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 /*

  * Copyright (c) 2000, 2010, 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.

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 #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"

 #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;

     // A pointer used for our internal work list

     Block*                           _next;

     bool                             _on_work_list;      // on the work list

     Block*                           _rpo_next;          // Reverse post order list

     // Loop info

     Loop*                            _loop;              // nearest loop

     bool                             _irreducible_entry; // entry to irreducible loop

     bool                             _exception_entry;   // entry to exception handler

     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; }

     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