1 /*
   2  * Copyright (c) 1998, 2021, 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          TransformedLongInnerLoop = 1<<18,
  81          TransformedLongOuterLoop = 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_transformed_long_inner_loop() const { return _loop_flags & TransformedLongInnerLoop; }
 107   bool is_transformed_long_outer_loop() const { return _loop_flags & TransformedLongOuterLoop; }
 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 mark_is_multiversioned() { _loop_flags |= IsMultiversioned; }
 118   void mark_strip_mined() { _loop_flags |= StripMined; }
 119   void clear_strip_mined() { _loop_flags &= ~StripMined; }
 120   void mark_profile_trip_failed() { _loop_flags |= ProfileTripFailed; }
 121   void mark_subword_loop() { _loop_flags |= SubwordLoop; }
 122   void mark_transformed_long_inner_loop() { _loop_flags |= TransformedLongInnerLoop; }
 123   void mark_transformed_long_outer_loop() { _loop_flags |= TransformedLongOuterLoop; }
 124 
 125   int unswitch_max() { return _unswitch_max; }
 126   int unswitch_count() { return _unswitch_count; }
 127 
 128   int has_been_range_checked() const { return _postloop_flags & LoopRCEChecked; }
 129   void set_has_been_range_checked() { _postloop_flags |= LoopRCEChecked; }
 130   int is_rce_post_loop() const { return _postloop_flags & RCEPostLoop; }
 131   void set_is_rce_post_loop() { _postloop_flags |= RCEPostLoop; }
 132 
 133   void set_unswitch_count(int val) {
 134     assert (val <= unswitch_max(), "too many unswitches");
 135     _unswitch_count = val;
 136   }
 137 
 138   void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
 139   float profile_trip_cnt()             { return _profile_trip_cnt; }
 140 
 141   LoopNode(Node *entry, Node *backedge)
 142     : RegionNode(3), _loop_flags(0), _unswitch_count(0),
 143       _postloop_flags(0), _profile_trip_cnt(COUNT_UNKNOWN)  {
 144     init_class_id(Class_Loop);
 145     init_req(EntryControl, entry);
 146     init_req(LoopBackControl, backedge);
 147   }
 148 
 149   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 150   virtual int Opcode() const;
 151   bool can_be_counted_loop(PhaseTransform* phase) const {
 152     return req() == 3 && in(0) != NULL &&
 153       in(1) != NULL && phase->type(in(1)) != Type::TOP &&
 154       in(2) != NULL && phase->type(in(2)) != Type::TOP;
 155   }
 156   bool is_valid_counted_loop(BasicType bt) const;
 157 #ifndef PRODUCT
 158   virtual void dump_spec(outputStream *st) const;
 159 #endif
 160 
 161   void verify_strip_mined(int expect_skeleton) const NOT_DEBUG_RETURN;
 162   virtual LoopNode* skip_strip_mined(int expect_skeleton = 1) { return this; }
 163   virtual IfTrueNode* outer_loop_tail() const { ShouldNotReachHere(); return NULL; }
 164   virtual OuterStripMinedLoopEndNode* outer_loop_end() const { ShouldNotReachHere(); return NULL; }
 165   virtual IfFalseNode* outer_loop_exit() const { ShouldNotReachHere(); return NULL; }
 166   virtual SafePointNode* outer_safepoint() const { ShouldNotReachHere(); return NULL; }
 167 };
 168 
 169 //------------------------------Counted Loops----------------------------------
 170 // Counted loops are all trip-counted loops, with exactly 1 trip-counter exit
 171 // path (and maybe some other exit paths).  The trip-counter exit is always
 172 // last in the loop.  The trip-counter have to stride by a constant;
 173 // the exit value is also loop invariant.
 174 
 175 // CountedLoopNodes and CountedLoopEndNodes come in matched pairs.  The
 176 // CountedLoopNode has the incoming loop control and the loop-back-control
 177 // which is always the IfTrue before the matching CountedLoopEndNode.  The
 178 // CountedLoopEndNode has an incoming control (possibly not the
 179 // CountedLoopNode if there is control flow in the loop), the post-increment
 180 // trip-counter value, and the limit.  The trip-counter value is always of
 181 // the form (Op old-trip-counter stride).  The old-trip-counter is produced
 182 // by a Phi connected to the CountedLoopNode.  The stride is constant.
 183 // The Op is any commutable opcode, including Add, Mul, Xor.  The
 184 // CountedLoopEndNode also takes in the loop-invariant limit value.
 185 
 186 // From a CountedLoopNode I can reach the matching CountedLoopEndNode via the
 187 // loop-back control.  From CountedLoopEndNodes I can reach CountedLoopNodes
 188 // via the old-trip-counter from the Op node.
 189 
 190 //------------------------------CountedLoopNode--------------------------------
 191 // CountedLoopNodes head simple counted loops.  CountedLoopNodes have as
 192 // inputs the incoming loop-start control and the loop-back control, so they
 193 // act like RegionNodes.  They also take in the initial trip counter, the
 194 // loop-invariant stride and the loop-invariant limit value.  CountedLoopNodes
 195 // produce a loop-body control and the trip counter value.  Since
 196 // CountedLoopNodes behave like RegionNodes I still have a standard CFG model.
 197 
 198 class BaseCountedLoopNode : public LoopNode {
 199 public:
 200   BaseCountedLoopNode(Node *entry, Node *backedge)
 201     : LoopNode(entry, backedge) {
 202   }
 203 
 204   Node *init_control() const { return in(EntryControl); }
 205   Node *back_control() const { return in(LoopBackControl); }
 206 
 207   Node* init_trip() const;
 208   Node* stride() const;
 209   bool stride_is_con() const;
 210   Node* limit() const;
 211   Node* incr() const;
 212   Node* phi() const;
 213 
 214   BaseCountedLoopEndNode* loopexit_or_null() const;
 215   BaseCountedLoopEndNode* loopexit() const;
 216 
 217   virtual BasicType bt() const = 0;
 218   virtual bool operates_on(BasicType bt, bool signed_int) const {
 219     assert(bt == T_INT || bt == T_LONG, "unsupported");
 220     return false;
 221   }
 222 
 223   static BaseCountedLoopNode* make(Node* entry, Node* backedge, BasicType bt);
 224 };
 225 
 226 
 227 class CountedLoopNode : public BaseCountedLoopNode {
 228   // Size is bigger to hold _main_idx.  However, _main_idx does not change
 229   // the semantics so it does not appear in the hash & cmp functions.
 230   virtual uint size_of() const { return sizeof(*this); }
 231 
 232   // For Pre- and Post-loops during debugging ONLY, this holds the index of
 233   // the Main CountedLoop.  Used to assert that we understand the graph shape.
 234   node_idx_t _main_idx;
 235 
 236   // Known trip count calculated by compute_exact_trip_count()
 237   uint  _trip_count;
 238 
 239   // Log2 of original loop bodies in unrolled loop
 240   int _unrolled_count_log2;
 241 
 242   // Node count prior to last unrolling - used to decide if
 243   // unroll,optimize,unroll,optimize,... is making progress
 244   int _node_count_before_unroll;
 245 
 246   // If slp analysis is performed we record the maximum
 247   // vector mapped unroll factor here
 248   int _slp_maximum_unroll_factor;
 249 
 250 public:
 251   CountedLoopNode(Node *entry, Node *backedge)
 252     : BaseCountedLoopNode(entry, backedge), _main_idx(0), _trip_count(max_juint),
 253       _unrolled_count_log2(0), _node_count_before_unroll(0),
 254       _slp_maximum_unroll_factor(0) {
 255     init_class_id(Class_CountedLoop);
 256     // Initialize _trip_count to the largest possible value.
 257     // Will be reset (lower) if the loop's trip count is known.
 258   }
 259 
 260   virtual int Opcode() const;
 261   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 262 
 263   CountedLoopEndNode* loopexit_or_null() const { return (CountedLoopEndNode*) BaseCountedLoopNode::loopexit_or_null(); }
 264   CountedLoopEndNode* loopexit() const { return (CountedLoopEndNode*) BaseCountedLoopNode::loopexit(); }
 265   int   stride_con() const;
 266 
 267   // Match increment with optional truncation
 268   static Node*
 269   match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInteger** trunc_type,
 270                                       BasicType bt);
 271 
 272   // A 'main' loop has a pre-loop and a post-loop.  The 'main' loop
 273   // can run short a few iterations and may start a few iterations in.
 274   // It will be RCE'd and unrolled and aligned.
 275 
 276   // A following 'post' loop will run any remaining iterations.  Used
 277   // during Range Check Elimination, the 'post' loop will do any final
 278   // iterations with full checks.  Also used by Loop Unrolling, where
 279   // the 'post' loop will do any epilog iterations needed.  Basically,
 280   // a 'post' loop can not profitably be further unrolled or RCE'd.
 281 
 282   // A preceding 'pre' loop will run at least 1 iteration (to do peeling),
 283   // it may do under-flow checks for RCE and may do alignment iterations
 284   // so the following main loop 'knows' that it is striding down cache
 285   // lines.
 286 
 287   // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or
 288   // Aligned, may be missing it's pre-loop.
 289   bool is_normal_loop   () const { return (_loop_flags&PreMainPostFlagsMask) == Normal; }
 290   bool is_pre_loop      () const { return (_loop_flags&PreMainPostFlagsMask) == Pre;    }
 291   bool is_main_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Main;   }
 292   bool is_post_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Post;   }
 293   bool is_reduction_loop() const { return (_loop_flags&HasReductions) == HasReductions; }
 294   bool was_slp_analyzed () const { return (_loop_flags&WasSlpAnalyzed) == WasSlpAnalyzed; }
 295   bool has_passed_slp   () const { return (_loop_flags&PassedSlpAnalysis) == PassedSlpAnalysis; }
 296   bool is_unroll_only   () const { return (_loop_flags&DoUnrollOnly) == DoUnrollOnly; }
 297   bool is_main_no_pre_loop() const { return _loop_flags & MainHasNoPreLoop; }
 298   bool has_atomic_post_loop  () const { return (_loop_flags & HasAtomicPostLoop) == HasAtomicPostLoop; }
 299   void set_main_no_pre_loop() { _loop_flags |= MainHasNoPreLoop; }
 300 
 301   int main_idx() const { return _main_idx; }
 302 
 303 
 304   void set_pre_loop  (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; }
 305   void set_main_loop (                     ) { assert(is_normal_loop(),""); _loop_flags |= Main;                         }
 306   void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; }
 307   void set_normal_loop(                    ) { _loop_flags &= ~PreMainPostFlagsMask; }
 308 
 309   void set_trip_count(uint tc) { _trip_count = tc; }
 310   uint trip_count()            { return _trip_count; }
 311 
 312   bool has_exact_trip_count() const { return (_loop_flags & HasExactTripCount) != 0; }
 313   void set_exact_trip_count(uint tc) {
 314     _trip_count = tc;
 315     _loop_flags |= HasExactTripCount;
 316   }
 317   void set_nonexact_trip_count() {
 318     _loop_flags &= ~HasExactTripCount;
 319   }
 320   void set_notpassed_slp() {
 321     _loop_flags &= ~PassedSlpAnalysis;
 322   }
 323 
 324   void double_unrolled_count() { _unrolled_count_log2++; }
 325   int  unrolled_count()        { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); }
 326 
 327   void set_node_count_before_unroll(int ct)  { _node_count_before_unroll = ct; }
 328   int  node_count_before_unroll()            { return _node_count_before_unroll; }
 329   void set_slp_max_unroll(int unroll_factor) { _slp_maximum_unroll_factor = unroll_factor; }
 330   int  slp_max_unroll() const                { return _slp_maximum_unroll_factor; }
 331 
 332   virtual LoopNode* skip_strip_mined(int expect_skeleton = 1);
 333   OuterStripMinedLoopNode* outer_loop() const;
 334   virtual IfTrueNode* outer_loop_tail() const;
 335   virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
 336   virtual IfFalseNode* outer_loop_exit() const;
 337   virtual SafePointNode* outer_safepoint() const;
 338 
 339   // If this is a main loop in a pre/main/post loop nest, walk over
 340   // the predicates that were inserted by
 341   // duplicate_predicates()/add_range_check_predicate()
 342   static Node* skip_predicates_from_entry(Node* ctrl);
 343   Node* skip_predicates();
 344 
 345   virtual bool operates_on(BasicType bt, bool signed_int) const {
 346     assert(bt == T_INT || bt == T_LONG, "unsupported");
 347     return bt == T_INT;
 348   }
 349   virtual BasicType bt() const {
 350     return T_INT;
 351   }
 352 
 353   Node* is_canonical_loop_entry();
 354 
 355 #ifndef PRODUCT
 356   virtual void dump_spec(outputStream *st) const;
 357 #endif
 358 };
 359 
 360 class LongCountedLoopNode : public BaseCountedLoopNode {
 361 public:
 362   LongCountedLoopNode(Node *entry, Node *backedge)
 363     : BaseCountedLoopNode(entry, backedge) {
 364     init_class_id(Class_LongCountedLoop);
 365   }
 366 
 367   virtual int Opcode() const;
 368 
 369   virtual bool operates_on(BasicType bt, bool signed_int) const {
 370     assert(bt == T_INT || bt == T_LONG, "unsupported");
 371     return bt == T_LONG;
 372   }
 373 
 374   virtual BasicType bt() const {
 375     return T_LONG;
 376   }
 377 
 378   LongCountedLoopEndNode* loopexit_or_null() const { return (LongCountedLoopEndNode*) BaseCountedLoopNode::loopexit_or_null(); }
 379   LongCountedLoopEndNode* loopexit() const { return (LongCountedLoopEndNode*) BaseCountedLoopNode::loopexit(); }
 380   jlong   stride_con() const;
 381 };
 382 
 383 
 384 //------------------------------CountedLoopEndNode-----------------------------
 385 // CountedLoopEndNodes end simple trip counted loops.  They act much like
 386 // IfNodes.
 387 
 388 class BaseCountedLoopEndNode : public IfNode {
 389 public:
 390   enum { TestControl, TestValue };
 391   BaseCountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 392     : IfNode(control, test, prob, cnt) {
 393     init_class_id(Class_BaseCountedLoopEnd);
 394   }
 395 
 396   Node *cmp_node() const            { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; }
 397   Node* incr() const                { Node* tmp = cmp_node(); return (tmp && tmp->req() == 3) ? tmp->in(1) : NULL; }
 398   Node* limit() const               { Node* tmp = cmp_node(); return (tmp && tmp->req() == 3) ? tmp->in(2) : NULL; }
 399   Node* stride() const              { Node* tmp = incr(); return (tmp && tmp->req() == 3) ? tmp->in(2) : NULL; }
 400   Node* init_trip() const           { Node* tmp = phi(); return (tmp && tmp->req() == 3) ? tmp->in(1) : NULL; }
 401   bool stride_is_con() const        { Node *tmp = stride(); return (tmp != NULL && tmp->is_Con()); }
 402 
 403   PhiNode* phi() const {
 404     Node* tmp = incr();
 405     if (tmp && tmp->req() == 3) {
 406       Node* phi = tmp->in(1);
 407       if (phi->is_Phi()) {
 408         return phi->as_Phi();
 409       }
 410     }
 411     return NULL;
 412   }
 413 
 414   BaseCountedLoopNode* loopnode() const {
 415     // The CountedLoopNode that goes with this CountedLoopEndNode may
 416     // have been optimized out by the IGVN so be cautious with the
 417     // pattern matching on the graph
 418     PhiNode* iv_phi = phi();
 419     if (iv_phi == NULL) {
 420       return NULL;
 421     }
 422     Node* ln = iv_phi->in(0);
 423     if (!ln->is_BaseCountedLoop() || ln->as_BaseCountedLoop()->loopexit_or_null() != this) {
 424       return NULL;
 425     }
 426     if (!ln->operates_on(bt(), true)) {
 427       return NULL;
 428     }
 429     return ln->as_BaseCountedLoop();
 430   }
 431 
 432   BoolTest::mask test_trip() const  { return in(TestValue)->as_Bool()->_test._test; }
 433   virtual bool operates_on(BasicType bt, bool signed_int) const {
 434     assert(bt == T_INT || bt == T_LONG, "unsupported");
 435     return false;
 436   }
 437 
 438   jlong stride_con() const;
 439   virtual BasicType bt() const = 0;
 440 
 441   static BaseCountedLoopEndNode* make(Node* control, Node* test, float prob, float cnt, BasicType bt);
 442 };
 443 
 444 class CountedLoopEndNode : public BaseCountedLoopEndNode {
 445 public:
 446 
 447   CountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 448     : BaseCountedLoopEndNode(control, test, prob, cnt) {
 449     init_class_id(Class_CountedLoopEnd);
 450   }
 451   virtual int Opcode() const;
 452 
 453   CountedLoopNode* loopnode() const {
 454     return (CountedLoopNode*) BaseCountedLoopEndNode::loopnode();
 455   }
 456   virtual bool operates_on(BasicType bt, bool signed_int) const {
 457     assert(bt == T_INT || bt == T_LONG, "unsupported");
 458     return bt == T_INT;
 459   }
 460 
 461   virtual BasicType bt() const {
 462     return T_INT;
 463   }
 464 
 465 #ifndef PRODUCT
 466   virtual void dump_spec(outputStream *st) const;
 467 #endif
 468 };
 469 
 470 class LongCountedLoopEndNode : public BaseCountedLoopEndNode {
 471 public:
 472   LongCountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 473     : BaseCountedLoopEndNode(control, test, prob, cnt) {
 474     init_class_id(Class_LongCountedLoopEnd);
 475   }
 476 
 477   LongCountedLoopNode* loopnode() const {
 478     return (LongCountedLoopNode*) BaseCountedLoopEndNode::loopnode();
 479   }
 480   virtual bool operates_on(BasicType bt, bool signed_int) const {
 481     assert(bt == T_INT || bt == T_LONG, "unsupported");
 482     return bt == T_LONG;
 483   }
 484   virtual int Opcode() const;
 485 
 486   virtual BasicType bt() const {
 487     return T_LONG;
 488   }
 489 };
 490 
 491 
 492 inline BaseCountedLoopEndNode* BaseCountedLoopNode::loopexit_or_null() const {
 493   Node* bctrl = back_control();
 494   if (bctrl == NULL) return NULL;
 495 
 496   Node* lexit = bctrl->in(0);
 497   if (!lexit->is_BaseCountedLoopEnd()) {
 498     return NULL;
 499   }
 500   BaseCountedLoopEndNode* result = lexit->as_BaseCountedLoopEnd();
 501   if (!result->operates_on(bt(), true)) {
 502     return NULL;
 503   }
 504   return result;
 505 }
 506 
 507 inline BaseCountedLoopEndNode* BaseCountedLoopNode::loopexit() const {
 508   BaseCountedLoopEndNode* cle = loopexit_or_null();
 509   assert(cle != NULL, "loopexit is NULL");
 510   return cle;
 511 }
 512 
 513 inline Node* BaseCountedLoopNode::init_trip() const {
 514   BaseCountedLoopEndNode* cle = loopexit_or_null();
 515   return cle != NULL ? cle->init_trip() : NULL;
 516 }
 517 inline Node* BaseCountedLoopNode::stride() const {
 518   BaseCountedLoopEndNode* cle = loopexit_or_null();
 519   return cle != NULL ? cle->stride() : NULL;
 520 }
 521 
 522 inline bool BaseCountedLoopNode::stride_is_con() const {
 523   BaseCountedLoopEndNode* cle = loopexit_or_null();
 524   return cle != NULL && cle->stride_is_con();
 525 }
 526 inline Node* BaseCountedLoopNode::limit() const {
 527   BaseCountedLoopEndNode* cle = loopexit_or_null();
 528   return cle != NULL ? cle->limit() : NULL;
 529 }
 530 inline Node* BaseCountedLoopNode::incr() const {
 531   BaseCountedLoopEndNode* cle = loopexit_or_null();
 532   return cle != NULL ? cle->incr() : NULL;
 533 }
 534 inline Node* BaseCountedLoopNode::phi() const {
 535   BaseCountedLoopEndNode* cle = loopexit_or_null();
 536   return cle != NULL ? cle->phi() : NULL;
 537 }
 538 
 539 //------------------------------LoopLimitNode-----------------------------
 540 // Counted Loop limit node which represents exact final iterator value:
 541 // trip_count = (limit - init_trip + stride - 1)/stride
 542 // final_value= trip_count * stride + init_trip.
 543 // Use HW instructions to calculate it when it can overflow in integer.
 544 // Note, final_value should fit into integer since counted loop has
 545 // limit check: limit <= max_int-stride.
 546 class LoopLimitNode : public Node {
 547   enum { Init=1, Limit=2, Stride=3 };
 548  public:
 549   LoopLimitNode( Compile* C, Node *init, Node *limit, Node *stride ) : Node(0,init,limit,stride) {
 550     // Put it on the Macro nodes list to optimize during macro nodes expansion.
 551     init_flags(Flag_is_macro);
 552     C->add_macro_node(this);
 553   }
 554   virtual int Opcode() const;
 555   virtual const Type *bottom_type() const { return TypeInt::INT; }
 556   virtual uint ideal_reg() const { return Op_RegI; }
 557   virtual const Type* Value(PhaseGVN* phase) const;
 558   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 559   virtual Node* Identity(PhaseGVN* phase);
 560 };
 561 
 562 // Support for strip mining
 563 class OuterStripMinedLoopNode : public LoopNode {
 564 private:
 565   CountedLoopNode* inner_loop() const;
 566 public:
 567   OuterStripMinedLoopNode(Compile* C, Node *entry, Node *backedge)
 568     : LoopNode(entry, backedge) {
 569     init_class_id(Class_OuterStripMinedLoop);
 570     init_flags(Flag_is_macro);
 571     C->add_macro_node(this);
 572   }
 573 
 574   virtual int Opcode() const;
 575 
 576   virtual IfTrueNode* outer_loop_tail() const;
 577   virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
 578   virtual IfFalseNode* outer_loop_exit() const;
 579   virtual SafePointNode* outer_safepoint() const;
 580   void adjust_strip_mined_loop(PhaseIterGVN* igvn);
 581 };
 582 
 583 class OuterStripMinedLoopEndNode : public IfNode {
 584 public:
 585   OuterStripMinedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 586     : IfNode(control, test, prob, cnt) {
 587     init_class_id(Class_OuterStripMinedLoopEnd);
 588   }
 589 
 590   virtual int Opcode() const;
 591 
 592   virtual const Type* Value(PhaseGVN* phase) const;
 593   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 594 
 595   bool is_expanded(PhaseGVN *phase) const;
 596 };
 597 
 598 // -----------------------------IdealLoopTree----------------------------------
 599 class IdealLoopTree : public ResourceObj {
 600 public:
 601   IdealLoopTree *_parent;       // Parent in loop tree
 602   IdealLoopTree *_next;         // Next sibling in loop tree
 603   IdealLoopTree *_child;        // First child in loop tree
 604 
 605   // The head-tail backedge defines the loop.
 606   // If a loop has multiple backedges, this is addressed during cleanup where
 607   // we peel off the multiple backedges,  merging all edges at the bottom and
 608   // ensuring that one proper backedge flow into the loop.
 609   Node *_head;                  // Head of loop
 610   Node *_tail;                  // Tail of loop
 611   inline Node *tail();          // Handle lazy update of _tail field
 612   inline Node *head();          // Handle lazy update of _head field
 613   PhaseIdealLoop* _phase;
 614   int _local_loop_unroll_limit;
 615   int _local_loop_unroll_factor;
 616 
 617   Node_List _body;              // Loop body for inner loops
 618 
 619   uint16_t _nest;               // Nesting depth
 620   uint8_t _irreducible:1,       // True if irreducible
 621           _has_call:1,          // True if has call safepoint
 622           _has_sfpt:1,          // True if has non-call safepoint
 623           _rce_candidate:1;     // True if candidate for range check elimination
 624 
 625   Node_List* _safepts;          // List of safepoints in this loop
 626   Node_List* _required_safept;  // A inner loop cannot delete these safepts;
 627   bool  _allow_optimizations;   // Allow loop optimizations
 628 
 629   IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail )
 630     : _parent(0), _next(0), _child(0),
 631       _head(head), _tail(tail),
 632       _phase(phase),
 633       _local_loop_unroll_limit(0), _local_loop_unroll_factor(0),
 634       _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0),
 635       _safepts(NULL),
 636       _required_safept(NULL),
 637       _allow_optimizations(true)
 638   {
 639     precond(_head != NULL);
 640     precond(_tail != NULL);
 641   }
 642 
 643   // Is 'l' a member of 'this'?
 644   bool is_member(const IdealLoopTree *l) const; // Test for nested membership
 645 
 646   // Set loop nesting depth.  Accumulate has_call bits.
 647   int set_nest( uint depth );
 648 
 649   // Split out multiple fall-in edges from the loop header.  Move them to a
 650   // private RegionNode before the loop.  This becomes the loop landing pad.
 651   void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt );
 652 
 653   // Split out the outermost loop from this shared header.
 654   void split_outer_loop( PhaseIdealLoop *phase );
 655 
 656   // Merge all the backedges from the shared header into a private Region.
 657   // Feed that region as the one backedge to this loop.
 658   void merge_many_backedges( PhaseIdealLoop *phase );
 659 
 660   // Split shared headers and insert loop landing pads.
 661   // Insert a LoopNode to replace the RegionNode.
 662   // Returns TRUE if loop tree is structurally changed.
 663   bool beautify_loops( PhaseIdealLoop *phase );
 664 
 665   // Perform optimization to use the loop predicates for null checks and range checks.
 666   // Applies to any loop level (not just the innermost one)
 667   bool loop_predication( PhaseIdealLoop *phase);
 668 
 669   // Perform iteration-splitting on inner loops.  Split iterations to
 670   // avoid range checks or one-shot null checks.  Returns false if the
 671   // current round of loop opts should stop.
 672   bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new );
 673 
 674   // Driver for various flavors of iteration splitting.  Returns false
 675   // if the current round of loop opts should stop.
 676   bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new );
 677 
 678   // Given dominators, try to find loops with calls that must always be
 679   // executed (call dominates loop tail).  These loops do not need non-call
 680   // safepoints (ncsfpt).
 681   void check_safepts(VectorSet &visited, Node_List &stack);
 682 
 683   // Allpaths backwards scan from loop tail, terminating each path at first safepoint
 684   // encountered.
 685   void allpaths_check_safepts(VectorSet &visited, Node_List &stack);
 686 
 687   // Remove safepoints from loop. Optionally keeping one.
 688   void remove_safepoints(PhaseIdealLoop* phase, bool keep_one);
 689 
 690   // Convert to counted loops where possible
 691   void counted_loop( PhaseIdealLoop *phase );
 692 
 693   // Check for Node being a loop-breaking test
 694   Node *is_loop_exit(Node *iff) const;
 695 
 696   // Remove simplistic dead code from loop body
 697   void DCE_loop_body();
 698 
 699   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
 700   // Replace with a 1-in-10 exit guess.
 701   void adjust_loop_exit_prob( PhaseIdealLoop *phase );
 702 
 703   // Return TRUE or FALSE if the loop should never be RCE'd or aligned.
 704   // Useful for unrolling loops with NO array accesses.
 705   bool policy_peel_only( PhaseIdealLoop *phase ) const;
 706 
 707   // Return TRUE or FALSE if the loop should be unswitched -- clone
 708   // loop with an invariant test
 709   bool policy_unswitching( PhaseIdealLoop *phase ) const;
 710 
 711   // Micro-benchmark spamming.  Remove empty loops.
 712   bool do_remove_empty_loop( PhaseIdealLoop *phase );
 713 
 714   // Convert one iteration loop into normal code.
 715   bool do_one_iteration_loop( PhaseIdealLoop *phase );
 716 
 717   // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
 718   // move some loop-invariant test (usually a null-check) before the loop.
 719   bool policy_peeling(PhaseIdealLoop *phase);
 720 
 721   uint estimate_peeling(PhaseIdealLoop *phase);
 722 
 723   // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any
 724   // known trip count in the counted loop node.
 725   bool policy_maximally_unroll(PhaseIdealLoop *phase) const;
 726 
 727   // Return TRUE or FALSE if the loop should be unrolled or not. Apply unroll
 728   // if the loop is a counted loop and the loop body is small enough.
 729   bool policy_unroll(PhaseIdealLoop *phase);
 730 
 731   // Loop analyses to map to a maximal superword unrolling for vectorization.
 732   void policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct);
 733 
 734   // Return TRUE or FALSE if the loop should be range-check-eliminated.
 735   // Gather a list of IF tests that are dominated by iteration splitting;
 736   // also gather the end of the first split and the start of the 2nd split.
 737   bool policy_range_check( PhaseIdealLoop *phase ) const;
 738 
 739   // Return TRUE if "iff" is a range check.
 740   bool is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar DEBUG_ONLY(COMMA ProjNode *predicate_proj)) const;
 741 
 742   // Estimate the number of nodes required when cloning a loop (body).
 743   uint est_loop_clone_sz(uint factor) const;
 744   // Estimate the number of nodes required when unrolling a loop (body).
 745   uint est_loop_unroll_sz(uint factor) const;
 746 
 747   // Compute loop trip count if possible
 748   void compute_trip_count(PhaseIdealLoop* phase);
 749 
 750   // Compute loop trip count from profile data
 751   float compute_profile_trip_cnt_helper(Node* n);
 752   void compute_profile_trip_cnt( PhaseIdealLoop *phase );
 753 
 754   // Reassociate invariant expressions.
 755   void reassociate_invariants(PhaseIdealLoop *phase);
 756   // Reassociate invariant binary expressions.
 757   Node* reassociate(Node* n1, PhaseIdealLoop *phase);
 758   // Reassociate invariant add and subtract expressions.
 759   Node* reassociate_add_sub(Node* n1, int inv1_idx, int inv2_idx, PhaseIdealLoop *phase);
 760   // Return nonzero index of invariant operand if invariant and variant
 761   // are combined with an associative binary. Helper for reassociate_invariants.
 762   int find_invariant(Node* n, PhaseIdealLoop *phase);
 763   // Return TRUE if "n" is associative.
 764   bool is_associative(Node* n, Node* base=NULL);
 765 
 766   // Return true if n is invariant
 767   bool is_invariant(Node* n) const;
 768 
 769   // Put loop body on igvn work list
 770   void record_for_igvn();
 771 
 772   bool is_root() { return _parent == NULL; }
 773   // A proper/reducible loop w/o any (occasional) dead back-edge.
 774   bool is_loop() { return !_irreducible && !tail()->is_top(); }
 775   bool is_counted()   { return is_loop() && _head->is_CountedLoop(); }
 776   bool is_innermost() { return is_loop() && _child == NULL; }
 777 
 778   void remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase);
 779 
 780 #ifndef PRODUCT
 781   void dump_head() const;       // Dump loop head only
 782   void dump() const;            // Dump this loop recursively
 783   void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const;
 784 #endif
 785 
 786  private:
 787   enum { EMPTY_LOOP_SIZE = 7 }; // Number of nodes in an empty loop.
 788 
 789   // Estimate the number of nodes resulting from control and data flow merge.
 790   uint est_loop_flow_merge_sz() const;
 791 };
 792 
 793 // -----------------------------PhaseIdealLoop---------------------------------
 794 // Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees
 795 // into a loop tree. Drives the loop-based transformations on the ideal graph.
 796 class PhaseIdealLoop : public PhaseTransform {
 797   friend class IdealLoopTree;
 798   friend class SuperWord;
 799   friend class CountedLoopReserveKit;
 800   friend class ShenandoahBarrierC2Support;
 801   friend class AutoNodeBudget;
 802 
 803   // Pre-computed def-use info
 804   PhaseIterGVN &_igvn;
 805 
 806   // Head of loop tree
 807   IdealLoopTree* _ltree_root;
 808 
 809   // Array of pre-order numbers, plus post-visited bit.
 810   // ZERO for not pre-visited.  EVEN for pre-visited but not post-visited.
 811   // ODD for post-visited.  Other bits are the pre-order number.
 812   uint *_preorders;
 813   uint _max_preorder;
 814 
 815   const PhaseIdealLoop* _verify_me;
 816   bool _verify_only;
 817 
 818   // Allocate _preorders[] array
 819   void allocate_preorders() {
 820     _max_preorder = C->unique()+8;
 821     _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder);
 822     memset(_preorders, 0, sizeof(uint) * _max_preorder);
 823   }
 824 
 825   // Allocate _preorders[] array
 826   void reallocate_preorders() {
 827     if ( _max_preorder < C->unique() ) {
 828       _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique());
 829       _max_preorder = C->unique();
 830     }
 831     memset(_preorders, 0, sizeof(uint) * _max_preorder);
 832   }
 833 
 834   // Check to grow _preorders[] array for the case when build_loop_tree_impl()
 835   // adds new nodes.
 836   void check_grow_preorders( ) {
 837     if ( _max_preorder < C->unique() ) {
 838       uint newsize = _max_preorder<<1;  // double size of array
 839       _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize);
 840       memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder));
 841       _max_preorder = newsize;
 842     }
 843   }
 844   // Check for pre-visited.  Zero for NOT visited; non-zero for visited.
 845   int is_visited( Node *n ) const { return _preorders[n->_idx]; }
 846   // Pre-order numbers are written to the Nodes array as low-bit-set values.
 847   void set_preorder_visited( Node *n, int pre_order ) {
 848     assert( !is_visited( n ), "already set" );
 849     _preorders[n->_idx] = (pre_order<<1);
 850   };
 851   // Return pre-order number.
 852   int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; }
 853 
 854   // Check for being post-visited.
 855   // Should be previsited already (checked with assert(is_visited(n))).
 856   int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; }
 857 
 858   // Mark as post visited
 859   void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; }
 860 
 861 public:
 862   // Set/get control node out.  Set lower bit to distinguish from IdealLoopTree
 863   // Returns true if "n" is a data node, false if it's a control node.
 864   bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; }
 865 
 866 private:
 867   // clear out dead code after build_loop_late
 868   Node_List _deadlist;
 869 
 870   // Support for faster execution of get_late_ctrl()/dom_lca()
 871   // when a node has many uses and dominator depth is deep.
 872   GrowableArray<jlong> _dom_lca_tags;
 873   uint _dom_lca_tags_round;
 874   void   init_dom_lca_tags();
 875 
 876   // Helper for debugging bad dominance relationships
 877   bool verify_dominance(Node* n, Node* use, Node* LCA, Node* early);
 878 
 879   Node* compute_lca_of_uses(Node* n, Node* early, bool verify = false);
 880 
 881   // Inline wrapper for frequent cases:
 882   // 1) only one use
 883   // 2) a use is the same as the current LCA passed as 'n1'
 884   Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) {
 885     assert( n->is_CFG(), "" );
 886     // Fast-path NULL lca
 887     if( lca != NULL && lca != n ) {
 888       assert( lca->is_CFG(), "" );
 889       // find LCA of all uses
 890       n = dom_lca_for_get_late_ctrl_internal( lca, n, tag );
 891     }
 892     return find_non_split_ctrl(n);
 893   }
 894   Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag );
 895 
 896   // Helper function for directing control inputs away from CFG split points.
 897   Node *find_non_split_ctrl( Node *ctrl ) const {
 898     if (ctrl != NULL) {
 899       if (ctrl->is_MultiBranch()) {
 900         ctrl = ctrl->in(0);
 901       }
 902       assert(ctrl->is_CFG(), "CFG");
 903     }
 904     return ctrl;
 905   }
 906 
 907   Node* cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop);
 908 
 909 #ifdef ASSERT
 910   void ensure_zero_trip_guard_proj(Node* node, bool is_main_loop);
 911 #endif
 912   void copy_skeleton_predicates_to_main_loop_helper(Node* predicate, Node* init, Node* stride, IdealLoopTree* outer_loop, LoopNode* outer_main_head,
 913                                                     uint dd_main_head, const uint idx_before_pre_post, const uint idx_after_post_before_pre,
 914                                                     Node* zero_trip_guard_proj_main, Node* zero_trip_guard_proj_post, const Node_List &old_new);
 915   void copy_skeleton_predicates_to_main_loop(CountedLoopNode* pre_head, Node* init, Node* stride, IdealLoopTree* outer_loop, LoopNode* outer_main_head,
 916                                              uint dd_main_head, const uint idx_before_pre_post, const uint idx_after_post_before_pre,
 917                                              Node* zero_trip_guard_proj_main, Node* zero_trip_guard_proj_post, const Node_List &old_new);
 918   Node* clone_skeleton_predicate_for_main_loop(Node* iff, Node* new_init, Node* new_stride, Node* predicate, Node* uncommon_proj, Node* control,
 919                                                IdealLoopTree* outer_loop, Node* input_proj);
 920   Node* clone_skeleton_predicate_bool(Node* iff, Node* new_init, Node* new_stride, Node* predicate, Node* uncommon_proj, Node* control,
 921                                       IdealLoopTree* outer_loop);
 922   static bool skeleton_predicate_has_opaque(IfNode* iff);
 923   static void get_skeleton_predicates(Node* predicate, Unique_Node_List& list, bool get_opaque = false);
 924   void update_main_loop_skeleton_predicates(Node* ctrl, CountedLoopNode* loop_head, Node* init, int stride_con);
 925   void insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol);
 926 #ifdef ASSERT
 927   bool only_has_infinite_loops();
 928 #endif
 929 
 930   void log_loop_tree();
 931 
 932 public:
 933 
 934   PhaseIterGVN &igvn() const { return _igvn; }
 935 
 936   bool has_node( Node* n ) const {
 937     guarantee(n != NULL, "No Node.");
 938     return _nodes[n->_idx] != NULL;
 939   }
 940   // check if transform created new nodes that need _ctrl recorded
 941   Node *get_late_ctrl( Node *n, Node *early );
 942   Node *get_early_ctrl( Node *n );
 943   Node *get_early_ctrl_for_expensive(Node *n, Node* earliest);
 944   void set_early_ctrl(Node* n, bool update_body);
 945   void set_subtree_ctrl(Node* n, bool update_body);
 946   void set_ctrl( Node *n, Node *ctrl ) {
 947     assert( !has_node(n) || has_ctrl(n), "" );
 948     assert( ctrl->in(0), "cannot set dead control node" );
 949     assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" );
 950     _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) );
 951   }
 952   // Set control and update loop membership
 953   void set_ctrl_and_loop(Node* n, Node* ctrl) {
 954     IdealLoopTree* old_loop = get_loop(get_ctrl(n));
 955     IdealLoopTree* new_loop = get_loop(ctrl);
 956     if (old_loop != new_loop) {
 957       if (old_loop->_child == NULL) old_loop->_body.yank(n);
 958       if (new_loop->_child == NULL) new_loop->_body.push(n);
 959     }
 960     set_ctrl(n, ctrl);
 961   }
 962   // Control nodes can be replaced or subsumed.  During this pass they
 963   // get their replacement Node in slot 1.  Instead of updating the block
 964   // location of all Nodes in the subsumed block, we lazily do it.  As we
 965   // pull such a subsumed block out of the array, we write back the final
 966   // correct block.
 967   Node *get_ctrl( Node *i ) {
 968 
 969     assert(has_node(i), "");
 970     Node *n = get_ctrl_no_update(i);
 971     _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) );
 972     assert(has_node(i) && has_ctrl(i), "");
 973     assert(n == find_non_split_ctrl(n), "must return legal ctrl" );
 974     return n;
 975   }
 976   // true if CFG node d dominates CFG node n
 977   bool is_dominator(Node *d, Node *n);
 978   // return get_ctrl for a data node and self(n) for a CFG node
 979   Node* ctrl_or_self(Node* n) {
 980     if (has_ctrl(n))
 981       return get_ctrl(n);
 982     else {
 983       assert (n->is_CFG(), "must be a CFG node");
 984       return n;
 985     }
 986   }
 987 
 988   Node *get_ctrl_no_update_helper(Node *i) const {
 989     assert(has_ctrl(i), "should be control, not loop");
 990     return (Node*)(((intptr_t)_nodes[i->_idx]) & ~1);
 991   }
 992 
 993   Node *get_ctrl_no_update(Node *i) const {
 994     assert( has_ctrl(i), "" );
 995     Node *n = get_ctrl_no_update_helper(i);
 996     if (!n->in(0)) {
 997       // Skip dead CFG nodes
 998       do {
 999         n = get_ctrl_no_update_helper(n);
1000       } while (!n->in(0));
1001       n = find_non_split_ctrl(n);
1002     }
1003     return n;
1004   }
1005 
1006   // Check for loop being set
1007   // "n" must be a control node. Returns true if "n" is known to be in a loop.
1008   bool has_loop( Node *n ) const {
1009     assert(!has_node(n) || !has_ctrl(n), "");
1010     return has_node(n);
1011   }
1012   // Set loop
1013   void set_loop( Node *n, IdealLoopTree *loop ) {
1014     _nodes.map(n->_idx, (Node*)loop);
1015   }
1016   // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms.  Replace
1017   // the 'old_node' with 'new_node'.  Kill old-node.  Add a reference
1018   // from old_node to new_node to support the lazy update.  Reference
1019   // replaces loop reference, since that is not needed for dead node.
1020   void lazy_update(Node *old_node, Node *new_node) {
1021     assert(old_node != new_node, "no cycles please");
1022     // Re-use the side array slot for this node to provide the
1023     // forwarding pointer.
1024     _nodes.map(old_node->_idx, (Node*)((intptr_t)new_node + 1));
1025   }
1026   void lazy_replace(Node *old_node, Node *new_node) {
1027     _igvn.replace_node(old_node, new_node);
1028     lazy_update(old_node, new_node);
1029   }
1030 
1031 private:
1032 
1033   // Place 'n' in some loop nest, where 'n' is a CFG node
1034   void build_loop_tree();
1035   int build_loop_tree_impl( Node *n, int pre_order );
1036   // Insert loop into the existing loop tree.  'innermost' is a leaf of the
1037   // loop tree, not the root.
1038   IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost );
1039 
1040   // Place Data nodes in some loop nest
1041   void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
1042   void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
1043   void build_loop_late_post_work(Node* n, bool pinned);
1044   void build_loop_late_post(Node* n);
1045   void verify_strip_mined_scheduling(Node *n, Node* least);
1046 
1047   // Array of immediate dominance info for each CFG node indexed by node idx
1048 private:
1049   uint _idom_size;
1050   Node **_idom;                  // Array of immediate dominators
1051   uint *_dom_depth;              // Used for fast LCA test
1052   GrowableArray<uint>* _dom_stk; // For recomputation of dom depth
1053 
1054   // build the loop tree and perform any requested optimizations
1055   void build_and_optimize(LoopOptsMode mode);
1056 
1057   // Dominators for the sea of nodes
1058   void Dominators();
1059 
1060   // Compute the Ideal Node to Loop mapping
1061   PhaseIdealLoop(PhaseIterGVN& igvn, LoopOptsMode mode) :
1062     PhaseTransform(Ideal_Loop),
1063     _igvn(igvn),
1064     _verify_me(nullptr),
1065     _verify_only(false),
1066     _nodes_required(UINT_MAX) {
1067     assert(mode != LoopOptsVerify, "wrong constructor to verify IdealLoop");
1068     build_and_optimize(mode);
1069   }
1070 
1071 #ifndef PRODUCT
1072   // Verify that verify_me made the same decisions as a fresh run
1073   // or only verify that the graph is valid if verify_me is null.
1074   PhaseIdealLoop(PhaseIterGVN& igvn, const PhaseIdealLoop* verify_me = nullptr) :
1075     PhaseTransform(Ideal_Loop),
1076     _igvn(igvn),
1077     _verify_me(verify_me),
1078     _verify_only(verify_me == nullptr),
1079     _nodes_required(UINT_MAX) {
1080     build_and_optimize(LoopOptsVerify);
1081   }
1082 #endif
1083 
1084 public:
1085   Node* idom_no_update(Node* d) const {
1086     return idom_no_update(d->_idx);
1087   }
1088 
1089   Node* idom_no_update(uint didx) const {
1090     assert(didx < _idom_size, "oob");
1091     Node* n = _idom[didx];
1092     assert(n != NULL,"Bad immediate dominator info.");
1093     while (n->in(0) == NULL) { // Skip dead CFG nodes
1094       n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
1095       assert(n != NULL,"Bad immediate dominator info.");
1096     }
1097     return n;
1098   }
1099 
1100   Node *idom(Node* d) const {
1101     return idom(d->_idx);
1102   }
1103 
1104   Node *idom(uint didx) const {
1105     Node *n = idom_no_update(didx);
1106     _idom[didx] = n; // Lazily remove dead CFG nodes from table.
1107     return n;
1108   }
1109 
1110   uint dom_depth(Node* d) const {
1111     guarantee(d != NULL, "Null dominator info.");
1112     guarantee(d->_idx < _idom_size, "");
1113     return _dom_depth[d->_idx];
1114   }
1115   void set_idom(Node* d, Node* n, uint dom_depth);
1116   // Locally compute IDOM using dom_lca call
1117   Node *compute_idom( Node *region ) const;
1118   // Recompute dom_depth
1119   void recompute_dom_depth();
1120 
1121   // Is safept not required by an outer loop?
1122   bool is_deleteable_safept(Node* sfpt);
1123 
1124   // Replace parallel induction variable (parallel to trip counter)
1125   void replace_parallel_iv(IdealLoopTree *loop);
1126 
1127   Node *dom_lca( Node *n1, Node *n2 ) const {
1128     return find_non_split_ctrl(dom_lca_internal(n1, n2));
1129   }
1130   Node *dom_lca_internal( Node *n1, Node *n2 ) const;
1131 
1132   // Build and verify the loop tree without modifying the graph.  This
1133   // is useful to verify that all inputs properly dominate their uses.
1134   static void verify(PhaseIterGVN& igvn) {
1135 #ifdef ASSERT
1136     ResourceMark rm;
1137     Compile::TracePhase tp("idealLoopVerify", &timers[_t_idealLoopVerify]);
1138     PhaseIdealLoop v(igvn);
1139 #endif
1140   }
1141 
1142   // Recommended way to use PhaseIdealLoop.
1143   // Run PhaseIdealLoop in some mode and allocates a local scope for memory allocations.
1144   static void optimize(PhaseIterGVN &igvn, LoopOptsMode mode) {
1145     ResourceMark rm;
1146     PhaseIdealLoop v(igvn, mode);
1147 
1148     Compile* C = Compile::current();
1149     if (!C->failing()) {
1150       // Cleanup any modified bits
1151       igvn.optimize();
1152 
1153       v.log_loop_tree();
1154     }
1155   }
1156 
1157   // True if the method has at least 1 irreducible loop
1158   bool _has_irreducible_loops;
1159 
1160   // Per-Node transform
1161   virtual Node* transform(Node* n) { return NULL; }
1162 
1163   Node* loop_exit_control(Node* x, IdealLoopTree* loop);
1164   Node* loop_exit_test(Node* back_control, IdealLoopTree* loop, Node*& incr, Node*& limit, BoolTest::mask& bt, float& cl_prob);
1165   Node* loop_iv_incr(Node* incr, Node* x, IdealLoopTree* loop, Node*& phi_incr);
1166   Node* loop_iv_stride(Node* incr, IdealLoopTree* loop, Node*& xphi);
1167   PhiNode* loop_iv_phi(Node* xphi, Node* phi_incr, Node* x, IdealLoopTree* loop);
1168 
1169   bool is_counted_loop(Node* x, IdealLoopTree*&loop, BasicType iv_bt);
1170 
1171   void long_loop_replace_long_iv(Node* iv_to_replace, Node* inner_iv, Node* outer_phi, Node* inner_head);
1172   bool transform_long_counted_loop(IdealLoopTree* loop, Node_List &old_new);
1173 #ifdef ASSERT
1174   bool convert_to_long_loop(Node* cmp, Node* phi, IdealLoopTree* loop);
1175 #endif
1176   void add_empty_predicate(Deoptimization::DeoptReason reason, Node* inner_head, IdealLoopTree* loop, SafePointNode* sfpt);
1177   SafePointNode* find_safepoint(Node* back_control, Node* x, IdealLoopTree* loop);
1178   IdealLoopTree* insert_outer_loop(IdealLoopTree* loop, LoopNode* outer_l, Node* outer_ift);
1179   IdealLoopTree* create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
1180                                                IdealLoopTree* loop, float cl_prob, float le_fcnt,
1181                                                Node*& entry_control, Node*& iffalse);
1182 
1183   Node* exact_limit( IdealLoopTree *loop );
1184 
1185   // Return a post-walked LoopNode
1186   IdealLoopTree *get_loop( Node *n ) const {
1187     // Dead nodes have no loop, so return the top level loop instead
1188     if (!has_node(n))  return _ltree_root;
1189     assert(!has_ctrl(n), "");
1190     return (IdealLoopTree*)_nodes[n->_idx];
1191   }
1192 
1193   IdealLoopTree* ltree_root() const { return _ltree_root; }
1194 
1195   // Is 'n' a (nested) member of 'loop'?
1196   int is_member( const IdealLoopTree *loop, Node *n ) const {
1197     return loop->is_member(get_loop(n)); }
1198 
1199   // This is the basic building block of the loop optimizations.  It clones an
1200   // entire loop body.  It makes an old_new loop body mapping; with this
1201   // mapping you can find the new-loop equivalent to an old-loop node.  All
1202   // new-loop nodes are exactly equal to their old-loop counterparts, all
1203   // edges are the same.  All exits from the old-loop now have a RegionNode
1204   // that merges the equivalent new-loop path.  This is true even for the
1205   // normal "loop-exit" condition.  All uses of loop-invariant old-loop values
1206   // now come from (one or more) Phis that merge their new-loop equivalents.
1207   // Parameter side_by_side_idom:
1208   //   When side_by_size_idom is NULL, the dominator tree is constructed for
1209   //      the clone loop to dominate the original.  Used in construction of
1210   //      pre-main-post loop sequence.
1211   //   When nonnull, the clone and original are side-by-side, both are
1212   //      dominated by the passed in side_by_side_idom node.  Used in
1213   //      construction of unswitched loops.
1214   enum CloneLoopMode {
1215     IgnoreStripMined = 0,        // Only clone inner strip mined loop
1216     CloneIncludesStripMined = 1, // clone both inner and outer strip mined loops
1217     ControlAroundStripMined = 2  // Only clone inner strip mined loop,
1218                                  // result control flow branches
1219                                  // either to inner clone or outer
1220                                  // strip mined loop.
1221   };
1222   void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
1223                   CloneLoopMode mode, Node* side_by_side_idom = NULL);
1224   void clone_loop_handle_data_uses(Node* old, Node_List &old_new,
1225                                    IdealLoopTree* loop, IdealLoopTree* companion_loop,
1226                                    Node_List*& split_if_set, Node_List*& split_bool_set,
1227                                    Node_List*& split_cex_set, Node_List& worklist,
1228                                    uint new_counter, CloneLoopMode mode);
1229   void clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
1230                         IdealLoopTree* outer_loop, int dd, Node_List &old_new,
1231                         Node_List& extra_data_nodes);
1232 
1233   // If we got the effect of peeling, either by actually peeling or by
1234   // making a pre-loop which must execute at least once, we can remove
1235   // all loop-invariant dominated tests in the main body.
1236   void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new );
1237 
1238   // Generate code to do a loop peel for the given loop (and body).
1239   // old_new is a temp array.
1240   void do_peeling( IdealLoopTree *loop, Node_List &old_new );
1241 
1242   // Add pre and post loops around the given loop.  These loops are used
1243   // during RCE, unrolling and aligning loops.
1244   void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only );
1245 
1246   // Add post loop after the given loop.
1247   Node *insert_post_loop(IdealLoopTree *loop, Node_List &old_new,
1248                          CountedLoopNode *main_head, CountedLoopEndNode *main_end,
1249                          Node *incr, Node *limit, CountedLoopNode *&post_head);
1250 
1251   // Add an RCE'd post loop which we will multi-version adapt for run time test path usage
1252   void insert_scalar_rced_post_loop( IdealLoopTree *loop, Node_List &old_new );
1253 
1254   // Add a vector post loop between a vector main loop and the current post loop
1255   void insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new);
1256   // If Node n lives in the back_ctrl block, we clone a private version of n
1257   // in preheader_ctrl block and return that, otherwise return n.
1258   Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones );
1259 
1260   // Take steps to maximally unroll the loop.  Peel any odd iterations, then
1261   // unroll to do double iterations.  The next round of major loop transforms
1262   // will repeat till the doubled loop body does all remaining iterations in 1
1263   // pass.
1264   void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new );
1265 
1266   // Unroll the loop body one step - make each trip do 2 iterations.
1267   void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip );
1268 
1269   // Mark vector reduction candidates before loop unrolling
1270   void mark_reductions( IdealLoopTree *loop );
1271 
1272   // Return true if exp is a constant times an induction var
1273   bool is_scaled_iv(Node* exp, Node* iv, int* p_scale);
1274 
1275   // Return true if exp is a scaled induction var plus (or minus) constant
1276   bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0);
1277 
1278   // Enum to determine the action to be performed in create_new_if_for_predicate() when processing phis of UCT regions.
1279   enum class UnswitchingAction {
1280     None,            // No special action.
1281     FastLoopCloning, // Need to clone nodes for the fast loop.
1282     SlowLoopRewiring // Need to rewire nodes for the slow loop.
1283   };
1284 
1285   // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted
1286   ProjNode* create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry, Deoptimization::DeoptReason reason,
1287                                         int opcode, bool if_cont_is_true_proj = true, Node_List* old_new = NULL,
1288                                         UnswitchingAction unswitching_action = UnswitchingAction::None);
1289 
1290   // Clone data nodes for the fast loop while creating a new If with create_new_if_for_predicate.
1291   Node* clone_data_nodes_for_fast_loop(Node* phi_input, ProjNode* uncommon_proj, Node* if_uct, Node_List* old_new);
1292 
1293   void register_control(Node* n, IdealLoopTree *loop, Node* pred, bool update_body = true);
1294 
1295   static Node* skip_all_loop_predicates(Node* entry);
1296   static Node* skip_loop_predicates(Node* entry);
1297 
1298   // Find a good location to insert a predicate
1299   static ProjNode* find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason);
1300   // Find a predicate
1301   static Node* find_predicate(Node* entry);
1302   // Construct a range check for a predicate if
1303   BoolNode* rc_predicate(IdealLoopTree *loop, Node* ctrl,
1304                          int scale, Node* offset,
1305                          Node* init, Node* limit, jint stride,
1306                          Node* range, bool upper, bool &overflow);
1307 
1308   // Implementation of the loop predication to promote checks outside the loop
1309   bool loop_predication_impl(IdealLoopTree *loop);
1310   bool loop_predication_impl_helper(IdealLoopTree *loop, ProjNode* proj, ProjNode *predicate_proj,
1311                                     CountedLoopNode *cl, ConNode* zero, Invariance& invar,
1312                                     Deoptimization::DeoptReason reason);
1313   bool loop_predication_should_follow_branches(IdealLoopTree *loop, ProjNode *predicate_proj, float& loop_trip_cnt);
1314   void loop_predication_follow_branches(Node *c, IdealLoopTree *loop, float loop_trip_cnt,
1315                                         PathFrequency& pf, Node_Stack& stack, VectorSet& seen,
1316                                         Node_List& if_proj_list);
1317   ProjNode* insert_initial_skeleton_predicate(IfNode* iff, IdealLoopTree *loop,
1318                                               ProjNode* proj, ProjNode *predicate_proj,
1319                                               ProjNode* upper_bound_proj,
1320                                               int scale, Node* offset,
1321                                               Node* init, Node* limit, jint stride,
1322                                               Node* rng, bool& overflow,
1323                                               Deoptimization::DeoptReason reason);
1324   Node* add_range_check_predicate(IdealLoopTree* loop, CountedLoopNode* cl,
1325                                   Node* predicate_proj, int scale_con, Node* offset,
1326                                   Node* limit, jint stride_con, Node* value);
1327 
1328   // Helper function to collect predicate for eliminating the useless ones
1329   void collect_potentially_useful_predicates(IdealLoopTree *loop, Unique_Node_List &predicate_opaque1);
1330   void eliminate_useless_predicates();
1331 
1332   // Change the control input of expensive nodes to allow commoning by
1333   // IGVN when it is guaranteed to not result in a more frequent
1334   // execution of the expensive node. Return true if progress.
1335   bool process_expensive_nodes();
1336 
1337   // Check whether node has become unreachable
1338   bool is_node_unreachable(Node *n) const {
1339     return !has_node(n) || n->is_unreachable(_igvn);
1340   }
1341 
1342   // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1343   int do_range_check( IdealLoopTree *loop, Node_List &old_new );
1344 
1345   // Check to see if do_range_check(...) cleaned the main loop of range-checks
1346   void has_range_checks(IdealLoopTree *loop);
1347 
1348   // Process post loops which have range checks and try to build a multi-version
1349   // guard to safely determine if we can execute the post loop which was RCE'd.
1350   bool multi_version_post_loops(IdealLoopTree *rce_loop, IdealLoopTree *legacy_loop);
1351 
1352   // Cause the rce'd post loop to optimized away, this happens if we cannot complete multiverioning
1353   void poison_rce_post_loop(IdealLoopTree *rce_loop);
1354 
1355   // Create a slow version of the loop by cloning the loop
1356   // and inserting an if to select fast-slow versions.
1357   // Return the inserted if.
1358   IfNode* create_slow_version_of_loop(IdealLoopTree *loop,
1359                                         Node_List &old_new,
1360                                         IfNode* unswitch_iff,
1361                                         CloneLoopMode mode);
1362 
1363   // Clone a loop and return the clone head (clone_loop_head).
1364   // Added nodes include int(1), int(0) - disconnected, If, IfTrue, IfFalse,
1365   // This routine was created for usage in CountedLoopReserveKit.
1366   //
1367   //    int(1) -> If -> IfTrue -> original_loop_head
1368   //              |
1369   //              V
1370   //           IfFalse -> clone_loop_head (returned by function pointer)
1371   //
1372   LoopNode* create_reserve_version_of_loop(IdealLoopTree *loop, CountedLoopReserveKit* lk);
1373   // Clone loop with an invariant test (that does not exit) and
1374   // insert a clone of the test that selects which version to
1375   // execute.
1376   void do_unswitching (IdealLoopTree *loop, Node_List &old_new);
1377 
1378   // Find candidate "if" for unswitching
1379   IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const;
1380 
1381   // Range Check Elimination uses this function!
1382   // Constrain the main loop iterations so the affine function:
1383   //    low_limit <= scale_con * I + offset  <  upper_limit
1384   // always holds true.  That is, either increase the number of iterations in
1385   // the pre-loop or the post-loop until the condition holds true in the main
1386   // loop.  Scale_con, offset and limit are all loop invariant.
1387   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);
1388   // Helper function for add_constraint().
1389   Node* adjust_limit(bool reduce, Node* scale, Node* offset, Node* rc_limit, Node* old_limit, Node* pre_ctrl, bool round);
1390 
1391   // Partially peel loop up through last_peel node.
1392   bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
1393 
1394   // Create a scheduled list of nodes control dependent on ctrl set.
1395   void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched );
1396   // Has a use in the vector set
1397   bool has_use_in_set( Node* n, VectorSet& vset );
1398   // Has use internal to the vector set (ie. not in a phi at the loop head)
1399   bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop );
1400   // clone "n" for uses that are outside of loop
1401   int  clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist );
1402   // clone "n" for special uses that are in the not_peeled region
1403   void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
1404                                           VectorSet& not_peel, Node_List& sink_list, Node_List& worklist );
1405   // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
1406   void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp );
1407 #ifdef ASSERT
1408   // Validate the loop partition sets: peel and not_peel
1409   bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel );
1410   // Ensure that uses outside of loop are of the right form
1411   bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
1412                                  uint orig_exit_idx, uint clone_exit_idx);
1413   bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx);
1414 #endif
1415 
1416   // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.)
1417   int stride_of_possible_iv( Node* iff );
1418   bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; }
1419   // Return the (unique) control output node that's in the loop (if it exists.)
1420   Node* stay_in_loop( Node* n, IdealLoopTree *loop);
1421   // Insert a signed compare loop exit cloned from an unsigned compare.
1422   IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop);
1423   void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop);
1424   // Utility to register node "n" with PhaseIdealLoop
1425   void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth);
1426   // Utility to create an if-projection
1427   ProjNode* proj_clone(ProjNode* p, IfNode* iff);
1428   // Force the iff control output to be the live_proj
1429   Node* short_circuit_if(IfNode* iff, ProjNode* live_proj);
1430   // Insert a region before an if projection
1431   RegionNode* insert_region_before_proj(ProjNode* proj);
1432   // Insert a new if before an if projection
1433   ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj);
1434 
1435   // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
1436   // "Nearly" because all Nodes have been cloned from the original in the loop,
1437   // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
1438   // through the Phi recursively, and return a Bool.
1439   Node *clone_iff( PhiNode *phi, IdealLoopTree *loop );
1440   CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop );
1441 
1442 
1443   // Rework addressing expressions to get the most loop-invariant stuff
1444   // moved out.  We'd like to do all associative operators, but it's especially
1445   // important (common) to do address expressions.
1446   Node *remix_address_expressions( Node *n );
1447 
1448   // Convert add to muladd to generate MuladdS2I under certain criteria
1449   Node * convert_add_to_muladd(Node * n);
1450 
1451   // Attempt to use a conditional move instead of a phi/branch
1452   Node *conditional_move( Node *n );
1453 
1454   // Reorganize offset computations to lower register pressure.
1455   // Mostly prevent loop-fallout uses of the pre-incremented trip counter
1456   // (which are then alive with the post-incremented trip counter
1457   // forcing an extra register move)
1458   void reorg_offsets( IdealLoopTree *loop );
1459 
1460   // Check for aggressive application of 'split-if' optimization,
1461   // using basic block level info.
1462   void  split_if_with_blocks     ( VectorSet &visited, Node_Stack &nstack);
1463   Node *split_if_with_blocks_pre ( Node *n );
1464   void  split_if_with_blocks_post( Node *n );
1465   Node *has_local_phi_input( Node *n );
1466   // Mark an IfNode as being dominated by a prior test,
1467   // without actually altering the CFG (and hence IDOM info).
1468   void dominated_by( Node *prevdom, Node *iff, bool flip = false, bool exclude_loop_predicate = false );
1469 
1470   // Split Node 'n' through merge point
1471   Node *split_thru_region( Node *n, Node *region );
1472   // Split Node 'n' through merge point if there is enough win.
1473   Node *split_thru_phi( Node *n, Node *region, int policy );
1474   // Found an If getting its condition-code input from a Phi in the
1475   // same block.  Split thru the Region.
1476   void do_split_if( Node *iff );
1477 
1478   // Conversion of fill/copy patterns into intrinsic versions
1479   bool do_intrinsify_fill();
1480   bool intrinsify_fill(IdealLoopTree* lpt);
1481   bool match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
1482                        Node*& shift, Node*& offset);
1483 
1484 private:
1485   // Return a type based on condition control flow
1486   const TypeInt* filtered_type( Node *n, Node* n_ctrl);
1487   const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); }
1488  // Helpers for filtered type
1489   const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl);
1490 
1491   // Helper functions
1492   Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache );
1493   Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true );
1494   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 );
1495   bool split_up( Node *n, Node *blk1, Node *blk2 );
1496   void sink_use( Node *use, Node *post_loop );
1497   Node* place_outside_loop(Node* useblock, IdealLoopTree* loop) const;
1498   Node* try_move_store_before_loop(Node* n, Node *n_ctrl);
1499   void try_move_store_after_loop(Node* n);
1500   bool identical_backtoback_ifs(Node *n);
1501   bool can_split_if(Node *n_ctrl);
1502 
1503   // Determine if a method is too big for a/another round of split-if, based on
1504   // a magic (approximate) ratio derived from the equally magic constant 35000,
1505   // previously used for this purpose (but without relating to the node limit).
1506   bool must_throttle_split_if() {
1507     uint threshold = C->max_node_limit() * 2 / 5;
1508     return C->live_nodes() > threshold;
1509   }
1510 
1511   // A simplistic node request tracking mechanism, where
1512   //   = UINT_MAX   Request not valid or made final.
1513   //   < UINT_MAX   Nodes currently requested (estimate).
1514   uint _nodes_required;
1515 
1516   enum { REQUIRE_MIN = 70 };
1517 
1518   uint nodes_required() const { return _nodes_required; }
1519 
1520   // Given the _currently_  available number of nodes, check  whether there is
1521   // "room" for an additional request or not, considering the already required
1522   // number of  nodes.  Return TRUE if  the new request is  exceeding the node
1523   // budget limit, otherwise return FALSE.  Note that this interpretation will
1524   // act pessimistic on  additional requests when new nodes  have already been
1525   // generated since the 'begin'.  This behaviour fits with the intention that
1526   // node estimates/requests should be made upfront.
1527   bool exceeding_node_budget(uint required = 0) {
1528     assert(C->live_nodes() < C->max_node_limit(), "sanity");
1529     uint available = C->max_node_limit() - C->live_nodes();
1530     return available < required + _nodes_required + REQUIRE_MIN;
1531   }
1532 
1533   uint require_nodes(uint require, uint minreq = REQUIRE_MIN) {
1534     precond(require > 0);
1535     _nodes_required += MAX2(require, minreq);
1536     return _nodes_required;
1537   }
1538 
1539   bool may_require_nodes(uint require, uint minreq = REQUIRE_MIN) {
1540     return !exceeding_node_budget(require) && require_nodes(require, minreq) > 0;
1541   }
1542 
1543   uint require_nodes_begin() {
1544     assert(_nodes_required == UINT_MAX, "Bad state (begin).");
1545     _nodes_required = 0;
1546     return C->live_nodes();
1547   }
1548 
1549   // When a node request is final,  optionally check that the requested number
1550   // of nodes was  reasonably correct with respect to the  number of new nodes
1551   // introduced since the last 'begin'. Always check that we have not exceeded
1552   // the maximum node limit.
1553   void require_nodes_final(uint live_at_begin, bool check_estimate) {
1554     assert(_nodes_required < UINT_MAX, "Bad state (final).");
1555 
1556 #ifdef ASSERT
1557     if (check_estimate) {
1558       // Check that the node budget request was not off by too much (x2).
1559       // Should this be the case we _surely_ need to improve the estimates
1560       // used in our budget calculations.
1561       if (C->live_nodes() - live_at_begin > 2 * _nodes_required) {
1562         log_info(compilation)("Bad node estimate: actual = %d >> request = %d",
1563                               C->live_nodes() - live_at_begin, _nodes_required);
1564       }
1565     }
1566 #endif
1567     // Assert that we have stayed within the node budget limit.
1568     assert(C->live_nodes() < C->max_node_limit(),
1569            "Exceeding node budget limit: %d + %d > %d (request = %d)",
1570            C->live_nodes() - live_at_begin, live_at_begin,
1571            C->max_node_limit(), _nodes_required);
1572 
1573     _nodes_required = UINT_MAX;
1574   }
1575 
1576   // Clone loop predicates to slow and fast loop when unswitching a loop
1577   void clone_predicates_to_unswitched_loop(IdealLoopTree* loop, Node_List& old_new, ProjNode*& iffast_pred, ProjNode*& ifslow_pred);
1578   ProjNode* clone_predicate_to_unswitched_loop(ProjNode* predicate_proj, Node* new_entry, Deoptimization::DeoptReason reason,
1579                                                Node_List* old_new = NULL);
1580   void clone_skeleton_predicates_to_unswitched_loop(IdealLoopTree* loop, const Node_List& old_new, Deoptimization::DeoptReason reason,
1581                                                     ProjNode* old_predicate_proj, ProjNode* iffast_pred, ProjNode* ifslow_pred);
1582   ProjNode* clone_skeleton_predicate_for_unswitched_loops(Node* iff, ProjNode* predicate, Node* uncommon_proj, Deoptimization::DeoptReason reason,
1583                                                           ProjNode* output_proj, IdealLoopTree* loop);
1584   static void check_created_predicate_for_unswitching(const Node* new_entry) PRODUCT_RETURN;
1585 
1586   bool _created_loop_node;
1587 #ifdef ASSERT
1588   void dump_real_LCA(Node* early, Node* wrong_lca);
1589   bool check_idom_chains_intersection(const Node* n, uint& idom_idx_new, uint& idom_idx_other, const Node_List* nodes_seen) const;
1590 #endif
1591 
1592 public:
1593   void set_created_loop_node() { _created_loop_node = true; }
1594   bool created_loop_node()     { return _created_loop_node; }
1595   void register_new_node(Node* n, Node* blk);
1596 
1597 #ifdef ASSERT
1598   void dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA);
1599 #endif
1600 
1601 #ifndef PRODUCT
1602   void dump() const;
1603   void dump_idom(Node* n) const;
1604   void dump(IdealLoopTree* loop, uint rpo_idx, Node_List &rpo_list) const;
1605   void verify() const;          // Major slow  :-)
1606   void verify_compare(Node* n, const PhaseIdealLoop* loop_verify, VectorSet &visited) const;
1607   IdealLoopTree* get_loop_idx(Node* n) const {
1608     // Dead nodes have no loop, so return the top level loop instead
1609     return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root;
1610   }
1611   // Print some stats
1612   static void print_statistics();
1613   static int _loop_invokes;     // Count of PhaseIdealLoop invokes
1614   static int _loop_work;        // Sum of PhaseIdealLoop x _unique
1615   static volatile int _long_loop_candidates;
1616   static volatile int _long_loop_nests;
1617   static volatile int _long_loop_counted_loops;
1618 #endif
1619 
1620   void rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const;
1621 
1622   void check_long_counted_loop(IdealLoopTree* loop, Node* x) NOT_DEBUG_RETURN;
1623 
1624   LoopNode* create_inner_head(IdealLoopTree* loop, LongCountedLoopNode* head, LongCountedLoopEndNode* exit_test);
1625 
1626   Node* get_late_ctrl_with_anti_dep(LoadNode* n, Node* early, Node* LCA);
1627 
1628   bool ctrl_of_use_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop, Node* ctrl);
1629 
1630   bool ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop);
1631 
1632   Node* compute_early_ctrl(Node* n, Node* n_ctrl);
1633 
1634   void try_sink_out_of_loop(Node* n);
1635 };
1636 
1637 
1638 class AutoNodeBudget : public StackObj
1639 {
1640 public:
1641   enum budget_check_t { BUDGET_CHECK, NO_BUDGET_CHECK };
1642 
1643   AutoNodeBudget(PhaseIdealLoop* phase, budget_check_t chk = BUDGET_CHECK)
1644     : _phase(phase),
1645       _check_at_final(chk == BUDGET_CHECK),
1646       _nodes_at_begin(0)
1647   {
1648     precond(_phase != NULL);
1649 
1650     _nodes_at_begin = _phase->require_nodes_begin();
1651   }
1652 
1653   ~AutoNodeBudget() {
1654 #ifndef PRODUCT
1655     if (TraceLoopOpts) {
1656       uint request = _phase->nodes_required();
1657       uint delta   = _phase->C->live_nodes() - _nodes_at_begin;
1658 
1659       if (request < delta) {
1660         tty->print_cr("Exceeding node budget: %d < %d", request, delta);
1661       } else {
1662         uint const REQUIRE_MIN = PhaseIdealLoop::REQUIRE_MIN;
1663         // Identify the worst estimates as "poor" ones.
1664         if (request > REQUIRE_MIN && delta > 0) {
1665           if ((delta >  REQUIRE_MIN && request >  3 * delta) ||
1666               (delta <= REQUIRE_MIN && request > 10 * delta)) {
1667             tty->print_cr("Poor node estimate: %d >> %d", request, delta);
1668           }
1669         }
1670       }
1671     }
1672 #endif // PRODUCT
1673     _phase->require_nodes_final(_nodes_at_begin, _check_at_final);
1674   }
1675 
1676 private:
1677   PhaseIdealLoop* _phase;
1678   bool _check_at_final;
1679   uint _nodes_at_begin;
1680 };
1681 
1682 
1683 // This kit may be used for making of a reserved copy of a loop before this loop
1684 //  goes under non-reversible changes.
1685 //
1686 // Function create_reserve() creates a reserved copy (clone) of the loop.
1687 // The reserved copy is created by calling
1688 // PhaseIdealLoop::create_reserve_version_of_loop - see there how
1689 // the original and reserved loops are connected in the outer graph.
1690 // If create_reserve succeeded, it returns 'true' and _has_reserved is set to 'true'.
1691 //
1692 // By default the reserved copy (clone) of the loop is created as dead code - it is
1693 // dominated in the outer loop by this node chain:
1694 //   intcon(1)->If->IfFalse->reserved_copy.
1695 // The original loop is dominated by the the same node chain but IfTrue projection:
1696 //   intcon(0)->If->IfTrue->original_loop.
1697 //
1698 // In this implementation of CountedLoopReserveKit the ctor includes create_reserve()
1699 // and the dtor, checks _use_new value.
1700 // If _use_new == false, it "switches" control to reserved copy of the loop
1701 // by simple replacing of node intcon(1) with node intcon(0).
1702 //
1703 // Here is a proposed example of usage (see also SuperWord::output in superword.cpp).
1704 //
1705 // void CountedLoopReserveKit_example()
1706 // {
1707 //    CountedLoopReserveKit lrk((phase, lpt, DoReserveCopy = true); // create local object
1708 //    if (DoReserveCopy && !lrk.has_reserved()) {
1709 //      return; //failed to create reserved loop copy
1710 //    }
1711 //    ...
1712 //    //something is wrong, switch to original loop
1713 ///   if(something_is_wrong) return; // ~CountedLoopReserveKit makes the switch
1714 //    ...
1715 //    //everything worked ok, return with the newly modified loop
1716 //    lrk.use_new();
1717 //    return; // ~CountedLoopReserveKit does nothing once use_new() was called
1718 //  }
1719 //
1720 // Keep in mind, that by default if create_reserve() is not followed by use_new()
1721 // the dtor will "switch to the original" loop.
1722 // NOTE. You you modify outside of the original loop this class is no help.
1723 //
1724 class CountedLoopReserveKit {
1725   private:
1726     PhaseIdealLoop* _phase;
1727     IdealLoopTree*  _lpt;
1728     LoopNode*       _lp;
1729     IfNode*         _iff;
1730     LoopNode*       _lp_reserved;
1731     bool            _has_reserved;
1732     bool            _use_new;
1733     const bool      _active; //may be set to false in ctor, then the object is dummy
1734 
1735   public:
1736     CountedLoopReserveKit(PhaseIdealLoop* phase, IdealLoopTree *loop, bool active);
1737     ~CountedLoopReserveKit();
1738     void use_new()                {_use_new = true;}
1739     void set_iff(IfNode* x)       {_iff = x;}
1740     bool has_reserved()     const { return _active && _has_reserved;}
1741   private:
1742     bool create_reserve();
1743 };// class CountedLoopReserveKit
1744 
1745 inline Node* IdealLoopTree::tail() {
1746   // Handle lazy update of _tail field.
1747   if (_tail->in(0) == NULL) {
1748     _tail = _phase->get_ctrl(_tail);
1749   }
1750   return _tail;
1751 }
1752 
1753 inline Node* IdealLoopTree::head() {
1754   // Handle lazy update of _head field.
1755   if (_head->in(0) == NULL) {
1756     _head = _phase->get_ctrl(_head);
1757   }
1758   return _head;
1759 }
1760 
1761 // Iterate over the loop tree using a preorder, left-to-right traversal.
1762 //
1763 // Example that visits all counted loops from within PhaseIdealLoop
1764 //
1765 //  for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
1766 //   IdealLoopTree* lpt = iter.current();
1767 //   if (!lpt->is_counted()) continue;
1768 //   ...
1769 class LoopTreeIterator : public StackObj {
1770 private:
1771   IdealLoopTree* _root;
1772   IdealLoopTree* _curnt;
1773 
1774 public:
1775   LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {}
1776 
1777   bool done() { return _curnt == NULL; }       // Finished iterating?
1778 
1779   void next();                                 // Advance to next loop tree
1780 
1781   IdealLoopTree* current() { return _curnt; }  // Return current value of iterator.
1782 };
1783 
1784 #endif // SHARE_OPTO_LOOPNODE_HPP