1 /*
   2  * Copyright (c) 1998, 2022, 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_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 BaseCountedLoopEndNode;
  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.
  59   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    = 1<<2,
  65          HasExactTripCount   = 1<<3,
  66          InnerLoop           = 1<<4,
  67          PartialPeelLoop     = 1<<5,
  68          PartialPeelFailed   = 1<<6,
  69          HasReductions       = 1<<7,
  70          WasSlpAnalyzed      = 1<<8,
  71          PassedSlpAnalysis   = 1<<9,
  72          DoUnrollOnly        = 1<<10,
  73          VectorizedLoop      = 1<<11,
  74          HasAtomicPostLoop   = 1<<12,
  75          HasRangeChecks      = 1<<13,
  76          IsMultiversioned    = 1<<14,
  77          StripMined          = 1<<15,
  78          SubwordLoop         = 1<<16,
  79          ProfileTripFailed   = 1<<17,
  80          LoopNestInnerLoop = 1 << 18,
  81          LoopNestLongOuterLoop = 1 << 19};
  82   char _unswitch_count;
  83   enum { _unswitch_max=3 };
  84   char _postloop_flags;
  85   enum { LoopNotRCEChecked = 0, LoopRCEChecked = 1, RCEPostLoop = 2 };
  86 
  87   // Expected trip count from profile data
  88   float _profile_trip_cnt;
  89 
  90 public:
  91   // Names for edge indices
  92   enum { Self=0, EntryControl, LoopBackControl };
  93 
  94   bool is_inner_loop() const { return _loop_flags & InnerLoop; }
  95   void set_inner_loop() { _loop_flags |= InnerLoop; }
  96 
  97   bool range_checks_present() const { return _loop_flags & HasRangeChecks; }
  98   bool is_multiversioned() const { return _loop_flags & IsMultiversioned; }
  99   bool is_vectorized_loop() const { return _loop_flags & VectorizedLoop; }
 100   bool is_partial_peel_loop() const { return _loop_flags & PartialPeelLoop; }
 101   void set_partial_peel_loop() { _loop_flags |= PartialPeelLoop; }
 102   bool partial_peel_has_failed() const { return _loop_flags & PartialPeelFailed; }
 103   bool is_strip_mined() const { return _loop_flags & StripMined; }
 104   bool is_profile_trip_failed() const { return _loop_flags & ProfileTripFailed; }
 105   bool is_subword_loop() const { return _loop_flags & SubwordLoop; }
 106   bool is_loop_nest_inner_loop() const { return _loop_flags & LoopNestInnerLoop; }
 107   bool is_loop_nest_outer_loop() const { return _loop_flags & LoopNestLongOuterLoop; }
 108 
 109   void mark_partial_peel_failed() { _loop_flags |= PartialPeelFailed; }
 110   void mark_has_reductions() { _loop_flags |= HasReductions; }
 111   void mark_was_slp() { _loop_flags |= WasSlpAnalyzed; }
 112   void mark_passed_slp() { _loop_flags |= PassedSlpAnalysis; }
 113   void mark_do_unroll_only() { _loop_flags |= DoUnrollOnly; }
 114   void mark_loop_vectorized() { _loop_flags |= VectorizedLoop; }
 115   void mark_has_atomic_post_loop() { _loop_flags |= HasAtomicPostLoop; }
 116   void mark_has_range_checks() { _loop_flags |=  HasRangeChecks; }
 117   void clear_has_range_checks() { _loop_flags &= ~HasRangeChecks; }
 118   void mark_is_multiversioned() { _loop_flags |= IsMultiversioned; }
 119   void mark_strip_mined() { _loop_flags |= StripMined; }
 120   void clear_strip_mined() { _loop_flags &= ~StripMined; }
 121   void mark_profile_trip_failed() { _loop_flags |= ProfileTripFailed; }
 122   void mark_subword_loop() { _loop_flags |= SubwordLoop; }
 123   void mark_loop_nest_inner_loop() { _loop_flags |= LoopNestInnerLoop; }
 124   void mark_loop_nest_outer_loop() { _loop_flags |= LoopNestLongOuterLoop; }
 125 
 126   int unswitch_max() { return _unswitch_max; }
 127   int unswitch_count() { return _unswitch_count; }
 128 
 129   int has_been_range_checked() const { return _postloop_flags & LoopRCEChecked; }
 130   void set_has_been_range_checked() { _postloop_flags |= LoopRCEChecked; }
 131   int is_rce_post_loop() const { return _postloop_flags & RCEPostLoop; }
 132   void set_is_rce_post_loop() { _postloop_flags |= RCEPostLoop; }
 133 
 134   void set_unswitch_count(int val) {
 135     assert (val <= unswitch_max(), "too many unswitches");
 136     _unswitch_count = val;
 137   }
 138 
 139   void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
 140   float profile_trip_cnt()             { return _profile_trip_cnt; }
 141 
 142   LoopNode(Node *entry, Node *backedge)
 143     : RegionNode(3), _loop_flags(0), _unswitch_count(0),
 144       _postloop_flags(0), _profile_trip_cnt(COUNT_UNKNOWN)  {
 145     init_class_id(Class_Loop);
 146     init_req(EntryControl, entry);
 147     init_req(LoopBackControl, backedge);
 148   }
 149 
 150   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 151   virtual int Opcode() const;
 152   bool can_be_counted_loop(PhaseTransform* phase) const {
 153     return req() == 3 && in(0) != NULL &&
 154       in(1) != NULL && phase->type(in(1)) != Type::TOP &&
 155       in(2) != NULL && phase->type(in(2)) != Type::TOP;
 156   }
 157   bool is_valid_counted_loop(BasicType bt) const;
 158 #ifndef PRODUCT
 159   virtual void dump_spec(outputStream *st) const;
 160 #endif
 161 
 162   void verify_strip_mined(int expect_skeleton) const NOT_DEBUG_RETURN;
 163   virtual LoopNode* skip_strip_mined(int expect_skeleton = 1) { return this; }
 164   virtual IfTrueNode* outer_loop_tail() const { ShouldNotReachHere(); return NULL; }
 165   virtual OuterStripMinedLoopEndNode* outer_loop_end() const { ShouldNotReachHere(); return NULL; }
 166   virtual IfFalseNode* outer_loop_exit() const { ShouldNotReachHere(); return NULL; }
 167   virtual SafePointNode* outer_safepoint() const { ShouldNotReachHere(); return NULL; }
 168 };
 169 
 170 //------------------------------Counted Loops----------------------------------
 171 // Counted loops are all trip-counted loops, with exactly 1 trip-counter exit
 172 // path (and maybe some other exit paths).  The trip-counter exit is always
 173 // last in the loop.  The trip-counter have to stride by a constant;
 174 // the exit value is also loop invariant.
 175 
 176 // CountedLoopNodes and CountedLoopEndNodes come in matched pairs.  The
 177 // CountedLoopNode has the incoming loop control and the loop-back-control
 178 // which is always the IfTrue before the matching CountedLoopEndNode.  The
 179 // CountedLoopEndNode has an incoming control (possibly not the
 180 // CountedLoopNode if there is control flow in the loop), the post-increment
 181 // trip-counter value, and the limit.  The trip-counter value is always of
 182 // the form (Op old-trip-counter stride).  The old-trip-counter is produced
 183 // by a Phi connected to the CountedLoopNode.  The stride is constant.
 184 // The Op is any commutable opcode, including Add, Mul, Xor.  The
 185 // CountedLoopEndNode also takes in the loop-invariant limit value.
 186 
 187 // From a CountedLoopNode I can reach the matching CountedLoopEndNode via the
 188 // loop-back control.  From CountedLoopEndNodes I can reach CountedLoopNodes
 189 // via the old-trip-counter from the Op node.
 190 
 191 //------------------------------CountedLoopNode--------------------------------
 192 // CountedLoopNodes head simple counted loops.  CountedLoopNodes have as
 193 // inputs the incoming loop-start control and the loop-back control, so they
 194 // act like RegionNodes.  They also take in the initial trip counter, the
 195 // loop-invariant stride and the loop-invariant limit value.  CountedLoopNodes
 196 // produce a loop-body control and the trip counter value.  Since
 197 // CountedLoopNodes behave like RegionNodes I still have a standard CFG model.
 198 
 199 class BaseCountedLoopNode : public LoopNode {
 200 public:
 201   BaseCountedLoopNode(Node *entry, Node *backedge)
 202     : LoopNode(entry, backedge) {
 203   }
 204 
 205   Node *init_control() const { return in(EntryControl); }
 206   Node *back_control() const { return in(LoopBackControl); }
 207 
 208   Node* init_trip() const;
 209   Node* stride() const;
 210   bool stride_is_con() const;
 211   Node* limit() const;
 212   Node* incr() const;
 213   Node* phi() const;
 214 
 215   BaseCountedLoopEndNode* loopexit_or_null() const;
 216   BaseCountedLoopEndNode* loopexit() const;
 217 
 218   virtual BasicType bt() const = 0;
 219 
 220   jlong stride_con() const;
 221 
 222   static BaseCountedLoopNode* make(Node* entry, Node* backedge, BasicType bt);
 223 };
 224 
 225 
 226 class CountedLoopNode : public BaseCountedLoopNode {
 227   // Size is bigger to hold _main_idx.  However, _main_idx does not change
 228   // the semantics so it does not appear in the hash & cmp functions.
 229   virtual uint size_of() const { return sizeof(*this); }
 230 
 231   // For Pre- and Post-loops during debugging ONLY, this holds the index of
 232   // the Main CountedLoop.  Used to assert that we understand the graph shape.
 233   node_idx_t _main_idx;
 234 
 235   // Known trip count calculated by compute_exact_trip_count()
 236   uint  _trip_count;
 237 
 238   // Log2 of original loop bodies in unrolled loop
 239   int _unrolled_count_log2;
 240 
 241   // Node count prior to last unrolling - used to decide if
 242   // unroll,optimize,unroll,optimize,... is making progress
 243   int _node_count_before_unroll;
 244 
 245   // If slp analysis is performed we record the maximum
 246   // vector mapped unroll factor here
 247   int _slp_maximum_unroll_factor;
 248 
 249 public:
 250   CountedLoopNode(Node *entry, Node *backedge)
 251     : BaseCountedLoopNode(entry, backedge), _main_idx(0), _trip_count(max_juint),
 252       _unrolled_count_log2(0), _node_count_before_unroll(0),
 253       _slp_maximum_unroll_factor(0) {
 254     init_class_id(Class_CountedLoop);
 255     // Initialize _trip_count to the largest possible value.
 256     // Will be reset (lower) if the loop's trip count is known.
 257   }
 258 
 259   virtual int Opcode() const;
 260   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 261 
 262   CountedLoopEndNode* loopexit_or_null() const { return (CountedLoopEndNode*) BaseCountedLoopNode::loopexit_or_null(); }
 263   CountedLoopEndNode* loopexit() const { return (CountedLoopEndNode*) BaseCountedLoopNode::loopexit(); }
 264   int   stride_con() const;
 265 
 266   // Match increment with optional truncation
 267   static Node*
 268   match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInteger** trunc_type,
 269                                       BasicType bt);
 270 
 271   // A 'main' loop has a pre-loop and a post-loop.  The 'main' loop
 272   // can run short a few iterations and may start a few iterations in.
 273   // It will be RCE'd and unrolled and aligned.
 274 
 275   // A following 'post' loop will run any remaining iterations.  Used
 276   // during Range Check Elimination, the 'post' loop will do any final
 277   // iterations with full checks.  Also used by Loop Unrolling, where
 278   // the 'post' loop will do any epilog iterations needed.  Basically,
 279   // a 'post' loop can not profitably be further unrolled or RCE'd.
 280 
 281   // A preceding 'pre' loop will run at least 1 iteration (to do peeling),
 282   // it may do under-flow checks for RCE and may do alignment iterations
 283   // so the following main loop 'knows' that it is striding down cache
 284   // lines.
 285 
 286   // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or
 287   // Aligned, may be missing it's pre-loop.
 288   bool is_normal_loop   () const { return (_loop_flags&PreMainPostFlagsMask) == Normal; }
 289   bool is_pre_loop      () const { return (_loop_flags&PreMainPostFlagsMask) == Pre;    }
 290   bool is_main_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Main;   }
 291   bool is_post_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Post;   }
 292   bool is_reduction_loop() const { return (_loop_flags&HasReductions) == HasReductions; }
 293   bool was_slp_analyzed () const { return (_loop_flags&WasSlpAnalyzed) == WasSlpAnalyzed; }
 294   bool has_passed_slp   () const { return (_loop_flags&PassedSlpAnalysis) == PassedSlpAnalysis; }
 295   bool is_unroll_only   () const { return (_loop_flags&DoUnrollOnly) == DoUnrollOnly; }
 296   bool is_main_no_pre_loop() const { return _loop_flags & MainHasNoPreLoop; }
 297   bool has_atomic_post_loop  () const { return (_loop_flags & HasAtomicPostLoop) == HasAtomicPostLoop; }
 298   void set_main_no_pre_loop() { _loop_flags |= MainHasNoPreLoop; }
 299 
 300   int main_idx() const { return _main_idx; }
 301 
 302 
 303   void set_pre_loop  (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; }
 304   void set_main_loop (                     ) { assert(is_normal_loop(),""); _loop_flags |= Main;                         }
 305   void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; }
 306   void set_normal_loop(                    ) { _loop_flags &= ~PreMainPostFlagsMask; }
 307 
 308   void set_trip_count(uint tc) { _trip_count = tc; }
 309   uint trip_count()            { return _trip_count; }
 310 
 311   bool has_exact_trip_count() const { return (_loop_flags & HasExactTripCount) != 0; }
 312   void set_exact_trip_count(uint tc) {
 313     _trip_count = tc;
 314     _loop_flags |= HasExactTripCount;
 315   }
 316   void set_nonexact_trip_count() {
 317     _loop_flags &= ~HasExactTripCount;
 318   }
 319   void set_notpassed_slp() {
 320     _loop_flags &= ~PassedSlpAnalysis;
 321   }
 322 
 323   void double_unrolled_count() { _unrolled_count_log2++; }
 324   int  unrolled_count()        { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); }
 325 
 326   void set_node_count_before_unroll(int ct)  { _node_count_before_unroll = ct; }
 327   int  node_count_before_unroll()            { return _node_count_before_unroll; }
 328   void set_slp_max_unroll(int unroll_factor) { _slp_maximum_unroll_factor = unroll_factor; }
 329   int  slp_max_unroll() const                { return _slp_maximum_unroll_factor; }
 330 
 331   virtual LoopNode* skip_strip_mined(int expect_skeleton = 1);
 332   OuterStripMinedLoopNode* outer_loop() const;
 333   virtual IfTrueNode* outer_loop_tail() const;
 334   virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
 335   virtual IfFalseNode* outer_loop_exit() const;
 336   virtual SafePointNode* outer_safepoint() const;
 337 
 338   // If this is a main loop in a pre/main/post loop nest, walk over
 339   // the predicates that were inserted by
 340   // duplicate_predicates()/add_range_check_predicate()
 341   static Node* skip_predicates_from_entry(Node* ctrl);
 342   Node* skip_predicates();
 343 
 344   virtual BasicType bt() const {
 345     return T_INT;
 346   }
 347 
 348   Node* is_canonical_loop_entry();
 349 
 350 #ifndef PRODUCT
 351   virtual void dump_spec(outputStream *st) const;
 352 #endif
 353 };
 354 
 355 class LongCountedLoopNode : public BaseCountedLoopNode {
 356 public:
 357   LongCountedLoopNode(Node *entry, Node *backedge)
 358     : BaseCountedLoopNode(entry, backedge) {
 359     init_class_id(Class_LongCountedLoop);
 360   }
 361 
 362   virtual int Opcode() const;
 363 
 364   virtual BasicType bt() const {
 365     return T_LONG;
 366   }
 367 
 368   LongCountedLoopEndNode* loopexit_or_null() const { return (LongCountedLoopEndNode*) BaseCountedLoopNode::loopexit_or_null(); }
 369   LongCountedLoopEndNode* loopexit() const { return (LongCountedLoopEndNode*) BaseCountedLoopNode::loopexit(); }
 370 };
 371 
 372 
 373 //------------------------------CountedLoopEndNode-----------------------------
 374 // CountedLoopEndNodes end simple trip counted loops.  They act much like
 375 // IfNodes.
 376 
 377 class BaseCountedLoopEndNode : public IfNode {
 378 public:
 379   enum { TestControl, TestValue };
 380   BaseCountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 381     : IfNode(control, test, prob, cnt) {
 382     init_class_id(Class_BaseCountedLoopEnd);
 383   }
 384 
 385   Node *cmp_node() const            { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; }
 386   Node* incr() const                { Node* tmp = cmp_node(); return (tmp && tmp->req() == 3) ? tmp->in(1) : NULL; }
 387   Node* limit() const               { Node* tmp = cmp_node(); return (tmp && tmp->req() == 3) ? tmp->in(2) : NULL; }
 388   Node* stride() const              { Node* tmp = incr(); return (tmp && tmp->req() == 3) ? tmp->in(2) : NULL; }
 389   Node* init_trip() const           { Node* tmp = phi(); return (tmp && tmp->req() == 3) ? tmp->in(1) : NULL; }
 390   bool stride_is_con() const        { Node *tmp = stride(); return (tmp != NULL && tmp->is_Con()); }
 391 
 392   PhiNode* phi() const {
 393     Node* tmp = incr();
 394     if (tmp && tmp->req() == 3) {
 395       Node* phi = tmp->in(1);
 396       if (phi->is_Phi()) {
 397         return phi->as_Phi();
 398       }
 399     }
 400     return NULL;
 401   }
 402 
 403   BaseCountedLoopNode* loopnode() const {
 404     // The CountedLoopNode that goes with this CountedLoopEndNode may
 405     // have been optimized out by the IGVN so be cautious with the
 406     // pattern matching on the graph
 407     PhiNode* iv_phi = phi();
 408     if (iv_phi == NULL) {
 409       return NULL;
 410     }
 411     Node* ln = iv_phi->in(0);
 412     if (!ln->is_BaseCountedLoop() || ln->as_BaseCountedLoop()->loopexit_or_null() != this) {
 413       return NULL;
 414     }
 415     if (ln->as_BaseCountedLoop()->bt() != bt()) {
 416       return NULL;
 417     }
 418     return ln->as_BaseCountedLoop();
 419   }
 420 
 421   BoolTest::mask test_trip() const  { return in(TestValue)->as_Bool()->_test._test; }
 422 
 423   jlong stride_con() const;
 424   virtual BasicType bt() const = 0;
 425 
 426   static BaseCountedLoopEndNode* make(Node* control, Node* test, float prob, float cnt, BasicType bt);
 427 };
 428 
 429 class CountedLoopEndNode : public BaseCountedLoopEndNode {
 430 public:
 431 
 432   CountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 433     : BaseCountedLoopEndNode(control, test, prob, cnt) {
 434     init_class_id(Class_CountedLoopEnd);
 435   }
 436   virtual int Opcode() const;
 437 
 438   CountedLoopNode* loopnode() const {
 439     return (CountedLoopNode*) BaseCountedLoopEndNode::loopnode();
 440   }
 441 
 442   virtual BasicType bt() const {
 443     return T_INT;
 444   }
 445 
 446 #ifndef PRODUCT
 447   virtual void dump_spec(outputStream *st) const;
 448 #endif
 449 };
 450 
 451 class LongCountedLoopEndNode : public BaseCountedLoopEndNode {
 452 public:
 453   LongCountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 454     : BaseCountedLoopEndNode(control, test, prob, cnt) {
 455     init_class_id(Class_LongCountedLoopEnd);
 456   }
 457 
 458   LongCountedLoopNode* loopnode() const {
 459     return (LongCountedLoopNode*) BaseCountedLoopEndNode::loopnode();
 460   }
 461 
 462   virtual int Opcode() const;
 463 
 464   virtual BasicType bt() const {
 465     return T_LONG;
 466   }
 467 };
 468 
 469 
 470 inline BaseCountedLoopEndNode* BaseCountedLoopNode::loopexit_or_null() const {
 471   Node* bctrl = back_control();
 472   if (bctrl == NULL) return NULL;
 473 
 474   Node* lexit = bctrl->in(0);
 475   if (!lexit->is_BaseCountedLoopEnd()) {
 476     return NULL;
 477   }
 478   BaseCountedLoopEndNode* result = lexit->as_BaseCountedLoopEnd();
 479   if (result->bt() != bt()) {
 480     return NULL;
 481   }
 482   return result;
 483 }
 484 
 485 inline BaseCountedLoopEndNode* BaseCountedLoopNode::loopexit() const {
 486   BaseCountedLoopEndNode* cle = loopexit_or_null();
 487   assert(cle != NULL, "loopexit is NULL");
 488   return cle;
 489 }
 490 
 491 inline Node* BaseCountedLoopNode::init_trip() const {
 492   BaseCountedLoopEndNode* cle = loopexit_or_null();
 493   return cle != NULL ? cle->init_trip() : NULL;
 494 }
 495 inline Node* BaseCountedLoopNode::stride() const {
 496   BaseCountedLoopEndNode* cle = loopexit_or_null();
 497   return cle != NULL ? cle->stride() : NULL;
 498 }
 499 
 500 inline bool BaseCountedLoopNode::stride_is_con() const {
 501   BaseCountedLoopEndNode* cle = loopexit_or_null();
 502   return cle != NULL && cle->stride_is_con();
 503 }
 504 inline Node* BaseCountedLoopNode::limit() const {
 505   BaseCountedLoopEndNode* cle = loopexit_or_null();
 506   return cle != NULL ? cle->limit() : NULL;
 507 }
 508 inline Node* BaseCountedLoopNode::incr() const {
 509   BaseCountedLoopEndNode* cle = loopexit_or_null();
 510   return cle != NULL ? cle->incr() : NULL;
 511 }
 512 inline Node* BaseCountedLoopNode::phi() const {
 513   BaseCountedLoopEndNode* cle = loopexit_or_null();
 514   return cle != NULL ? cle->phi() : NULL;
 515 }
 516 
 517 inline jlong BaseCountedLoopNode::stride_con() const {
 518   BaseCountedLoopEndNode* cle = loopexit_or_null();
 519   return cle != NULL ? cle->stride_con() : 0;
 520 }
 521 
 522 
 523 //------------------------------LoopLimitNode-----------------------------
 524 // Counted Loop limit node which represents exact final iterator value:
 525 // trip_count = (limit - init_trip + stride - 1)/stride
 526 // final_value= trip_count * stride + init_trip.
 527 // Use HW instructions to calculate it when it can overflow in integer.
 528 // Note, final_value should fit into integer since counted loop has
 529 // limit check: limit <= max_int-stride.
 530 class LoopLimitNode : public Node {
 531   enum { Init=1, Limit=2, Stride=3 };
 532  public:
 533   LoopLimitNode( Compile* C, Node *init, Node *limit, Node *stride ) : Node(0,init,limit,stride) {
 534     // Put it on the Macro nodes list to optimize during macro nodes expansion.
 535     init_flags(Flag_is_macro);
 536     C->add_macro_node(this);
 537   }
 538   virtual int Opcode() const;
 539   virtual const Type *bottom_type() const { return TypeInt::INT; }
 540   virtual uint ideal_reg() const { return Op_RegI; }
 541   virtual const Type* Value(PhaseGVN* phase) const;
 542   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 543   virtual Node* Identity(PhaseGVN* phase);
 544 };
 545 
 546 // Support for strip mining
 547 class OuterStripMinedLoopNode : public LoopNode {
 548 private:
 549   static void fix_sunk_stores(CountedLoopEndNode* inner_cle, LoopNode* inner_cl, PhaseIterGVN* igvn, PhaseIdealLoop* iloop);
 550 
 551 public:
 552   OuterStripMinedLoopNode(Compile* C, Node *entry, Node *backedge)
 553     : LoopNode(entry, backedge) {
 554     init_class_id(Class_OuterStripMinedLoop);
 555     init_flags(Flag_is_macro);
 556     C->add_macro_node(this);
 557   }
 558 
 559   virtual int Opcode() const;
 560 
 561   virtual IfTrueNode* outer_loop_tail() const;
 562   virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
 563   virtual IfFalseNode* outer_loop_exit() const;
 564   virtual SafePointNode* outer_safepoint() const;
 565   void adjust_strip_mined_loop(PhaseIterGVN* igvn);
 566 
 567   void remove_outer_loop_and_safepoint(PhaseIterGVN* igvn) const;
 568 
 569   void transform_to_counted_loop(PhaseIterGVN* igvn, PhaseIdealLoop* iloop);
 570 
 571   static Node* register_new_node(Node* node, LoopNode* ctrl, PhaseIterGVN* igvn, PhaseIdealLoop* iloop);
 572 
 573   Node* register_control(Node* node, Node* loop, Node* idom, PhaseIterGVN* igvn,
 574                          PhaseIdealLoop* iloop);
 575 };
 576 
 577 class OuterStripMinedLoopEndNode : public IfNode {
 578 public:
 579   OuterStripMinedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 580     : IfNode(control, test, prob, cnt) {
 581     init_class_id(Class_OuterStripMinedLoopEnd);
 582   }
 583 
 584   virtual int Opcode() const;
 585 
 586   virtual const Type* Value(PhaseGVN* phase) const;
 587   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 588 
 589   bool is_expanded(PhaseGVN *phase) const;
 590 };
 591 
 592 // -----------------------------IdealLoopTree----------------------------------
 593 class IdealLoopTree : public ResourceObj {
 594 public:
 595   IdealLoopTree *_parent;       // Parent in loop tree
 596   IdealLoopTree *_next;         // Next sibling in loop tree
 597   IdealLoopTree *_child;        // First child in loop tree
 598 
 599   // The head-tail backedge defines the loop.
 600   // If a loop has multiple backedges, this is addressed during cleanup where
 601   // we peel off the multiple backedges,  merging all edges at the bottom and
 602   // ensuring that one proper backedge flow into the loop.
 603   Node *_head;                  // Head of loop
 604   Node *_tail;                  // Tail of loop
 605   inline Node *tail();          // Handle lazy update of _tail field
 606   inline Node *head();          // Handle lazy update of _head field
 607   PhaseIdealLoop* _phase;
 608   int _local_loop_unroll_limit;
 609   int _local_loop_unroll_factor;
 610 
 611   Node_List _body;              // Loop body for inner loops
 612 
 613   uint16_t _nest;               // Nesting depth
 614   uint8_t _irreducible:1,       // True if irreducible
 615           _has_call:1,          // True if has call safepoint
 616           _has_sfpt:1,          // True if has non-call safepoint
 617           _rce_candidate:1;     // True if candidate for range check elimination
 618 
 619   Node_List* _safepts;          // List of safepoints in this loop
 620   Node_List* _required_safept;  // A inner loop cannot delete these safepts;
 621   bool  _allow_optimizations;   // Allow loop optimizations
 622 
 623   IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail )
 624     : _parent(0), _next(0), _child(0),
 625       _head(head), _tail(tail),
 626       _phase(phase),
 627       _local_loop_unroll_limit(0), _local_loop_unroll_factor(0),
 628       _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0),
 629       _safepts(NULL),
 630       _required_safept(NULL),
 631       _allow_optimizations(true)
 632   {
 633     precond(_head != NULL);
 634     precond(_tail != NULL);
 635   }
 636 
 637   // Is 'l' a member of 'this'?
 638   bool is_member(const IdealLoopTree *l) const; // Test for nested membership
 639 
 640   // Set loop nesting depth.  Accumulate has_call bits.
 641   int set_nest( uint depth );
 642 
 643   // Split out multiple fall-in edges from the loop header.  Move them to a
 644   // private RegionNode before the loop.  This becomes the loop landing pad.
 645   void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt );
 646 
 647   // Split out the outermost loop from this shared header.
 648   void split_outer_loop( PhaseIdealLoop *phase );
 649 
 650   // Merge all the backedges from the shared header into a private Region.
 651   // Feed that region as the one backedge to this loop.
 652   void merge_many_backedges( PhaseIdealLoop *phase );
 653 
 654   // Split shared headers and insert loop landing pads.
 655   // Insert a LoopNode to replace the RegionNode.
 656   // Returns TRUE if loop tree is structurally changed.
 657   bool beautify_loops( PhaseIdealLoop *phase );
 658 
 659   // Perform optimization to use the loop predicates for null checks and range checks.
 660   // Applies to any loop level (not just the innermost one)
 661   bool loop_predication( PhaseIdealLoop *phase);
 662 
 663   // Perform iteration-splitting on inner loops.  Split iterations to
 664   // avoid range checks or one-shot null checks.  Returns false if the
 665   // current round of loop opts should stop.
 666   bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new );
 667 
 668   // Driver for various flavors of iteration splitting.  Returns false
 669   // if the current round of loop opts should stop.
 670   bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new );
 671 
 672   // Given dominators, try to find loops with calls that must always be
 673   // executed (call dominates loop tail).  These loops do not need non-call
 674   // safepoints (ncsfpt).
 675   void check_safepts(VectorSet &visited, Node_List &stack);
 676 
 677   // Allpaths backwards scan from loop tail, terminating each path at first safepoint
 678   // encountered.
 679   void allpaths_check_safepts(VectorSet &visited, Node_List &stack);
 680 
 681   // Remove safepoints from loop. Optionally keeping one.
 682   void remove_safepoints(PhaseIdealLoop* phase, bool keep_one);
 683 
 684   // Convert to counted loops where possible
 685   void counted_loop( PhaseIdealLoop *phase );
 686 
 687   // Check for Node being a loop-breaking test
 688   Node *is_loop_exit(Node *iff) const;
 689 
 690   // Remove simplistic dead code from loop body
 691   void DCE_loop_body();
 692 
 693   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
 694   // Replace with a 1-in-10 exit guess.
 695   void adjust_loop_exit_prob( PhaseIdealLoop *phase );
 696 
 697   // Return TRUE or FALSE if the loop should never be RCE'd or aligned.
 698   // Useful for unrolling loops with NO array accesses.
 699   bool policy_peel_only( PhaseIdealLoop *phase ) const;
 700 
 701   // Return TRUE or FALSE if the loop should be unswitched -- clone
 702   // loop with an invariant test
 703   bool policy_unswitching( PhaseIdealLoop *phase ) const;
 704 
 705   // Micro-benchmark spamming.  Remove empty loops.
 706   bool do_remove_empty_loop( PhaseIdealLoop *phase );
 707 
 708   // Convert one iteration loop into normal code.
 709   bool do_one_iteration_loop( PhaseIdealLoop *phase );
 710 
 711   // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
 712   // move some loop-invariant test (usually a null-check) before the loop.
 713   bool policy_peeling(PhaseIdealLoop *phase);
 714 
 715   uint estimate_peeling(PhaseIdealLoop *phase);
 716 
 717   // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any
 718   // known trip count in the counted loop node.
 719   bool policy_maximally_unroll(PhaseIdealLoop *phase) const;
 720 
 721   // Return TRUE or FALSE if the loop should be unrolled or not. Apply unroll
 722   // if the loop is a counted loop and the loop body is small enough.
 723   bool policy_unroll(PhaseIdealLoop *phase);
 724 
 725   // Loop analyses to map to a maximal superword unrolling for vectorization.
 726   void policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct);
 727 
 728   // Return TRUE or FALSE if the loop should be range-check-eliminated.
 729   // Gather a list of IF tests that are dominated by iteration splitting;
 730   // also gather the end of the first split and the start of the 2nd split.
 731   bool policy_range_check(PhaseIdealLoop* phase, bool provisional, BasicType bt) const;
 732 
 733   // Return TRUE if "iff" is a range check.
 734   bool is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar DEBUG_ONLY(COMMA ProjNode *predicate_proj)) const;
 735   bool is_range_check_if(IfNode* iff, PhaseIdealLoop* phase, BasicType bt, Node* iv, Node*& range, Node*& offset,
 736                          jlong& scale) const;
 737 
 738   // Estimate the number of nodes required when cloning a loop (body).
 739   uint est_loop_clone_sz(uint factor) const;
 740   // Estimate the number of nodes required when unrolling a loop (body).
 741   uint est_loop_unroll_sz(uint factor) const;
 742 
 743   // Compute loop trip count if possible
 744   void compute_trip_count(PhaseIdealLoop* phase);
 745 
 746   // Compute loop trip count from profile data
 747   float compute_profile_trip_cnt_helper(Node* n);
 748   void compute_profile_trip_cnt( PhaseIdealLoop *phase );
 749 
 750   // Reassociate invariant expressions.
 751   void reassociate_invariants(PhaseIdealLoop *phase);
 752   // Reassociate invariant binary expressions.
 753   Node* reassociate(Node* n1, PhaseIdealLoop *phase);
 754   // Reassociate invariant add and subtract expressions.
 755   Node* reassociate_add_sub(Node* n1, int inv1_idx, int inv2_idx, PhaseIdealLoop *phase);
 756   // Return nonzero index of invariant operand if invariant and variant
 757   // are combined with an associative binary. Helper for reassociate_invariants.
 758   int find_invariant(Node* n, PhaseIdealLoop *phase);
 759   // Return TRUE if "n" is associative.
 760   bool is_associative(Node* n, Node* base=NULL);
 761 
 762   // Return true if n is invariant
 763   bool is_invariant(Node* n) const;
 764 
 765   // Put loop body on igvn work list
 766   void record_for_igvn();
 767 
 768   bool is_root() { return _parent == NULL; }
 769   // A proper/reducible loop w/o any (occasional) dead back-edge.
 770   bool is_loop() { return !_irreducible && !tail()->is_top(); }
 771   bool is_counted()   { return is_loop() && _head->is_CountedLoop(); }
 772   bool is_innermost() { return is_loop() && _child == NULL; }
 773 
 774   void remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase);
 775 
 776 #ifndef PRODUCT
 777   void dump_head() const;       // Dump loop head only
 778   void dump() const;            // Dump this loop recursively
 779   void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const;
 780 #endif
 781 
 782  private:
 783   enum { EMPTY_LOOP_SIZE = 7 }; // Number of nodes in an empty loop.
 784 
 785   // Estimate the number of nodes resulting from control and data flow merge.
 786   uint est_loop_flow_merge_sz() const;
 787 
 788   // Check if the number of residual iterations is large with unroll_cnt.
 789   // Return true if the residual iterations are more than 10% of the trip count.
 790   bool is_residual_iters_large(int unroll_cnt, CountedLoopNode *cl) const {
 791     return (unroll_cnt - 1) * (100.0 / LoopPercentProfileLimit) > cl->profile_trip_cnt();
 792   }
 793 };
 794 
 795 // -----------------------------PhaseIdealLoop---------------------------------
 796 // Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees
 797 // into a loop tree. Drives the loop-based transformations on the ideal graph.
 798 class PhaseIdealLoop : public PhaseTransform {
 799   friend class IdealLoopTree;
 800   friend class SuperWord;
 801   friend class CountedLoopReserveKit;
 802   friend class ShenandoahBarrierC2Support;
 803   friend class AutoNodeBudget;
 804 
 805   // Pre-computed def-use info
 806   PhaseIterGVN &_igvn;
 807 
 808   // Head of loop tree
 809   IdealLoopTree* _ltree_root;
 810 
 811   // Array of pre-order numbers, plus post-visited bit.
 812   // ZERO for not pre-visited.  EVEN for pre-visited but not post-visited.
 813   // ODD for post-visited.  Other bits are the pre-order number.
 814   uint *_preorders;
 815   uint _max_preorder;
 816 
 817   const PhaseIdealLoop* _verify_me;
 818   bool _verify_only;
 819 
 820   // Allocate _preorders[] array
 821   void allocate_preorders() {
 822     _max_preorder = C->unique()+8;
 823     _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder);
 824     memset(_preorders, 0, sizeof(uint) * _max_preorder);
 825   }
 826 
 827   // Allocate _preorders[] array
 828   void reallocate_preorders() {
 829     if ( _max_preorder < C->unique() ) {
 830       _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique());
 831       _max_preorder = C->unique();
 832     }
 833     memset(_preorders, 0, sizeof(uint) * _max_preorder);
 834   }
 835 
 836   // Check to grow _preorders[] array for the case when build_loop_tree_impl()
 837   // adds new nodes.
 838   void check_grow_preorders( ) {
 839     if ( _max_preorder < C->unique() ) {
 840       uint newsize = _max_preorder<<1;  // double size of array
 841       _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize);
 842       memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder));
 843       _max_preorder = newsize;
 844     }
 845   }
 846   // Check for pre-visited.  Zero for NOT visited; non-zero for visited.
 847   int is_visited( Node *n ) const { return _preorders[n->_idx]; }
 848   // Pre-order numbers are written to the Nodes array as low-bit-set values.
 849   void set_preorder_visited( Node *n, int pre_order ) {
 850     assert( !is_visited( n ), "already set" );
 851     _preorders[n->_idx] = (pre_order<<1);
 852   };
 853   // Return pre-order number.
 854   int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; }
 855 
 856   // Check for being post-visited.
 857   // Should be previsited already (checked with assert(is_visited(n))).
 858   int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; }
 859 
 860   // Mark as post visited
 861   void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; }
 862 
 863 public:
 864   // Set/get control node out.  Set lower bit to distinguish from IdealLoopTree
 865   // Returns true if "n" is a data node, false if it's a control node.
 866   bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; }
 867 
 868 private:
 869   // clear out dead code after build_loop_late
 870   Node_List _deadlist;
 871 
 872   // Support for faster execution of get_late_ctrl()/dom_lca()
 873   // when a node has many uses and dominator depth is deep.
 874   GrowableArray<jlong> _dom_lca_tags;
 875   uint _dom_lca_tags_round;
 876   void   init_dom_lca_tags();
 877 
 878   // Helper for debugging bad dominance relationships
 879   bool verify_dominance(Node* n, Node* use, Node* LCA, Node* early);
 880 
 881   Node* compute_lca_of_uses(Node* n, Node* early, bool verify = false);
 882 
 883   // Inline wrapper for frequent cases:
 884   // 1) only one use
 885   // 2) a use is the same as the current LCA passed as 'n1'
 886   Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) {
 887     assert( n->is_CFG(), "" );
 888     // Fast-path NULL lca
 889     if( lca != NULL && lca != n ) {
 890       assert( lca->is_CFG(), "" );
 891       // find LCA of all uses
 892       n = dom_lca_for_get_late_ctrl_internal( lca, n, tag );
 893     }
 894     return find_non_split_ctrl(n);
 895   }
 896   Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag );
 897 
 898   // Helper function for directing control inputs away from CFG split points.
 899   Node *find_non_split_ctrl( Node *ctrl ) const {
 900     if (ctrl != NULL) {
 901       if (ctrl->is_MultiBranch()) {
 902         ctrl = ctrl->in(0);
 903       }
 904       assert(ctrl->is_CFG(), "CFG");
 905     }
 906     return ctrl;
 907   }
 908 
 909   Node* cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop);
 910 
 911 #ifdef ASSERT
 912   void ensure_zero_trip_guard_proj(Node* node, bool is_main_loop);
 913 #endif
 914   void copy_skeleton_predicates_to_main_loop_helper(Node* predicate, Node* init, Node* stride, IdealLoopTree* outer_loop, LoopNode* outer_main_head,
 915                                                     uint dd_main_head, const uint idx_before_pre_post, const uint idx_after_post_before_pre,
 916                                                     Node* zero_trip_guard_proj_main, Node* zero_trip_guard_proj_post, const Node_List &old_new);
 917   void copy_skeleton_predicates_to_main_loop(CountedLoopNode* pre_head, Node* init, Node* stride, IdealLoopTree* outer_loop, LoopNode* outer_main_head,
 918                                              uint dd_main_head, const uint idx_before_pre_post, const uint idx_after_post_before_pre,
 919                                              Node* zero_trip_guard_proj_main, Node* zero_trip_guard_proj_post, const Node_List &old_new);
 920   Node* clone_skeleton_predicate_for_main_or_post_loop(Node* iff, Node* new_init, Node* new_stride, Node* predicate, Node* uncommon_proj, Node* control,
 921                                                        IdealLoopTree* outer_loop, Node* input_proj);
 922   Node* clone_skeleton_predicate_bool(Node* iff, Node* new_init, Node* new_stride, Node* control);
 923   static bool skeleton_predicate_has_opaque(IfNode* iff);
 924   static void get_skeleton_predicates(Node* predicate, Unique_Node_List& list, bool get_opaque = false);
 925   void update_main_loop_skeleton_predicates(Node* ctrl, CountedLoopNode* loop_head, Node* init, int stride_con);
 926   void copy_skeleton_predicates_to_post_loop(LoopNode* main_loop_head, CountedLoopNode* post_loop_head, Node* init, Node* stride);
 927   void insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol);
 928 #ifdef ASSERT
 929   bool only_has_infinite_loops();
 930 #endif
 931 
 932   void log_loop_tree();
 933 
 934 public:
 935 
 936   PhaseIterGVN &igvn() const { return _igvn; }
 937 
 938   bool has_node( Node* n ) const {
 939     guarantee(n != NULL, "No Node.");
 940     return _nodes[n->_idx] != NULL;
 941   }
 942   // check if transform created new nodes that need _ctrl recorded
 943   Node *get_late_ctrl( Node *n, Node *early );
 944   Node *get_early_ctrl( Node *n );
 945   Node *get_early_ctrl_for_expensive(Node *n, Node* earliest);
 946   void set_early_ctrl(Node* n, bool update_body);
 947   void set_subtree_ctrl(Node* n, bool update_body);
 948   void set_ctrl( Node *n, Node *ctrl ) {
 949     assert( !has_node(n) || has_ctrl(n), "" );
 950     assert( ctrl->in(0), "cannot set dead control node" );
 951     assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" );
 952     _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) );
 953   }
 954   // Set control and update loop membership
 955   void set_ctrl_and_loop(Node* n, Node* ctrl) {
 956     IdealLoopTree* old_loop = get_loop(get_ctrl(n));
 957     IdealLoopTree* new_loop = get_loop(ctrl);
 958     if (old_loop != new_loop) {
 959       if (old_loop->_child == NULL) old_loop->_body.yank(n);
 960       if (new_loop->_child == NULL) new_loop->_body.push(n);
 961     }
 962     set_ctrl(n, ctrl);
 963   }
 964   // Control nodes can be replaced or subsumed.  During this pass they
 965   // get their replacement Node in slot 1.  Instead of updating the block
 966   // location of all Nodes in the subsumed block, we lazily do it.  As we
 967   // pull such a subsumed block out of the array, we write back the final
 968   // correct block.
 969   Node *get_ctrl( Node *i ) {
 970 
 971     assert(has_node(i), "");
 972     Node *n = get_ctrl_no_update(i);
 973     _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) );
 974     assert(has_node(i) && has_ctrl(i), "");
 975     assert(n == find_non_split_ctrl(n), "must return legal ctrl" );
 976     return n;
 977   }
 978   // true if CFG node d dominates CFG node n
 979   bool is_dominator(Node *d, Node *n);
 980   // return get_ctrl for a data node and self(n) for a CFG node
 981   Node* ctrl_or_self(Node* n) {
 982     if (has_ctrl(n))
 983       return get_ctrl(n);
 984     else {
 985       assert (n->is_CFG(), "must be a CFG node");
 986       return n;
 987     }
 988   }
 989 
 990   Node *get_ctrl_no_update_helper(Node *i) const {
 991     assert(has_ctrl(i), "should be control, not loop");
 992     return (Node*)(((intptr_t)_nodes[i->_idx]) & ~1);
 993   }
 994 
 995   Node *get_ctrl_no_update(Node *i) const {
 996     assert( has_ctrl(i), "" );
 997     Node *n = get_ctrl_no_update_helper(i);
 998     if (!n->in(0)) {
 999       // Skip dead CFG nodes
1000       do {
1001         n = get_ctrl_no_update_helper(n);
1002       } while (!n->in(0));
1003       n = find_non_split_ctrl(n);
1004     }
1005     return n;
1006   }
1007 
1008   // Check for loop being set
1009   // "n" must be a control node. Returns true if "n" is known to be in a loop.
1010   bool has_loop( Node *n ) const {
1011     assert(!has_node(n) || !has_ctrl(n), "");
1012     return has_node(n);
1013   }
1014   // Set loop
1015   void set_loop( Node *n, IdealLoopTree *loop ) {
1016     _nodes.map(n->_idx, (Node*)loop);
1017   }
1018   // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms.  Replace
1019   // the 'old_node' with 'new_node'.  Kill old-node.  Add a reference
1020   // from old_node to new_node to support the lazy update.  Reference
1021   // replaces loop reference, since that is not needed for dead node.
1022   void lazy_update(Node *old_node, Node *new_node) {
1023     assert(old_node != new_node, "no cycles please");
1024     // Re-use the side array slot for this node to provide the
1025     // forwarding pointer.
1026     _nodes.map(old_node->_idx, (Node*)((intptr_t)new_node + 1));
1027   }
1028   void lazy_replace(Node *old_node, Node *new_node) {
1029     _igvn.replace_node(old_node, new_node);
1030     lazy_update(old_node, new_node);
1031   }
1032 
1033 private:
1034 
1035   // Place 'n' in some loop nest, where 'n' is a CFG node
1036   void build_loop_tree();
1037   int build_loop_tree_impl( Node *n, int pre_order );
1038   // Insert loop into the existing loop tree.  'innermost' is a leaf of the
1039   // loop tree, not the root.
1040   IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost );
1041 
1042   // Place Data nodes in some loop nest
1043   void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
1044   void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
1045   void build_loop_late_post_work(Node* n, bool pinned);
1046   void build_loop_late_post(Node* n);
1047   void verify_strip_mined_scheduling(Node *n, Node* least);
1048 
1049   // Array of immediate dominance info for each CFG node indexed by node idx
1050 private:
1051   uint _idom_size;
1052   Node **_idom;                  // Array of immediate dominators
1053   uint *_dom_depth;              // Used for fast LCA test
1054   GrowableArray<uint>* _dom_stk; // For recomputation of dom depth
1055   LoopOptsMode _mode;
1056 
1057   // build the loop tree and perform any requested optimizations
1058   void build_and_optimize();
1059 
1060   // Dominators for the sea of nodes
1061   void Dominators();
1062 
1063   // Compute the Ideal Node to Loop mapping
1064   PhaseIdealLoop(PhaseIterGVN& igvn, LoopOptsMode mode) :
1065     PhaseTransform(Ideal_Loop),
1066     _igvn(igvn),
1067     _verify_me(nullptr),
1068     _verify_only(false),
1069     _mode(mode),
1070     _nodes_required(UINT_MAX) {
1071     assert(mode != LoopOptsVerify, "wrong constructor to verify IdealLoop");
1072     build_and_optimize();
1073   }
1074 
1075 #ifndef PRODUCT
1076   // Verify that verify_me made the same decisions as a fresh run
1077   // or only verify that the graph is valid if verify_me is null.
1078   PhaseIdealLoop(PhaseIterGVN& igvn, const PhaseIdealLoop* verify_me = nullptr) :
1079     PhaseTransform(Ideal_Loop),
1080     _igvn(igvn),
1081     _verify_me(verify_me),
1082     _verify_only(verify_me == nullptr),
1083     _mode(LoopOptsVerify),
1084     _nodes_required(UINT_MAX) {
1085     build_and_optimize();
1086   }
1087 #endif
1088 
1089 public:
1090   Node* idom_no_update(Node* d) const {
1091     return idom_no_update(d->_idx);
1092   }
1093 
1094   Node* idom_no_update(uint didx) const {
1095     assert(didx < _idom_size, "oob");
1096     Node* n = _idom[didx];
1097     assert(n != NULL,"Bad immediate dominator info.");
1098     while (n->in(0) == NULL) { // Skip dead CFG nodes
1099       n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
1100       assert(n != NULL,"Bad immediate dominator info.");
1101     }
1102     return n;
1103   }
1104 
1105   Node *idom(Node* d) const {
1106     return idom(d->_idx);
1107   }
1108 
1109   Node *idom(uint didx) const {
1110     Node *n = idom_no_update(didx);
1111     _idom[didx] = n; // Lazily remove dead CFG nodes from table.
1112     return n;
1113   }
1114 
1115   uint dom_depth(Node* d) const {
1116     guarantee(d != NULL, "Null dominator info.");
1117     guarantee(d->_idx < _idom_size, "");
1118     return _dom_depth[d->_idx];
1119   }
1120   void set_idom(Node* d, Node* n, uint dom_depth);
1121   // Locally compute IDOM using dom_lca call
1122   Node *compute_idom( Node *region ) const;
1123   // Recompute dom_depth
1124   void recompute_dom_depth();
1125 
1126   // Is safept not required by an outer loop?
1127   bool is_deleteable_safept(Node* sfpt);
1128 
1129   // Replace parallel induction variable (parallel to trip counter)
1130   void replace_parallel_iv(IdealLoopTree *loop);
1131 
1132   Node *dom_lca( Node *n1, Node *n2 ) const {
1133     return find_non_split_ctrl(dom_lca_internal(n1, n2));
1134   }
1135   Node *dom_lca_internal( Node *n1, Node *n2 ) const;
1136 
1137   // Build and verify the loop tree without modifying the graph.  This
1138   // is useful to verify that all inputs properly dominate their uses.
1139   static void verify(PhaseIterGVN& igvn) {
1140 #ifdef ASSERT
1141     ResourceMark rm;
1142     Compile::TracePhase tp("idealLoopVerify", &timers[_t_idealLoopVerify]);
1143     PhaseIdealLoop v(igvn);
1144 #endif
1145   }
1146 
1147   // Recommended way to use PhaseIdealLoop.
1148   // Run PhaseIdealLoop in some mode and allocates a local scope for memory allocations.
1149   static void optimize(PhaseIterGVN &igvn, LoopOptsMode mode) {
1150     ResourceMark rm;
1151     PhaseIdealLoop v(igvn, mode);
1152 
1153     Compile* C = Compile::current();
1154     if (!C->failing()) {
1155       // Cleanup any modified bits
1156       igvn.optimize();
1157 
1158       v.log_loop_tree();
1159     }
1160   }
1161 
1162   // True if the method has at least 1 irreducible loop
1163   bool _has_irreducible_loops;
1164 
1165   // Per-Node transform
1166   virtual Node* transform(Node* n) { return NULL; }
1167 
1168   Node* loop_exit_control(Node* x, IdealLoopTree* loop);
1169   Node* loop_exit_test(Node* back_control, IdealLoopTree* loop, Node*& incr, Node*& limit, BoolTest::mask& bt, float& cl_prob);
1170   Node* loop_iv_incr(Node* incr, Node* x, IdealLoopTree* loop, Node*& phi_incr);
1171   Node* loop_iv_stride(Node* incr, IdealLoopTree* loop, Node*& xphi);
1172   PhiNode* loop_iv_phi(Node* xphi, Node* phi_incr, Node* x, IdealLoopTree* loop);
1173 
1174   bool is_counted_loop(Node* x, IdealLoopTree*&loop, BasicType iv_bt);
1175 
1176   Node* loop_nest_replace_iv(Node* iv_to_replace, Node* inner_iv, Node* outer_phi, Node* inner_head, BasicType bt);
1177   bool create_loop_nest(IdealLoopTree* loop, Node_List &old_new);
1178 #ifdef ASSERT
1179   bool convert_to_long_loop(Node* cmp, Node* phi, IdealLoopTree* loop);
1180 #endif
1181   void add_empty_predicate(Deoptimization::DeoptReason reason, Node* inner_head, IdealLoopTree* loop, SafePointNode* sfpt);
1182   SafePointNode* find_safepoint(Node* back_control, Node* x, IdealLoopTree* loop);
1183   IdealLoopTree* insert_outer_loop(IdealLoopTree* loop, LoopNode* outer_l, Node* outer_ift);
1184   IdealLoopTree* create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
1185                                                IdealLoopTree* loop, float cl_prob, float le_fcnt,
1186                                                Node*& entry_control, Node*& iffalse);
1187 
1188   Node* exact_limit( IdealLoopTree *loop );
1189 
1190   // Return a post-walked LoopNode
1191   IdealLoopTree *get_loop( Node *n ) const {
1192     // Dead nodes have no loop, so return the top level loop instead
1193     if (!has_node(n))  return _ltree_root;
1194     assert(!has_ctrl(n), "");
1195     return (IdealLoopTree*)_nodes[n->_idx];
1196   }
1197 
1198   IdealLoopTree* ltree_root() const { return _ltree_root; }
1199 
1200   // Is 'n' a (nested) member of 'loop'?
1201   int is_member( const IdealLoopTree *loop, Node *n ) const {
1202     return loop->is_member(get_loop(n)); }
1203 
1204   // This is the basic building block of the loop optimizations.  It clones an
1205   // entire loop body.  It makes an old_new loop body mapping; with this
1206   // mapping you can find the new-loop equivalent to an old-loop node.  All
1207   // new-loop nodes are exactly equal to their old-loop counterparts, all
1208   // edges are the same.  All exits from the old-loop now have a RegionNode
1209   // that merges the equivalent new-loop path.  This is true even for the
1210   // normal "loop-exit" condition.  All uses of loop-invariant old-loop values
1211   // now come from (one or more) Phis that merge their new-loop equivalents.
1212   // Parameter side_by_side_idom:
1213   //   When side_by_size_idom is NULL, the dominator tree is constructed for
1214   //      the clone loop to dominate the original.  Used in construction of
1215   //      pre-main-post loop sequence.
1216   //   When nonnull, the clone and original are side-by-side, both are
1217   //      dominated by the passed in side_by_side_idom node.  Used in
1218   //      construction of unswitched loops.
1219   enum CloneLoopMode {
1220     IgnoreStripMined = 0,        // Only clone inner strip mined loop
1221     CloneIncludesStripMined = 1, // clone both inner and outer strip mined loops
1222     ControlAroundStripMined = 2  // Only clone inner strip mined loop,
1223                                  // result control flow branches
1224                                  // either to inner clone or outer
1225                                  // strip mined loop.
1226   };
1227   void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
1228                   CloneLoopMode mode, Node* side_by_side_idom = NULL);
1229   void clone_loop_handle_data_uses(Node* old, Node_List &old_new,
1230                                    IdealLoopTree* loop, IdealLoopTree* companion_loop,
1231                                    Node_List*& split_if_set, Node_List*& split_bool_set,
1232                                    Node_List*& split_cex_set, Node_List& worklist,
1233                                    uint new_counter, CloneLoopMode mode);
1234   void clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
1235                         IdealLoopTree* outer_loop, int dd, Node_List &old_new,
1236                         Node_List& extra_data_nodes);
1237 
1238   // If we got the effect of peeling, either by actually peeling or by
1239   // making a pre-loop which must execute at least once, we can remove
1240   // all loop-invariant dominated tests in the main body.
1241   void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new );
1242 
1243   // Generate code to do a loop peel for the given loop (and body).
1244   // old_new is a temp array.
1245   void do_peeling( IdealLoopTree *loop, Node_List &old_new );
1246 
1247   // Add pre and post loops around the given loop.  These loops are used
1248   // during RCE, unrolling and aligning loops.
1249   void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only );
1250 
1251   // Add post loop after the given loop.
1252   Node *insert_post_loop(IdealLoopTree* loop, Node_List& old_new,
1253                          CountedLoopNode* main_head, CountedLoopEndNode* main_end,
1254                          Node*& incr, Node* limit, CountedLoopNode*& post_head);
1255 
1256   // Add an RCE'd post loop which we will multi-version adapt for run time test path usage
1257   void insert_scalar_rced_post_loop( IdealLoopTree *loop, Node_List &old_new );
1258 
1259   // Add a vector post loop between a vector main loop and the current post loop
1260   void insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new);
1261   // If Node n lives in the back_ctrl block, we clone a private version of n
1262   // in preheader_ctrl block and return that, otherwise return n.
1263   Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones );
1264 
1265   // Take steps to maximally unroll the loop.  Peel any odd iterations, then
1266   // unroll to do double iterations.  The next round of major loop transforms
1267   // will repeat till the doubled loop body does all remaining iterations in 1
1268   // pass.
1269   void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new );
1270 
1271   // Unroll the loop body one step - make each trip do 2 iterations.
1272   void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip );
1273 
1274   // Mark vector reduction candidates before loop unrolling
1275   void mark_reductions( IdealLoopTree *loop );
1276 
1277   // Return true if exp is a constant times an induction var
1278   bool is_scaled_iv(Node* exp, Node* iv, BasicType bt, jlong* p_scale, bool* p_short_scale, int depth = 0);
1279 
1280   bool is_iv(Node* exp, Node* iv, BasicType bt);
1281 
1282   // Return true if exp is a scaled induction var plus (or minus) constant
1283   bool is_scaled_iv_plus_offset(Node* exp, Node* iv, BasicType bt, jlong* p_scale, Node** p_offset, bool* p_short_scale = NULL, int depth = 0);
1284   bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset) {
1285     jlong long_scale;
1286     if (is_scaled_iv_plus_offset(exp, iv, T_INT, &long_scale, p_offset)) {
1287       int int_scale = checked_cast<int>(long_scale);
1288       if (p_scale != NULL) {
1289         *p_scale = int_scale;
1290       }
1291       return true;
1292     }
1293     return false;
1294   }
1295   // Helper for finding more complex matches to is_scaled_iv_plus_offset.
1296   bool is_scaled_iv_plus_extra_offset(Node* exp1, Node* offset2, Node* iv,
1297                                       BasicType bt,
1298                                       jlong* p_scale, Node** p_offset,
1299                                       bool* p_short_scale, int depth);
1300 
1301 
1302   // Enum to determine the action to be performed in create_new_if_for_predicate() when processing phis of UCT regions.
1303   enum class UnswitchingAction {
1304     None,            // No special action.
1305     FastLoopCloning, // Need to clone nodes for the fast loop.
1306     SlowLoopRewiring // Need to rewire nodes for the slow loop.
1307   };
1308 
1309   // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted
1310   ProjNode* create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry, Deoptimization::DeoptReason reason,
1311                                         int opcode, bool if_cont_is_true_proj = true, Node_List* old_new = NULL,
1312                                         UnswitchingAction unswitching_action = UnswitchingAction::None);
1313 
1314   // Clone data nodes for the fast loop while creating a new If with create_new_if_for_predicate.
1315   Node* clone_data_nodes_for_fast_loop(Node* phi_input, ProjNode* uncommon_proj, Node* if_uct, Node_List* old_new);
1316 
1317   void register_control(Node* n, IdealLoopTree *loop, Node* pred, bool update_body = true);
1318 
1319   static Node* skip_all_loop_predicates(Node* entry);
1320   static Node* skip_loop_predicates(Node* entry);
1321 
1322   // Find a good location to insert a predicate
1323   static ProjNode* find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason);
1324   // Find a predicate
1325   static Node* find_predicate(Node* entry);
1326   // Construct a range check for a predicate if
1327   BoolNode* rc_predicate(IdealLoopTree *loop, Node* ctrl,
1328                          int scale, Node* offset,
1329                          Node* init, Node* limit, jint stride,
1330                          Node* range, bool upper, bool &overflow,
1331                          bool negate);
1332 
1333   // Implementation of the loop predication to promote checks outside the loop
1334   bool loop_predication_impl(IdealLoopTree *loop);
1335   bool loop_predication_impl_helper(IdealLoopTree *loop, ProjNode* proj, ProjNode *predicate_proj,
1336                                     CountedLoopNode *cl, ConNode* zero, Invariance& invar,
1337                                     Deoptimization::DeoptReason reason);
1338   bool loop_predication_should_follow_branches(IdealLoopTree *loop, ProjNode *predicate_proj, float& loop_trip_cnt);
1339   void loop_predication_follow_branches(Node *c, IdealLoopTree *loop, float loop_trip_cnt,
1340                                         PathFrequency& pf, Node_Stack& stack, VectorSet& seen,
1341                                         Node_List& if_proj_list);
1342   ProjNode* insert_initial_skeleton_predicate(IfNode* iff, IdealLoopTree *loop,
1343                                               ProjNode* proj, ProjNode *predicate_proj,
1344                                               ProjNode* upper_bound_proj,
1345                                               int scale, Node* offset,
1346                                               Node* init, Node* limit, jint stride,
1347                                               Node* rng, bool& overflow,
1348                                               Deoptimization::DeoptReason reason);
1349   Node* add_range_check_predicate(IdealLoopTree* loop, CountedLoopNode* cl,
1350                                   Node* predicate_proj, int scale_con, Node* offset,
1351                                   Node* limit, jint stride_con, Node* value);
1352 
1353   // Helper function to collect predicate for eliminating the useless ones
1354   void collect_potentially_useful_predicates(IdealLoopTree *loop, Unique_Node_List &predicate_opaque1);
1355   void eliminate_useless_predicates();
1356 
1357   // Change the control input of expensive nodes to allow commoning by
1358   // IGVN when it is guaranteed to not result in a more frequent
1359   // execution of the expensive node. Return true if progress.
1360   bool process_expensive_nodes();
1361 
1362   // Check whether node has become unreachable
1363   bool is_node_unreachable(Node *n) const {
1364     return !has_node(n) || n->is_unreachable(_igvn);
1365   }
1366 
1367   // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1368   int do_range_check( IdealLoopTree *loop, Node_List &old_new );
1369 
1370   // Check to see if do_range_check(...) cleaned the main loop of range-checks
1371   void has_range_checks(IdealLoopTree *loop);
1372 
1373   // Process post loops which have range checks and try to build a multi-version
1374   // guard to safely determine if we can execute the post loop which was RCE'd.
1375   bool multi_version_post_loops(IdealLoopTree *rce_loop, IdealLoopTree *legacy_loop);
1376 
1377   // Cause the rce'd post loop to optimized away, this happens if we cannot complete multiverioning
1378   void poison_rce_post_loop(IdealLoopTree *rce_loop);
1379 
1380   // Create a slow version of the loop by cloning the loop
1381   // and inserting an if to select fast-slow versions.
1382   // Return the inserted if.
1383   IfNode* create_slow_version_of_loop(IdealLoopTree *loop,
1384                                         Node_List &old_new,
1385                                         IfNode* unswitch_iff,
1386                                         CloneLoopMode mode);
1387 
1388   // Clone a loop and return the clone head (clone_loop_head).
1389   // Added nodes include int(1), int(0) - disconnected, If, IfTrue, IfFalse,
1390   // This routine was created for usage in CountedLoopReserveKit.
1391   //
1392   //    int(1) -> If -> IfTrue -> original_loop_head
1393   //              |
1394   //              V
1395   //           IfFalse -> clone_loop_head (returned by function pointer)
1396   //
1397   LoopNode* create_reserve_version_of_loop(IdealLoopTree *loop, CountedLoopReserveKit* lk);
1398   // Clone loop with an invariant test (that does not exit) and
1399   // insert a clone of the test that selects which version to
1400   // execute.
1401   void do_unswitching (IdealLoopTree *loop, Node_List &old_new);
1402 
1403   // Find candidate "if" for unswitching
1404   IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const;
1405 
1406   // Range Check Elimination uses this function!
1407   // Constrain the main loop iterations so the affine function:
1408   //    low_limit <= scale_con * I + offset  <  upper_limit
1409   // always holds true.  That is, either increase the number of iterations in
1410   // the pre-loop or the post-loop until the condition holds true in the main
1411   // loop.  Scale_con, offset and limit are all loop invariant.
1412   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);
1413   // Helper function for add_constraint().
1414   Node* adjust_limit(bool reduce, Node* scale, Node* offset, Node* rc_limit, Node* old_limit, Node* pre_ctrl, bool round);
1415 
1416   // Partially peel loop up through last_peel node.
1417   bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
1418 
1419   // Create a scheduled list of nodes control dependent on ctrl set.
1420   void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched );
1421   // Has a use in the vector set
1422   bool has_use_in_set( Node* n, VectorSet& vset );
1423   // Has use internal to the vector set (ie. not in a phi at the loop head)
1424   bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop );
1425   // clone "n" for uses that are outside of loop
1426   int  clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist );
1427   // clone "n" for special uses that are in the not_peeled region
1428   void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
1429                                           VectorSet& not_peel, Node_List& sink_list, Node_List& worklist );
1430   // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
1431   void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp );
1432 #ifdef ASSERT
1433   // Validate the loop partition sets: peel and not_peel
1434   bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel );
1435   // Ensure that uses outside of loop are of the right form
1436   bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
1437                                  uint orig_exit_idx, uint clone_exit_idx);
1438   bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx);
1439 #endif
1440 
1441   // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.)
1442   int stride_of_possible_iv( Node* iff );
1443   bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; }
1444   // Return the (unique) control output node that's in the loop (if it exists.)
1445   Node* stay_in_loop( Node* n, IdealLoopTree *loop);
1446   // Insert a signed compare loop exit cloned from an unsigned compare.
1447   IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop);
1448   void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop);
1449   // Utility to register node "n" with PhaseIdealLoop
1450   void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth);
1451   // Utility to create an if-projection
1452   ProjNode* proj_clone(ProjNode* p, IfNode* iff);
1453   // Force the iff control output to be the live_proj
1454   Node* short_circuit_if(IfNode* iff, ProjNode* live_proj);
1455   // Insert a region before an if projection
1456   RegionNode* insert_region_before_proj(ProjNode* proj);
1457   // Insert a new if before an if projection
1458   ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj);
1459 
1460   // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
1461   // "Nearly" because all Nodes have been cloned from the original in the loop,
1462   // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
1463   // through the Phi recursively, and return a Bool.
1464   Node *clone_iff( PhiNode *phi, IdealLoopTree *loop );
1465   CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop );
1466 
1467 
1468   // Rework addressing expressions to get the most loop-invariant stuff
1469   // moved out.  We'd like to do all associative operators, but it's especially
1470   // important (common) to do address expressions.
1471   Node* remix_address_expressions(Node* n);
1472   Node* remix_address_expressions_add_left_shift(Node* n, IdealLoopTree* n_loop, Node* n_ctrl, BasicType bt);
1473 
1474   // Convert add to muladd to generate MuladdS2I under certain criteria
1475   Node * convert_add_to_muladd(Node * n);
1476 
1477   // Attempt to use a conditional move instead of a phi/branch
1478   Node *conditional_move( Node *n );
1479 
1480   // Reorganize offset computations to lower register pressure.
1481   // Mostly prevent loop-fallout uses of the pre-incremented trip counter
1482   // (which are then alive with the post-incremented trip counter
1483   // forcing an extra register move)
1484   void reorg_offsets( IdealLoopTree *loop );
1485 
1486   // Check for aggressive application of 'split-if' optimization,
1487   // using basic block level info.
1488   void  split_if_with_blocks     ( VectorSet &visited, Node_Stack &nstack);
1489   Node *split_if_with_blocks_pre ( Node *n );
1490   void  split_if_with_blocks_post( Node *n );
1491   Node *has_local_phi_input( Node *n );
1492   // Mark an IfNode as being dominated by a prior test,
1493   // without actually altering the CFG (and hence IDOM info).
1494   void dominated_by(IfProjNode* prevdom, IfNode* iff, bool flip = false, bool exclude_loop_predicate = false);
1495 
1496   // Split Node 'n' through merge point
1497   RegionNode* split_thru_region(Node* n, RegionNode* region);
1498   // Split Node 'n' through merge point if there is enough win.
1499   Node *split_thru_phi( Node *n, Node *region, int policy );
1500   // Found an If getting its condition-code input from a Phi in the
1501   // same block.  Split thru the Region.
1502   void do_split_if(Node *iff, RegionNode** new_false_region = NULL, RegionNode** new_true_region = NULL);
1503 
1504   // Conversion of fill/copy patterns into intrinsic versions
1505   bool do_intrinsify_fill();
1506   bool intrinsify_fill(IdealLoopTree* lpt);
1507   bool match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
1508                        Node*& shift, Node*& offset);
1509 
1510 private:
1511   // Return a type based on condition control flow
1512   const TypeInt* filtered_type( Node *n, Node* n_ctrl);
1513   const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); }
1514  // Helpers for filtered type
1515   const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl);
1516 
1517   // Helper functions
1518   Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache );
1519   Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true );
1520   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 );
1521   bool split_up( Node *n, Node *blk1, Node *blk2 );
1522   void sink_use( Node *use, Node *post_loop );
1523   Node* place_outside_loop(Node* useblock, IdealLoopTree* loop) const;
1524   Node* try_move_store_before_loop(Node* n, Node *n_ctrl);
1525   void try_move_store_after_loop(Node* n);
1526   bool identical_backtoback_ifs(Node *n);
1527   bool can_split_if(Node *n_ctrl);
1528 
1529   // Determine if a method is too big for a/another round of split-if, based on
1530   // a magic (approximate) ratio derived from the equally magic constant 35000,
1531   // previously used for this purpose (but without relating to the node limit).
1532   bool must_throttle_split_if() {
1533     uint threshold = C->max_node_limit() * 2 / 5;
1534     return C->live_nodes() > threshold;
1535   }
1536 
1537   // A simplistic node request tracking mechanism, where
1538   //   = UINT_MAX   Request not valid or made final.
1539   //   < UINT_MAX   Nodes currently requested (estimate).
1540   uint _nodes_required;
1541 
1542   enum { REQUIRE_MIN = 70 };
1543 
1544   uint nodes_required() const { return _nodes_required; }
1545 
1546   // Given the _currently_  available number of nodes, check  whether there is
1547   // "room" for an additional request or not, considering the already required
1548   // number of  nodes.  Return TRUE if  the new request is  exceeding the node
1549   // budget limit, otherwise return FALSE.  Note that this interpretation will
1550   // act pessimistic on  additional requests when new nodes  have already been
1551   // generated since the 'begin'.  This behaviour fits with the intention that
1552   // node estimates/requests should be made upfront.
1553   bool exceeding_node_budget(uint required = 0) {
1554     assert(C->live_nodes() < C->max_node_limit(), "sanity");
1555     uint available = C->max_node_limit() - C->live_nodes();
1556     return available < required + _nodes_required + REQUIRE_MIN;
1557   }
1558 
1559   uint require_nodes(uint require, uint minreq = REQUIRE_MIN) {
1560     precond(require > 0);
1561     _nodes_required += MAX2(require, minreq);
1562     return _nodes_required;
1563   }
1564 
1565   bool may_require_nodes(uint require, uint minreq = REQUIRE_MIN) {
1566     return !exceeding_node_budget(require) && require_nodes(require, minreq) > 0;
1567   }
1568 
1569   uint require_nodes_begin() {
1570     assert(_nodes_required == UINT_MAX, "Bad state (begin).");
1571     _nodes_required = 0;
1572     return C->live_nodes();
1573   }
1574 
1575   // When a node request is final,  optionally check that the requested number
1576   // of nodes was  reasonably correct with respect to the  number of new nodes
1577   // introduced since the last 'begin'. Always check that we have not exceeded
1578   // the maximum node limit.
1579   void require_nodes_final(uint live_at_begin, bool check_estimate) {
1580     assert(_nodes_required < UINT_MAX, "Bad state (final).");
1581 
1582 #ifdef ASSERT
1583     if (check_estimate) {
1584       // Check that the node budget request was not off by too much (x2).
1585       // Should this be the case we _surely_ need to improve the estimates
1586       // used in our budget calculations.
1587       if (C->live_nodes() - live_at_begin > 2 * _nodes_required) {
1588         log_info(compilation)("Bad node estimate: actual = %d >> request = %d",
1589                               C->live_nodes() - live_at_begin, _nodes_required);
1590       }
1591     }
1592 #endif
1593     // Assert that we have stayed within the node budget limit.
1594     assert(C->live_nodes() < C->max_node_limit(),
1595            "Exceeding node budget limit: %d + %d > %d (request = %d)",
1596            C->live_nodes() - live_at_begin, live_at_begin,
1597            C->max_node_limit(), _nodes_required);
1598 
1599     _nodes_required = UINT_MAX;
1600   }
1601 
1602   // Clone loop predicates to slow and fast loop when unswitching a loop
1603   void clone_predicates_to_unswitched_loop(IdealLoopTree* loop, Node_List& old_new, ProjNode*& iffast_pred, ProjNode*& ifslow_pred);
1604   ProjNode* clone_predicate_to_unswitched_loop(ProjNode* predicate_proj, Node* new_entry, Deoptimization::DeoptReason reason,
1605                                                Node_List* old_new = NULL);
1606   void clone_skeleton_predicates_to_unswitched_loop(IdealLoopTree* loop, const Node_List& old_new, Deoptimization::DeoptReason reason,
1607                                                     ProjNode* old_predicate_proj, ProjNode* iffast_pred, ProjNode* ifslow_pred);
1608   ProjNode* clone_skeleton_predicate_for_unswitched_loops(Node* iff, ProjNode* predicate,
1609                                                           Deoptimization::DeoptReason reason,
1610                                                           ProjNode* output_proj);
1611   static void check_created_predicate_for_unswitching(const Node* new_entry) PRODUCT_RETURN;
1612 
1613   bool _created_loop_node;
1614 #ifdef ASSERT
1615   void dump_real_LCA(Node* early, Node* wrong_lca);
1616   bool check_idom_chains_intersection(const Node* n, uint& idom_idx_new, uint& idom_idx_other, const Node_List* nodes_seen) const;
1617 #endif
1618 
1619 public:
1620   void set_created_loop_node() { _created_loop_node = true; }
1621   bool created_loop_node()     { return _created_loop_node; }
1622   void register_new_node(Node* n, Node* blk);
1623 
1624 #ifdef ASSERT
1625   void dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA);
1626 #endif
1627 
1628 #ifndef PRODUCT
1629   void dump() const;
1630   void dump_idom(Node* n) const;
1631   void dump(IdealLoopTree* loop, uint rpo_idx, Node_List &rpo_list) const;
1632   void verify() const;          // Major slow  :-)
1633   void verify_compare(Node* n, const PhaseIdealLoop* loop_verify, VectorSet &visited) const;
1634   IdealLoopTree* get_loop_idx(Node* n) const {
1635     // Dead nodes have no loop, so return the top level loop instead
1636     return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root;
1637   }
1638   // Print some stats
1639   static void print_statistics();
1640   static int _loop_invokes;     // Count of PhaseIdealLoop invokes
1641   static int _loop_work;        // Sum of PhaseIdealLoop x _unique
1642   static volatile int _long_loop_candidates;
1643   static volatile int _long_loop_nests;
1644   static volatile int _long_loop_counted_loops;
1645 #endif
1646 
1647   void rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const;
1648 
1649   void check_counted_loop_shape(IdealLoopTree* loop, Node* x, BasicType bt) NOT_DEBUG_RETURN;
1650 
1651   LoopNode* create_inner_head(IdealLoopTree* loop, BaseCountedLoopNode* head, IfNode* exit_test);
1652 
1653 
1654   int extract_long_range_checks(const IdealLoopTree* loop, jlong stride_con, int iters_limit, PhiNode* phi,
1655                                       Node_List &range_checks);
1656 
1657   void transform_long_range_checks(int stride_con, const Node_List &range_checks, Node* outer_phi,
1658                                    Node* inner_iters_actual_int, Node* inner_phi,
1659                                    Node* iv_add, LoopNode* inner_head);
1660 
1661   Node* get_late_ctrl_with_anti_dep(LoadNode* n, Node* early, Node* LCA);
1662 
1663   bool ctrl_of_use_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop, Node* ctrl);
1664 
1665   bool ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop);
1666 
1667   Node* compute_early_ctrl(Node* n, Node* n_ctrl);
1668 
1669   void try_sink_out_of_loop(Node* n);
1670 
1671   Node* clamp(Node* R, Node* L, Node* H);
1672 
1673   bool safe_for_if_replacement(const Node* dom) const;
1674 
1675   void push_pinned_nodes_thru_region(IfNode* dom_if, Node* region);
1676 
1677   bool try_merge_identical_ifs(Node* n);
1678 };
1679 
1680 
1681 class AutoNodeBudget : public StackObj
1682 {
1683 public:
1684   enum budget_check_t { BUDGET_CHECK, NO_BUDGET_CHECK };
1685 
1686   AutoNodeBudget(PhaseIdealLoop* phase, budget_check_t chk = BUDGET_CHECK)
1687     : _phase(phase),
1688       _check_at_final(chk == BUDGET_CHECK),
1689       _nodes_at_begin(0)
1690   {
1691     precond(_phase != NULL);
1692 
1693     _nodes_at_begin = _phase->require_nodes_begin();
1694   }
1695 
1696   ~AutoNodeBudget() {
1697 #ifndef PRODUCT
1698     if (TraceLoopOpts) {
1699       uint request = _phase->nodes_required();
1700       uint delta   = _phase->C->live_nodes() - _nodes_at_begin;
1701 
1702       if (request < delta) {
1703         tty->print_cr("Exceeding node budget: %d < %d", request, delta);
1704       } else {
1705         uint const REQUIRE_MIN = PhaseIdealLoop::REQUIRE_MIN;
1706         // Identify the worst estimates as "poor" ones.
1707         if (request > REQUIRE_MIN && delta > 0) {
1708           if ((delta >  REQUIRE_MIN && request >  3 * delta) ||
1709               (delta <= REQUIRE_MIN && request > 10 * delta)) {
1710             tty->print_cr("Poor node estimate: %d >> %d", request, delta);
1711           }
1712         }
1713       }
1714     }
1715 #endif // PRODUCT
1716     _phase->require_nodes_final(_nodes_at_begin, _check_at_final);
1717   }
1718 
1719 private:
1720   PhaseIdealLoop* _phase;
1721   bool _check_at_final;
1722   uint _nodes_at_begin;
1723 };
1724 
1725 
1726 // This kit may be used for making of a reserved copy of a loop before this loop
1727 //  goes under non-reversible changes.
1728 //
1729 // Function create_reserve() creates a reserved copy (clone) of the loop.
1730 // The reserved copy is created by calling
1731 // PhaseIdealLoop::create_reserve_version_of_loop - see there how
1732 // the original and reserved loops are connected in the outer graph.
1733 // If create_reserve succeeded, it returns 'true' and _has_reserved is set to 'true'.
1734 //
1735 // By default the reserved copy (clone) of the loop is created as dead code - it is
1736 // dominated in the outer loop by this node chain:
1737 //   intcon(1)->If->IfFalse->reserved_copy.
1738 // The original loop is dominated by the the same node chain but IfTrue projection:
1739 //   intcon(0)->If->IfTrue->original_loop.
1740 //
1741 // In this implementation of CountedLoopReserveKit the ctor includes create_reserve()
1742 // and the dtor, checks _use_new value.
1743 // If _use_new == false, it "switches" control to reserved copy of the loop
1744 // by simple replacing of node intcon(1) with node intcon(0).
1745 //
1746 // Here is a proposed example of usage (see also SuperWord::output in superword.cpp).
1747 //
1748 // void CountedLoopReserveKit_example()
1749 // {
1750 //    CountedLoopReserveKit lrk((phase, lpt, DoReserveCopy = true); // create local object
1751 //    if (DoReserveCopy && !lrk.has_reserved()) {
1752 //      return; //failed to create reserved loop copy
1753 //    }
1754 //    ...
1755 //    //something is wrong, switch to original loop
1756 ///   if(something_is_wrong) return; // ~CountedLoopReserveKit makes the switch
1757 //    ...
1758 //    //everything worked ok, return with the newly modified loop
1759 //    lrk.use_new();
1760 //    return; // ~CountedLoopReserveKit does nothing once use_new() was called
1761 //  }
1762 //
1763 // Keep in mind, that by default if create_reserve() is not followed by use_new()
1764 // the dtor will "switch to the original" loop.
1765 // NOTE. You you modify outside of the original loop this class is no help.
1766 //
1767 class CountedLoopReserveKit {
1768   private:
1769     PhaseIdealLoop* _phase;
1770     IdealLoopTree*  _lpt;
1771     LoopNode*       _lp;
1772     IfNode*         _iff;
1773     LoopNode*       _lp_reserved;
1774     bool            _has_reserved;
1775     bool            _use_new;
1776     const bool      _active; //may be set to false in ctor, then the object is dummy
1777 
1778   public:
1779     CountedLoopReserveKit(PhaseIdealLoop* phase, IdealLoopTree *loop, bool active);
1780     ~CountedLoopReserveKit();
1781     void use_new()                {_use_new = true;}
1782     void set_iff(IfNode* x)       {_iff = x;}
1783     bool has_reserved()     const { return _active && _has_reserved;}
1784   private:
1785     bool create_reserve();
1786 };// class CountedLoopReserveKit
1787 
1788 inline Node* IdealLoopTree::tail() {
1789   // Handle lazy update of _tail field.
1790   if (_tail->in(0) == NULL) {
1791     _tail = _phase->get_ctrl(_tail);
1792   }
1793   return _tail;
1794 }
1795 
1796 inline Node* IdealLoopTree::head() {
1797   // Handle lazy update of _head field.
1798   if (_head->in(0) == NULL) {
1799     _head = _phase->get_ctrl(_head);
1800   }
1801   return _head;
1802 }
1803 
1804 // Iterate over the loop tree using a preorder, left-to-right traversal.
1805 //
1806 // Example that visits all counted loops from within PhaseIdealLoop
1807 //
1808 //  for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
1809 //   IdealLoopTree* lpt = iter.current();
1810 //   if (!lpt->is_counted()) continue;
1811 //   ...
1812 class LoopTreeIterator : public StackObj {
1813 private:
1814   IdealLoopTree* _root;
1815   IdealLoopTree* _curnt;
1816 
1817 public:
1818   LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {}
1819 
1820   bool done() { return _curnt == NULL; }       // Finished iterating?
1821 
1822   void next();                                 // Advance to next loop tree
1823 
1824   IdealLoopTree* current() { return _curnt; }  // Return current value of iterator.
1825 };
1826 
1827 #endif // SHARE_OPTO_LOOPNODE_HPP