1 /*
   2  * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_CI_CITYPEFLOW_HPP
  26 #define SHARE_VM_CI_CITYPEFLOW_HPP
  27 
  28 #ifdef COMPILER2
  29 #include "ci/ciEnv.hpp"
  30 #include "ci/ciKlass.hpp"
  31 #include "ci/ciMethodBlocks.hpp"
  32 #endif
  33 #ifdef SHARK
  34 #include "ci/ciEnv.hpp"
  35 #include "ci/ciKlass.hpp"
  36 #include "ci/ciMethodBlocks.hpp"
  37 #endif
  38 
  39 
  40 class ciTypeFlow : public ResourceObj {
  41 private:
  42   ciEnv*    _env;
  43   ciMethod* _method;
  44   ciMethodBlocks* _methodBlocks;
  45   int       _osr_bci;
  46 
  47   // information cached from the method:
  48   int _max_locals;
  49   int _max_stack;
  50   int _code_size;
  51   bool      _has_irreducible_entry;
  52 
  53   const char* _failure_reason;
  54 
  55 public:
  56   class StateVector;
  57   class Loop;
  58   class Block;
  59 
  60   // Build a type flow analyzer
  61   // Do an OSR analysis if osr_bci >= 0.
  62   ciTypeFlow(ciEnv* env, ciMethod* method, int osr_bci = InvocationEntryBci);
  63 
  64   // Accessors
  65   ciMethod* method() const     { return _method; }
  66   ciEnv*    env()              { return _env; }
  67   Arena*    arena()            { return _env->arena(); }
  68   bool      is_osr_flow() const{ return _osr_bci != InvocationEntryBci; }
  69   int       start_bci() const  { return is_osr_flow()? _osr_bci: 0; }
  70   int       max_locals() const { return _max_locals; }
  71   int       max_stack() const  { return _max_stack; }
  72   int       max_cells() const  { return _max_locals + _max_stack; }
  73   int       code_size() const  { return _code_size; }
  74   bool      has_irreducible_entry() const { return _has_irreducible_entry; }
  75 
  76   // Represents information about an "active" jsr call.  This
  77   // class represents a call to the routine at some entry address
  78   // with some distinct return address.
  79   class JsrRecord : public ResourceObj {
  80   private:
  81     int _entry_address;
  82     int _return_address;
  83   public:
  84     JsrRecord(int entry_address, int return_address) {
  85       _entry_address = entry_address;
  86       _return_address = return_address;
  87     }
  88 
  89     int entry_address() const  { return _entry_address; }
  90     int return_address() const { return _return_address; }
  91 
  92     void print_on(outputStream* st) const {
  93 #ifndef PRODUCT
  94       st->print("%d->%d", entry_address(), return_address());
  95 #endif
  96     }
  97   };
  98 
  99   // A JsrSet represents some set of JsrRecords.  This class
 100   // is used to record a set of all jsr routines which we permit
 101   // execution to return (ret) from.
 102   //
 103   // During abstract interpretation, JsrSets are used to determine
 104   // whether two paths which reach a given block are unique, and
 105   // should be cloned apart, or are compatible, and should merge
 106   // together.
 107   //
 108   // Note that different amounts of effort can be expended determining
 109   // if paths are compatible.  <DISCUSSION>
 110   class JsrSet : public ResourceObj {
 111   private:
 112     GrowableArray<JsrRecord*>* _set;
 113 
 114     JsrRecord* record_at(int i) {
 115       return _set->at(i);
 116     }
 117 
 118     // Insert the given JsrRecord into the JsrSet, maintaining the order
 119     // of the set and replacing any element with the same entry address.
 120     void insert_jsr_record(JsrRecord* record);
 121 
 122     // Remove the JsrRecord with the given return address from the JsrSet.
 123     void remove_jsr_record(int return_address);
 124 
 125   public:
 126     JsrSet(Arena* arena, int default_len = 4);
 127 
 128     // Copy this JsrSet.
 129     void copy_into(JsrSet* jsrs);
 130 
 131     // Is this JsrSet compatible with some other JsrSet?
 132     bool is_compatible_with(JsrSet* other);
 133 
 134     // Apply the effect of a single bytecode to the JsrSet.
 135     void apply_control(ciTypeFlow* analyzer,
 136                        ciBytecodeStream* str,
 137                        StateVector* state);
 138 
 139     // What is the cardinality of this set?
 140     int size() const { return _set->length(); }
 141 
 142     void print_on(outputStream* st) const PRODUCT_RETURN;
 143   };
 144 
 145   class LocalSet VALUE_OBJ_CLASS_SPEC {
 146   private:
 147     enum Constants { max = 63 };
 148     uint64_t _bits;
 149   public:
 150     LocalSet() : _bits(0) {}
 151     void add(uint32_t i)        { if (i < (uint32_t)max) _bits |=  (1LL << i); }
 152     void add(LocalSet* ls)      { _bits |= ls->_bits; }
 153     bool test(uint32_t i) const { return i < (uint32_t)max ? (_bits>>i)&1U : true; }
 154     void clear()                { _bits = 0; }
 155     void print_on(outputStream* st, int limit) const  PRODUCT_RETURN;
 156   };
 157 
 158   // Used as a combined index for locals and temps
 159   enum Cell {
 160     Cell_0, Cell_max = INT_MAX
 161   };
 162 
 163   // A StateVector summarizes the type information at some
 164   // point in the program
 165   class StateVector : public ResourceObj {
 166   private:
 167     ciType**    _types;
 168     int         _stack_size;
 169     int         _monitor_count;
 170     ciTypeFlow* _outer;
 171 
 172     int         _trap_bci;
 173     int         _trap_index;
 174 
 175     LocalSet    _def_locals;  // For entire block
 176 
 177     static ciType* type_meet_internal(ciType* t1, ciType* t2, ciTypeFlow* analyzer);
 178 
 179   public:
 180     // Special elements in our type lattice.
 181     enum {
 182       T_TOP     = T_VOID,      // why not?
 183       T_BOTTOM  = T_CONFLICT,
 184       T_LONG2   = T_SHORT,     // 2nd word of T_LONG
 185       T_DOUBLE2 = T_CHAR,      // 2nd word of T_DOUBLE
 186       T_NULL    = T_BYTE       // for now.
 187     };
 188     static ciType* top_type()    { return ciType::make((BasicType)T_TOP); }
 189     static ciType* bottom_type() { return ciType::make((BasicType)T_BOTTOM); }
 190     static ciType* long2_type()  { return ciType::make((BasicType)T_LONG2); }
 191     static ciType* double2_type(){ return ciType::make((BasicType)T_DOUBLE2); }
 192     static ciType* null_type()   { return ciType::make((BasicType)T_NULL); }
 193 
 194     static ciType* half_type(ciType* t) {
 195       switch (t->basic_type()) {
 196       case T_LONG:    return long2_type();
 197       case T_DOUBLE:  return double2_type();
 198       default:        ShouldNotReachHere(); return NULL;
 199       }
 200     }
 201 
 202     // The meet operation for our type lattice.
 203     ciType* type_meet(ciType* t1, ciType* t2) {
 204       return type_meet_internal(t1, t2, outer());
 205     }
 206 
 207     // Accessors
 208     ciTypeFlow* outer() const          { return _outer; }
 209 
 210     int         stack_size() const     { return _stack_size; }
 211     void    set_stack_size(int ss)     { _stack_size = ss; }
 212 
 213     int         monitor_count() const  { return _monitor_count; }
 214     void    set_monitor_count(int mc)  { _monitor_count = mc; }
 215 
 216     LocalSet* def_locals() { return &_def_locals; }
 217     const LocalSet* def_locals() const { return &_def_locals; }
 218 
 219     static Cell start_cell()           { return (Cell)0; }
 220     static Cell next_cell(Cell c)      { return (Cell)(((int)c) + 1); }
 221     Cell        limit_cell() const {
 222       return (Cell)(outer()->max_locals() + stack_size());
 223     }
 224 
 225     // Cell creation
 226     Cell      local(int lnum) const {
 227       assert(lnum < outer()->max_locals(), "index check");
 228       return (Cell)(lnum);
 229     }
 230 
 231     Cell      stack(int snum) const {
 232       assert(snum < stack_size(), "index check");
 233       return (Cell)(outer()->max_locals() + snum);
 234     }
 235 
 236     Cell      tos() const { return stack(stack_size()-1); }
 237 
 238     // For external use only:
 239     ciType* local_type_at(int i) const { return type_at(local(i)); }
 240     ciType* stack_type_at(int i) const { return type_at(stack(i)); }
 241 
 242     // Accessors for the type of some Cell c
 243     ciType*   type_at(Cell c) const {
 244       assert(start_cell() <= c && c < limit_cell(), "out of bounds");
 245       return _types[c];
 246     }
 247 
 248     void      set_type_at(Cell c, ciType* type) {
 249       assert(start_cell() <= c && c < limit_cell(), "out of bounds");
 250       _types[c] = type;
 251     }
 252 
 253     // Top-of-stack operations.
 254     void      set_type_at_tos(ciType* type) { set_type_at(tos(), type); }
 255     ciType*   type_at_tos() const           { return type_at(tos()); }
 256 
 257     void      push(ciType* type) {
 258       _stack_size++;
 259       set_type_at_tos(type);
 260     }
 261     void      pop() {
 262       debug_only(set_type_at_tos(bottom_type()));
 263       _stack_size--;
 264     }
 265     ciType*   pop_value() {
 266       ciType* t = type_at_tos();
 267       pop();
 268       return t;
 269     }
 270 
 271     // Convenience operations.
 272     bool      is_reference(ciType* type) const {
 273       return type == null_type() || !type->is_primitive_type();
 274     }
 275     bool      is_int(ciType* type) const {
 276       return type->basic_type() == T_INT;
 277     }
 278     bool      is_long(ciType* type) const {
 279       return type->basic_type() == T_LONG;
 280     }
 281     bool      is_float(ciType* type) const {
 282       return type->basic_type() == T_FLOAT;
 283     }
 284     bool      is_double(ciType* type) const {
 285       return type->basic_type() == T_DOUBLE;
 286     }
 287 
 288     void store_to_local(int lnum) {
 289       _def_locals.add((uint) lnum);
 290     }
 291 
 292     void      push_translate(ciType* type);
 293 
 294     void      push_int() {
 295       push(ciType::make(T_INT));
 296     }
 297     void      pop_int() {
 298       assert(is_int(type_at_tos()), "must be integer");
 299       pop();
 300     }
 301     void      check_int(Cell c) {
 302       assert(is_int(type_at(c)), "must be integer");
 303     }
 304     void      push_double() {
 305       push(ciType::make(T_DOUBLE));
 306       push(double2_type());
 307     }
 308     void      pop_double() {
 309       assert(type_at_tos() == double2_type(), "must be 2nd half");
 310       pop();
 311       assert(is_double(type_at_tos()), "must be double");
 312       pop();
 313     }
 314     void      push_float() {
 315       push(ciType::make(T_FLOAT));
 316     }
 317     void      pop_float() {
 318       assert(is_float(type_at_tos()), "must be float");
 319       pop();
 320     }
 321     void      push_long() {
 322       push(ciType::make(T_LONG));
 323       push(long2_type());
 324     }
 325     void      pop_long() {
 326       assert(type_at_tos() == long2_type(), "must be 2nd half");
 327       pop();
 328       assert(is_long(type_at_tos()), "must be long");
 329       pop();
 330     }
 331     void      push_object(ciKlass* klass) {
 332       push(klass);
 333     }
 334     void      pop_object() {
 335       assert(is_reference(type_at_tos()), "must be reference type");
 336       pop();
 337     }
 338     void      pop_array() {
 339       assert(type_at_tos() == null_type() ||
 340              type_at_tos()->is_array_klass(), "must be array type");
 341       pop();
 342     }
 343     // pop_objArray and pop_typeArray narrow the tos to ciObjArrayKlass
 344     // or ciTypeArrayKlass (resp.).  In the rare case that an explicit
 345     // null is popped from the stack, we return NULL.  Caller beware.
 346     ciObjArrayKlass* pop_objArray() {
 347       ciType* array = pop_value();
 348       if (array == null_type())  return NULL;
 349       assert(array->is_obj_array_klass(), "must be object array type");
 350       return array->as_obj_array_klass();
 351     }
 352     ciTypeArrayKlass* pop_typeArray() {
 353       ciType* array = pop_value();
 354       if (array == null_type())  return NULL;
 355       assert(array->is_type_array_klass(), "must be prim array type");
 356       return array->as_type_array_klass();
 357     }
 358     void      push_null() {
 359       push(null_type());
 360     }
 361     void      do_null_assert(ciKlass* unloaded_klass);
 362 
 363     // Helper convenience routines.
 364     void do_aaload(ciBytecodeStream* str);
 365     void do_checkcast(ciBytecodeStream* str);
 366     void do_getfield(ciBytecodeStream* str);
 367     void do_getstatic(ciBytecodeStream* str);
 368     void do_invoke(ciBytecodeStream* str, bool has_receiver);
 369     void do_jsr(ciBytecodeStream* str);
 370     void do_ldc(ciBytecodeStream* str);
 371     void do_multianewarray(ciBytecodeStream* str);
 372     void do_new(ciBytecodeStream* str);
 373     void do_newarray(ciBytecodeStream* str);
 374     void do_putfield(ciBytecodeStream* str);
 375     void do_putstatic(ciBytecodeStream* str);
 376     void do_ret(ciBytecodeStream* str);
 377 
 378     void overwrite_local_double_long(int index) {
 379       // Invalidate the previous local if it contains first half of
 380       // a double or long value since it's seconf half is being overwritten.
 381       int prev_index = index - 1;
 382       if (prev_index >= 0 &&
 383           (is_double(type_at(local(prev_index))) ||
 384            is_long(type_at(local(prev_index))))) {
 385         set_type_at(local(prev_index), bottom_type());
 386       }
 387     }
 388 
 389     void load_local_object(int index) {
 390       ciType* type = type_at(local(index));
 391       assert(is_reference(type), "must be reference type");
 392       push(type);
 393     }
 394     void store_local_object(int index) {
 395       ciType* type = pop_value();
 396       assert(is_reference(type) || type->is_return_address(),
 397              "must be reference type or return address");
 398       overwrite_local_double_long(index);
 399       set_type_at(local(index), type);
 400       store_to_local(index);
 401     }
 402 
 403     void load_local_double(int index) {
 404       ciType* type = type_at(local(index));
 405       ciType* type2 = type_at(local(index+1));
 406       assert(is_double(type), "must be double type");
 407       assert(type2 == double2_type(), "must be 2nd half");
 408       push(type);
 409       push(double2_type());
 410     }
 411     void store_local_double(int index) {
 412       ciType* type2 = pop_value();
 413       ciType* type = pop_value();
 414       assert(is_double(type), "must be double");
 415       assert(type2 == double2_type(), "must be 2nd half");
 416       overwrite_local_double_long(index);
 417       set_type_at(local(index), type);
 418       set_type_at(local(index+1), type2);
 419       store_to_local(index);
 420       store_to_local(index+1);
 421     }
 422 
 423     void load_local_float(int index) {
 424       ciType* type = type_at(local(index));
 425       assert(is_float(type), "must be float type");
 426       push(type);
 427     }
 428     void store_local_float(int index) {
 429       ciType* type = pop_value();
 430       assert(is_float(type), "must be float type");
 431       overwrite_local_double_long(index);
 432       set_type_at(local(index), type);
 433       store_to_local(index);
 434     }
 435 
 436     void load_local_int(int index) {
 437       ciType* type = type_at(local(index));
 438       assert(is_int(type), "must be int type");
 439       push(type);
 440     }
 441     void store_local_int(int index) {
 442       ciType* type = pop_value();
 443       assert(is_int(type), "must be int type");
 444       overwrite_local_double_long(index);
 445       set_type_at(local(index), type);
 446       store_to_local(index);
 447     }
 448 
 449     void load_local_long(int index) {
 450       ciType* type = type_at(local(index));
 451       ciType* type2 = type_at(local(index+1));
 452       assert(is_long(type), "must be long type");
 453       assert(type2 == long2_type(), "must be 2nd half");
 454       push(type);
 455       push(long2_type());
 456     }
 457     void store_local_long(int index) {
 458       ciType* type2 = pop_value();
 459       ciType* type = pop_value();
 460       assert(is_long(type), "must be long");
 461       assert(type2 == long2_type(), "must be 2nd half");
 462       overwrite_local_double_long(index);
 463       set_type_at(local(index), type);
 464       set_type_at(local(index+1), type2);
 465       store_to_local(index);
 466       store_to_local(index+1);
 467     }
 468 
 469     // Stop interpretation of this path with a trap.
 470     void trap(ciBytecodeStream* str, ciKlass* klass, int index);
 471 
 472   public:
 473     StateVector(ciTypeFlow* outer);
 474 
 475     // Copy our value into some other StateVector
 476     void copy_into(StateVector* copy) const;
 477 
 478     // Meets this StateVector with another, destructively modifying this
 479     // one.  Returns true if any modification takes place.
 480     bool meet(const StateVector* incoming);
 481 
 482     // Ditto, except that the incoming state is coming from an exception.
 483     bool meet_exception(ciInstanceKlass* exc, const StateVector* incoming);
 484 
 485     // Apply the effect of one bytecode to this StateVector
 486     bool apply_one_bytecode(ciBytecodeStream* stream);
 487 
 488     // What is the bci of the trap?
 489     int  trap_bci() { return _trap_bci; }
 490 
 491     // What is the index associated with the trap?
 492     int  trap_index() { return _trap_index; }
 493 
 494     void print_cell_on(outputStream* st, Cell c) const PRODUCT_RETURN;
 495     void print_on(outputStream* st) const              PRODUCT_RETURN;
 496   };
 497 
 498   // Parameter for "find_block" calls:
 499   // Describes the difference between a public and backedge copy.
 500   enum CreateOption {
 501     create_public_copy,
 502     create_backedge_copy,
 503     no_create
 504   };
 505 
 506   // Successor iterator
 507   class SuccIter : public StackObj {
 508   private:
 509     Block* _pred;
 510     int    _index;
 511     Block* _succ;
 512   public:
 513     SuccIter()                        : _pred(NULL), _index(-1), _succ(NULL) {}
 514     SuccIter(Block* pred)             : _pred(pred), _index(-1), _succ(NULL) { next(); }
 515     int    index()     { return _index; }
 516     Block* pred()      { return _pred; }           // Return predecessor
 517     bool   done()      { return _index < 0; }      // Finished?
 518     Block* succ()      { return _succ; }           // Return current successor
 519     void   next();                                 // Advance
 520     void   set_succ(Block* succ);                  // Update current successor
 521     bool   is_normal_ctrl() { return index() < _pred->successors()->length(); }
 522   };
 523 
 524   // A basic block
 525   class Block : public ResourceObj {
 526   private:
 527     ciBlock*                          _ciblock;
 528     GrowableArray<Block*>*           _exceptions;
 529     GrowableArray<ciInstanceKlass*>* _exc_klasses;
 530     GrowableArray<Block*>*           _successors;
 531     StateVector*                     _state;
 532     JsrSet*                          _jsrs;
 533 
 534     int                              _trap_bci;
 535     int                              _trap_index;
 536 
 537     // pre_order, assigned at first visit. Used as block ID and "visited" tag
 538     int                              _pre_order;
 539 
 540     // A post-order, used to compute the reverse post order (RPO) provided to the client
 541     int                              _post_order;  // used to compute rpo
 542 
 543     // Has this block been cloned for a loop backedge?
 544     bool                             _backedge_copy;
 545 
 546     // A pointer used for our internal work list
 547     Block*                           _next;
 548     bool                             _on_work_list;      // on the work list
 549     Block*                           _rpo_next;          // Reverse post order list
 550 
 551     // Loop info
 552     Loop*                            _loop;              // nearest loop
 553     bool                             _irreducible_entry; // entry to irreducible loop
 554     bool                             _exception_entry;   // entry to exception handler
 555 
 556     ciBlock*     ciblock() const     { return _ciblock; }
 557     StateVector* state() const     { return _state; }
 558 
 559     // Compute the exceptional successors and types for this Block.
 560     void compute_exceptions();
 561 
 562   public:
 563     // constructors
 564     Block(ciTypeFlow* outer, ciBlock* ciblk, JsrSet* jsrs);
 565 
 566     void set_trap(int trap_bci, int trap_index) {
 567       _trap_bci = trap_bci;
 568       _trap_index = trap_index;
 569       assert(has_trap(), "");
 570     }
 571     bool has_trap()   const  { return _trap_bci != -1; }
 572     int  trap_bci()   const  { assert(has_trap(), ""); return _trap_bci; }
 573     int  trap_index() const  { assert(has_trap(), ""); return _trap_index; }
 574 
 575     // accessors
 576     ciTypeFlow* outer() const { return state()->outer(); }
 577     int start() const         { return _ciblock->start_bci(); }
 578     int limit() const         { return _ciblock->limit_bci(); }
 579     int control() const       { return _ciblock->control_bci(); }
 580     JsrSet* jsrs() const      { return _jsrs; }
 581 
 582     bool    is_backedge_copy() const       { return _backedge_copy; }
 583     void   set_backedge_copy(bool z);
 584     int        backedge_copy_count() const { return outer()->backedge_copy_count(ciblock()->index(), _jsrs); }
 585 
 586     // access to entry state
 587     int     stack_size() const         { return _state->stack_size(); }
 588     int     monitor_count() const      { return _state->monitor_count(); }
 589     ciType* local_type_at(int i) const { return _state->local_type_at(i); }
 590     ciType* stack_type_at(int i) const { return _state->stack_type_at(i); }
 591 
 592     // Data flow on locals
 593     bool is_invariant_local(uint v) const {
 594       assert(is_loop_head(), "only loop heads");
 595       // Find outermost loop with same loop head
 596       Loop* lp = loop();
 597       while (lp->parent() != NULL) {
 598         if (lp->parent()->head() != lp->head()) break;
 599         lp = lp->parent();
 600       }
 601       return !lp->def_locals()->test(v);
 602     }
 603     LocalSet* def_locals() { return _state->def_locals(); }
 604     const LocalSet* def_locals() const { return _state->def_locals(); }
 605 
 606     // Get the successors for this Block.
 607     GrowableArray<Block*>* successors(ciBytecodeStream* str,
 608                                       StateVector* state,
 609                                       JsrSet* jsrs);
 610     GrowableArray<Block*>* successors() {
 611       assert(_successors != NULL, "must be filled in");
 612       return _successors;
 613     }
 614 
 615     // Get the exceptional successors for this Block.
 616     GrowableArray<Block*>* exceptions() {
 617       if (_exceptions == NULL) {
 618         compute_exceptions();
 619       }
 620       return _exceptions;
 621     }
 622 
 623     // Get the exception klasses corresponding to the
 624     // exceptional successors for this Block.
 625     GrowableArray<ciInstanceKlass*>* exc_klasses() {
 626       if (_exc_klasses == NULL) {
 627         compute_exceptions();
 628       }
 629       return _exc_klasses;
 630     }
 631 
 632     // Is this Block compatible with a given JsrSet?
 633     bool is_compatible_with(JsrSet* other) {
 634       return _jsrs->is_compatible_with(other);
 635     }
 636 
 637     // Copy the value of our state vector into another.
 638     void copy_state_into(StateVector* copy) const {
 639       _state->copy_into(copy);
 640     }
 641 
 642     // Copy the value of our JsrSet into another
 643     void copy_jsrs_into(JsrSet* copy) const {
 644       _jsrs->copy_into(copy);
 645     }
 646 
 647     // Meets the start state of this block with another state, destructively
 648     // modifying this one.  Returns true if any modification takes place.
 649     bool meet(const StateVector* incoming) {
 650       return state()->meet(incoming);
 651     }
 652 
 653     // Ditto, except that the incoming state is coming from an
 654     // exception path.  This means the stack is replaced by the
 655     // appropriate exception type.
 656     bool meet_exception(ciInstanceKlass* exc, const StateVector* incoming) {
 657       return state()->meet_exception(exc, incoming);
 658     }
 659 
 660     // Work list manipulation
 661     void   set_next(Block* block) { _next = block; }
 662     Block* next() const           { return _next; }
 663 
 664     void   set_on_work_list(bool c) { _on_work_list = c; }
 665     bool   is_on_work_list() const  { return _on_work_list; }
 666 
 667     bool   has_pre_order() const  { return _pre_order >= 0; }
 668     void   set_pre_order(int po)  { assert(!has_pre_order(), ""); _pre_order = po; }
 669     int    pre_order() const      { assert(has_pre_order(), ""); return _pre_order; }
 670     void   set_next_pre_order()   { set_pre_order(outer()->inc_next_pre_order()); }
 671     bool   is_start() const       { return _pre_order == outer()->start_block_num(); }
 672 
 673     // Reverse post order
 674     void   df_init();
 675     bool   has_post_order() const { return _post_order >= 0; }
 676     void   set_post_order(int po) { assert(!has_post_order() && po >= 0, ""); _post_order = po; }
 677     void   reset_post_order(int o){ _post_order = o; }
 678     int    post_order() const     { assert(has_post_order(), ""); return _post_order; }
 679 
 680     bool   has_rpo() const        { return has_post_order() && outer()->have_block_count(); }
 681     int    rpo() const            { assert(has_rpo(), ""); return outer()->block_count() - post_order() - 1; }
 682     void   set_rpo_next(Block* b) { _rpo_next = b; }
 683     Block* rpo_next()             { return _rpo_next; }
 684 
 685     // Loops
 686     Loop*  loop() const                  { return _loop; }
 687     void   set_loop(Loop* lp)            { _loop = lp; }
 688     bool   is_loop_head() const          { return _loop && _loop->head() == this; }
 689     void   set_irreducible_entry(bool c) { _irreducible_entry = c; }
 690     bool   is_irreducible_entry() const  { return _irreducible_entry; }
 691     bool   is_visited() const            { return has_pre_order(); }
 692     bool   is_post_visited() const       { return has_post_order(); }
 693     bool   is_clonable_exit(Loop* lp);
 694     Block* looping_succ(Loop* lp);       // Successor inside of loop
 695     bool   is_single_entry_loop_head() const {
 696       if (!is_loop_head()) return false;
 697       for (Loop* lp = loop(); lp != NULL && lp->head() == this; lp = lp->parent())
 698         if (lp->is_irreducible()) return false;
 699       return true;
 700     }
 701 
 702     void   print_value_on(outputStream* st) const PRODUCT_RETURN;
 703     void   print_on(outputStream* st) const       PRODUCT_RETURN;
 704   };
 705 
 706   // Loop
 707   class Loop : public ResourceObj {
 708   private:
 709     Loop* _parent;
 710     Loop* _sibling;  // List of siblings, null terminated
 711     Loop* _child;    // Head of child list threaded thru sibling pointer
 712     Block* _head;    // Head of loop
 713     Block* _tail;    // Tail of loop
 714     bool   _irreducible;
 715     LocalSet _def_locals;
 716 
 717   public:
 718     Loop(Block* head, Block* tail) :
 719       _head(head),   _tail(tail),
 720       _parent(NULL), _sibling(NULL), _child(NULL),
 721       _irreducible(false), _def_locals() {}
 722 
 723     Loop* parent()  const { return _parent; }
 724     Loop* sibling() const { return _sibling; }
 725     Loop* child()   const { return _child; }
 726     Block* head()   const { return _head; }
 727     Block* tail()   const { return _tail; }
 728     void set_parent(Loop* p)  { _parent = p; }
 729     void set_sibling(Loop* s) { _sibling = s; }
 730     void set_child(Loop* c)   { _child = c; }
 731     void set_head(Block* hd)  { _head = hd; }
 732     void set_tail(Block* tl)  { _tail = tl; }
 733 
 734     int depth() const;              // nesting depth
 735 
 736     // Returns true if lp is a nested loop or us.
 737     bool contains(Loop* lp) const;
 738     bool contains(Block* blk) const { return contains(blk->loop()); }
 739 
 740     // Data flow on locals
 741     LocalSet* def_locals() { return &_def_locals; }
 742     const LocalSet* def_locals() const { return &_def_locals; }
 743 
 744     // Merge the branch lp into this branch, sorting on the loop head
 745     // pre_orders. Returns the new branch.
 746     Loop* sorted_merge(Loop* lp);
 747 
 748     // Mark non-single entry to loop
 749     void set_irreducible(Block* entry) {
 750       _irreducible = true;
 751       entry->set_irreducible_entry(true);
 752     }
 753     bool is_irreducible() const { return _irreducible; }
 754 
 755     bool is_root() const { return _tail->pre_order() == max_jint; }
 756 
 757     void print(outputStream* st = tty, int indent = 0) const PRODUCT_RETURN;
 758   };
 759 
 760   // Postorder iteration over the loop tree.
 761   class PostorderLoops : public StackObj {
 762   private:
 763     Loop* _root;
 764     Loop* _current;
 765   public:
 766     PostorderLoops(Loop* root) : _root(root), _current(root) {
 767       while (_current->child() != NULL) {
 768         _current = _current->child();
 769       }
 770     }
 771     bool done() { return _current == NULL; }  // Finished iterating?
 772     void next();                            // Advance to next loop
 773     Loop* current() { return _current; }      // Return current loop.
 774   };
 775 
 776   // Preorder iteration over the loop tree.
 777   class PreorderLoops : public StackObj {
 778   private:
 779     Loop* _root;
 780     Loop* _current;
 781   public:
 782     PreorderLoops(Loop* root) : _root(root), _current(root) {}
 783     bool done() { return _current == NULL; }  // Finished iterating?
 784     void next();                            // Advance to next loop
 785     Loop* current() { return _current; }      // Return current loop.
 786   };
 787 
 788   // Standard indexes of successors, for various bytecodes.
 789   enum {
 790     FALL_THROUGH   = 0,  // normal control
 791     IF_NOT_TAKEN   = 0,  // the not-taken branch of an if (i.e., fall-through)
 792     IF_TAKEN       = 1,  // the taken branch of an if
 793     GOTO_TARGET    = 0,  // unique successor for goto, jsr, or ret
 794     SWITCH_DEFAULT = 0,  // default branch of a switch
 795     SWITCH_CASES   = 1   // first index for any non-default switch branches
 796     // Unlike in other blocks, the successors of a switch are listed uniquely.
 797   };
 798 
 799 private:
 800   // A mapping from pre_order to Blocks.  This array is created
 801   // only at the end of the flow.
 802   Block** _block_map;
 803 
 804   // For each ciBlock index, a list of Blocks which share this ciBlock.
 805   GrowableArray<Block*>** _idx_to_blocklist;
 806   // count of ciBlocks
 807   int _ciblock_count;
 808 
 809   // Tells if a given instruction is able to generate an exception edge.
 810   bool can_trap(ciBytecodeStream& str);
 811 
 812   // Clone the loop heads. Returns true if any cloning occurred.
 813   bool clone_loop_heads(Loop* lp, StateVector* temp_vector, JsrSet* temp_set);
 814 
 815   // Clone lp's head and replace tail's successors with clone.
 816   Block* clone_loop_head(Loop* lp, StateVector* temp_vector, JsrSet* temp_set);
 817 
 818 public:
 819   // Return the block beginning at bci which has a JsrSet compatible
 820   // with jsrs.
 821   Block* block_at(int bci, JsrSet* set, CreateOption option = create_public_copy);
 822 
 823   // block factory
 824   Block* get_block_for(int ciBlockIndex, JsrSet* jsrs, CreateOption option = create_public_copy);
 825 
 826   // How many of the blocks have the backedge_copy bit set?
 827   int backedge_copy_count(int ciBlockIndex, JsrSet* jsrs) const;
 828 
 829   // Return an existing block containing bci which has a JsrSet compatible
 830   // with jsrs, or NULL if there is none.
 831   Block* existing_block_at(int bci, JsrSet* set) { return block_at(bci, set, no_create); }
 832 
 833   // Tell whether the flow analysis has encountered an error of some sort.
 834   bool failing() { return env()->failing() || _failure_reason != NULL; }
 835 
 836   // Reason this compilation is failing, such as "too many basic blocks".
 837   const char* failure_reason() { return _failure_reason; }
 838 
 839   // Note a failure.
 840   void record_failure(const char* reason);
 841 
 842   // Return the block of a given pre-order number.
 843   int have_block_count() const      { return _block_map != NULL; }
 844   int block_count() const           { assert(have_block_count(), "");
 845                                       return _next_pre_order; }
 846   Block* pre_order_at(int po) const { assert(0 <= po && po < block_count(), "out of bounds");
 847                                       return _block_map[po]; }
 848   Block* start_block() const        { return pre_order_at(start_block_num()); }
 849   int start_block_num() const       { return 0; }
 850   Block* rpo_at(int rpo) const      { assert(0 <= rpo && rpo < block_count(), "out of bounds");
 851                                       return _block_map[rpo]; }
 852   int next_pre_order()              { return _next_pre_order; }
 853   int inc_next_pre_order()          { return _next_pre_order++; }
 854 
 855 private:
 856   // A work list used during flow analysis.
 857   Block* _work_list;
 858 
 859   // List of blocks in reverse post order
 860   Block* _rpo_list;
 861 
 862   // Next Block::_pre_order.  After mapping, doubles as block_count.
 863   int _next_pre_order;
 864 
 865   // Are there more blocks on the work list?
 866   bool work_list_empty() { return _work_list == NULL; }
 867 
 868   // Get the next basic block from our work list.
 869   Block* work_list_next();
 870 
 871   // Add a basic block to our work list.
 872   void add_to_work_list(Block* block);
 873 
 874   // Prepend a basic block to rpo list.
 875   void prepend_to_rpo_list(Block* blk) {
 876     blk->set_rpo_next(_rpo_list);
 877     _rpo_list = blk;
 878   }
 879 
 880   // Root of the loop tree
 881   Loop* _loop_tree_root;
 882 
 883   // State used for make_jsr_record
 884   int _jsr_count;
 885   GrowableArray<JsrRecord*>* _jsr_records;
 886 
 887 public:
 888   // Make a JsrRecord for a given (entry, return) pair, if such a record
 889   // does not already exist.
 890   JsrRecord* make_jsr_record(int entry_address, int return_address);
 891 
 892   void  set_loop_tree_root(Loop* ltr) { _loop_tree_root = ltr; }
 893   Loop* loop_tree_root()              { return _loop_tree_root; }
 894 
 895 private:
 896   // Get the initial state for start_bci:
 897   const StateVector* get_start_state();
 898 
 899   // Merge the current state into all exceptional successors at the
 900   // current point in the code.
 901   void flow_exceptions(GrowableArray<Block*>* exceptions,
 902                        GrowableArray<ciInstanceKlass*>* exc_klasses,
 903                        StateVector* state);
 904 
 905   // Merge the current state into all successors at the current point
 906   // in the code.
 907   void flow_successors(GrowableArray<Block*>* successors,
 908                        StateVector* state);
 909 
 910   // Interpret the effects of the bytecodes on the incoming state
 911   // vector of a basic block.  Push the changed state to succeeding
 912   // basic blocks.
 913   void flow_block(Block* block,
 914                   StateVector* scratch_state,
 915                   JsrSet* scratch_jsrs);
 916 
 917   // Perform the type flow analysis, creating and cloning Blocks as
 918   // necessary.
 919   void flow_types();
 920 
 921   // Perform the depth first type flow analysis. Helper for flow_types.
 922   void df_flow_types(Block* start,
 923                      bool do_flow,
 924                      StateVector* temp_vector,
 925                      JsrSet* temp_set);
 926 
 927   // Incrementally build loop tree.
 928   void build_loop_tree(Block* blk);
 929 
 930   // Create the block map, which indexes blocks in pre_order.
 931   void map_blocks();
 932 
 933 public:
 934   // Perform type inference flow analysis.
 935   void do_flow();
 936 
 937   void print_on(outputStream* st) const PRODUCT_RETURN;
 938 
 939   void rpo_print_on(outputStream* st) const PRODUCT_RETURN;
 940 };
 941 
 942 #endif // SHARE_VM_CI_CITYPEFLOW_HPP