1 /*
  2  * Copyright (c) 2000, 2020, 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_CI_CITYPEFLOW_HPP
 26 #define SHARE_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 
 34 
 35 class ciTypeFlow : public ResourceObj {
 36 private:
 37   ciEnv*    _env;
 38   ciMethod* _method;
 39   int       _osr_bci;
 40 
 41   bool      _has_irreducible_entry;
 42 
 43   const char* _failure_reason;
 44 
 45 public:
 46   class StateVector;
 47   class Loop;
 48   class Block;
 49 
 50   // Build a type flow analyzer
 51   // Do an OSR analysis if osr_bci >= 0.
 52   ciTypeFlow(ciEnv* env, ciMethod* method, int osr_bci = InvocationEntryBci);
 53 
 54   // Accessors
 55   ciMethod* method() const     { return _method; }
 56   ciEnv*    env()              { return _env; }
 57   Arena*    arena()            { return _env->arena(); }
 58   bool      is_osr_flow() const{ return _osr_bci != InvocationEntryBci; }
 59   int       start_bci() const  { return is_osr_flow()? _osr_bci: 0; }
 60   int       max_locals() const { return method()->max_locals(); }
 61   int       max_stack() const  { return method()->max_stack(); }
 62   int       max_cells() const  { return max_locals() + max_stack(); }
 63   int       code_size() const  { return method()->code_size(); }
 64   bool      has_irreducible_entry() const { return _has_irreducible_entry; }
 65 
 66   // Represents information about an "active" jsr call.  This
 67   // class represents a call to the routine at some entry address
 68   // with some distinct return address.
 69   class JsrRecord : public ResourceObj {
 70   private:
 71     int _entry_address;
 72     int _return_address;
 73   public:
 74     JsrRecord(int entry_address, int return_address) {
 75       _entry_address = entry_address;
 76       _return_address = return_address;
 77     }
 78 
 79     int entry_address() const  { return _entry_address; }
 80     int return_address() const { return _return_address; }
 81 
 82     void print_on(outputStream* st) const {
 83 #ifndef PRODUCT
 84       st->print("%d->%d", entry_address(), return_address());
 85 #endif
 86     }
 87   };
 88 
 89   // A JsrSet represents some set of JsrRecords.  This class
 90   // is used to record a set of all jsr routines which we permit
 91   // execution to return (ret) from.
 92   //
 93   // During abstract interpretation, JsrSets are used to determine
 94   // whether two paths which reach a given block are unique, and
 95   // should be cloned apart, or are compatible, and should merge
 96   // together.
 97   //
 98   // Note that different amounts of effort can be expended determining
 99   // if paths are compatible.  <DISCUSSION>
100   class JsrSet : public ResourceObj {
101   private:
102     GrowableArray<JsrRecord*> _set;
103 
104     JsrRecord* record_at(int i) {
105       return _set.at(i);
106     }
107 
108     // Insert the given JsrRecord into the JsrSet, maintaining the order
109     // of the set and replacing any element with the same entry address.
110     void insert_jsr_record(JsrRecord* record);
111 
112     // Remove the JsrRecord with the given return address from the JsrSet.
113     void remove_jsr_record(int return_address);
114 
115   public:
116     JsrSet(Arena* arena, int default_len = 4);
117     JsrSet(int default_len = 4);
118 
119     // Copy this JsrSet.
120     void copy_into(JsrSet* jsrs);
121 
122     // Is this JsrSet compatible with some other JsrSet?
123     bool is_compatible_with(JsrSet* other);
124 
125     // Apply the effect of a single bytecode to the JsrSet.
126     void apply_control(ciTypeFlow* analyzer,
127                        ciBytecodeStream* str,
128                        StateVector* state);
129 
130     // What is the cardinality of this set?
131     int size() const { return _set.length(); }
132 
133     void print_on(outputStream* st) const PRODUCT_RETURN;
134   };
135 
136   class LocalSet {
137   private:
138     enum Constants { max = 63 };
139     uint64_t _bits;
140   public:
141     LocalSet() : _bits(0) {}
142     void add(uint32_t i)        { if (i < (uint32_t)max) _bits |=  (1LL << i); }
143     void add(LocalSet* ls)      { _bits |= ls->_bits; }
144     bool test(uint32_t i) const { return i < (uint32_t)max ? (_bits>>i)&1U : true; }
145     void clear()                { _bits = 0; }
146     void print_on(outputStream* st, int limit) const  PRODUCT_RETURN;
147   };
148 
149   // Used as a combined index for locals and temps
150   enum Cell {
151     Cell_0, Cell_max = INT_MAX
152   };
153 
154   // A StateVector summarizes the type information at some
155   // point in the program
156   class StateVector : public ResourceObj {
157   private:
158     ciType**    _types;
159     int         _stack_size;
160     int         _monitor_count;
161     ciTypeFlow* _outer;
162 
163     int         _trap_bci;
164     int         _trap_index;
165 
166     LocalSet    _def_locals;  // For entire block
167 
168     static ciType* type_meet_internal(ciType* t1, ciType* t2, ciTypeFlow* analyzer);
169 
170   public:
171     // Special elements in our type lattice.
172     enum {
173       T_TOP     = T_VOID,      // why not?
174       T_BOTTOM  = T_CONFLICT,
175       T_LONG2   = T_SHORT,     // 2nd word of T_LONG
176       T_DOUBLE2 = T_CHAR,      // 2nd word of T_DOUBLE
177       T_NULL    = T_BYTE       // for now.
178     };
179     static ciType* top_type()    { return ciType::make((BasicType)T_TOP); }
180     static ciType* bottom_type() { return ciType::make((BasicType)T_BOTTOM); }
181     static ciType* long2_type()  { return ciType::make((BasicType)T_LONG2); }
182     static ciType* double2_type(){ return ciType::make((BasicType)T_DOUBLE2); }
183     static ciType* null_type()   { return ciType::make((BasicType)T_NULL); }
184 
185     static ciType* half_type(ciType* t) {
186       switch (t->basic_type()) {
187       case T_LONG:    return long2_type();
188       case T_DOUBLE:  return double2_type();
189       default:        ShouldNotReachHere(); return NULL;
190       }
191     }
192 
193     // The meet operation for our type lattice.
194     ciType* type_meet(ciType* t1, ciType* t2) {
195       return type_meet_internal(t1, t2, outer());
196     }
197 
198     // Accessors
199     ciTypeFlow* outer() const          { return _outer; }
200 
201     int         stack_size() const     { return _stack_size; }
202     void    set_stack_size(int ss)     { _stack_size = ss; }
203 
204     int         monitor_count() const  { return _monitor_count; }
205     void    set_monitor_count(int mc)  { _monitor_count = mc; }
206 
207     LocalSet* def_locals() { return &_def_locals; }
208     const LocalSet* def_locals() const { return &_def_locals; }
209 
210     static Cell start_cell()           { return (Cell)0; }
211     static Cell next_cell(Cell c)      { return (Cell)(((int)c) + 1); }
212     Cell        limit_cell() const {
213       return (Cell)(outer()->max_locals() + stack_size());
214     }
215 
216     // Cell creation
217     Cell      local(int lnum) const {
218       assert(lnum < outer()->max_locals(), "index check");
219       return (Cell)(lnum);
220     }
221 
222     Cell      stack(int snum) const {
223       assert(snum < stack_size(), "index check");
224       return (Cell)(outer()->max_locals() + snum);
225     }
226 
227     Cell      tos() const { return stack(stack_size()-1); }
228 
229     // For external use only:
230     ciType* local_type_at(int i) const { return type_at(local(i)); }
231     ciType* stack_type_at(int i) const { return type_at(stack(i)); }
232 
233     // Accessors for the type of some Cell c
234     ciType*   type_at(Cell c) const {
235       assert(start_cell() <= c && c < limit_cell(), "out of bounds");
236       return _types[c];
237     }
238 
239     void      set_type_at(Cell c, ciType* type) {
240       assert(start_cell() <= c && c < limit_cell(), "out of bounds");
241       _types[c] = type;
242     }
243 
244     // Top-of-stack operations.
245     void      set_type_at_tos(ciType* type) { set_type_at(tos(), type); }
246     ciType*   type_at_tos() const           { return type_at(tos()); }
247 
248     void      push(ciType* type) {
249       _stack_size++;
250       set_type_at_tos(type);
251     }
252     void      pop() {
253       debug_only(set_type_at_tos(bottom_type()));
254       _stack_size--;
255     }
256     ciType*   pop_value() {
257       ciType* t = type_at_tos();
258       pop();
259       return t;
260     }
261 
262     // Convenience operations.
263     bool      is_reference(ciType* type) const {
264       return type == null_type() || !type->is_primitive_type();
265     }
266     bool      is_int(ciType* type) const {
267       return type->basic_type() == T_INT;
268     }
269     bool      is_long(ciType* type) const {
270       return type->basic_type() == T_LONG;
271     }
272     bool      is_float(ciType* type) const {
273       return type->basic_type() == T_FLOAT;
274     }
275     bool      is_double(ciType* type) const {
276       return type->basic_type() == T_DOUBLE;
277     }
278 
279     void store_to_local(int lnum) {
280       _def_locals.add((uint) lnum);
281     }
282 
283     void      push_translate(ciType* type);
284 
285     void      push_int() {
286       push(ciType::make(T_INT));
287     }
288     void      pop_int() {
289       assert(is_int(type_at_tos()), "must be integer");
290       pop();
291     }
292     void      check_int(Cell c) {
293       assert(is_int(type_at(c)), "must be integer");
294     }
295     void      push_double() {
296       push(ciType::make(T_DOUBLE));
297       push(double2_type());
298     }
299     void      pop_double() {
300       assert(type_at_tos() == double2_type(), "must be 2nd half");
301       pop();
302       assert(is_double(type_at_tos()), "must be double");
303       pop();
304     }
305     void      push_float() {
306       push(ciType::make(T_FLOAT));
307     }
308     void      pop_float() {
309       assert(is_float(type_at_tos()), "must be float");
310       pop();
311     }
312     void      push_long() {
313       push(ciType::make(T_LONG));
314       push(long2_type());
315     }
316     void      pop_long() {
317       assert(type_at_tos() == long2_type(), "must be 2nd half");
318       pop();
319       assert(is_long(type_at_tos()), "must be long");
320       pop();
321     }
322     void      push_object(ciKlass* klass) {
323       push(klass);
324     }
325     void      pop_object() {
326       assert(is_reference(type_at_tos()), "must be reference type");
327       pop();
328     }
329     void      pop_array() {
330       assert(type_at_tos() == null_type() ||
331              type_at_tos()->is_array_klass(), "must be array type");
332       pop();
333     }
334     // pop_objOrFlatArray and pop_typeArray narrow the tos to ciObjArrayKlass,
335     // ciFlatArrayKlass or ciTypeArrayKlass (resp.). In the rare case that an explicit
336     // null is popped from the stack, we return NULL.  Caller beware.
337     ciArrayKlass* pop_objOrFlatArray() {
338       ciType* array = pop_value();
339       if (array == null_type())  return NULL;
340       assert(array->is_obj_array_klass() || array->is_flat_array_klass(),
341              "must be a flat or an object array type");
342       return array->as_array_klass();
343     }
344     ciTypeArrayKlass* pop_typeArray() {
345       ciType* array = pop_value();
346       if (array == null_type())  return NULL;
347       assert(array->is_type_array_klass(), "must be prim array type");
348       return array->as_type_array_klass();
349     }
350     void      push_null() {
351       push(null_type());
352     }
353     void      do_null_assert(ciKlass* unloaded_klass);
354 
355     // Helper convenience routines.
356     void do_aload(ciBytecodeStream* str);
357     void do_checkcast(ciBytecodeStream* str);
358     void do_getfield(ciBytecodeStream* str);
359     void do_getstatic(ciBytecodeStream* str);
360     void do_invoke(ciBytecodeStream* str, bool has_receiver);
361     void do_jsr(ciBytecodeStream* str);
362     void do_ldc(ciBytecodeStream* str);
363     void do_multianewarray(ciBytecodeStream* str);
364     void do_new(ciBytecodeStream* str);
365     void do_defaultvalue(ciBytecodeStream* str);
366     void do_withfield(ciBytecodeStream* str);
367     void do_newarray(ciBytecodeStream* str);
368     void do_putfield(ciBytecodeStream* str);
369     void do_putstatic(ciBytecodeStream* str);
370     void do_ret(ciBytecodeStream* str);
371 
372     void overwrite_local_double_long(int index) {
373       // Invalidate the previous local if it contains first half of
374       // a double or long value since it's seconf half is being overwritten.
375       int prev_index = index - 1;
376       if (prev_index >= 0 &&
377           (is_double(type_at(local(prev_index))) ||
378            is_long(type_at(local(prev_index))))) {
379         set_type_at(local(prev_index), bottom_type());
380       }
381     }
382 
383     void load_local_object(int index) {
384       ciType* type = type_at(local(index));
385       assert(is_reference(type), "must be reference type");
386       push(type);
387     }
388     void store_local_object(int index) {
389       ciType* type = pop_value();
390       assert(is_reference(type) || type->is_return_address(),
391              "must be reference type or return address");
392       overwrite_local_double_long(index);
393       set_type_at(local(index), type);
394       store_to_local(index);
395     }
396 
397     void load_local_double(int index) {
398       ciType* type = type_at(local(index));
399       ciType* type2 = type_at(local(index+1));
400       assert(is_double(type), "must be double type");
401       assert(type2 == double2_type(), "must be 2nd half");
402       push(type);
403       push(double2_type());
404     }
405     void store_local_double(int index) {
406       ciType* type2 = pop_value();
407       ciType* type = pop_value();
408       assert(is_double(type), "must be double");
409       assert(type2 == double2_type(), "must be 2nd half");
410       overwrite_local_double_long(index);
411       set_type_at(local(index), type);
412       set_type_at(local(index+1), type2);
413       store_to_local(index);
414       store_to_local(index+1);
415     }
416 
417     void load_local_float(int index) {
418       ciType* type = type_at(local(index));
419       assert(is_float(type), "must be float type");
420       push(type);
421     }
422     void store_local_float(int index) {
423       ciType* type = pop_value();
424       assert(is_float(type), "must be float type");
425       overwrite_local_double_long(index);
426       set_type_at(local(index), type);
427       store_to_local(index);
428     }
429 
430     void load_local_int(int index) {
431       ciType* type = type_at(local(index));
432       assert(is_int(type), "must be int type");
433       push(type);
434     }
435     void store_local_int(int index) {
436       ciType* type = pop_value();
437       assert(is_int(type), "must be int type");
438       overwrite_local_double_long(index);
439       set_type_at(local(index), type);
440       store_to_local(index);
441     }
442 
443     void load_local_long(int index) {
444       ciType* type = type_at(local(index));
445       ciType* type2 = type_at(local(index+1));
446       assert(is_long(type), "must be long type");
447       assert(type2 == long2_type(), "must be 2nd half");
448       push(type);
449       push(long2_type());
450     }
451     void store_local_long(int index) {
452       ciType* type2 = pop_value();
453       ciType* type = pop_value();
454       assert(is_long(type), "must be long");
455       assert(type2 == long2_type(), "must be 2nd half");
456       overwrite_local_double_long(index);
457       set_type_at(local(index), type);
458       set_type_at(local(index+1), type2);
459       store_to_local(index);
460       store_to_local(index+1);
461     }
462 
463     // Stop interpretation of this path with a trap.
464     void trap(ciBytecodeStream* str, ciKlass* klass, int index);
465 
466   public:
467     StateVector(ciTypeFlow* outer);
468 
469     // Copy our value into some other StateVector
470     void copy_into(StateVector* copy) const;
471 
472     // Meets this StateVector with another, destructively modifying this
473     // one.  Returns true if any modification takes place.
474     bool meet(const StateVector* incoming);
475 
476     // Ditto, except that the incoming state is coming from an exception.
477     bool meet_exception(ciInstanceKlass* exc, const StateVector* incoming);
478 
479     // Apply the effect of one bytecode to this StateVector
480     bool apply_one_bytecode(ciBytecodeStream* stream);
481 
482     // What is the bci of the trap?
483     int  trap_bci() { return _trap_bci; }
484 
485     // What is the index associated with the trap?
486     int  trap_index() { return _trap_index; }
487 
488     void print_cell_on(outputStream* st, Cell c) const PRODUCT_RETURN;
489     void print_on(outputStream* st) const              PRODUCT_RETURN;
490   };
491 
492   // Parameter for "find_block" calls:
493   // Describes the difference between a public and backedge copy.
494   enum CreateOption {
495     create_public_copy,
496     create_backedge_copy,
497     no_create
498   };
499 
500   // Successor iterator
501   class SuccIter : public StackObj {
502   private:
503     Block* _pred;
504     int    _index;
505     Block* _succ;
506   public:
507     SuccIter()                        : _pred(NULL), _index(-1), _succ(NULL) {}
508     SuccIter(Block* pred)             : _pred(pred), _index(-1), _succ(NULL) { next(); }
509     int    index()     { return _index; }
510     Block* pred()      { return _pred; }           // Return predecessor
511     bool   done()      { return _index < 0; }      // Finished?
512     Block* succ()      { return _succ; }           // Return current successor
513     void   next();                                 // Advance
514     void   set_succ(Block* succ);                  // Update current successor
515     bool   is_normal_ctrl() { return index() < _pred->successors()->length(); }
516   };
517 
518   // A basic block
519   class Block : public ResourceObj {
520   private:
521     ciBlock*                          _ciblock;
522     GrowableArray<Block*>*           _exceptions;
523     GrowableArray<ciInstanceKlass*>* _exc_klasses;
524     GrowableArray<Block*>*           _successors;
525     GrowableArray<Block*>            _predecessors;
526     StateVector*                     _state;
527     JsrSet*                          _jsrs;
528 
529     int                              _trap_bci;
530     int                              _trap_index;
531 
532     // pre_order, assigned at first visit. Used as block ID and "visited" tag
533     int                              _pre_order;
534 
535     // A post-order, used to compute the reverse post order (RPO) provided to the client
536     int                              _post_order;  // used to compute rpo
537 
538     // Has this block been cloned for a loop backedge?
539     bool                             _backedge_copy;
540 
541     // This block is entry to irreducible loop.
542     bool                             _irreducible_entry;
543 
544     // This block has monitor entry point.
545     bool                             _has_monitorenter;
546 
547     // A pointer used for our internal work list
548     bool                             _on_work_list;      // on the work list
549     Block*                           _next;
550     Block*                           _rpo_next;          // Reverse post order list
551 
552     // Loop info
553     Loop*                            _loop;              // nearest loop
554 
555     ciBlock*     ciblock() const     { return _ciblock; }
556     StateVector* state() const     { return _state; }
557 
558     // Compute the exceptional successors and types for this Block.
559     void compute_exceptions();
560 
561   public:
562     // constructors
563     Block(ciTypeFlow* outer, ciBlock* ciblk, JsrSet* jsrs);
564 
565     void set_trap(int trap_bci, int trap_index) {
566       _trap_bci = trap_bci;
567       _trap_index = trap_index;
568       assert(has_trap(), "");
569     }
570     bool has_trap()   const  { return _trap_bci != -1; }
571     int  trap_bci()   const  { assert(has_trap(), ""); return _trap_bci; }
572     int  trap_index() const  { assert(has_trap(), ""); return _trap_index; }
573 
574     // accessors
575     ciTypeFlow* outer() const { return state()->outer(); }
576     int start() const         { return _ciblock->start_bci(); }
577     int limit() const         { return _ciblock->limit_bci(); }
578     int control() const       { return _ciblock->control_bci(); }
579     JsrSet* jsrs() const      { return _jsrs; }
580 
581     bool    is_backedge_copy() const       { return _backedge_copy; }
582     void   set_backedge_copy(bool z);
583     int        backedge_copy_count() const { return outer()->backedge_copy_count(ciblock()->index(), _jsrs); }
584 
585     // access to entry state
586     int     stack_size() const         { return _state->stack_size(); }
587     int     monitor_count() const      { return _state->monitor_count(); }
588     ciType* local_type_at(int i) const { return _state->local_type_at(i); }
589     ciType* stack_type_at(int i) const { return _state->stack_type_at(i); }
590 
591     // Data flow on locals
592     bool is_invariant_local(uint v) const {
593       assert(is_loop_head(), "only loop heads");
594       // Find outermost loop with same loop head
595       Loop* lp = loop();
596       while (lp->parent() != NULL) {
597         if (lp->parent()->head() != lp->head()) break;
598         lp = lp->parent();
599       }
600       return !lp->def_locals()->test(v);
601     }
602     LocalSet* def_locals() { return _state->def_locals(); }
603     const LocalSet* def_locals() const { return _state->def_locals(); }
604 
605     // Get the successors for this Block.
606     GrowableArray<Block*>* successors(ciBytecodeStream* str,
607                                       StateVector* state,
608                                       JsrSet* jsrs);
609     GrowableArray<Block*>* successors() {
610       assert(_successors != NULL, "must be filled in");
611       return _successors;
612     }
613 
614     // Predecessors of this block (including exception edges)
615     GrowableArray<Block*>* predecessors() {
616       return &_predecessors;
617     }
618 
619     // Get the exceptional successors for this Block.
620     GrowableArray<Block*>* exceptions() {
621       if (_exceptions == NULL) {
622         compute_exceptions();
623       }
624       return _exceptions;
625     }
626 
627     // Get the exception klasses corresponding to the
628     // exceptional successors for this Block.
629     GrowableArray<ciInstanceKlass*>* exc_klasses() {
630       if (_exc_klasses == NULL) {
631         compute_exceptions();
632       }
633       return _exc_klasses;
634     }
635 
636     // Is this Block compatible with a given JsrSet?
637     bool is_compatible_with(JsrSet* other) {
638       return _jsrs->is_compatible_with(other);
639     }
640 
641     // Copy the value of our state vector into another.
642     void copy_state_into(StateVector* copy) const {
643       _state->copy_into(copy);
644     }
645 
646     // Copy the value of our JsrSet into another
647     void copy_jsrs_into(JsrSet* copy) const {
648       _jsrs->copy_into(copy);
649     }
650 
651     // Meets the start state of this block with another state, destructively
652     // modifying this one.  Returns true if any modification takes place.
653     bool meet(const StateVector* incoming) {
654       return state()->meet(incoming);
655     }
656 
657     // Ditto, except that the incoming state is coming from an
658     // exception path.  This means the stack is replaced by the
659     // appropriate exception type.
660     bool meet_exception(ciInstanceKlass* exc, const StateVector* incoming) {
661       return state()->meet_exception(exc, incoming);
662     }
663 
664     // Work list manipulation
665     void   set_next(Block* block) { _next = block; }
666     Block* next() const           { return _next; }
667 
668     void   set_on_work_list(bool c) { _on_work_list = c; }
669     bool   is_on_work_list() const  { return _on_work_list; }
670 
671     bool   has_pre_order() const  { return _pre_order >= 0; }
672     void   set_pre_order(int po)  { assert(!has_pre_order(), ""); _pre_order = po; }
673     int    pre_order() const      { assert(has_pre_order(), ""); return _pre_order; }
674     void   set_next_pre_order()   { set_pre_order(outer()->inc_next_pre_order()); }
675     bool   is_start() const       { return _pre_order == outer()->start_block_num(); }
676 
677     // Reverse post order
678     void   df_init();
679     bool   has_post_order() const { return _post_order >= 0; }
680     void   set_post_order(int po) { assert(!has_post_order() && po >= 0, ""); _post_order = po; }
681     void   reset_post_order(int o){ _post_order = o; }
682     int    post_order() const     { assert(has_post_order(), ""); return _post_order; }
683 
684     bool   has_rpo() const        { return has_post_order() && outer()->have_block_count(); }
685     int    rpo() const            { assert(has_rpo(), ""); return outer()->block_count() - post_order() - 1; }
686     void   set_rpo_next(Block* b) { _rpo_next = b; }
687     Block* rpo_next()             { return _rpo_next; }
688 
689     // Loops
690     Loop*  loop() const                  { return _loop; }
691     void   set_loop(Loop* lp)            { _loop = lp; }
692     bool   is_loop_head() const          { return _loop && _loop->head() == this; }
693     void   set_irreducible_entry(bool c) { _irreducible_entry = c; }
694     bool   is_irreducible_entry() const  { return _irreducible_entry; }
695     void   set_has_monitorenter()        { _has_monitorenter = true; }
696     bool   has_monitorenter() const      { return _has_monitorenter; }
697     bool   is_visited() const            { return has_pre_order(); }
698     bool   is_post_visited() const       { return has_post_order(); }
699     bool   is_clonable_exit(Loop* lp);
700     Block* looping_succ(Loop* lp);       // Successor inside of loop
701     bool   is_single_entry_loop_head() const {
702       if (!is_loop_head()) return false;
703       for (Loop* lp = loop(); lp != NULL && lp->head() == this; lp = lp->parent())
704         if (lp->is_irreducible()) return false;
705       return true;
706     }
707 
708     void   print_value_on(outputStream* st) const PRODUCT_RETURN;
709     void   print_on(outputStream* st) const       PRODUCT_RETURN;
710   };
711 
712   // Loop
713   class Loop : public ResourceObj {
714   private:
715     Loop* _parent;
716     Loop* _sibling;  // List of siblings, null terminated
717     Loop* _child;    // Head of child list threaded thru sibling pointer
718     Block* _head;    // Head of loop
719     Block* _tail;    // Tail of loop
720     bool   _irreducible;
721     LocalSet _def_locals;
722 
723   public:
724     Loop(Block* head, Block* tail) :
725       _parent(NULL), _sibling(NULL), _child(NULL),
726       _head(head),   _tail(tail),
727       _irreducible(false), _def_locals() {}
728 
729     Loop* parent()  const { return _parent; }
730     Loop* sibling() const { return _sibling; }
731     Loop* child()   const { return _child; }
732     Block* head()   const { return _head; }
733     Block* tail()   const { return _tail; }
734     void set_parent(Loop* p)  { _parent = p; }
735     void set_sibling(Loop* s) { _sibling = s; }
736     void set_child(Loop* c)   { _child = c; }
737     void set_head(Block* hd)  { _head = hd; }
738     void set_tail(Block* tl)  { _tail = tl; }
739 
740     int depth() const;              // nesting depth
741 
742     // Returns true if lp is a nested loop or us.
743     bool contains(Loop* lp) const;
744     bool contains(Block* blk) const { return contains(blk->loop()); }
745 
746     // Data flow on locals
747     LocalSet* def_locals() { return &_def_locals; }
748     const LocalSet* def_locals() const { return &_def_locals; }
749 
750     // Merge the branch lp into this branch, sorting on the loop head
751     // pre_orders. Returns the new branch.
752     Loop* sorted_merge(Loop* lp);
753 
754     // Mark non-single entry to loop
755     void set_irreducible(Block* entry) {
756       _irreducible = true;
757       entry->set_irreducible_entry(true);
758     }
759     bool is_irreducible() const { return _irreducible; }
760 
761     bool is_root() const { return _tail->pre_order() == max_jint; }
762 
763     void print(outputStream* st = tty, int indent = 0) const PRODUCT_RETURN;
764   };
765 
766   // Preorder iteration over the loop tree.
767   class PreorderLoops : public StackObj {
768   private:
769     Loop* _root;
770     Loop* _current;
771   public:
772     PreorderLoops(Loop* root) : _root(root), _current(root) {}
773     bool done() { return _current == NULL; }  // Finished iterating?
774     void next();                            // Advance to next loop
775     Loop* current() { return _current; }      // Return current loop.
776   };
777 
778   // Standard indexes of successors, for various bytecodes.
779   enum {
780     FALL_THROUGH   = 0,  // normal control
781     IF_NOT_TAKEN   = 0,  // the not-taken branch of an if (i.e., fall-through)
782     IF_TAKEN       = 1,  // the taken branch of an if
783     GOTO_TARGET    = 0,  // unique successor for goto, jsr, or ret
784     SWITCH_DEFAULT = 0,  // default branch of a switch
785     SWITCH_CASES   = 1   // first index for any non-default switch branches
786     // Unlike in other blocks, the successors of a switch are listed uniquely.
787   };
788 
789 private:
790   // A mapping from pre_order to Blocks.  This array is created
791   // only at the end of the flow.
792   Block** _block_map;
793 
794   // For each ciBlock index, a list of Blocks which share this ciBlock.
795   GrowableArray<Block*>** _idx_to_blocklist;
796 
797   // Tells if a given instruction is able to generate an exception edge.
798   bool can_trap(ciBytecodeStream& str);
799 
800   // Clone the loop heads. Returns true if any cloning occurred.
801   bool clone_loop_heads(Loop* lp, StateVector* temp_vector, JsrSet* temp_set);
802 
803   // Clone lp's head and replace tail's successors with clone.
804   Block* clone_loop_head(Loop* lp, StateVector* temp_vector, JsrSet* temp_set);
805 
806 public:
807   // Return the block beginning at bci which has a JsrSet compatible
808   // with jsrs.
809   Block* block_at(int bci, JsrSet* set, CreateOption option = create_public_copy);
810 
811   // block factory
812   Block* get_block_for(int ciBlockIndex, JsrSet* jsrs, CreateOption option = create_public_copy);
813 
814   // How many of the blocks have the backedge_copy bit set?
815   int backedge_copy_count(int ciBlockIndex, JsrSet* jsrs) const;
816 
817   // Return an existing block containing bci which has a JsrSet compatible
818   // with jsrs, or NULL if there is none.
819   Block* existing_block_at(int bci, JsrSet* set) { return block_at(bci, set, no_create); }
820 
821   // Tell whether the flow analysis has encountered an error of some sort.
822   bool failing() { return env()->failing() || _failure_reason != NULL; }
823 
824   // Reason this compilation is failing, such as "too many basic blocks".
825   const char* failure_reason() { return _failure_reason; }
826 
827   // Note a failure.
828   void record_failure(const char* reason);
829 
830   // Return the block of a given pre-order number.
831   int have_block_count() const      { return _block_map != NULL; }
832   int block_count() const           { assert(have_block_count(), "");
833                                       return _next_pre_order; }
834   Block* pre_order_at(int po) const { assert(0 <= po && po < block_count(), "out of bounds");
835                                       return _block_map[po]; }
836   Block* start_block() const        { return pre_order_at(start_block_num()); }
837   int start_block_num() const       { return 0; }
838   Block* rpo_at(int rpo) const      { assert(0 <= rpo && rpo < block_count(), "out of bounds");
839                                       return _block_map[rpo]; }
840   int inc_next_pre_order()          { return _next_pre_order++; }
841 
842   ciType* mark_as_null_free(ciType* type);
843 
844 private:
845   // A work list used during flow analysis.
846   Block* _work_list;
847 
848   // List of blocks in reverse post order
849   Block* _rpo_list;
850 
851   // Next Block::_pre_order.  After mapping, doubles as block_count.
852   int _next_pre_order;
853 
854   // Are there more blocks on the work list?
855   bool work_list_empty() { return _work_list == NULL; }
856 
857   // Get the next basic block from our work list.
858   Block* work_list_next();
859 
860   // Add a basic block to our work list.
861   void add_to_work_list(Block* block);
862 
863   // Prepend a basic block to rpo list.
864   void prepend_to_rpo_list(Block* blk) {
865     blk->set_rpo_next(_rpo_list);
866     _rpo_list = blk;
867   }
868 
869   // Root of the loop tree
870   Loop* _loop_tree_root;
871 
872   // State used for make_jsr_record
873   GrowableArray<JsrRecord*>* _jsr_records;
874 
875 public:
876   // Make a JsrRecord for a given (entry, return) pair, if such a record
877   // does not already exist.
878   JsrRecord* make_jsr_record(int entry_address, int return_address);
879 
880   void  set_loop_tree_root(Loop* ltr) { _loop_tree_root = ltr; }
881   Loop* loop_tree_root()              { return _loop_tree_root; }
882 
883 private:
884   // Get the initial state for start_bci:
885   const StateVector* get_start_state();
886 
887   // Merge the current state into all exceptional successors at the
888   // current point in the code.
889   void flow_exceptions(GrowableArray<Block*>* exceptions,
890                        GrowableArray<ciInstanceKlass*>* exc_klasses,
891                        StateVector* state);
892 
893   // Merge the current state into all successors at the current point
894   // in the code.
895   void flow_successors(GrowableArray<Block*>* successors,
896                        StateVector* state);
897 
898   // Interpret the effects of the bytecodes on the incoming state
899   // vector of a basic block.  Push the changed state to succeeding
900   // basic blocks.
901   void flow_block(Block* block,
902                   StateVector* scratch_state,
903                   JsrSet* scratch_jsrs);
904 
905   // Perform the type flow analysis, creating and cloning Blocks as
906   // necessary.
907   void flow_types();
908 
909   // Perform the depth first type flow analysis. Helper for flow_types.
910   void df_flow_types(Block* start,
911                      bool do_flow,
912                      StateVector* temp_vector,
913                      JsrSet* temp_set);
914 
915   // Incrementally build loop tree.
916   void build_loop_tree(Block* blk);
917 
918   // Create the block map, which indexes blocks in pre_order.
919   void map_blocks();
920 
921 public:
922   // Perform type inference flow analysis.
923   void do_flow();
924 
925   // Determine if bci is dominated by dom_bci
926   bool is_dominated_by(int bci, int dom_bci);
927 
928   void print_on(outputStream* st) const PRODUCT_RETURN;
929 
930   void rpo_print_on(outputStream* st) const PRODUCT_RETURN;
931 };
932 
933 #endif // SHARE_CI_CITYPEFLOW_HPP