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24 
25 #ifndef SHARE_OPTO_LOOPNODE_HPP
26 #define SHARE_OPTO_LOOPNODE_HPP
27 
28 #include "opto/cfgnode.hpp"
29 #include "opto/multnode.hpp"
30 #include "opto/phaseX.hpp"
31 #include "opto/subnode.hpp"
32 #include "opto/type.hpp"
33 
34 class CmpNode;
35 class CountedLoopEndNode;
36 class CountedLoopNode;
37 class IdealLoopTree;
38 class LoopNode;
39 class Node;
40 class OuterStripMinedLoopEndNode;
41 class PathFrequency;
42 class PhaseIdealLoop;
43 class CountedLoopReserveKit;
44 class VectorSet;
45 class Invariance;
46 struct small_cache;
47 
48 //
49 //                  I D E A L I Z E D   L O O P S
50 //
51 // Idealized loops are the set of loops I perform more interesting
52 // transformations on, beyond simple hoisting.
53 
54 //------------------------------LoopNode---------------------------------------
55 // Simple loop header.  Fall in path on left, loop-back path on right.
56 class LoopNode : public RegionNode {
57   // Size is bigger to hold the flags.  However, the flags do not change
58   // the semantics so it does not appear in the hash & cmp functions.
size_of() const59   virtual uint size_of() const { return sizeof(*this); }
60 protected:
61   uint _loop_flags;
62   // Names for flag bitfields
63   enum { Normal=0, Pre=1, Main=2, Post=3, PreMainPostFlagsMask=3,
64          MainHasNoPreLoop=4,
65          HasExactTripCount=8,
66          InnerLoop=16,
67          PartialPeelLoop=32,
68          PartialPeelFailed=64,
69          HasReductions=128,
70          WasSlpAnalyzed=256,
71          PassedSlpAnalysis=512,
72          DoUnrollOnly=1024,
73          VectorizedLoop=2048,
74          HasAtomicPostLoop=4096,
75          HasRangeChecks=8192,
76          IsMultiversioned=16384,
77          StripMined=32768,
78          SubwordLoop=65536,
79          ProfileTripFailed=131072};
80   char _unswitch_count;
81   enum { _unswitch_max=3 };
82   char _postloop_flags;
83   enum { LoopNotRCEChecked = 0, LoopRCEChecked = 1, RCEPostLoop = 2 };
84 
85   // Expected trip count from profile data
86   float _profile_trip_cnt;
87 
88 public:
89   // Names for edge indices
90   enum { Self=0, EntryControl, LoopBackControl };
91 
is_inner_loop() const92   bool is_inner_loop() const { return _loop_flags & InnerLoop; }
set_inner_loop()93   void set_inner_loop() { _loop_flags |= InnerLoop; }
94 
range_checks_present() const95   bool range_checks_present() const { return _loop_flags & HasRangeChecks; }
is_multiversioned() const96   bool is_multiversioned() const { return _loop_flags & IsMultiversioned; }
is_vectorized_loop() const97   bool is_vectorized_loop() const { return _loop_flags & VectorizedLoop; }
is_partial_peel_loop() const98   bool is_partial_peel_loop() const { return _loop_flags & PartialPeelLoop; }
set_partial_peel_loop()99   void set_partial_peel_loop() { _loop_flags |= PartialPeelLoop; }
partial_peel_has_failed() const100   bool partial_peel_has_failed() const { return _loop_flags & PartialPeelFailed; }
is_strip_mined() const101   bool is_strip_mined() const { return _loop_flags & StripMined; }
is_profile_trip_failed() const102   bool is_profile_trip_failed() const { return _loop_flags & ProfileTripFailed; }
is_subword_loop() const103   bool is_subword_loop() const { return _loop_flags & SubwordLoop; }
104 
mark_partial_peel_failed()105   void mark_partial_peel_failed() { _loop_flags |= PartialPeelFailed; }
mark_has_reductions()106   void mark_has_reductions() { _loop_flags |= HasReductions; }
mark_was_slp()107   void mark_was_slp() { _loop_flags |= WasSlpAnalyzed; }
mark_passed_slp()108   void mark_passed_slp() { _loop_flags |= PassedSlpAnalysis; }
mark_do_unroll_only()109   void mark_do_unroll_only() { _loop_flags |= DoUnrollOnly; }
mark_loop_vectorized()110   void mark_loop_vectorized() { _loop_flags |= VectorizedLoop; }
mark_has_atomic_post_loop()111   void mark_has_atomic_post_loop() { _loop_flags |= HasAtomicPostLoop; }
mark_has_range_checks()112   void mark_has_range_checks() { _loop_flags |=  HasRangeChecks; }
mark_is_multiversioned()113   void mark_is_multiversioned() { _loop_flags |= IsMultiversioned; }
mark_strip_mined()114   void mark_strip_mined() { _loop_flags |= StripMined; }
clear_strip_mined()115   void clear_strip_mined() { _loop_flags &= ~StripMined; }
mark_profile_trip_failed()116   void mark_profile_trip_failed() { _loop_flags |= ProfileTripFailed; }
mark_subword_loop()117   void mark_subword_loop() { _loop_flags |= SubwordLoop; }
118 
unswitch_max()119   int unswitch_max() { return _unswitch_max; }
unswitch_count()120   int unswitch_count() { return _unswitch_count; }
121 
has_been_range_checked() const122   int has_been_range_checked() const { return _postloop_flags & LoopRCEChecked; }
set_has_been_range_checked()123   void set_has_been_range_checked() { _postloop_flags |= LoopRCEChecked; }
is_rce_post_loop() const124   int is_rce_post_loop() const { return _postloop_flags & RCEPostLoop; }
set_is_rce_post_loop()125   void set_is_rce_post_loop() { _postloop_flags |= RCEPostLoop; }
126 
set_unswitch_count(int val)127   void set_unswitch_count(int val) {
128     assert (val <= unswitch_max(), "too many unswitches");
129     _unswitch_count = val;
130   }
131 
set_profile_trip_cnt(float ptc)132   void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
profile_trip_cnt()133   float profile_trip_cnt()             { return _profile_trip_cnt; }
134 
LoopNode(Node * entry,Node * backedge)135   LoopNode(Node *entry, Node *backedge)
136     : RegionNode(3), _loop_flags(0), _unswitch_count(0),
137       _postloop_flags(0), _profile_trip_cnt(COUNT_UNKNOWN)  {
138     init_class_id(Class_Loop);
139     init_req(EntryControl, entry);
140     init_req(LoopBackControl, backedge);
141   }
142 
143   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
144   virtual int Opcode() const;
can_be_counted_loop(PhaseTransform * phase) const145   bool can_be_counted_loop(PhaseTransform* phase) const {
146     return req() == 3 && in(0) != NULL &&
147       in(1) != NULL && phase->type(in(1)) != Type::TOP &&
148       in(2) != NULL && phase->type(in(2)) != Type::TOP;
149   }
150   bool is_valid_counted_loop() const;
151 #ifndef PRODUCT
152   virtual void dump_spec(outputStream *st) const;
153 #endif
154 
155   void verify_strip_mined(int expect_skeleton) const NOT_DEBUG_RETURN;
skip_strip_mined(int expect_skeleton=1)156   virtual LoopNode* skip_strip_mined(int expect_skeleton = 1) { return this; }
outer_loop_tail() const157   virtual IfTrueNode* outer_loop_tail() const { ShouldNotReachHere(); return NULL; }
outer_loop_end() const158   virtual OuterStripMinedLoopEndNode* outer_loop_end() const { ShouldNotReachHere(); return NULL; }
outer_loop_exit() const159   virtual IfFalseNode* outer_loop_exit() const { ShouldNotReachHere(); return NULL; }
outer_safepoint() const160   virtual SafePointNode* outer_safepoint() const { ShouldNotReachHere(); return NULL; }
161 };
162 
163 //------------------------------Counted Loops----------------------------------
164 // Counted loops are all trip-counted loops, with exactly 1 trip-counter exit
165 // path (and maybe some other exit paths).  The trip-counter exit is always
166 // last in the loop.  The trip-counter have to stride by a constant;
167 // the exit value is also loop invariant.
168 
169 // CountedLoopNodes and CountedLoopEndNodes come in matched pairs.  The
170 // CountedLoopNode has the incoming loop control and the loop-back-control
171 // which is always the IfTrue before the matching CountedLoopEndNode.  The
172 // CountedLoopEndNode has an incoming control (possibly not the
173 // CountedLoopNode if there is control flow in the loop), the post-increment
174 // trip-counter value, and the limit.  The trip-counter value is always of
175 // the form (Op old-trip-counter stride).  The old-trip-counter is produced
176 // by a Phi connected to the CountedLoopNode.  The stride is constant.
177 // The Op is any commutable opcode, including Add, Mul, Xor.  The
178 // CountedLoopEndNode also takes in the loop-invariant limit value.
179 
180 // From a CountedLoopNode I can reach the matching CountedLoopEndNode via the
181 // loop-back control.  From CountedLoopEndNodes I can reach CountedLoopNodes
182 // via the old-trip-counter from the Op node.
183 
184 //------------------------------CountedLoopNode--------------------------------
185 // CountedLoopNodes head simple counted loops.  CountedLoopNodes have as
186 // inputs the incoming loop-start control and the loop-back control, so they
187 // act like RegionNodes.  They also take in the initial trip counter, the
188 // loop-invariant stride and the loop-invariant limit value.  CountedLoopNodes
189 // produce a loop-body control and the trip counter value.  Since
190 // CountedLoopNodes behave like RegionNodes I still have a standard CFG model.
191 
192 class CountedLoopNode : public LoopNode {
193   // Size is bigger to hold _main_idx.  However, _main_idx does not change
194   // the semantics so it does not appear in the hash & cmp functions.
size_of() const195   virtual uint size_of() const { return sizeof(*this); }
196 
197   // For Pre- and Post-loops during debugging ONLY, this holds the index of
198   // the Main CountedLoop.  Used to assert that we understand the graph shape.
199   node_idx_t _main_idx;
200 
201   // Known trip count calculated by compute_exact_trip_count()
202   uint  _trip_count;
203 
204   // Log2 of original loop bodies in unrolled loop
205   int _unrolled_count_log2;
206 
207   // Node count prior to last unrolling - used to decide if
208   // unroll,optimize,unroll,optimize,... is making progress
209   int _node_count_before_unroll;
210 
211   // If slp analysis is performed we record the maximum
212   // vector mapped unroll factor here
213   int _slp_maximum_unroll_factor;
214 
215 public:
CountedLoopNode(Node * entry,Node * backedge)216   CountedLoopNode( Node *entry, Node *backedge )
217     : LoopNode(entry, backedge), _main_idx(0), _trip_count(max_juint),
218       _unrolled_count_log2(0), _node_count_before_unroll(0),
219       _slp_maximum_unroll_factor(0) {
220     init_class_id(Class_CountedLoop);
221     // Initialize _trip_count to the largest possible value.
222     // Will be reset (lower) if the loop's trip count is known.
223   }
224 
225   virtual int Opcode() const;
226   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
227 
init_control() const228   Node *init_control() const { return in(EntryControl); }
back_control() const229   Node *back_control() const { return in(LoopBackControl); }
230   CountedLoopEndNode *loopexit_or_null() const;
231   CountedLoopEndNode *loopexit() const;
232   Node *init_trip() const;
233   Node *stride() const;
234   int   stride_con() const;
235   bool  stride_is_con() const;
236   Node *limit() const;
237   Node *incr() const;
238   Node *phi() const;
239 
240   // Match increment with optional truncation
241   static Node* match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type);
242 
243   // A 'main' loop has a pre-loop and a post-loop.  The 'main' loop
244   // can run short a few iterations and may start a few iterations in.
245   // It will be RCE'd and unrolled and aligned.
246 
247   // A following 'post' loop will run any remaining iterations.  Used
248   // during Range Check Elimination, the 'post' loop will do any final
249   // iterations with full checks.  Also used by Loop Unrolling, where
250   // the 'post' loop will do any epilog iterations needed.  Basically,
251   // a 'post' loop can not profitably be further unrolled or RCE'd.
252 
253   // A preceding 'pre' loop will run at least 1 iteration (to do peeling),
254   // it may do under-flow checks for RCE and may do alignment iterations
255   // so the following main loop 'knows' that it is striding down cache
256   // lines.
257 
258   // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or
259   // Aligned, may be missing it's pre-loop.
is_normal_loop() const260   bool is_normal_loop   () const { return (_loop_flags&PreMainPostFlagsMask) == Normal; }
is_pre_loop() const261   bool is_pre_loop      () const { return (_loop_flags&PreMainPostFlagsMask) == Pre;    }
is_main_loop() const262   bool is_main_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Main;   }
is_post_loop() const263   bool is_post_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Post;   }
is_reduction_loop() const264   bool is_reduction_loop() const { return (_loop_flags&HasReductions) == HasReductions; }
was_slp_analyzed() const265   bool was_slp_analyzed () const { return (_loop_flags&WasSlpAnalyzed) == WasSlpAnalyzed; }
has_passed_slp() const266   bool has_passed_slp   () const { return (_loop_flags&PassedSlpAnalysis) == PassedSlpAnalysis; }
is_unroll_only() const267   bool is_unroll_only   () const { return (_loop_flags&DoUnrollOnly) == DoUnrollOnly; }
is_main_no_pre_loop() const268   bool is_main_no_pre_loop() const { return _loop_flags & MainHasNoPreLoop; }
has_atomic_post_loop() const269   bool has_atomic_post_loop  () const { return (_loop_flags & HasAtomicPostLoop) == HasAtomicPostLoop; }
set_main_no_pre_loop()270   void set_main_no_pre_loop() { _loop_flags |= MainHasNoPreLoop; }
271 
main_idx() const272   int main_idx() const { return _main_idx; }
273 
274 
set_pre_loop(CountedLoopNode * main)275   void set_pre_loop  (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; }
set_main_loop()276   void set_main_loop (                     ) { assert(is_normal_loop(),""); _loop_flags |= Main;                         }
set_post_loop(CountedLoopNode * main)277   void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; }
set_normal_loop()278   void set_normal_loop(                    ) { _loop_flags &= ~PreMainPostFlagsMask; }
279 
set_trip_count(uint tc)280   void set_trip_count(uint tc) { _trip_count = tc; }
trip_count()281   uint trip_count()            { return _trip_count; }
282 
has_exact_trip_count() const283   bool has_exact_trip_count() const { return (_loop_flags & HasExactTripCount) != 0; }
set_exact_trip_count(uint tc)284   void set_exact_trip_count(uint tc) {
285     _trip_count = tc;
286     _loop_flags |= HasExactTripCount;
287   }
set_nonexact_trip_count()288   void set_nonexact_trip_count() {
289     _loop_flags &= ~HasExactTripCount;
290   }
set_notpassed_slp()291   void set_notpassed_slp() {
292     _loop_flags &= ~PassedSlpAnalysis;
293   }
294 
double_unrolled_count()295   void double_unrolled_count() { _unrolled_count_log2++; }
unrolled_count()296   int  unrolled_count()        { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); }
297 
set_node_count_before_unroll(int ct)298   void set_node_count_before_unroll(int ct)  { _node_count_before_unroll = ct; }
node_count_before_unroll()299   int  node_count_before_unroll()            { return _node_count_before_unroll; }
set_slp_max_unroll(int unroll_factor)300   void set_slp_max_unroll(int unroll_factor) { _slp_maximum_unroll_factor = unroll_factor; }
slp_max_unroll() const301   int  slp_max_unroll() const                { return _slp_maximum_unroll_factor; }
302 
303   virtual LoopNode* skip_strip_mined(int expect_skeleton = 1);
304   OuterStripMinedLoopNode* outer_loop() const;
305   virtual IfTrueNode* outer_loop_tail() const;
306   virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
307   virtual IfFalseNode* outer_loop_exit() const;
308   virtual SafePointNode* outer_safepoint() const;
309 
310   // If this is a main loop in a pre/main/post loop nest, walk over
311   // the predicates that were inserted by
312   // duplicate_predicates()/add_range_check_predicate()
313   static Node* skip_predicates_from_entry(Node* ctrl);
314   Node* skip_predicates();
315 
316 #ifndef PRODUCT
317   virtual void dump_spec(outputStream *st) const;
318 #endif
319 };
320 
321 //------------------------------CountedLoopEndNode-----------------------------
322 // CountedLoopEndNodes end simple trip counted loops.  They act much like
323 // IfNodes.
324 class CountedLoopEndNode : public IfNode {
325 public:
326   enum { TestControl, TestValue };
327 
CountedLoopEndNode(Node * control,Node * test,float prob,float cnt)328   CountedLoopEndNode( Node *control, Node *test, float prob, float cnt )
329     : IfNode( control, test, prob, cnt) {
330     init_class_id(Class_CountedLoopEnd);
331   }
332   virtual int Opcode() const;
333 
cmp_node() const334   Node *cmp_node() const            { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; }
incr() const335   Node *incr() const                { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
limit() const336   Node *limit() const               { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
stride() const337   Node *stride() const              { Node *tmp = incr    (); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
init_trip() const338   Node *init_trip() const           { Node *tmp = phi     (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
339   int stride_con() const;
stride_is_con() const340   bool stride_is_con() const        { Node *tmp = stride  (); return (tmp != NULL && tmp->is_Con()); }
test_trip() const341   BoolTest::mask test_trip() const  { return in(TestValue)->as_Bool()->_test._test; }
phi() const342   PhiNode *phi() const {
343     Node *tmp = incr();
344     if (tmp && tmp->req() == 3) {
345       Node* phi = tmp->in(1);
346       if (phi->is_Phi()) {
347         return phi->as_Phi();
348       }
349     }
350     return NULL;
351   }
loopnode() const352   CountedLoopNode *loopnode() const {
353     // The CountedLoopNode that goes with this CountedLoopEndNode may
354     // have been optimized out by the IGVN so be cautious with the
355     // pattern matching on the graph
356     PhiNode* iv_phi = phi();
357     if (iv_phi == NULL) {
358       return NULL;
359     }
360     Node *ln = iv_phi->in(0);
361     if (ln->is_CountedLoop() && ln->as_CountedLoop()->loopexit_or_null() == this) {
362       return (CountedLoopNode*)ln;
363     }
364     return NULL;
365   }
366 
367 #ifndef PRODUCT
368   virtual void dump_spec(outputStream *st) const;
369 #endif
370 };
371 
372 
loopexit_or_null() const373 inline CountedLoopEndNode* CountedLoopNode::loopexit_or_null() const {
374   Node* bctrl = back_control();
375   if (bctrl == NULL) return NULL;
376 
377   Node* lexit = bctrl->in(0);
378   return (CountedLoopEndNode*)
379       (lexit->Opcode() == Op_CountedLoopEnd ? lexit : NULL);
380 }
381 
loopexit() const382 inline CountedLoopEndNode* CountedLoopNode::loopexit() const {
383   CountedLoopEndNode* cle = loopexit_or_null();
384   assert(cle != NULL, "loopexit is NULL");
385   return cle;
386 }
387 
init_trip() const388 inline Node* CountedLoopNode::init_trip() const {
389   CountedLoopEndNode* cle = loopexit_or_null();
390   return cle != NULL ? cle->init_trip() : NULL;
391 }
stride() const392 inline Node* CountedLoopNode::stride() const {
393   CountedLoopEndNode* cle = loopexit_or_null();
394   return cle != NULL ? cle->stride() : NULL;
395 }
stride_con() const396 inline int CountedLoopNode::stride_con() const {
397   CountedLoopEndNode* cle = loopexit_or_null();
398   return cle != NULL ? cle->stride_con() : 0;
399 }
stride_is_con() const400 inline bool CountedLoopNode::stride_is_con() const {
401   CountedLoopEndNode* cle = loopexit_or_null();
402   return cle != NULL && cle->stride_is_con();
403 }
limit() const404 inline Node* CountedLoopNode::limit() const {
405   CountedLoopEndNode* cle = loopexit_or_null();
406   return cle != NULL ? cle->limit() : NULL;
407 }
incr() const408 inline Node* CountedLoopNode::incr() const {
409   CountedLoopEndNode* cle = loopexit_or_null();
410   return cle != NULL ? cle->incr() : NULL;
411 }
phi() const412 inline Node* CountedLoopNode::phi() const {
413   CountedLoopEndNode* cle = loopexit_or_null();
414   return cle != NULL ? cle->phi() : NULL;
415 }
416 
417 //------------------------------LoopLimitNode-----------------------------
418 // Counted Loop limit node which represents exact final iterator value:
419 // trip_count = (limit - init_trip + stride - 1)/stride
420 // final_value= trip_count * stride + init_trip.
421 // Use HW instructions to calculate it when it can overflow in integer.
422 // Note, final_value should fit into integer since counted loop has
423 // limit check: limit <= max_int-stride.
424 class LoopLimitNode : public Node {
425   enum { Init=1, Limit=2, Stride=3 };
426  public:
LoopLimitNode(Compile * C,Node * init,Node * limit,Node * stride)427   LoopLimitNode( Compile* C, Node *init, Node *limit, Node *stride ) : Node(0,init,limit,stride) {
428     // Put it on the Macro nodes list to optimize during macro nodes expansion.
429     init_flags(Flag_is_macro);
430     C->add_macro_node(this);
431   }
432   virtual int Opcode() const;
bottom_type() const433   virtual const Type *bottom_type() const { return TypeInt::INT; }
ideal_reg() const434   virtual uint ideal_reg() const { return Op_RegI; }
435   virtual const Type* Value(PhaseGVN* phase) const;
436   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
437   virtual Node* Identity(PhaseGVN* phase);
438 };
439 
440 // Support for strip mining
441 class OuterStripMinedLoopNode : public LoopNode {
442 private:
443   CountedLoopNode* inner_loop() const;
444 public:
OuterStripMinedLoopNode(Compile * C,Node * entry,Node * backedge)445   OuterStripMinedLoopNode(Compile* C, Node *entry, Node *backedge)
446     : LoopNode(entry, backedge) {
447     init_class_id(Class_OuterStripMinedLoop);
448     init_flags(Flag_is_macro);
449     C->add_macro_node(this);
450   }
451 
452   virtual int Opcode() const;
453 
454   virtual IfTrueNode* outer_loop_tail() const;
455   virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
456   virtual IfFalseNode* outer_loop_exit() const;
457   virtual SafePointNode* outer_safepoint() const;
458   void adjust_strip_mined_loop(PhaseIterGVN* igvn);
459 };
460 
461 class OuterStripMinedLoopEndNode : public IfNode {
462 public:
OuterStripMinedLoopEndNode(Node * control,Node * test,float prob,float cnt)463   OuterStripMinedLoopEndNode(Node *control, Node *test, float prob, float cnt)
464     : IfNode(control, test, prob, cnt) {
465     init_class_id(Class_OuterStripMinedLoopEnd);
466   }
467 
468   virtual int Opcode() const;
469 
470   virtual const Type* Value(PhaseGVN* phase) const;
471   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
472 
473   bool is_expanded(PhaseGVN *phase) const;
474 };
475 
476 // -----------------------------IdealLoopTree----------------------------------
477 class IdealLoopTree : public ResourceObj {
478 public:
479   IdealLoopTree *_parent;       // Parent in loop tree
480   IdealLoopTree *_next;         // Next sibling in loop tree
481   IdealLoopTree *_child;        // First child in loop tree
482 
483   // The head-tail backedge defines the loop.
484   // If a loop has multiple backedges, this is addressed during cleanup where
485   // we peel off the multiple backedges,  merging all edges at the bottom and
486   // ensuring that one proper backedge flow into the loop.
487   Node *_head;                  // Head of loop
488   Node *_tail;                  // Tail of loop
489   inline Node *tail();          // Handle lazy update of _tail field
490   inline Node *head();          // Handle lazy update of _head field
491   PhaseIdealLoop* _phase;
492   int _local_loop_unroll_limit;
493   int _local_loop_unroll_factor;
494 
495   Node_List _body;              // Loop body for inner loops
496 
497   uint8_t _nest;                // Nesting depth
498   uint8_t _irreducible:1,       // True if irreducible
499           _has_call:1,          // True if has call safepoint
500           _has_sfpt:1,          // True if has non-call safepoint
501           _rce_candidate:1;     // True if candidate for range check elimination
502 
503   Node_List* _safepts;          // List of safepoints in this loop
504   Node_List* _required_safept;  // A inner loop cannot delete these safepts;
505   bool  _allow_optimizations;   // Allow loop optimizations
506 
IdealLoopTree(PhaseIdealLoop * phase,Node * head,Node * tail)507   IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail )
508     : _parent(0), _next(0), _child(0),
509       _head(head), _tail(tail),
510       _phase(phase),
511       _local_loop_unroll_limit(0), _local_loop_unroll_factor(0),
512       _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0),
513       _safepts(NULL),
514       _required_safept(NULL),
515       _allow_optimizations(true)
516   {
517     precond(_head != NULL);
518     precond(_tail != NULL);
519   }
520 
521   // Is 'l' a member of 'this'?
522   bool is_member(const IdealLoopTree *l) const; // Test for nested membership
523 
524   // Set loop nesting depth.  Accumulate has_call bits.
525   int set_nest( uint depth );
526 
527   // Split out multiple fall-in edges from the loop header.  Move them to a
528   // private RegionNode before the loop.  This becomes the loop landing pad.
529   void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt );
530 
531   // Split out the outermost loop from this shared header.
532   void split_outer_loop( PhaseIdealLoop *phase );
533 
534   // Merge all the backedges from the shared header into a private Region.
535   // Feed that region as the one backedge to this loop.
536   void merge_many_backedges( PhaseIdealLoop *phase );
537 
538   // Split shared headers and insert loop landing pads.
539   // Insert a LoopNode to replace the RegionNode.
540   // Returns TRUE if loop tree is structurally changed.
541   bool beautify_loops( PhaseIdealLoop *phase );
542 
543   // Perform optimization to use the loop predicates for null checks and range checks.
544   // Applies to any loop level (not just the innermost one)
545   bool loop_predication( PhaseIdealLoop *phase);
546 
547   // Perform iteration-splitting on inner loops.  Split iterations to
548   // avoid range checks or one-shot null checks.  Returns false if the
549   // current round of loop opts should stop.
550   bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new );
551 
552   // Driver for various flavors of iteration splitting.  Returns false
553   // if the current round of loop opts should stop.
554   bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new );
555 
556   // Given dominators, try to find loops with calls that must always be
557   // executed (call dominates loop tail).  These loops do not need non-call
558   // safepoints (ncsfpt).
559   void check_safepts(VectorSet &visited, Node_List &stack);
560 
561   // Allpaths backwards scan from loop tail, terminating each path at first safepoint
562   // encountered.
563   void allpaths_check_safepts(VectorSet &visited, Node_List &stack);
564 
565   // Remove safepoints from loop. Optionally keeping one.
566   void remove_safepoints(PhaseIdealLoop* phase, bool keep_one);
567 
568   // Convert to counted loops where possible
569   void counted_loop( PhaseIdealLoop *phase );
570 
571   // Check for Node being a loop-breaking test
572   Node *is_loop_exit(Node *iff) const;
573 
574   // Remove simplistic dead code from loop body
575   void DCE_loop_body();
576 
577   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
578   // Replace with a 1-in-10 exit guess.
579   void adjust_loop_exit_prob( PhaseIdealLoop *phase );
580 
581   // Return TRUE or FALSE if the loop should never be RCE'd or aligned.
582   // Useful for unrolling loops with NO array accesses.
583   bool policy_peel_only( PhaseIdealLoop *phase ) const;
584 
585   // Return TRUE or FALSE if the loop should be unswitched -- clone
586   // loop with an invariant test
587   bool policy_unswitching( PhaseIdealLoop *phase ) const;
588 
589   // Micro-benchmark spamming.  Remove empty loops.
590   bool do_remove_empty_loop( PhaseIdealLoop *phase );
591 
592   // Convert one iteration loop into normal code.
593   bool do_one_iteration_loop( PhaseIdealLoop *phase );
594 
595   // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
596   // move some loop-invariant test (usually a null-check) before the loop.
597   bool policy_peeling(PhaseIdealLoop *phase);
598 
599   uint estimate_peeling(PhaseIdealLoop *phase);
600 
601   // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any
602   // known trip count in the counted loop node.
603   bool policy_maximally_unroll(PhaseIdealLoop *phase) const;
604 
605   // Return TRUE or FALSE if the loop should be unrolled or not. Apply unroll
606   // if the loop is a counted loop and the loop body is small enough.
607   bool policy_unroll(PhaseIdealLoop *phase);
608 
609   // Loop analyses to map to a maximal superword unrolling for vectorization.
610   void policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct);
611 
612   // Return TRUE or FALSE if the loop should be range-check-eliminated.
613   // Gather a list of IF tests that are dominated by iteration splitting;
614   // also gather the end of the first split and the start of the 2nd split.
615   bool policy_range_check( PhaseIdealLoop *phase ) const;
616 
617   // Return TRUE or FALSE if the loop should be cache-line aligned.
618   // Gather the expression that does the alignment.  Note that only
619   // one array base can be aligned in a loop (unless the VM guarantees
620   // mutual alignment).  Note that if we vectorize short memory ops
621   // into longer memory ops, we may want to increase alignment.
622   bool policy_align( PhaseIdealLoop *phase ) const;
623 
624   // Return TRUE if "iff" is a range check.
625   bool is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const;
626 
627   // Estimate the number of nodes required when cloning a loop (body).
628   uint est_loop_clone_sz(uint factor) const;
629   // Estimate the number of nodes required when unrolling a loop (body).
630   uint est_loop_unroll_sz(uint factor) const;
631 
632   // Compute loop trip count if possible
633   void compute_trip_count(PhaseIdealLoop* phase);
634 
635   // Compute loop trip count from profile data
636   float compute_profile_trip_cnt_helper(Node* n);
637   void compute_profile_trip_cnt( PhaseIdealLoop *phase );
638 
639   // Reassociate invariant expressions.
640   void reassociate_invariants(PhaseIdealLoop *phase);
641   // Reassociate invariant add and subtract expressions.
642   Node* reassociate_add_sub(Node* n1, PhaseIdealLoop *phase);
643   // Return nonzero index of invariant operand if invariant and variant
644   // are combined with an Add or Sub. Helper for reassociate_invariants.
645   int is_invariant_addition(Node* n, PhaseIdealLoop *phase);
646 
647   // Return true if n is invariant
648   bool is_invariant(Node* n) const;
649 
650   // Put loop body on igvn work list
651   void record_for_igvn();
652 
is_root()653   bool is_root() { return _parent == NULL; }
654   // A proper/reducible loop w/o any (occasional) dead back-edge.
is_loop()655   bool is_loop() { return !_irreducible && !tail()->is_top(); }
is_counted()656   bool is_counted()   { return is_loop() && _head->is_CountedLoop(); }
is_innermost()657   bool is_innermost() { return is_loop() && _child == NULL; }
658 
659   void remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase);
660 
661 #ifndef PRODUCT
662   void dump_head() const;       // Dump loop head only
663   void dump() const;            // Dump this loop recursively
664   void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const;
665 #endif
666 
667  private:
668   enum { EMPTY_LOOP_SIZE = 7 }; // Number of nodes in an empty loop.
669 
670   // Estimate the number of nodes resulting from control and data flow merge.
671   uint est_loop_flow_merge_sz() const;
672 };
673 
674 // -----------------------------PhaseIdealLoop---------------------------------
675 // Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees
676 // into a loop tree. Drives the loop-based transformations on the ideal graph.
677 class PhaseIdealLoop : public PhaseTransform {
678   friend class IdealLoopTree;
679   friend class SuperWord;
680   friend class CountedLoopReserveKit;
681   friend class ShenandoahBarrierC2Support;
682   friend class AutoNodeBudget;
683 
684   // Pre-computed def-use info
685   PhaseIterGVN &_igvn;
686 
687   // Head of loop tree
688   IdealLoopTree* _ltree_root;
689 
690   // Array of pre-order numbers, plus post-visited bit.
691   // ZERO for not pre-visited.  EVEN for pre-visited but not post-visited.
692   // ODD for post-visited.  Other bits are the pre-order number.
693   uint *_preorders;
694   uint _max_preorder;
695 
696   const PhaseIdealLoop* _verify_me;
697   bool _verify_only;
698 
699   // Allocate _preorders[] array
allocate_preorders()700   void allocate_preorders() {
701     _max_preorder = C->unique()+8;
702     _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder);
703     memset(_preorders, 0, sizeof(uint) * _max_preorder);
704   }
705 
706   // Allocate _preorders[] array
reallocate_preorders()707   void reallocate_preorders() {
708     if ( _max_preorder < C->unique() ) {
709       _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique());
710       _max_preorder = C->unique();
711     }
712     memset(_preorders, 0, sizeof(uint) * _max_preorder);
713   }
714 
715   // Check to grow _preorders[] array for the case when build_loop_tree_impl()
716   // adds new nodes.
check_grow_preorders()717   void check_grow_preorders( ) {
718     if ( _max_preorder < C->unique() ) {
719       uint newsize = _max_preorder<<1;  // double size of array
720       _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize);
721       memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder));
722       _max_preorder = newsize;
723     }
724   }
725   // Check for pre-visited.  Zero for NOT visited; non-zero for visited.
is_visited(Node * n) const726   int is_visited( Node *n ) const { return _preorders[n->_idx]; }
727   // Pre-order numbers are written to the Nodes array as low-bit-set values.
set_preorder_visited(Node * n,int pre_order)728   void set_preorder_visited( Node *n, int pre_order ) {
729     assert( !is_visited( n ), "already set" );
730     _preorders[n->_idx] = (pre_order<<1);
731   };
732   // Return pre-order number.
get_preorder(Node * n) const733   int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; }
734 
735   // Check for being post-visited.
736   // Should be previsited already (checked with assert(is_visited(n))).
is_postvisited(Node * n) const737   int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; }
738 
739   // Mark as post visited
set_postvisited(Node * n)740   void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; }
741 
742 public:
743   // Set/get control node out.  Set lower bit to distinguish from IdealLoopTree
744   // Returns true if "n" is a data node, false if it's a control node.
has_ctrl(Node * n) const745   bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; }
746 
747 private:
748   // clear out dead code after build_loop_late
749   Node_List _deadlist;
750 
751   // Support for faster execution of get_late_ctrl()/dom_lca()
752   // when a node has many uses and dominator depth is deep.
753   Node_Array _dom_lca_tags;
754   void   init_dom_lca_tags();
755   void   clear_dom_lca_tags();
756 
757   // Helper for debugging bad dominance relationships
758   bool verify_dominance(Node* n, Node* use, Node* LCA, Node* early);
759 
760   Node* compute_lca_of_uses(Node* n, Node* early, bool verify = false);
761 
762   // Inline wrapper for frequent cases:
763   // 1) only one use
764   // 2) a use is the same as the current LCA passed as 'n1'
dom_lca_for_get_late_ctrl(Node * lca,Node * n,Node * tag)765   Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) {
766     assert( n->is_CFG(), "" );
767     // Fast-path NULL lca
768     if( lca != NULL && lca != n ) {
769       assert( lca->is_CFG(), "" );
770       // find LCA of all uses
771       n = dom_lca_for_get_late_ctrl_internal( lca, n, tag );
772     }
773     return find_non_split_ctrl(n);
774   }
775   Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag );
776 
777   // Helper function for directing control inputs away from CFG split points.
find_non_split_ctrl(Node * ctrl) const778   Node *find_non_split_ctrl( Node *ctrl ) const {
779     if (ctrl != NULL) {
780       if (ctrl->is_MultiBranch()) {
781         ctrl = ctrl->in(0);
782       }
783       assert(ctrl->is_CFG(), "CFG");
784     }
785     return ctrl;
786   }
787 
788   Node* cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop);
789 
790 #ifdef ASSERT
791   void ensure_zero_trip_guard_proj(Node* node, bool is_main_loop);
792 #endif
793   void copy_skeleton_predicates_to_main_loop_helper(Node* predicate, Node* init, Node* stride, IdealLoopTree* outer_loop, LoopNode* outer_main_head,
794                                                     uint dd_main_head, const uint idx_before_pre_post, const uint idx_after_post_before_pre,
795                                                     Node* zero_trip_guard_proj_main, Node* zero_trip_guard_proj_post, const Node_List &old_new);
796   void copy_skeleton_predicates_to_main_loop(CountedLoopNode* pre_head, Node* init, Node* stride, IdealLoopTree* outer_loop, LoopNode* outer_main_head,
797                                              uint dd_main_head, const uint idx_before_pre_post, const uint idx_after_post_before_pre,
798                                              Node* zero_trip_guard_proj_main, Node* zero_trip_guard_proj_post, const Node_List &old_new);
799   Node* clone_skeleton_predicate(Node* iff, Node* new_init, Node* new_stride, Node* predicate, Node* uncommon_proj,
800                                  Node* current_proj, IdealLoopTree* outer_loop, Node* prev_proj);
801   bool skeleton_predicate_has_opaque(IfNode* iff);
802   void update_main_loop_skeleton_predicates(Node* ctrl, CountedLoopNode* loop_head, Node* init, int stride_con);
803   void insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol);
804 
805 public:
806 
igvn() const807   PhaseIterGVN &igvn() const { return _igvn; }
808 
809   static bool is_canonical_loop_entry(CountedLoopNode* cl);
810 
has_node(Node * n) const811   bool has_node( Node* n ) const {
812     guarantee(n != NULL, "No Node.");
813     return _nodes[n->_idx] != NULL;
814   }
815   // check if transform created new nodes that need _ctrl recorded
816   Node *get_late_ctrl( Node *n, Node *early );
817   Node *get_early_ctrl( Node *n );
818   Node *get_early_ctrl_for_expensive(Node *n, Node* earliest);
819   void set_early_ctrl( Node *n );
820   void set_subtree_ctrl( Node *root );
set_ctrl(Node * n,Node * ctrl)821   void set_ctrl( Node *n, Node *ctrl ) {
822     assert( !has_node(n) || has_ctrl(n), "" );
823     assert( ctrl->in(0), "cannot set dead control node" );
824     assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" );
825     _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) );
826   }
827   // Set control and update loop membership
set_ctrl_and_loop(Node * n,Node * ctrl)828   void set_ctrl_and_loop(Node* n, Node* ctrl) {
829     IdealLoopTree* old_loop = get_loop(get_ctrl(n));
830     IdealLoopTree* new_loop = get_loop(ctrl);
831     if (old_loop != new_loop) {
832       if (old_loop->_child == NULL) old_loop->_body.yank(n);
833       if (new_loop->_child == NULL) new_loop->_body.push(n);
834     }
835     set_ctrl(n, ctrl);
836   }
837   // Control nodes can be replaced or subsumed.  During this pass they
838   // get their replacement Node in slot 1.  Instead of updating the block
839   // location of all Nodes in the subsumed block, we lazily do it.  As we
840   // pull such a subsumed block out of the array, we write back the final
841   // correct block.
get_ctrl(Node * i)842   Node *get_ctrl( Node *i ) {
843 
844     assert(has_node(i), "");
845     Node *n = get_ctrl_no_update(i);
846     _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) );
847     assert(has_node(i) && has_ctrl(i), "");
848     assert(n == find_non_split_ctrl(n), "must return legal ctrl" );
849     return n;
850   }
851   // true if CFG node d dominates CFG node n
852   bool is_dominator(Node *d, Node *n);
853   // return get_ctrl for a data node and self(n) for a CFG node
ctrl_or_self(Node * n)854   Node* ctrl_or_self(Node* n) {
855     if (has_ctrl(n))
856       return get_ctrl(n);
857     else {
858       assert (n->is_CFG(), "must be a CFG node");
859       return n;
860     }
861   }
862 
get_ctrl_no_update_helper(Node * i) const863   Node *get_ctrl_no_update_helper(Node *i) const {
864     assert(has_ctrl(i), "should be control, not loop");
865     return (Node*)(((intptr_t)_nodes[i->_idx]) & ~1);
866   }
867 
get_ctrl_no_update(Node * i) const868   Node *get_ctrl_no_update(Node *i) const {
869     assert( has_ctrl(i), "" );
870     Node *n = get_ctrl_no_update_helper(i);
871     if (!n->in(0)) {
872       // Skip dead CFG nodes
873       do {
874         n = get_ctrl_no_update_helper(n);
875       } while (!n->in(0));
876       n = find_non_split_ctrl(n);
877     }
878     return n;
879   }
880 
881   // Check for loop being set
882   // "n" must be a control node. Returns true if "n" is known to be in a loop.
has_loop(Node * n) const883   bool has_loop( Node *n ) const {
884     assert(!has_node(n) || !has_ctrl(n), "");
885     return has_node(n);
886   }
887   // Set loop
set_loop(Node * n,IdealLoopTree * loop)888   void set_loop( Node *n, IdealLoopTree *loop ) {
889     _nodes.map(n->_idx, (Node*)loop);
890   }
891   // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms.  Replace
892   // the 'old_node' with 'new_node'.  Kill old-node.  Add a reference
893   // from old_node to new_node to support the lazy update.  Reference
894   // replaces loop reference, since that is not needed for dead node.
lazy_update(Node * old_node,Node * new_node)895   void lazy_update(Node *old_node, Node *new_node) {
896     assert(old_node != new_node, "no cycles please");
897     // Re-use the side array slot for this node to provide the
898     // forwarding pointer.
899     _nodes.map(old_node->_idx, (Node*)((intptr_t)new_node + 1));
900   }
lazy_replace(Node * old_node,Node * new_node)901   void lazy_replace(Node *old_node, Node *new_node) {
902     _igvn.replace_node(old_node, new_node);
903     lazy_update(old_node, new_node);
904   }
905 
906 private:
907 
908   // Place 'n' in some loop nest, where 'n' is a CFG node
909   void build_loop_tree();
910   int build_loop_tree_impl( Node *n, int pre_order );
911   // Insert loop into the existing loop tree.  'innermost' is a leaf of the
912   // loop tree, not the root.
913   IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost );
914 
915   // Place Data nodes in some loop nest
916   void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
917   void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
918   void build_loop_late_post_work(Node* n, bool pinned);
919   void build_loop_late_post(Node* n);
920   void verify_strip_mined_scheduling(Node *n, Node* least);
921 
922   // Array of immediate dominance info for each CFG node indexed by node idx
923 private:
924   uint _idom_size;
925   Node **_idom;                  // Array of immediate dominators
926   uint *_dom_depth;              // Used for fast LCA test
927   GrowableArray<uint>* _dom_stk; // For recomputation of dom depth
928 
929   // Perform verification that the graph is valid.
PhaseIdealLoop(PhaseIterGVN & igvn)930   PhaseIdealLoop( PhaseIterGVN &igvn) :
931     PhaseTransform(Ideal_Loop),
932     _igvn(igvn),
933     _verify_me(NULL),
934     _verify_only(true),
935     _dom_lca_tags(arena()),  // Thread::resource_area
936     _nodes_required(UINT_MAX) {
937     build_and_optimize(LoopOptsVerify);
938   }
939 
940   // build the loop tree and perform any requested optimizations
941   void build_and_optimize(LoopOptsMode mode);
942 
943   // Dominators for the sea of nodes
944   void Dominators();
945 
946   // Compute the Ideal Node to Loop mapping
PhaseIdealLoop(PhaseIterGVN & igvn,LoopOptsMode mode)947   PhaseIdealLoop(PhaseIterGVN &igvn, LoopOptsMode mode) :
948     PhaseTransform(Ideal_Loop),
949     _igvn(igvn),
950     _verify_me(NULL),
951     _verify_only(false),
952     _dom_lca_tags(arena()),  // Thread::resource_area
953     _nodes_required(UINT_MAX) {
954     build_and_optimize(mode);
955   }
956 
957   // Verify that verify_me made the same decisions as a fresh run.
PhaseIdealLoop(PhaseIterGVN & igvn,const PhaseIdealLoop * verify_me)958   PhaseIdealLoop(PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me) :
959     PhaseTransform(Ideal_Loop),
960     _igvn(igvn),
961     _verify_me(verify_me),
962     _verify_only(false),
963     _dom_lca_tags(arena()),  // Thread::resource_area
964     _nodes_required(UINT_MAX) {
965     build_and_optimize(LoopOptsVerify);
966   }
967 
968 public:
idom_no_update(Node * d) const969   Node* idom_no_update(Node* d) const {
970     return idom_no_update(d->_idx);
971   }
972 
idom_no_update(uint didx) const973   Node* idom_no_update(uint didx) const {
974     assert(didx < _idom_size, "oob");
975     Node* n = _idom[didx];
976     assert(n != NULL,"Bad immediate dominator info.");
977     while (n->in(0) == NULL) { // Skip dead CFG nodes
978       n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
979       assert(n != NULL,"Bad immediate dominator info.");
980     }
981     return n;
982   }
983 
idom(Node * d) const984   Node *idom(Node* d) const {
985     return idom(d->_idx);
986   }
987 
idom(uint didx) const988   Node *idom(uint didx) const {
989     Node *n = idom_no_update(didx);
990     _idom[didx] = n; // Lazily remove dead CFG nodes from table.
991     return n;
992   }
993 
dom_depth(Node * d) const994   uint dom_depth(Node* d) const {
995     guarantee(d != NULL, "Null dominator info.");
996     guarantee(d->_idx < _idom_size, "");
997     return _dom_depth[d->_idx];
998   }
999   void set_idom(Node* d, Node* n, uint dom_depth);
1000   // Locally compute IDOM using dom_lca call
1001   Node *compute_idom( Node *region ) const;
1002   // Recompute dom_depth
1003   void recompute_dom_depth();
1004 
1005   // Is safept not required by an outer loop?
1006   bool is_deleteable_safept(Node* sfpt);
1007 
1008   // Replace parallel induction variable (parallel to trip counter)
1009   void replace_parallel_iv(IdealLoopTree *loop);
1010 
dom_lca(Node * n1,Node * n2) const1011   Node *dom_lca( Node *n1, Node *n2 ) const {
1012     return find_non_split_ctrl(dom_lca_internal(n1, n2));
1013   }
1014   Node *dom_lca_internal( Node *n1, Node *n2 ) const;
1015 
1016   // Build and verify the loop tree without modifying the graph.  This
1017   // is useful to verify that all inputs properly dominate their uses.
verify(PhaseIterGVN & igvn)1018   static void verify(PhaseIterGVN& igvn) {
1019 #ifdef ASSERT
1020     ResourceMark rm;
1021     PhaseIdealLoop v(igvn);
1022 #endif
1023   }
1024 
1025   // Recommended way to use PhaseIdealLoop.
1026   // Run PhaseIdealLoop in some mode and allocates a local scope for memory allocations.
optimize(PhaseIterGVN & igvn,LoopOptsMode mode)1027   static void optimize(PhaseIterGVN &igvn, LoopOptsMode mode) {
1028     ResourceMark rm;
1029     PhaseIdealLoop v(igvn, mode);
1030   }
1031 
1032   // True if the method has at least 1 irreducible loop
1033   bool _has_irreducible_loops;
1034 
1035   // Per-Node transform
transform(Node * n)1036   virtual Node* transform(Node* n) { return NULL; }
1037 
1038   Node* loop_exit_control(Node* x, IdealLoopTree* loop);
1039   Node* loop_exit_test(Node* back_control, IdealLoopTree* loop, Node*& incr, Node*& limit, BoolTest::mask& bt, float& cl_prob);
1040   Node* loop_iv_incr(Node* incr, Node* x, IdealLoopTree* loop, Node*& phi_incr);
1041   Node* loop_iv_stride(Node* incr, IdealLoopTree* loop, Node*& xphi);
1042   PhiNode* loop_iv_phi(Node* xphi, Node* phi_incr, Node* x, IdealLoopTree* loop);
1043 
1044   bool is_counted_loop(Node* n, IdealLoopTree* &loop);
1045   IdealLoopTree* insert_outer_loop(IdealLoopTree* loop, LoopNode* outer_l, Node* outer_ift);
1046   IdealLoopTree* create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
1047                                                IdealLoopTree* loop, float cl_prob, float le_fcnt,
1048                                                Node*& entry_control, Node*& iffalse);
1049 
1050   Node* exact_limit( IdealLoopTree *loop );
1051 
1052   // Return a post-walked LoopNode
get_loop(Node * n) const1053   IdealLoopTree *get_loop( Node *n ) const {
1054     // Dead nodes have no loop, so return the top level loop instead
1055     if (!has_node(n))  return _ltree_root;
1056     assert(!has_ctrl(n), "");
1057     return (IdealLoopTree*)_nodes[n->_idx];
1058   }
1059 
ltree_root() const1060   IdealLoopTree* ltree_root() const { return _ltree_root; }
1061 
1062   // Is 'n' a (nested) member of 'loop'?
is_member(const IdealLoopTree * loop,Node * n) const1063   int is_member( const IdealLoopTree *loop, Node *n ) const {
1064     return loop->is_member(get_loop(n)); }
1065 
1066   // This is the basic building block of the loop optimizations.  It clones an
1067   // entire loop body.  It makes an old_new loop body mapping; with this
1068   // mapping you can find the new-loop equivalent to an old-loop node.  All
1069   // new-loop nodes are exactly equal to their old-loop counterparts, all
1070   // edges are the same.  All exits from the old-loop now have a RegionNode
1071   // that merges the equivalent new-loop path.  This is true even for the
1072   // normal "loop-exit" condition.  All uses of loop-invariant old-loop values
1073   // now come from (one or more) Phis that merge their new-loop equivalents.
1074   // Parameter side_by_side_idom:
1075   //   When side_by_size_idom is NULL, the dominator tree is constructed for
1076   //      the clone loop to dominate the original.  Used in construction of
1077   //      pre-main-post loop sequence.
1078   //   When nonnull, the clone and original are side-by-side, both are
1079   //      dominated by the passed in side_by_side_idom node.  Used in
1080   //      construction of unswitched loops.
1081   enum CloneLoopMode {
1082     IgnoreStripMined = 0,        // Only clone inner strip mined loop
1083     CloneIncludesStripMined = 1, // clone both inner and outer strip mined loops
1084     ControlAroundStripMined = 2  // Only clone inner strip mined loop,
1085                                  // result control flow branches
1086                                  // either to inner clone or outer
1087                                  // strip mined loop.
1088   };
1089   void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
1090                   CloneLoopMode mode, Node* side_by_side_idom = NULL);
1091   void clone_loop_handle_data_uses(Node* old, Node_List &old_new,
1092                                    IdealLoopTree* loop, IdealLoopTree* companion_loop,
1093                                    Node_List*& split_if_set, Node_List*& split_bool_set,
1094                                    Node_List*& split_cex_set, Node_List& worklist,
1095                                    uint new_counter, CloneLoopMode mode);
1096   void clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
1097                         IdealLoopTree* outer_loop, int dd, Node_List &old_new,
1098                         Node_List& extra_data_nodes);
1099 
1100   // If we got the effect of peeling, either by actually peeling or by
1101   // making a pre-loop which must execute at least once, we can remove
1102   // all loop-invariant dominated tests in the main body.
1103   void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new );
1104 
1105   // Generate code to do a loop peel for the given loop (and body).
1106   // old_new is a temp array.
1107   void do_peeling( IdealLoopTree *loop, Node_List &old_new );
1108 
1109   // Add pre and post loops around the given loop.  These loops are used
1110   // during RCE, unrolling and aligning loops.
1111   void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only );
1112 
1113   // Add post loop after the given loop.
1114   Node *insert_post_loop(IdealLoopTree *loop, Node_List &old_new,
1115                          CountedLoopNode *main_head, CountedLoopEndNode *main_end,
1116                          Node *incr, Node *limit, CountedLoopNode *&post_head);
1117 
1118   // Add an RCE'd post loop which we will multi-version adapt for run time test path usage
1119   void insert_scalar_rced_post_loop( IdealLoopTree *loop, Node_List &old_new );
1120 
1121   // Add a vector post loop between a vector main loop and the current post loop
1122   void insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new);
1123   // If Node n lives in the back_ctrl block, we clone a private version of n
1124   // in preheader_ctrl block and return that, otherwise return n.
1125   Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones );
1126 
1127   // Take steps to maximally unroll the loop.  Peel any odd iterations, then
1128   // unroll to do double iterations.  The next round of major loop transforms
1129   // will repeat till the doubled loop body does all remaining iterations in 1
1130   // pass.
1131   void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new );
1132 
1133   // Unroll the loop body one step - make each trip do 2 iterations.
1134   void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip );
1135 
1136   // Mark vector reduction candidates before loop unrolling
1137   void mark_reductions( IdealLoopTree *loop );
1138 
1139   // Return true if exp is a constant times an induction var
1140   bool is_scaled_iv(Node* exp, Node* iv, int* p_scale);
1141 
1142   // Return true if exp is a scaled induction var plus (or minus) constant
1143   bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0);
1144 
1145   // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted
1146   ProjNode* create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry, Deoptimization::DeoptReason reason,
1147                                         int opcode, bool if_cont_is_true_proj = true);
1148 
1149   void register_control(Node* n, IdealLoopTree *loop, Node* pred, bool update_body = true);
1150 
1151   static Node* skip_all_loop_predicates(Node* entry);
1152   static Node* skip_loop_predicates(Node* entry);
1153 
1154   // Find a good location to insert a predicate
1155   static ProjNode* find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason);
1156   // Find a predicate
1157   static Node* find_predicate(Node* entry);
1158   // Construct a range check for a predicate if
1159   BoolNode* rc_predicate(IdealLoopTree *loop, Node* ctrl,
1160                          int scale, Node* offset,
1161                          Node* init, Node* limit, jint stride,
1162                          Node* range, bool upper, bool &overflow);
1163 
1164   // Implementation of the loop predication to promote checks outside the loop
1165   bool loop_predication_impl(IdealLoopTree *loop);
1166   bool loop_predication_impl_helper(IdealLoopTree *loop, ProjNode* proj, ProjNode *predicate_proj,
1167                                     CountedLoopNode *cl, ConNode* zero, Invariance& invar,
1168                                     Deoptimization::DeoptReason reason);
1169   bool loop_predication_should_follow_branches(IdealLoopTree *loop, ProjNode *predicate_proj, float& loop_trip_cnt);
1170   void loop_predication_follow_branches(Node *c, IdealLoopTree *loop, float loop_trip_cnt,
1171                                         PathFrequency& pf, Node_Stack& stack, VectorSet& seen,
1172                                         Node_List& if_proj_list);
1173   ProjNode* insert_initial_skeleton_predicate(IfNode* iff, IdealLoopTree *loop,
1174                                               ProjNode* proj, ProjNode *predicate_proj,
1175                                               ProjNode* upper_bound_proj,
1176                                               int scale, Node* offset,
1177                                               Node* init, Node* limit, jint stride,
1178                                               Node* rng, bool& overflow,
1179                                               Deoptimization::DeoptReason reason);
1180   Node* add_range_check_predicate(IdealLoopTree* loop, CountedLoopNode* cl,
1181                                   Node* predicate_proj, int scale_con, Node* offset,
1182                                   Node* limit, jint stride_con, Node* value);
1183 
1184   // Helper function to collect predicate for eliminating the useless ones
1185   void collect_potentially_useful_predicates(IdealLoopTree *loop, Unique_Node_List &predicate_opaque1);
1186   void eliminate_useless_predicates();
1187 
1188   // Change the control input of expensive nodes to allow commoning by
1189   // IGVN when it is guaranteed to not result in a more frequent
1190   // execution of the expensive node. Return true if progress.
1191   bool process_expensive_nodes();
1192 
1193   // Check whether node has become unreachable
is_node_unreachable(Node * n) const1194   bool is_node_unreachable(Node *n) const {
1195     return !has_node(n) || n->is_unreachable(_igvn);
1196   }
1197 
1198   // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1199   int do_range_check( IdealLoopTree *loop, Node_List &old_new );
1200 
1201   // Check to see if do_range_check(...) cleaned the main loop of range-checks
1202   void has_range_checks(IdealLoopTree *loop);
1203 
1204   // Process post loops which have range checks and try to build a multi-version
1205   // guard to safely determine if we can execute the post loop which was RCE'd.
1206   bool multi_version_post_loops(IdealLoopTree *rce_loop, IdealLoopTree *legacy_loop);
1207 
1208   // Cause the rce'd post loop to optimized away, this happens if we cannot complete multiverioning
1209   void poison_rce_post_loop(IdealLoopTree *rce_loop);
1210 
1211   // Create a slow version of the loop by cloning the loop
1212   // and inserting an if to select fast-slow versions.
1213   ProjNode* create_slow_version_of_loop(IdealLoopTree *loop,
1214                                         Node_List &old_new,
1215                                         int opcode,
1216                                         CloneLoopMode mode);
1217 
1218   // Clone a loop and return the clone head (clone_loop_head).
1219   // Added nodes include int(1), int(0) - disconnected, If, IfTrue, IfFalse,
1220   // This routine was created for usage in CountedLoopReserveKit.
1221   //
1222   //    int(1) -> If -> IfTrue -> original_loop_head
1223   //              |
1224   //              V
1225   //           IfFalse -> clone_loop_head (returned by function pointer)
1226   //
1227   LoopNode* create_reserve_version_of_loop(IdealLoopTree *loop, CountedLoopReserveKit* lk);
1228   // Clone loop with an invariant test (that does not exit) and
1229   // insert a clone of the test that selects which version to
1230   // execute.
1231   void do_unswitching (IdealLoopTree *loop, Node_List &old_new);
1232 
1233   // Find candidate "if" for unswitching
1234   IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const;
1235 
1236   // Range Check Elimination uses this function!
1237   // Constrain the main loop iterations so the affine function:
1238   //    low_limit <= scale_con * I + offset  <  upper_limit
1239   // always holds true.  That is, either increase the number of iterations in
1240   // the pre-loop or the post-loop until the condition holds true in the main
1241   // loop.  Scale_con, offset and limit are all loop invariant.
1242   void add_constraint(jlong stride_con, jlong scale_con, Node* offset, Node* low_limit, Node* upper_limit, Node* pre_ctrl, Node** pre_limit, Node** main_limit);
1243   // Helper function for add_constraint().
1244   Node* adjust_limit(bool reduce, Node* scale, Node* offset, Node* rc_limit, Node* old_limit, Node* pre_ctrl, bool round);
1245 
1246   // Partially peel loop up through last_peel node.
1247   bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
1248 
1249   // Create a scheduled list of nodes control dependent on ctrl set.
1250   void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched );
1251   // Has a use in the vector set
1252   bool has_use_in_set( Node* n, VectorSet& vset );
1253   // Has use internal to the vector set (ie. not in a phi at the loop head)
1254   bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop );
1255   // clone "n" for uses that are outside of loop
1256   int  clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist );
1257   // clone "n" for special uses that are in the not_peeled region
1258   void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
1259                                           VectorSet& not_peel, Node_List& sink_list, Node_List& worklist );
1260   // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
1261   void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp );
1262 #ifdef ASSERT
1263   // Validate the loop partition sets: peel and not_peel
1264   bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel );
1265   // Ensure that uses outside of loop are of the right form
1266   bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
1267                                  uint orig_exit_idx, uint clone_exit_idx);
1268   bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx);
1269 #endif
1270 
1271   // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.)
1272   int stride_of_possible_iv( Node* iff );
is_possible_iv_test(Node * iff)1273   bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; }
1274   // Return the (unique) control output node that's in the loop (if it exists.)
1275   Node* stay_in_loop( Node* n, IdealLoopTree *loop);
1276   // Insert a signed compare loop exit cloned from an unsigned compare.
1277   IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop);
1278   void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop);
1279   // Utility to register node "n" with PhaseIdealLoop
1280   void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth);
1281   // Utility to create an if-projection
1282   ProjNode* proj_clone(ProjNode* p, IfNode* iff);
1283   // Force the iff control output to be the live_proj
1284   Node* short_circuit_if(IfNode* iff, ProjNode* live_proj);
1285   // Insert a region before an if projection
1286   RegionNode* insert_region_before_proj(ProjNode* proj);
1287   // Insert a new if before an if projection
1288   ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj);
1289 
1290   // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
1291   // "Nearly" because all Nodes have been cloned from the original in the loop,
1292   // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
1293   // through the Phi recursively, and return a Bool.
1294   Node *clone_iff( PhiNode *phi, IdealLoopTree *loop );
1295   CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop );
1296 
1297 
1298   // Rework addressing expressions to get the most loop-invariant stuff
1299   // moved out.  We'd like to do all associative operators, but it's especially
1300   // important (common) to do address expressions.
1301   Node *remix_address_expressions( Node *n );
1302 
1303   // Convert add to muladd to generate MuladdS2I under certain criteria
1304   Node * convert_add_to_muladd(Node * n);
1305 
1306   // Attempt to use a conditional move instead of a phi/branch
1307   Node *conditional_move( Node *n );
1308 
1309   // Reorganize offset computations to lower register pressure.
1310   // Mostly prevent loop-fallout uses of the pre-incremented trip counter
1311   // (which are then alive with the post-incremented trip counter
1312   // forcing an extra register move)
1313   void reorg_offsets( IdealLoopTree *loop );
1314 
1315   // Check for aggressive application of 'split-if' optimization,
1316   // using basic block level info.
1317   void  split_if_with_blocks     ( VectorSet &visited, Node_Stack &nstack);
1318   Node *split_if_with_blocks_pre ( Node *n );
1319   void  split_if_with_blocks_post( Node *n );
1320   Node *has_local_phi_input( Node *n );
1321   // Mark an IfNode as being dominated by a prior test,
1322   // without actually altering the CFG (and hence IDOM info).
1323   void dominated_by( Node *prevdom, Node *iff, bool flip = false, bool exclude_loop_predicate = false );
1324 
1325   // Split Node 'n' through merge point
1326   Node *split_thru_region( Node *n, Node *region );
1327   // Split Node 'n' through merge point if there is enough win.
1328   Node *split_thru_phi( Node *n, Node *region, int policy );
1329   // Found an If getting its condition-code input from a Phi in the
1330   // same block.  Split thru the Region.
1331   void do_split_if( Node *iff );
1332 
1333   // Conversion of fill/copy patterns into intrinsic versions
1334   bool do_intrinsify_fill();
1335   bool intrinsify_fill(IdealLoopTree* lpt);
1336   bool match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
1337                        Node*& shift, Node*& offset);
1338 
1339 private:
1340   // Return a type based on condition control flow
1341   const TypeInt* filtered_type( Node *n, Node* n_ctrl);
filtered_type(Node * n)1342   const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); }
1343  // Helpers for filtered type
1344   const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl);
1345 
1346   // Helper functions
1347   Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache );
1348   Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true );
1349   void handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true );
1350   bool split_up( Node *n, Node *blk1, Node *blk2 );
1351   void sink_use( Node *use, Node *post_loop );
1352   Node *place_near_use( Node *useblock ) const;
1353   Node* try_move_store_before_loop(Node* n, Node *n_ctrl);
1354   void try_move_store_after_loop(Node* n);
1355   bool identical_backtoback_ifs(Node *n);
1356   bool can_split_if(Node *n_ctrl);
1357 
1358   // Determine if a method is too big for a/another round of split-if, based on
1359   // a magic (approximate) ratio derived from the equally magic constant 35000,
1360   // previously used for this purpose (but without relating to the node limit).
must_throttle_split_if()1361   bool must_throttle_split_if() {
1362     uint threshold = C->max_node_limit() * 2 / 5;
1363     return C->live_nodes() > threshold;
1364   }
1365 
1366   // A simplistic node request tracking mechanism, where
1367   //   = UINT_MAX   Request not valid or made final.
1368   //   < UINT_MAX   Nodes currently requested (estimate).
1369   uint _nodes_required;
1370 
1371   enum { REQUIRE_MIN = 70 };
1372 
nodes_required() const1373   uint nodes_required() const { return _nodes_required; }
1374 
1375   // Given the _currently_  available number of nodes, check  whether there is
1376   // "room" for an additional request or not, considering the already required
1377   // number of  nodes.  Return TRUE if  the new request is  exceeding the node
1378   // budget limit, otherwise return FALSE.  Note that this interpretation will
1379   // act pessimistic on  additional requests when new nodes  have already been
1380   // generated since the 'begin'.  This behaviour fits with the intention that
1381   // node estimates/requests should be made upfront.
exceeding_node_budget(uint required=0)1382   bool exceeding_node_budget(uint required = 0) {
1383     assert(C->live_nodes() < C->max_node_limit(), "sanity");
1384     uint available = C->max_node_limit() - C->live_nodes();
1385     return available < required + _nodes_required + REQUIRE_MIN;
1386   }
1387 
require_nodes(uint require,uint minreq=REQUIRE_MIN)1388   uint require_nodes(uint require, uint minreq = REQUIRE_MIN) {
1389     precond(require > 0);
1390     _nodes_required += MAX2(require, minreq);
1391     return _nodes_required;
1392   }
1393 
may_require_nodes(uint require,uint minreq=REQUIRE_MIN)1394   bool may_require_nodes(uint require, uint minreq = REQUIRE_MIN) {
1395     return !exceeding_node_budget(require) && require_nodes(require, minreq) > 0;
1396   }
1397 
require_nodes_begin()1398   uint require_nodes_begin() {
1399     assert(_nodes_required == UINT_MAX, "Bad state (begin).");
1400     _nodes_required = 0;
1401     return C->live_nodes();
1402   }
1403 
1404   // When a node request is final,  optionally check that the requested number
1405   // of nodes was  reasonably correct with respect to the  number of new nodes
1406   // introduced since the last 'begin'. Always check that we have not exceeded
1407   // the maximum node limit.
require_nodes_final(uint live_at_begin,bool check_estimate)1408   void require_nodes_final(uint live_at_begin, bool check_estimate) {
1409     assert(_nodes_required < UINT_MAX, "Bad state (final).");
1410 
1411 #ifdef ASSERT
1412     if (check_estimate) {
1413       // Check that the node budget request was not off by too much (x2).
1414       // Should this be the case we _surely_ need to improve the estimates
1415       // used in our budget calculations.
1416       if (C->live_nodes() - live_at_begin > 2 * _nodes_required) {
1417         log_info(compilation)("Bad node estimate: actual = %d >> request = %d",
1418                               C->live_nodes() - live_at_begin, _nodes_required);
1419       }
1420     }
1421 #endif
1422     // Assert that we have stayed within the node budget limit.
1423     assert(C->live_nodes() < C->max_node_limit(),
1424            "Exceeding node budget limit: %d + %d > %d (request = %d)",
1425            C->live_nodes() - live_at_begin, live_at_begin,
1426            C->max_node_limit(), _nodes_required);
1427 
1428     _nodes_required = UINT_MAX;
1429   }
1430 
1431   // Clone loop predicates to slow and fast loop when unswitching a loop
1432   Node* clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check, bool is_slow_loop,
1433                               uint idx_before_clone, Node_List &old_new);
1434   ProjNode* clone_loop_predicate(ProjNode* predicate_proj, Node* new_entry, Deoptimization::DeoptReason reason,
1435                                  bool is_slow_loop, uint idx_before_clone, Node_List &old_new);
1436   void clone_concrete_loop_predicates(Deoptimization::DeoptReason reason, ProjNode* old_predicate_proj,
1437                                       ProjNode* new_predicate_proj, bool is_slow_loop,
1438                                       uint idx_before_clone, Node_List &old_new);
1439 
1440   bool _created_loop_node;
1441 
1442 public:
set_created_loop_node()1443   void set_created_loop_node() { _created_loop_node = true; }
created_loop_node()1444   bool created_loop_node()     { return _created_loop_node; }
1445   void register_new_node(Node* n, Node* blk);
1446 
1447 #ifdef ASSERT
1448   void dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA);
1449 #endif
1450 
1451 #ifndef PRODUCT
1452   void dump() const;
1453   void dump(IdealLoopTree* loop, uint rpo_idx, Node_List &rpo_list) const;
1454   void verify() const;          // Major slow  :-)
1455   void verify_compare(Node* n, const PhaseIdealLoop* loop_verify, VectorSet &visited) const;
get_loop_idx(Node * n) const1456   IdealLoopTree* get_loop_idx(Node* n) const {
1457     // Dead nodes have no loop, so return the top level loop instead
1458     return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root;
1459   }
1460   // Print some stats
1461   static void print_statistics();
1462   static int _loop_invokes;     // Count of PhaseIdealLoop invokes
1463   static int _loop_work;        // Sum of PhaseIdealLoop x _unique
1464 #endif
1465 
1466   void rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const;
1467 };
1468 
1469 
1470 class AutoNodeBudget : public StackObj
1471 {
1472 public:
1473   enum budget_check_t { BUDGET_CHECK, NO_BUDGET_CHECK };
1474 
AutoNodeBudget(PhaseIdealLoop * phase,budget_check_t chk=BUDGET_CHECK)1475   AutoNodeBudget(PhaseIdealLoop* phase, budget_check_t chk = BUDGET_CHECK)
1476     : _phase(phase),
1477       _check_at_final(chk == BUDGET_CHECK),
1478       _nodes_at_begin(0)
1479   {
1480     precond(_phase != NULL);
1481 
1482     _nodes_at_begin = _phase->require_nodes_begin();
1483   }
1484 
~AutoNodeBudget()1485   ~AutoNodeBudget() {
1486 #ifndef PRODUCT
1487     if (TraceLoopOpts) {
1488       uint request = _phase->nodes_required();
1489       uint delta   = _phase->C->live_nodes() - _nodes_at_begin;
1490 
1491       if (request < delta) {
1492         tty->print_cr("Exceeding node budget: %d < %d", request, delta);
1493       } else {
1494         uint const REQUIRE_MIN = PhaseIdealLoop::REQUIRE_MIN;
1495         // Identify the worst estimates as "poor" ones.
1496         if (request > REQUIRE_MIN && delta > 0) {
1497           if ((delta >  REQUIRE_MIN && request >  3 * delta) ||
1498               (delta <= REQUIRE_MIN && request > 10 * delta)) {
1499             tty->print_cr("Poor node estimate: %d >> %d", request, delta);
1500           }
1501         }
1502       }
1503     }
1504 #endif // PRODUCT
1505     _phase->require_nodes_final(_nodes_at_begin, _check_at_final);
1506   }
1507 
1508 private:
1509   PhaseIdealLoop* _phase;
1510   bool _check_at_final;
1511   uint _nodes_at_begin;
1512 };
1513 
1514 
1515 // This kit may be used for making of a reserved copy of a loop before this loop
1516 //  goes under non-reversible changes.
1517 //
1518 // Function create_reserve() creates a reserved copy (clone) of the loop.
1519 // The reserved copy is created by calling
1520 // PhaseIdealLoop::create_reserve_version_of_loop - see there how
1521 // the original and reserved loops are connected in the outer graph.
1522 // If create_reserve succeeded, it returns 'true' and _has_reserved is set to 'true'.
1523 //
1524 // By default the reserved copy (clone) of the loop is created as dead code - it is
1525 // dominated in the outer loop by this node chain:
1526 //   intcon(1)->If->IfFalse->reserved_copy.
1527 // The original loop is dominated by the the same node chain but IfTrue projection:
1528 //   intcon(0)->If->IfTrue->original_loop.
1529 //
1530 // In this implementation of CountedLoopReserveKit the ctor includes create_reserve()
1531 // and the dtor, checks _use_new value.
1532 // If _use_new == false, it "switches" control to reserved copy of the loop
1533 // by simple replacing of node intcon(1) with node intcon(0).
1534 //
1535 // Here is a proposed example of usage (see also SuperWord::output in superword.cpp).
1536 //
1537 // void CountedLoopReserveKit_example()
1538 // {
1539 //    CountedLoopReserveKit lrk((phase, lpt, DoReserveCopy = true); // create local object
1540 //    if (DoReserveCopy && !lrk.has_reserved()) {
1541 //      return; //failed to create reserved loop copy
1542 //    }
1543 //    ...
1544 //    //something is wrong, switch to original loop
1545 ///   if(something_is_wrong) return; // ~CountedLoopReserveKit makes the switch
1546 //    ...
1547 //    //everything worked ok, return with the newly modified loop
1548 //    lrk.use_new();
1549 //    return; // ~CountedLoopReserveKit does nothing once use_new() was called
1550 //  }
1551 //
1552 // Keep in mind, that by default if create_reserve() is not followed by use_new()
1553 // the dtor will "switch to the original" loop.
1554 // NOTE. You you modify outside of the original loop this class is no help.
1555 //
1556 class CountedLoopReserveKit {
1557   private:
1558     PhaseIdealLoop* _phase;
1559     IdealLoopTree*  _lpt;
1560     LoopNode*       _lp;
1561     IfNode*         _iff;
1562     LoopNode*       _lp_reserved;
1563     bool            _has_reserved;
1564     bool            _use_new;
1565     const bool      _active; //may be set to false in ctor, then the object is dummy
1566 
1567   public:
1568     CountedLoopReserveKit(PhaseIdealLoop* phase, IdealLoopTree *loop, bool active);
1569     ~CountedLoopReserveKit();
use_new()1570     void use_new()                {_use_new = true;}
set_iff(IfNode * x)1571     void set_iff(IfNode* x)       {_iff = x;}
has_reserved() const1572     bool has_reserved()     const { return _active && _has_reserved;}
1573   private:
1574     bool create_reserve();
1575 };// class CountedLoopReserveKit
1576 
tail()1577 inline Node* IdealLoopTree::tail() {
1578   // Handle lazy update of _tail field.
1579   if (_tail->in(0) == NULL) {
1580     _tail = _phase->get_ctrl(_tail);
1581   }
1582   return _tail;
1583 }
1584 
head()1585 inline Node* IdealLoopTree::head() {
1586   // Handle lazy update of _head field.
1587   if (_head->in(0) == NULL) {
1588     _head = _phase->get_ctrl(_head);
1589   }
1590   return _head;
1591 }
1592 
1593 // Iterate over the loop tree using a preorder, left-to-right traversal.
1594 //
1595 // Example that visits all counted loops from within PhaseIdealLoop
1596 //
1597 //  for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
1598 //   IdealLoopTree* lpt = iter.current();
1599 //   if (!lpt->is_counted()) continue;
1600 //   ...
1601 class LoopTreeIterator : public StackObj {
1602 private:
1603   IdealLoopTree* _root;
1604   IdealLoopTree* _curnt;
1605 
1606 public:
LoopTreeIterator(IdealLoopTree * root)1607   LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {}
1608 
done()1609   bool done() { return _curnt == NULL; }       // Finished iterating?
1610 
1611   void next();                                 // Advance to next loop tree
1612 
current()1613   IdealLoopTree* current() { return _curnt; }  // Return current value of iterator.
1614 };
1615 
1616 #endif // SHARE_OPTO_LOOPNODE_HPP
1617