType* double2_type(){ return ciType::make((BasicType)T_DOUBLE2); }
    static ciType* null_type()   { return ciType::make((BasicType)T_NULL); }

    static ciType* half_type(ciType* t) {
      switch (t->basic_type()) {
      case T_LONG:    return long2_type();
      case T_DOUBLE:  return double2_type();
      default:        ShouldNotReachHere(); return NULL;
      }
    }

    // The meet operation for our type lattice.
    ciType* type_meet(ciType* t1, ciType* t2) {
      return type_meet_internal(t1, t2, outer());
    }

    // Accessors
    ciTypeFlow* outer() const          { return _outer; }

    int         stack_size() const     { return _stack_size; }
    void    set_stack_size(int ss)     { _stack_size = ss; }

    int         monitor_count() const  { return _monitor_count; }
    void    set_monitor_count(int mc)  { _monitor_count = mc; }

    LocalSet* def_locals() { return &_def_locals; }
    const LocalSet* def_locals() const { return &_def_locals; }

    static Cell start_cell()           { return (Cell)0; }
    static Cell next_cell(Cell c)      { return (Cell)(((int)c) + 1); }
    Cell        limit_cell() const {
      return (Cell)(outer()->max_locals() + stack_size());
    }

    // Cell creation
    Cell      local(int lnum) const {
      assert(lnum < outer()->max_locals(), "index check");
      return (Cell)(lnum);
    }

    Cell      stack(int snum) const {
      assert(snum < stack_size(), "index check");
      return (Cell)(outer()->max_locals() + snum);
    }

    Cell      tos() const { return stack(stack_size()-1); }

    // For external use only:
    ciType* local_type_at(int i) const { return type_at(local(i)); }
    ciType* stack_type_at(int i) const { return type_at(stack(i)); }

    // Accessors for the type of some Cell c
    ciType*   type_at(Cell c) const {
      assert(start_cell() <= c && c < limit_cell(), "out of bounds");
      return _types[c];
    }

    void      set_type_at(Cell c, ciType* type) {
      assert(start_cell() <= c && c < limit_cell(), "out of bounds");
      _types[c] = type;
    }

    // Top-of-stack operations.
    void      set_type_at_tos(ciType* type) { set_type_at(tos(), type); }
    ciType*   type_at_tos() const           { return type_at(tos()); }

    void      push(ciType* type) {
      _stack_size++;
      set_type_at_tos(type);
    }
    void      pop() {
      debug_only(set_type_at_tos(bottom_type()));
      _stack_size--;
    }
    ciType*   pop_value() {
      ciType* t = type_at_tos();
      pop();
      return t;
    }

    // Convenience operations.
    bool      is_reference(ciType* type) const {
      return type == null_type() || !type->is_primitive_type();
    }
    bool      is_int(ciType* type) const {
      return type->basic_type() == T_INT;
    }
    bool      is_long(ciType* type) const {
      return type->basic_type() == T_LONG;
    }
    bool      is_float(ciType* type) const {
      return type->basic_type() == T_FLOAT;
    }
    bool      is_double(ciType* type) const {
      return type->basic_type() == T_DOUBLE;
    }

    void store_to_local(int lnum) {
      _def_locals.add((uint) lnum);
    }

    void      push_translate(ciType* type);

    void      push_int() {
      push(ciType::make(T_INT));
    }
    void      pop_int() {
      assert(is_int(type_at_tos()), "must be integer");
      pop();
    }
    void      check_int(Cell c) {
      assert(is_int(type_at(c)), "must be integer");
    }
    void      push_double() {
      push(ciType::make(T_DOUBLE));
      push(double2_type());
    }
    void      pop_double() {
      assert(type_at_tos() == double2_type(), "must be 2nd half");
      pop();
      assert(is_double(type_at_tos()), "must be double");
      pop();
    }
    void      push_float() {
      push(ciType::make(T_FLOAT));
    }
    void      pop_float() {
      assert(is_float(type_at_tos()), "must be float");
      pop();
    }
    void      push_long() {
      push(ciType::make(T_LONG));
      push(long2_type());
    }
    void      pop_long() {
      assert(type_at_tos() == long2_type(), "must be 2nd half");
      pop();
      assert(is_long(type_at_tos()), "must be long");
      pop();
    }
    void      push_object(ciKlass* klass) {
      push(klass);
    }
    void      pop_object() {
      assert(is_reference(type_at_tos()), "must be reference type");
      pop();
    }
    void      pop_array() {
      assert(type_at_tos() == null_type() ||
             type_at_tos()->is_array_klass(), "must be array type");
      pop();
    }
    // pop_objArray and pop_typeArray narrow the tos to ciObjArrayKlass
    // or ciTypeArrayKlass (resp.).  In the rare case that an explicit
    // null is popped from the stack, we return NULL.  Caller beware.
    ciObjArrayKlass* pop_objArray() {
      ciType* array = pop_value();
      if (array == null_type())  return NULL;
      assert(array->is_obj_array_klass(), "must be object array type");
      return array->as_obj_array_klass();
    }
    ciTypeArrayKlass* pop_typeArray() {
      ciType* array = pop_value();
      if (array == null_type())  return NULL;
      assert(array->is_type_array_klass(), "must be prim array type");
      return array->as_type_array_klass();
    }
    void      push_null() {
      push(null_type());
    }
    void      do_null_assert(ciKlass* unloaded_klass);

    // Helper convenience routines.
    void do_aaload(ciBytecodeStream* str);
    void do_checkcast(ciBytecodeStream* str);
    void do_getfield(ciBytecodeStream* str);
    void do_getstatic(ciBytecodeStream* str);
    void do_invoke(ciBytecodeStream* str, bool has_receiver);
    void do_jsr(ciBytecodeStream* str);
    void do_ldc(ciBytecodeStream* str);
    void do_multianewarray(ciBytecodeStream* str);
    void do_new(ciBytecodeStream* str);
    void do_newarray(ciBytecodeStream* str);
    void do_putfield(ciBytecodeStream* str);
    void do_putstatic(ciBytecodeStream* str);
    void do_ret(ciBytecodeStream* str);

    void overwrite_local_double_long(int index) {
      // Invalidate the previous local if it contains first half of
      // a double or long value since it's seconf half is being overwritten.
      int prev_index = index - 1;
      if (prev_index >= 0 &&
          (is_double(type_at(local(prev_index))) ||
           is_long(type_at(local(prev_index))))) {
        set_type_at(local(prev_index), bottom_type());
      }
    }

    void load_local_object(int index) {
      ciType* type = type_at(local(index));
      assert(is_reference(type), "must be reference type");
      push(type);
    }
    void store_local_object(int index) {
      ciType* type = pop_value();
      assert(is_reference(type) || type->is_return_address(),
             "must be reference type or return address");
      overwrite_local_double_long(index);
      set_type_at(local(index), type);
      store_to_local(index);
    }

    void load_local_double(int index) {
      ciType* type = type_at(local(index));
      ciType* type2 = type_at(local(index+1));
      assert(is_double(type), "must be double type");
      assert(type2 == double2_type(), "must be 2nd half");
      push(type);
      push(double2_type());
    }
    void store_local_double(int index) {
      ciType* type2 = pop_value();
      ciType* type = pop_value();
      assert(is_double(type), "must be double");
      assert(type2 == double2_type(), "must be 2nd half");
      overwrite_local_double_long(index);
      set_type_at(local(index), type);
      set_type_at(local(index+1), type2);
      store_to_local(index);
      store_to_local(index+1);
    }

    void load_local_float(int index) {
      ciType* type = type_at(local(index));
      assert(is_float(type), "must be float type");
      push(type);
    }
    void store_local_float(int index) {
      ciType* type = pop_value();
      assert(is_float(type), "must be float type");
      overwrite_local_double_long(index);
      set_type_at(local(index), type);
      store_to_local(index);
    }

    void load_local_int(int index) {
      ciType* type = type_at(local(index));
      assert(is_int(type), "must be int type");
      push(type);
    }
    void store_local_int(int index) {
      ciType* type = pop_value();
      assert(is_int(type), "must be int type");
      overwrite_local_double_long(index);
      set_type_at(local(index), type);
      store_to_local(index);
    }

    void load_local_long(int index) {
      ciType* type = type_at(local(index));
      ciType* type2 = type_at(local(index+1));
      assert(is_long(type), "must be long type");
      assert(type2 == long2_type(), "must be 2nd half");
      push(type);
      push(long2_type());
    }
    void store_local_long(int index) {
      ciType* type2 = pop_value();
      ciType* type = pop_value();
      assert(is_long(type), "must be long");
      assert(type2 == long2_type(), "must be 2nd half");
      overwrite_local_double_long(index);
      set_type_at(local(index), type);
      set_type_at(local(index+1), type2);
      store_to_local(index);
      store_to_local(index+1);
    }

    // Stop interpretation of this path with a trap.
    void trap(ciBytecodeStream* str, ciKlass* klass, int index);

  public:
    StateVector(ciTypeFlow* outer);

    // Copy our value into some other StateVector
    void copy_into(StateVector* copy) const;

    // Meets this StateVector with another, destructively modifying this
    // one.  Returns true if any modification takes place.
    bool meet(const StateVector* incoming);

    // Ditto, except that the incoming state is coming from an exception.
    bool meet_exception(ciInstanceKlass* exc, const StateVector* incoming);

    // Apply the effect of one bytecode to this StateVector
    bool apply_one_bytecode(ciBytecodeStream* stream);

    // What is the bci of the trap?
    int  trap_bci() { return _trap_bci; }

    // What is the index associated with the trap?
    int  trap_index() { return _trap_index; }

    void print_cell_on(outputStream* st, Cell c) const PRODUCT_RETURN;
    void print_on(outputStream* st) const              PRODUCT_RETURN;
  };

  // Parameter for "find_block" calls:
  // Describes the difference between a public and backedge copy.
  enum CreateOption {
    create_public_copy,
    create_backedge_copy,
    no_create
  };

  // Successor iterator
  class SuccIter : public StackObj {
  private:
    Block* _pred;
    int    _index;
    Block* _succ;
  public:
    SuccIter()                        : _pred(NULL), _index(-1), _succ(NULL) {}
    SuccIter(Block* pred)             : _pred(pred), _index(-1), _succ(NULL) { next(); }
    int    index()     { return _index; }
    Block* pred()      { return _pred; }           // Return predecessor
    bool   done()      { return _index < 0; }      // Finished?
    Block* succ()      { return _succ; }           // Return current successor
    void   next();                                 // Advance
    void   set_succ(Block* succ);                  // Update current successor
    bool   is_normal_ctrl() { return index() < _pred->successors()->length(); }
  };

  // A basic block
  class Block : public ResourceObj {
  private:
    ciBlock*                          _ciblock;
    GrowableArray<Block*>*           _exceptions;
    GrowableArray<ciInstanceKlass*>* _exc_klasses;
    GrowableArray<Block*>*           _successors;
    StateVector*                     _state;
    JsrSet*                          _jsrs;

    int                              _trap_bci;
    int                              _trap_index;

    // pre_order, assigned at first visit. Used as block ID and "visited" tag
    int                              _pre_order;

    // A post-order, used to compute the reverse post order (RPO) provided to the client
    int                              _post_order;  // used to compute rpo

    // Has this block been cloned for a loop backedge?
    bool                             _backedge_copy;

    // This block is entry to irreducible loop.
    bool                             _irreducible_entry;

    // This block has monitor entry point.
    bool                             _has_monitorenter;

    // A pointer used for our internal work list
    bool                             _on_work_list;      // on the work list
    Block*                           _next;
    Block*                           _rpo_next;          // Reverse post order list

    // Loop info
    Loop*                            _loop;              // nearest loop

    ciBlock*     ciblock() const     { return _ciblock; }
    StateVector* state() const     { return _state; }

    // Compute the exceptional successors and types for this Block.
    void compute_exceptions();

  public:
    // constructors
    Block(ciTypeFlow* outer, ciBlock* ciblk, JsrSet* jsrs);

    void set_trap(int trap_bci, int trap_index) {
      _trap_bci = trap_bci;
      _trap_index = trap_index;
      assert(has_trap(), "");
    }
    bool has_trap()   const  { return _trap_bci != -1; }
    int  trap_bci()   const  { assert(has_trap(), ""); return _trap_bci; }
    int  trap_index() const  { assert(has_trap(), ""); return _trap_index; }

    // accessors
    ciTypeFlow* outer() const { return state()->outer(); }
    int start() const         { return _ciblock->start_bci(); }
    int limit() const         { return _ciblock->limit_bci(); }
    int control() const       { return _ciblock->control_bci(); }
    JsrSet* jsrs() const      { return _jsrs; }

    bool    is_backedge_copy() const       { return _backedge_copy; }
    void   set_backedge_copy(bool z);
    int        backedge_copy_count() const { return outer()->backedge_copy_count(ciblock()->index(), _jsrs); }

    // access to entry state
    int     stack_size() const         { return _state->stack_size(); }
    int     monitor_count() const      { return _state->monitor_count(); }
    ciType* local_type_at(int i) const { return _state->local_type_at(i); }
    ciType* stack_type_at(int i) const { return _state->stack_type_at(i); }

    // Data flow on locals
    bool is_invariant_local(uint v) const {
      assert(is_loop_head(), "only loop heads");
      // Find outermost loop with same loop head
      Loop* lp = loop();
      while (lp->parent() != NULL) {
        if (lp->parent()->head() != lp->head()) break;
        lp = lp->parent();
      }
      return !lp->def_locals()->test(v);
    }
    LocalSet* def_locals() { return _state->def_locals(); }
    const LocalSet* def_locals() const { return _state->def_locals(); }

    // Get the successors for this Block.
    GrowableArray<Block*>* successors(ciBytecodeStream* str,
                                      StateVector* state,
                                      JsrSet* jsrs);
    GrowableArray<Block*>* successors() {
      assert(_successors != NULL, "must be filled in");
      return _successors;
    }

    // Get the exceptional successors for this Block.
    GrowableArray<Block*>* exceptions() {
      if (_exceptions == NULL) {
        compute_exceptions();
      }
      return _exceptions;
    }

    // Get the exception klasses corresponding to the
    // exceptional successors for this Block.
    GrowableArray<ciInstanceKlass*>* exc_klasses() {
      if (_exc_klasses == NULL) {
        compute_exceptions();
      }
      return _exc_klasses;
    }

    // Is this Block compatible with a given JsrSet?
    bool is_compatible_with(JsrSet* other) {
      return _jsrs->is_compatible_with(other);
    }

    // Copy the value of our state vector into another.
    void copy_state_into(StateVector* copy) const {
      _state->copy_into(copy);
    }

    // Copy the value of our JsrSet into another
    void copy_jsrs_into(JsrSet* copy) const {
      _jsrs->copy_into(copy);
    }

    // Meets the start state of this block with another state, destructively
    // modifying this one.  Returns true if any modification takes place.
    bool meet(const StateVector* incoming) {
      return state()->meet(incoming);
    }

    // Ditto, except that the incoming state is coming from an
    // exception path.  This means the stack is replaced by the
    // appropriate exception type.
    bool meet_exception(ciInstanceKlass* exc, const StateVector* incoming) {
      return state()->meet_exception(exc, incoming);
    }

    // Work list manipulation
    void   set_next(Block* block) { _next = block; }
    Block* next() const           { return _next; }

    void   set_on_work_list(bool c) { _on_work_list = c; }
    bool   is_on_work_list() const  { return _on_work_list; }

    bool   has_pre_order() const  { return _pre_order >= 0; }
    void   set_pre_order(int po)  { assert(!has_pre_order(), ""); _pre_order = po; }
    int    pre_order() const      { assert(has_pre_order(), ""); return _pre_order; }
    void   set_next_pre_order()   { set_pre_order(outer()->inc_next_pre_order()); }
    bool   is_start() const       { return _pre_order == outer()->start_block_num(); }

    // Reverse post order
    void   df_init();
    bool   has_post_order() const { return _post_order >= 0; }
    void   set_post_order(int po) { assert(!has_post_order() && po >= 0, ""); _post_order = po; }
    void   reset_post_order(int o){ _post_order = o; }
    int    post_order() const     { assert(has_post_order(), ""); return _post_order; }

    bool   has_rpo() const        { return has_post_order() && outer()->have_block_count(); }
    int    rpo() const            { assert(has_rpo(), ""); return outer()->block_count() - post_order() - 1; }
    void   set_rpo_next(Block* b) { _rpo_next = b; }
    Block* rpo_next()             { return _rpo_next; }

    // Loops
    Loop*  loop() const                  { return _loop; }
    void   set_loop(Loop* lp)            { _loop = lp; }
    bool   is_loop_head() const          { return _loop && _loop->head() == this; }
    void   set_irreducible_entry(bool c) { _irreducible_entry = c; }
    bool   is_irreducible_entry() const  { return _irreducible_entry; }
    void   set_has_monitorenter()        { _has_monitorenter = true; }
    bool   has_monitorenter() const      { return _has_monitorenter; }
    bool   is_visited() const            { return has_pre_order(); }
    bool   is_post_visited() const       { return has_post_order(); }
    bool   is_clonable_exit(Loop* lp);
    Block* looping_succ(Loop* lp);       // Successor inside of loop
    bool   is_single_entry_loop_head() const {
      if (!is_loop_head()) return false;
      for (Loop* lp = loop(); lp != NULL && lp->head() == this; lp = lp->parent())
        if (lp->is_irreducible()) return false;
      return true;
    }

    void   print_value_on(outputStream* st) const PRODUCT_RETURN;
    void   print_on(outputStream* st) const       PRODUCT_RETURN;
  };

  // Loop
  class Loop : public ResourceObj {
  private:
    Loop* _parent;
    Loop* _sibling;  // List of siblings, null terminated
    Loop* _child;    // Head of child list threaded thru sibling pointer
    Block* _head;    // Head of loop
    Block* _tail;    // Tail of loop
    bool   _irreducible;
    LocalSet _def_locals;

  public:
    Loop(Block* head, Block* tail) :
      _head(head),   _tail(tail),
      _parent(NULL), _sibling(NULL), _child(NULL),
      _irreducible(false), _def_locals() {}

    Loop* parent()  const { return _parent; }
    Loop* sibling() const { return _sibling; }
    Loop* child()   const { return _child; }
    Block* head()   const { return _head; }
    Block* tail()   const { return _tail; }
    void set_parent(Loop* p)  { _parent = p; }
    void set_sibling(Loop* s) { _sibling = s; }
    void set_child(Loop* c)   { _child = c; }
    void set_head(Block* hd)  { _head = hd; }
    void set_tail(Block* tl)  { _tail = tl; }

    int depth() const;              // nesting depth

    // Returns true if lp is a nested loop or us.
    bool contains(Loop* lp) const;
    bool contains(Block* blk) const { return contains(blk->loop()); }

    // Data flow on locals
    LocalSet* def_locals() { return &_def_locals; }
    const LocalSet* def_locals() const { return &_def_locals; }

    // Merge the branch lp into this branch, sorting on the loop head
    // pre_orders. Returns the new branch.
    Loop* sorted_merge(Loop* lp);

    // Mark non-single entry to loop
    void set_irreducible(Block* entry) {
      _irreducible = true;
      entry->set_irreducible_entry(true);
    }
    bool is_irreducible() const { return _irreducible; }

    bool is_root() const { return _tail->pre_order() == max_jint; }

    void print(outputStream* st = tty, int indent = 0) const PRODUCT_RETURN;
  };

  // Postorder iteration over the loop tree.
  class PostorderLoops : public StackObj {
  private:
    Loop* _root;
    Loop* _current;
  public:
    PostorderLoops(Loop* root) : _root(root), _current(root) {
      while (_current->child() != NULL) {
        _current = _current->child();
      }
    }
    bool done() { return _current == NULL; }  // Finished iterating?
    void next();                            // Advance to next loop
    Loop* current() { return _current; }      // Return current loop.
  };

  // Preorder iteration over the loop tree.
  class PreorderLoops : public StackObj {
  private:
    Loop* _root;
    Loop* _current;
  public:
    PreorderLoops(Loop* root) : _root(root), _current(root) {}
    bool done() { return _current == NULL; }  // Finished iterating?
    void next();                            // Advance to next loop
    Loop* current() { return _current; }      // Return current loop.
  };

  // Standard indexes of successors, for various bytecodes.
  enum {
    FALL_THROUGH   = 0,  // normal control
    IF_NOT_TAKEN   = 0,  // the not-taken branch of an if (i.e., fall-through)
    IF_TAKEN       = 1,  // the taken branch of an if
    GOTO_TARGET    = 0,  // unique successor for goto, jsr, or ret
    SWITCH_DEFAULT = 0,  // default branch of a switch
    SWITCH_CASES   = 1   // first index for any non-default switch branches
    // Unlike in other blocks, the successors of a switch are listed uniquely.
  };

private:
  // A mapping from pre_order to Blocks.  This array is created
  // only at the end of the flow.
  Block** _block_map;

  // For each ciBlock index, a list of Blocks which share this ciBlock.
  GrowableArray<Block*>** _idx_to_blocklist;
  // count of ciBlocks
  int _ciblock_count;

  // Tells if a given instruction is able to generate an exception edge.
  bool can_trap(ciBytecodeStream& str);

  // Clone the loop heads. Returns true if any cloning occurred.
  bool clone_loop_heads(Loop* lp, StateVector* temp_vector, JsrSet* temp_set);

  // Clone lp's head and replace tail's successors with clone.
  Block* clone_loop_head(Loop* lp, StateVector* temp_vector, JsrSet* temp_set);

public:
  // Return the block beginning at bci which has a JsrSet compatible
  // with jsrs.
  Block* block_at(int bci, JsrSet* set, CreateOption option = create_public_copy);

  // block factory
  Block* get_block_for(int ciBlockIndex, JsrSet* jsrs, CreateOption option = create_public_copy);

  // How many of the blocks have the backedge_copy bit set?
  int backedge_copy_count(int ciBlockIndex, JsrSet* jsrs) const;

  // Return an existing block containing bci which has a JsrSet compatible
  // with jsrs, or NULL if there is none.
  Block* existing_block_at(int bci, JsrSet* set) { return block_at(bci, set, no_create); }

  // Tell whether the flow analysis has encountered an error of some sort.
  bool failing() { return env()->failing() || _failure_reason != NULL; }

  // Reason this compilation is failing, such as "too many basic blocks".
  const char* failure_reason() { return _failure_reason; }

  // Note a failure.
  void record_failure(const char* reason);

  // Return the block of a given pre-order number.
  int have_block_count() const      { return _block_map != NULL; }
  int block_count() const           { assert(have_block_count(), "");
                                      return _next_pre_order; }
  Block* pre_order_at(int po) const { assert(0 <= po && po < block_count(), "out of bounds");
                                      return _block_map[po]; }
  Block* start_block() const        { return pre_order_at(start_block_num()); }
  int start_block_num() const       { return 0; }
  Block* rpo_at(int rpo) const      { assert(0 <= rpo && rpo < block_count(), "out of bounds");
                                      return _block_map[rpo]; }
  int next_pre_order()              { return _next_pre_order; }
  int inc_next_pre_order()          { return _next_pre_order++; }

private:
  // A work list used during flow analysis.
  Block* _work_list;

  // List of blocks in reverse post order
  Block* _rpo_list;

  // Next Block::_pre_order.  After mapping, doubles as block_count.
  int _next_pre_order;

  // Are there more blocks on the work list?
  bool work_list_empty() { return _work_list == NULL; }

  // Get the next basic block from our work list.
  Block* work_list_next();

  // Add a basic block to our work list.
  void add_to_work_list(Block* block);

  // Prepend a basic block to rpo list.
  void prepend_to_rpo_list(Block* blk) {
    blk->set_rpo_next(_rpo_list);
    _rpo_list = blk;
  }

  // Root of the loop tree
  Loop* _loop_tree_root;

  // State used for make_jsr_record
  int _jsr_count;
  GrowableArray<JsrRecord*>* _jsr_records;

public:
  // Make a JsrRecord for a given (entry, return) pair, if such a record
  // does not already exist.
  JsrRecord* make_jsr_record(int entry_address, int return_address);

  void  set_loop_tree_root(Loop* ltr) { _loop_tree_root = ltr; }
  Loop* loop_tree_root()              { return _loop_tree_root; }

private:
  // Get the initial state for start_bci:
  const StateVector* get_start_state();

  // Merge the current state into all exceptional successors at the
  // current point in the code.
  void flow_exceptions(GrowableArray<Block*>* exceptions,
                       GrowableArray<ciInstanceKlass*>* exc_klasses,
                       StateVector* state);

  // Merge the current state into all successors at the current point
  // in the code.
  void flow_successors(GrowableArray<Block*>* successors,
                       StateVector* state);

  // Interpret the effects of the bytecodes on the incoming state
  // vector of a basic block.  Push the changed state to succeeding
  // basic blocks.
  void flow_block(Block* block,
                  StateVector* scratch_state,
                  JsrSet* scratch_jsrs);

  // Perform the type flow analysis, creating and cloning Blocks as
  // necessary.
  void flow_types();

  // Perform the depth first type flow analysis. Helper for flow_types.
  void df_flow_types(Block* start,
                     bool do_flow,
                     StateVector* temp_vector,
                     JsrSet* temp_set);

  // Incrementally build loop tree.
  void build_loop_tree(Block* blk);

  // Create the block map, which indexes blocks in pre_order.
  void map_blocks();

public:
  // Perform type inference flow analysis.
  void do_flow();

  void print_on(outputStream* st) const PRODUCT_RETURN;

  void rpo_print_on(outputStream* st) const PRODUCT_RETURN;
};

#endif // SHARE_VM_CI_CITYPEFLOW_HPP

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