1 /*
   2  * Copyright (c) 1998, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_OPTO_LOOPNODE_HPP
  26 #define SHARE_VM_OPTO_LOOPNODE_HPP
  27 
  28 #include "opto/cfgnode.hpp"
  29 #include "opto/multnode.hpp"
  30 #include "opto/phaseX.hpp"
  31 #include "opto/subnode.hpp"
  32 #include "opto/type.hpp"
  33 
  34 class CmpNode;
  35 class CountedLoopEndNode;
  36 class CountedLoopNode;
  37 class IdealLoopTree;
  38 class LoopNode;
  39 class Node;
  40 class OuterStripMinedLoopEndNode;
  41 class PathFrequency;
  42 class PhaseIdealLoop;
  43 class CountedLoopReserveKit;
  44 class VectorSet;
  45 class Invariance;
  46 struct small_cache;
  47 
  48 //
  49 //                  I D E A L I Z E D   L O O P S
  50 //
  51 // Idealized loops are the set of loops I perform more interesting
  52 // transformations on, beyond simple hoisting.
  53 
  54 //------------------------------LoopNode---------------------------------------
  55 // Simple loop header.  Fall in path on left, loop-back path on right.
  56 class LoopNode : public RegionNode {
  57   // Size is bigger to hold the flags.  However, the flags do not change
  58   // the semantics so it does not appear in the hash & cmp functions.
  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=4,
  65          HasExactTripCount=8,
  66          InnerLoop=16,
  67          PartialPeelLoop=32,
  68          PartialPeelFailed=64,
  69          HasReductions=128,
  70          WasSlpAnalyzed=256,
  71          PassedSlpAnalysis=512,
  72          DoUnrollOnly=1024,
  73          VectorizedLoop=2048,
  74          HasAtomicPostLoop=4096,
  75          HasRangeChecks=8192,
  76          IsMultiversioned=16384,
  77          StripMined=32768,
  78          SubwordLoop=65536,
  79          ProfileTripFailed=131072};
  80   char _unswitch_count;
  81   enum { _unswitch_max=3 };
  82   char _postloop_flags;
  83   enum { LoopNotRCEChecked = 0, LoopRCEChecked = 1, RCEPostLoop = 2 };
  84 
  85   // Expected trip count from profile data
  86   float _profile_trip_cnt;
  87 
  88 public:
  89   // Names for edge indices
  90   enum { Self=0, EntryControl, LoopBackControl };
  91 
  92   bool is_inner_loop() const { return _loop_flags & InnerLoop; }
  93   void set_inner_loop() { _loop_flags |= InnerLoop; }
  94 
  95   bool range_checks_present() const { return _loop_flags & HasRangeChecks; }
  96   bool is_multiversioned() const { return _loop_flags & IsMultiversioned; }
  97   bool is_vectorized_loop() const { return _loop_flags & VectorizedLoop; }
  98   bool is_partial_peel_loop() const { return _loop_flags & PartialPeelLoop; }
  99   void set_partial_peel_loop() { _loop_flags |= PartialPeelLoop; }
 100   bool partial_peel_has_failed() const { return _loop_flags & PartialPeelFailed; }
 101   bool is_strip_mined() const { return _loop_flags & StripMined; }
 102   bool is_profile_trip_failed() const { return _loop_flags & ProfileTripFailed; }
 103   bool is_subword_loop() const { return _loop_flags & SubwordLoop; }
 104 
 105   void mark_partial_peel_failed() { _loop_flags |= PartialPeelFailed; }
 106   void mark_has_reductions() { _loop_flags |= HasReductions; }
 107   void mark_was_slp() { _loop_flags |= WasSlpAnalyzed; }
 108   void mark_passed_slp() { _loop_flags |= PassedSlpAnalysis; }
 109   void mark_do_unroll_only() { _loop_flags |= DoUnrollOnly; }
 110   void mark_loop_vectorized() { _loop_flags |= VectorizedLoop; }
 111   void mark_has_atomic_post_loop() { _loop_flags |= HasAtomicPostLoop; }
 112   void mark_has_range_checks() { _loop_flags |=  HasRangeChecks; }
 113   void mark_is_multiversioned() { _loop_flags |= IsMultiversioned; }
 114   void mark_strip_mined() { _loop_flags |= StripMined; }
 115   void clear_strip_mined() { _loop_flags &= ~StripMined; }
 116   void mark_profile_trip_failed() { _loop_flags |= ProfileTripFailed; }
 117   void mark_subword_loop() { _loop_flags |= SubwordLoop; }
 118 
 119   int unswitch_max() { return _unswitch_max; }
 120   int unswitch_count() { return _unswitch_count; }
 121 
 122   int has_been_range_checked() const { return _postloop_flags & LoopRCEChecked; }
 123   void set_has_been_range_checked() { _postloop_flags |= LoopRCEChecked; }
 124   int is_rce_post_loop() const { return _postloop_flags & RCEPostLoop; }
 125   void set_is_rce_post_loop() { _postloop_flags |= RCEPostLoop; }
 126 
 127   void set_unswitch_count(int val) {
 128     assert (val <= unswitch_max(), "too many unswitches");
 129     _unswitch_count = val;
 130   }
 131 
 132   void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
 133   float profile_trip_cnt()             { return _profile_trip_cnt; }
 134 
 135   LoopNode(Node *entry, Node *backedge)
 136     : RegionNode(3), _loop_flags(0), _unswitch_count(0),
 137       _postloop_flags(0), _profile_trip_cnt(COUNT_UNKNOWN)  {
 138     init_class_id(Class_Loop);
 139     init_req(EntryControl, entry);
 140     init_req(LoopBackControl, backedge);
 141   }
 142 
 143   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 144   virtual int Opcode() const;
 145   bool can_be_counted_loop(PhaseTransform* phase) const {
 146     return req() == 3 && in(0) != NULL &&
 147       in(1) != NULL && phase->type(in(1)) != Type::TOP &&
 148       in(2) != NULL && phase->type(in(2)) != Type::TOP;
 149   }
 150   bool is_valid_counted_loop() const;
 151 #ifndef PRODUCT
 152   virtual void dump_spec(outputStream *st) const;
 153 #endif
 154 
 155   void verify_strip_mined(int expect_skeleton) const;
 156   virtual LoopNode* skip_strip_mined(int expect_skeleton = 1) { return this; }
 157   virtual IfTrueNode* outer_loop_tail() const { ShouldNotReachHere(); return NULL; }
 158   virtual OuterStripMinedLoopEndNode* outer_loop_end() const { ShouldNotReachHere(); return NULL; }
 159   virtual IfFalseNode* outer_loop_exit() const { ShouldNotReachHere(); return NULL; }
 160   virtual SafePointNode* outer_safepoint() const { ShouldNotReachHere(); return NULL; }
 161 };
 162 
 163 //------------------------------Counted Loops----------------------------------
 164 // Counted loops are all trip-counted loops, with exactly 1 trip-counter exit
 165 // path (and maybe some other exit paths).  The trip-counter exit is always
 166 // last in the loop.  The trip-counter have to stride by a constant;
 167 // the exit value is also loop invariant.
 168 
 169 // CountedLoopNodes and CountedLoopEndNodes come in matched pairs.  The
 170 // CountedLoopNode has the incoming loop control and the loop-back-control
 171 // which is always the IfTrue before the matching CountedLoopEndNode.  The
 172 // CountedLoopEndNode has an incoming control (possibly not the
 173 // CountedLoopNode if there is control flow in the loop), the post-increment
 174 // trip-counter value, and the limit.  The trip-counter value is always of
 175 // the form (Op old-trip-counter stride).  The old-trip-counter is produced
 176 // by a Phi connected to the CountedLoopNode.  The stride is constant.
 177 // The Op is any commutable opcode, including Add, Mul, Xor.  The
 178 // CountedLoopEndNode also takes in the loop-invariant limit value.
 179 
 180 // From a CountedLoopNode I can reach the matching CountedLoopEndNode via the
 181 // loop-back control.  From CountedLoopEndNodes I can reach CountedLoopNodes
 182 // via the old-trip-counter from the Op node.
 183 
 184 //------------------------------CountedLoopNode--------------------------------
 185 // CountedLoopNodes head simple counted loops.  CountedLoopNodes have as
 186 // inputs the incoming loop-start control and the loop-back control, so they
 187 // act like RegionNodes.  They also take in the initial trip counter, the
 188 // loop-invariant stride and the loop-invariant limit value.  CountedLoopNodes
 189 // produce a loop-body control and the trip counter value.  Since
 190 // CountedLoopNodes behave like RegionNodes I still have a standard CFG model.
 191 
 192 class CountedLoopNode : public LoopNode {
 193   // Size is bigger to hold _main_idx.  However, _main_idx does not change
 194   // the semantics so it does not appear in the hash & cmp functions.
 195   virtual uint size_of() const { return sizeof(*this); }
 196 
 197   // For Pre- and Post-loops during debugging ONLY, this holds the index of
 198   // the Main CountedLoop.  Used to assert that we understand the graph shape.
 199   node_idx_t _main_idx;
 200 
 201   // Known trip count calculated by compute_exact_trip_count()
 202   uint  _trip_count;
 203 
 204   // Log2 of original loop bodies in unrolled loop
 205   int _unrolled_count_log2;
 206 
 207   // Node count prior to last unrolling - used to decide if
 208   // unroll,optimize,unroll,optimize,... is making progress
 209   int _node_count_before_unroll;
 210 
 211   // If slp analysis is performed we record the maximum
 212   // vector mapped unroll factor here
 213   int _slp_maximum_unroll_factor;
 214 
 215 public:
 216   CountedLoopNode( Node *entry, Node *backedge )
 217     : LoopNode(entry, backedge), _main_idx(0), _trip_count(max_juint),
 218       _unrolled_count_log2(0), _node_count_before_unroll(0),
 219       _slp_maximum_unroll_factor(0) {
 220     init_class_id(Class_CountedLoop);
 221     // Initialize _trip_count to the largest possible value.
 222     // Will be reset (lower) if the loop's trip count is known.
 223   }
 224 
 225   virtual int Opcode() const;
 226   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 227 
 228   Node *init_control() const { return in(EntryControl); }
 229   Node *back_control() const { return in(LoopBackControl); }
 230   CountedLoopEndNode *loopexit_or_null() const;
 231   CountedLoopEndNode *loopexit() const;
 232   Node *init_trip() const;
 233   Node *stride() const;
 234   int   stride_con() const;
 235   bool  stride_is_con() const;
 236   Node *limit() const;
 237   Node *incr() const;
 238   Node *phi() const;
 239 
 240   // Match increment with optional truncation
 241   static Node* match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type);
 242 
 243   // A 'main' loop has a pre-loop and a post-loop.  The 'main' loop
 244   // can run short a few iterations and may start a few iterations in.
 245   // It will be RCE'd and unrolled and aligned.
 246 
 247   // A following 'post' loop will run any remaining iterations.  Used
 248   // during Range Check Elimination, the 'post' loop will do any final
 249   // iterations with full checks.  Also used by Loop Unrolling, where
 250   // the 'post' loop will do any epilog iterations needed.  Basically,
 251   // a 'post' loop can not profitably be further unrolled or RCE'd.
 252 
 253   // A preceding 'pre' loop will run at least 1 iteration (to do peeling),
 254   // it may do under-flow checks for RCE and may do alignment iterations
 255   // so the following main loop 'knows' that it is striding down cache
 256   // lines.
 257 
 258   // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or
 259   // Aligned, may be missing it's pre-loop.
 260   bool is_normal_loop   () const { return (_loop_flags&PreMainPostFlagsMask) == Normal; }
 261   bool is_pre_loop      () const { return (_loop_flags&PreMainPostFlagsMask) == Pre;    }
 262   bool is_main_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Main;   }
 263   bool is_post_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Post;   }
 264   bool is_reduction_loop() const { return (_loop_flags&HasReductions) == HasReductions; }
 265   bool was_slp_analyzed () const { return (_loop_flags&WasSlpAnalyzed) == WasSlpAnalyzed; }
 266   bool has_passed_slp   () const { return (_loop_flags&PassedSlpAnalysis) == PassedSlpAnalysis; }
 267   bool do_unroll_only      () const { return (_loop_flags&DoUnrollOnly) == DoUnrollOnly; }
 268   bool is_main_no_pre_loop() const { return _loop_flags & MainHasNoPreLoop; }
 269   bool has_atomic_post_loop  () const { return (_loop_flags & HasAtomicPostLoop) == HasAtomicPostLoop; }
 270   void set_main_no_pre_loop() { _loop_flags |= MainHasNoPreLoop; }
 271 
 272   int main_idx() const { return _main_idx; }
 273 
 274 
 275   void set_pre_loop  (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; }
 276   void set_main_loop (                     ) { assert(is_normal_loop(),""); _loop_flags |= Main;                         }
 277   void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; }
 278   void set_normal_loop(                    ) { _loop_flags &= ~PreMainPostFlagsMask; }
 279 
 280   void set_trip_count(uint tc) { _trip_count = tc; }
 281   uint trip_count()            { return _trip_count; }
 282 
 283   bool has_exact_trip_count() const { return (_loop_flags & HasExactTripCount) != 0; }
 284   void set_exact_trip_count(uint tc) {
 285     _trip_count = tc;
 286     _loop_flags |= HasExactTripCount;
 287   }
 288   void set_nonexact_trip_count() {
 289     _loop_flags &= ~HasExactTripCount;
 290   }
 291   void set_notpassed_slp() {
 292     _loop_flags &= ~PassedSlpAnalysis;
 293   }
 294 
 295   void double_unrolled_count() { _unrolled_count_log2++; }
 296   int  unrolled_count()        { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); }
 297 
 298   void set_node_count_before_unroll(int ct)  { _node_count_before_unroll = ct; }
 299   int  node_count_before_unroll()            { return _node_count_before_unroll; }
 300   void set_slp_max_unroll(int unroll_factor) { _slp_maximum_unroll_factor = unroll_factor; }
 301   int  slp_max_unroll() const                { return _slp_maximum_unroll_factor; }
 302 
 303   virtual LoopNode* skip_strip_mined(int expect_opaq = 1);
 304   OuterStripMinedLoopNode* outer_loop() const;
 305   virtual IfTrueNode* outer_loop_tail() const;
 306   virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
 307   virtual IfFalseNode* outer_loop_exit() const;
 308   virtual SafePointNode* outer_safepoint() const;
 309 
 310   // If this is a main loop in a pre/main/post loop nest, walk over
 311   // the predicates that were inserted by
 312   // duplicate_predicates()/add_range_check_predicate()
 313   static Node* skip_predicates_from_entry(Node* ctrl);
 314   Node* skip_predicates();
 315 
 316 #ifndef PRODUCT
 317   virtual void dump_spec(outputStream *st) const;
 318 #endif
 319 };
 320 
 321 //------------------------------CountedLoopEndNode-----------------------------
 322 // CountedLoopEndNodes end simple trip counted loops.  They act much like
 323 // IfNodes.
 324 class CountedLoopEndNode : public IfNode {
 325 public:
 326   enum { TestControl, TestValue };
 327 
 328   CountedLoopEndNode( Node *control, Node *test, float prob, float cnt )
 329     : IfNode( control, test, prob, cnt) {
 330     init_class_id(Class_CountedLoopEnd);
 331   }
 332   virtual int Opcode() const;
 333 
 334   Node *cmp_node() const            { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; }
 335   Node *incr() const                { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
 336   Node *limit() const               { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
 337   Node *stride() const              { Node *tmp = incr    (); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
 338   Node *init_trip() const           { Node *tmp = phi     (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
 339   int stride_con() const;
 340   bool stride_is_con() const        { Node *tmp = stride  (); return (tmp != NULL && tmp->is_Con()); }
 341   BoolTest::mask test_trip() const  { return in(TestValue)->as_Bool()->_test._test; }
 342   PhiNode *phi() const {
 343     Node *tmp = incr();
 344     if (tmp && tmp->req() == 3) {
 345       Node* phi = tmp->in(1);
 346       if (phi->is_Phi()) {
 347         return phi->as_Phi();
 348       }
 349     }
 350     return NULL;
 351   }
 352   CountedLoopNode *loopnode() const {
 353     // The CountedLoopNode that goes with this CountedLoopEndNode may
 354     // have been optimized out by the IGVN so be cautious with the
 355     // pattern matching on the graph
 356     PhiNode* iv_phi = phi();
 357     if (iv_phi == NULL) {
 358       return NULL;
 359     }
 360     Node *ln = iv_phi->in(0);
 361     if (ln->is_CountedLoop() && ln->as_CountedLoop()->loopexit_or_null() == this) {
 362       return (CountedLoopNode*)ln;
 363     }
 364     return NULL;
 365   }
 366 
 367 #ifndef PRODUCT
 368   virtual void dump_spec(outputStream *st) const;
 369 #endif
 370 };
 371 
 372 
 373 inline CountedLoopEndNode *CountedLoopNode::loopexit_or_null() const {
 374   Node *bc = back_control();
 375   if( bc == NULL ) return NULL;
 376   Node *le = bc->in(0);
 377   if( le->Opcode() != Op_CountedLoopEnd )
 378     return NULL;
 379   return (CountedLoopEndNode*)le;
 380 }
 381 inline CountedLoopEndNode *CountedLoopNode::loopexit() const {
 382   CountedLoopEndNode* cle = loopexit_or_null();
 383   assert(cle != NULL, "loopexit is NULL");
 384   return cle;
 385 }
 386 inline Node *CountedLoopNode::init_trip() const { return loopexit_or_null() ? loopexit()->init_trip() : NULL; }
 387 inline Node *CountedLoopNode::stride() const { return loopexit_or_null() ? loopexit()->stride() : NULL; }
 388 inline int CountedLoopNode::stride_con() const { return loopexit_or_null() ? loopexit()->stride_con() : 0; }
 389 inline bool CountedLoopNode::stride_is_con() const { return loopexit_or_null() && loopexit()->stride_is_con(); }
 390 inline Node *CountedLoopNode::limit() const { return loopexit_or_null() ? loopexit()->limit() : NULL; }
 391 inline Node *CountedLoopNode::incr() const { return loopexit_or_null() ? loopexit()->incr() : NULL; }
 392 inline Node *CountedLoopNode::phi() const { return loopexit_or_null() ? loopexit()->phi() : NULL; }
 393 
 394 //------------------------------LoopLimitNode-----------------------------
 395 // Counted Loop limit node which represents exact final iterator value:
 396 // trip_count = (limit - init_trip + stride - 1)/stride
 397 // final_value= trip_count * stride + init_trip.
 398 // Use HW instructions to calculate it when it can overflow in integer.
 399 // Note, final_value should fit into integer since counted loop has
 400 // limit check: limit <= max_int-stride.
 401 class LoopLimitNode : public Node {
 402   enum { Init=1, Limit=2, Stride=3 };
 403  public:
 404   LoopLimitNode( Compile* C, Node *init, Node *limit, Node *stride ) : Node(0,init,limit,stride) {
 405     // Put it on the Macro nodes list to optimize during macro nodes expansion.
 406     init_flags(Flag_is_macro);
 407     C->add_macro_node(this);
 408   }
 409   virtual int Opcode() const;
 410   virtual const Type *bottom_type() const { return TypeInt::INT; }
 411   virtual uint ideal_reg() const { return Op_RegI; }
 412   virtual const Type* Value(PhaseGVN* phase) const;
 413   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 414   virtual Node* Identity(PhaseGVN* phase);
 415 };
 416 
 417 // Support for strip mining
 418 class OuterStripMinedLoopNode : public LoopNode {
 419 private:
 420   CountedLoopNode* inner_loop() const;
 421 public:
 422   OuterStripMinedLoopNode(Compile* C, Node *entry, Node *backedge)
 423     : LoopNode(entry, backedge) {
 424     init_class_id(Class_OuterStripMinedLoop);
 425     init_flags(Flag_is_macro);
 426     C->add_macro_node(this);
 427   }
 428 
 429   virtual int Opcode() const;
 430 
 431   virtual IfTrueNode* outer_loop_tail() const;
 432   virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
 433   virtual IfFalseNode* outer_loop_exit() const;
 434   virtual SafePointNode* outer_safepoint() const;
 435   void adjust_strip_mined_loop(PhaseIterGVN* igvn);
 436 };
 437 
 438 class OuterStripMinedLoopEndNode : public IfNode {
 439 public:
 440   OuterStripMinedLoopEndNode(Node *control, Node *test, float prob, float cnt)
 441     : IfNode(control, test, prob, cnt) {
 442     init_class_id(Class_OuterStripMinedLoopEnd);
 443   }
 444 
 445   virtual int Opcode() const;
 446 
 447   virtual const Type* Value(PhaseGVN* phase) const;
 448   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 449 };
 450 
 451 // -----------------------------IdealLoopTree----------------------------------
 452 class IdealLoopTree : public ResourceObj {
 453 public:
 454   IdealLoopTree *_parent;       // Parent in loop tree
 455   IdealLoopTree *_next;         // Next sibling in loop tree
 456   IdealLoopTree *_child;        // First child in loop tree
 457 
 458   // The head-tail backedge defines the loop.
 459   // If tail is NULL then this loop has multiple backedges as part of the
 460   // same loop.  During cleanup I'll peel off the multiple backedges; merge
 461   // them at the loop bottom and flow 1 real backedge into the loop.
 462   Node *_head;                  // Head of loop
 463   Node *_tail;                  // Tail of loop
 464   inline Node *tail();          // Handle lazy update of _tail field
 465   PhaseIdealLoop* _phase;
 466   int _local_loop_unroll_limit;
 467   int _local_loop_unroll_factor;
 468 
 469   Node_List _body;              // Loop body for inner loops
 470 
 471   uint8_t _nest;                // Nesting depth
 472   uint8_t _irreducible:1,       // True if irreducible
 473           _has_call:1,          // True if has call safepoint
 474           _has_sfpt:1,          // True if has non-call safepoint
 475           _rce_candidate:1;     // True if candidate for range check elimination
 476 
 477   Node_List* _safepts;          // List of safepoints in this loop
 478   Node_List* _required_safept;  // A inner loop cannot delete these safepts;
 479   bool  _allow_optimizations;   // Allow loop optimizations
 480 
 481   IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail )
 482     : _parent(0), _next(0), _child(0),
 483       _head(head), _tail(tail),
 484       _phase(phase),
 485       _local_loop_unroll_limit(0), _local_loop_unroll_factor(0),
 486       _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0),
 487       _safepts(NULL),
 488       _required_safept(NULL),
 489       _allow_optimizations(true)
 490   { }
 491 
 492   // Is 'l' a member of 'this'?
 493   bool is_member(const IdealLoopTree *l) const; // Test for nested membership
 494 
 495   // Set loop nesting depth.  Accumulate has_call bits.
 496   int set_nest( uint depth );
 497 
 498   // Split out multiple fall-in edges from the loop header.  Move them to a
 499   // private RegionNode before the loop.  This becomes the loop landing pad.
 500   void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt );
 501 
 502   // Split out the outermost loop from this shared header.
 503   void split_outer_loop( PhaseIdealLoop *phase );
 504 
 505   // Merge all the backedges from the shared header into a private Region.
 506   // Feed that region as the one backedge to this loop.
 507   void merge_many_backedges( PhaseIdealLoop *phase );
 508 
 509   // Split shared headers and insert loop landing pads.
 510   // Insert a LoopNode to replace the RegionNode.
 511   // Returns TRUE if loop tree is structurally changed.
 512   bool beautify_loops( PhaseIdealLoop *phase );
 513 
 514   // Perform optimization to use the loop predicates for null checks and range checks.
 515   // Applies to any loop level (not just the innermost one)
 516   bool loop_predication( PhaseIdealLoop *phase);
 517 
 518   // Perform iteration-splitting on inner loops.  Split iterations to
 519   // avoid range checks or one-shot null checks.  Returns false if the
 520   // current round of loop opts should stop.
 521   bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new );
 522 
 523   // Driver for various flavors of iteration splitting.  Returns false
 524   // if the current round of loop opts should stop.
 525   bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new );
 526 
 527   // Given dominators, try to find loops with calls that must always be
 528   // executed (call dominates loop tail).  These loops do not need non-call
 529   // safepoints (ncsfpt).
 530   void check_safepts(VectorSet &visited, Node_List &stack);
 531 
 532   // Allpaths backwards scan from loop tail, terminating each path at first safepoint
 533   // encountered.
 534   void allpaths_check_safepts(VectorSet &visited, Node_List &stack);
 535 
 536   // Remove safepoints from loop. Optionally keeping one.
 537   void remove_safepoints(PhaseIdealLoop* phase, bool keep_one);
 538 
 539   // Convert to counted loops where possible
 540   void counted_loop( PhaseIdealLoop *phase );
 541 
 542   // Check for Node being a loop-breaking test
 543   Node *is_loop_exit(Node *iff) const;
 544 
 545   // Remove simplistic dead code from loop body
 546   void DCE_loop_body();
 547 
 548   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
 549   // Replace with a 1-in-10 exit guess.
 550   void adjust_loop_exit_prob( PhaseIdealLoop *phase );
 551 
 552   // Return TRUE or FALSE if the loop should never be RCE'd or aligned.
 553   // Useful for unrolling loops with NO array accesses.
 554   bool policy_peel_only( PhaseIdealLoop *phase ) const;
 555 
 556   // Return TRUE or FALSE if the loop should be unswitched -- clone
 557   // loop with an invariant test
 558   bool policy_unswitching( PhaseIdealLoop *phase ) const;
 559 
 560   // Micro-benchmark spamming.  Remove empty loops.
 561   bool policy_do_remove_empty_loop( PhaseIdealLoop *phase );
 562 
 563   // Convert one iteration loop into normal code.
 564   bool policy_do_one_iteration_loop( PhaseIdealLoop *phase );
 565 
 566   // Return TRUE or FALSE if the loop should be peeled or not.  Peel if we can
 567   // make some loop-invariant test (usually a null-check) happen before the
 568   // loop.
 569   bool policy_peeling( PhaseIdealLoop *phase ) const;
 570 
 571   // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any
 572   // known trip count in the counted loop node.
 573   bool policy_maximally_unroll( PhaseIdealLoop *phase ) const;
 574 
 575   // Return TRUE or FALSE if the loop should be unrolled or not.  Unroll if
 576   // the loop is a CountedLoop and the body is small enough.
 577   bool policy_unroll(PhaseIdealLoop *phase);
 578 
 579   // Loop analyses to map to a maximal superword unrolling for vectorization.
 580   void policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct);
 581 
 582   // Return TRUE or FALSE if the loop should be range-check-eliminated.
 583   // Gather a list of IF tests that are dominated by iteration splitting;
 584   // also gather the end of the first split and the start of the 2nd split.
 585   bool policy_range_check( PhaseIdealLoop *phase ) const;
 586 
 587   // Return TRUE or FALSE if the loop should be cache-line aligned.
 588   // Gather the expression that does the alignment.  Note that only
 589   // one array base can be aligned in a loop (unless the VM guarantees
 590   // mutual alignment).  Note that if we vectorize short memory ops
 591   // into longer memory ops, we may want to increase alignment.
 592   bool policy_align( PhaseIdealLoop *phase ) const;
 593 
 594   // Return TRUE if "iff" is a range check.
 595   bool is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const;
 596 
 597   // Compute loop trip count if possible
 598   void compute_trip_count(PhaseIdealLoop* phase);
 599 
 600   // Compute loop trip count from profile data
 601   float compute_profile_trip_cnt_helper(Node* n);
 602   void compute_profile_trip_cnt( PhaseIdealLoop *phase );
 603 
 604   // Reassociate invariant expressions.
 605   void reassociate_invariants(PhaseIdealLoop *phase);
 606   // Reassociate invariant add and subtract expressions.
 607   Node* reassociate_add_sub(Node* n1, PhaseIdealLoop *phase);
 608   // Return nonzero index of invariant operand if invariant and variant
 609   // are combined with an Add or Sub. Helper for reassociate_invariants.
 610   int is_invariant_addition(Node* n, PhaseIdealLoop *phase);
 611 
 612   // Return true if n is invariant
 613   bool is_invariant(Node* n) const;
 614 
 615   // Put loop body on igvn work list
 616   void record_for_igvn();
 617 
 618   bool is_loop()    { return !_irreducible && _tail && !_tail->is_top(); }
 619   bool is_inner()   { return is_loop() && _child == NULL; }
 620   bool is_counted() { return is_loop() && _head != NULL && _head->is_CountedLoop(); }
 621 
 622   void remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase);
 623 
 624 #ifndef PRODUCT
 625   void dump_head( ) const;      // Dump loop head only
 626   void dump() const;            // Dump this loop recursively
 627   void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const;
 628 #endif
 629 
 630 };
 631 
 632 // -----------------------------PhaseIdealLoop---------------------------------
 633 // Computes the mapping from Nodes to IdealLoopTrees.  Organizes IdealLoopTrees into a
 634 // loop tree.  Drives the loop-based transformations on the ideal graph.
 635 class PhaseIdealLoop : public PhaseTransform {
 636   friend class IdealLoopTree;
 637   friend class SuperWord;
 638   friend class CountedLoopReserveKit;
 639 
 640   // Pre-computed def-use info
 641   PhaseIterGVN &_igvn;
 642 
 643   // Head of loop tree
 644   IdealLoopTree *_ltree_root;
 645 
 646   // Array of pre-order numbers, plus post-visited bit.
 647   // ZERO for not pre-visited.  EVEN for pre-visited but not post-visited.
 648   // ODD for post-visited.  Other bits are the pre-order number.
 649   uint *_preorders;
 650   uint _max_preorder;
 651 
 652   const PhaseIdealLoop* _verify_me;
 653   bool _verify_only;
 654 
 655   // Allocate _preorders[] array
 656   void allocate_preorders() {
 657     _max_preorder = C->unique()+8;
 658     _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder);
 659     memset(_preorders, 0, sizeof(uint) * _max_preorder);
 660   }
 661 
 662   // Allocate _preorders[] array
 663   void reallocate_preorders() {
 664     if ( _max_preorder < C->unique() ) {
 665       _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique());
 666       _max_preorder = C->unique();
 667     }
 668     memset(_preorders, 0, sizeof(uint) * _max_preorder);
 669   }
 670 
 671   // Check to grow _preorders[] array for the case when build_loop_tree_impl()
 672   // adds new nodes.
 673   void check_grow_preorders( ) {
 674     if ( _max_preorder < C->unique() ) {
 675       uint newsize = _max_preorder<<1;  // double size of array
 676       _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize);
 677       memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder));
 678       _max_preorder = newsize;
 679     }
 680   }
 681   // Check for pre-visited.  Zero for NOT visited; non-zero for visited.
 682   int is_visited( Node *n ) const { return _preorders[n->_idx]; }
 683   // Pre-order numbers are written to the Nodes array as low-bit-set values.
 684   void set_preorder_visited( Node *n, int pre_order ) {
 685     assert( !is_visited( n ), "already set" );
 686     _preorders[n->_idx] = (pre_order<<1);
 687   };
 688   // Return pre-order number.
 689   int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; }
 690 
 691   // Check for being post-visited.
 692   // Should be previsited already (checked with assert(is_visited(n))).
 693   int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; }
 694 
 695   // Mark as post visited
 696   void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; }
 697 
 698 public:
 699   // Set/get control node out.  Set lower bit to distinguish from IdealLoopTree
 700   // Returns true if "n" is a data node, false if it's a control node.
 701   bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; }
 702 
 703 private:
 704   // clear out dead code after build_loop_late
 705   Node_List _deadlist;
 706 
 707   // Support for faster execution of get_late_ctrl()/dom_lca()
 708   // when a node has many uses and dominator depth is deep.
 709   Node_Array _dom_lca_tags;
 710   void   init_dom_lca_tags();
 711   void   clear_dom_lca_tags();
 712 
 713   // Helper for debugging bad dominance relationships
 714   bool verify_dominance(Node* n, Node* use, Node* LCA, Node* early);
 715 
 716   Node* compute_lca_of_uses(Node* n, Node* early, bool verify = false);
 717 
 718   // Inline wrapper for frequent cases:
 719   // 1) only one use
 720   // 2) a use is the same as the current LCA passed as 'n1'
 721   Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) {
 722     assert( n->is_CFG(), "" );
 723     // Fast-path NULL lca
 724     if( lca != NULL && lca != n ) {
 725       assert( lca->is_CFG(), "" );
 726       // find LCA of all uses
 727       n = dom_lca_for_get_late_ctrl_internal( lca, n, tag );
 728     }
 729     return find_non_split_ctrl(n);
 730   }
 731   Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag );
 732 
 733   // Helper function for directing control inputs away from CFG split
 734   // points.
 735   Node *find_non_split_ctrl( Node *ctrl ) const {
 736     if (ctrl != NULL) {
 737       if (ctrl->is_MultiBranch()) {
 738         ctrl = ctrl->in(0);
 739       }
 740       assert(ctrl->is_CFG(), "CFG");
 741     }
 742     return ctrl;
 743   }
 744 
 745   Node* cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop);
 746   void duplicate_predicates_helper(Node* predicate, Node* castii, IdealLoopTree* outer_loop,
 747                                    LoopNode* outer_main_head, uint dd_main_head);
 748   void duplicate_predicates(CountedLoopNode* pre_head, Node* castii, IdealLoopTree* outer_loop,
 749                             LoopNode* outer_main_head, uint dd_main_head);
 750   Node* update_skeleton_predicate(Node* iff, Node* value, Node* predicate = NULL, Node* uncommon_proj = NULL,
 751                                   Node* current_proj = NULL, IdealLoopTree* outer_loop = NULL, Node* prev_proj = NULL);
 752 
 753 public:
 754 
 755   PhaseIterGVN &igvn() const { return _igvn; }
 756 
 757   static bool is_canonical_loop_entry(CountedLoopNode* cl);
 758 
 759   bool has_node( Node* n ) const {
 760     guarantee(n != NULL, "No Node.");
 761     return _nodes[n->_idx] != NULL;
 762   }
 763   // check if transform created new nodes that need _ctrl recorded
 764   Node *get_late_ctrl( Node *n, Node *early );
 765   Node *get_early_ctrl( Node *n );
 766   Node *get_early_ctrl_for_expensive(Node *n, Node* earliest);
 767   void set_early_ctrl( Node *n );
 768   void set_subtree_ctrl( Node *root );
 769   void set_ctrl( Node *n, Node *ctrl ) {
 770     assert( !has_node(n) || has_ctrl(n), "" );
 771     assert( ctrl->in(0), "cannot set dead control node" );
 772     assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" );
 773     _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) );
 774   }
 775   // Set control and update loop membership
 776   void set_ctrl_and_loop(Node* n, Node* ctrl) {
 777     IdealLoopTree* old_loop = get_loop(get_ctrl(n));
 778     IdealLoopTree* new_loop = get_loop(ctrl);
 779     if (old_loop != new_loop) {
 780       if (old_loop->_child == NULL) old_loop->_body.yank(n);
 781       if (new_loop->_child == NULL) new_loop->_body.push(n);
 782     }
 783     set_ctrl(n, ctrl);
 784   }
 785   // Control nodes can be replaced or subsumed.  During this pass they
 786   // get their replacement Node in slot 1.  Instead of updating the block
 787   // location of all Nodes in the subsumed block, we lazily do it.  As we
 788   // pull such a subsumed block out of the array, we write back the final
 789   // correct block.
 790   Node *get_ctrl( Node *i ) {
 791     assert(has_node(i), "");
 792     Node *n = get_ctrl_no_update(i);
 793     _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) );
 794     assert(has_node(i) && has_ctrl(i), "");
 795     assert(n == find_non_split_ctrl(n), "must return legal ctrl" );
 796     return n;
 797   }
 798   // true if CFG node d dominates CFG node n
 799   bool is_dominator(Node *d, Node *n);
 800   // return get_ctrl for a data node and self(n) for a CFG node
 801   Node* ctrl_or_self(Node* n) {
 802     if (has_ctrl(n))
 803       return get_ctrl(n);
 804     else {
 805       assert (n->is_CFG(), "must be a CFG node");
 806       return n;
 807     }
 808   }
 809 
 810   Node *get_ctrl_no_update_helper(Node *i) const {
 811     assert(has_ctrl(i), "should be control, not loop");
 812     return (Node*)(((intptr_t)_nodes[i->_idx]) & ~1);
 813   }
 814 
 815   Node *get_ctrl_no_update(Node *i) const {
 816     assert( has_ctrl(i), "" );
 817     Node *n = get_ctrl_no_update_helper(i);
 818     if (!n->in(0)) {
 819       // Skip dead CFG nodes
 820       do {
 821         n = get_ctrl_no_update_helper(n);
 822       } while (!n->in(0));
 823       n = find_non_split_ctrl(n);
 824     }
 825     return n;
 826   }
 827 
 828   // Check for loop being set
 829   // "n" must be a control node. Returns true if "n" is known to be in a loop.
 830   bool has_loop( Node *n ) const {
 831     assert(!has_node(n) || !has_ctrl(n), "");
 832     return has_node(n);
 833   }
 834   // Set loop
 835   void set_loop( Node *n, IdealLoopTree *loop ) {
 836     _nodes.map(n->_idx, (Node*)loop);
 837   }
 838   // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms.  Replace
 839   // the 'old_node' with 'new_node'.  Kill old-node.  Add a reference
 840   // from old_node to new_node to support the lazy update.  Reference
 841   // replaces loop reference, since that is not needed for dead node.
 842   void lazy_update(Node *old_node, Node *new_node) {
 843     assert(old_node != new_node, "no cycles please");
 844     // Re-use the side array slot for this node to provide the
 845     // forwarding pointer.
 846     _nodes.map(old_node->_idx, (Node*)((intptr_t)new_node + 1));
 847   }
 848   void lazy_replace(Node *old_node, Node *new_node) {
 849     _igvn.replace_node(old_node, new_node);
 850     lazy_update(old_node, new_node);
 851   }
 852 
 853 private:
 854 
 855   // Place 'n' in some loop nest, where 'n' is a CFG node
 856   void build_loop_tree();
 857   int build_loop_tree_impl( Node *n, int pre_order );
 858   // Insert loop into the existing loop tree.  'innermost' is a leaf of the
 859   // loop tree, not the root.
 860   IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost );
 861 
 862   // Place Data nodes in some loop nest
 863   void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
 864   void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
 865   void build_loop_late_post ( Node* n );
 866   void verify_strip_mined_scheduling(Node *n, Node* least);
 867 
 868   // Array of immediate dominance info for each CFG node indexed by node idx
 869 private:
 870   uint _idom_size;
 871   Node **_idom;                  // Array of immediate dominators
 872   uint *_dom_depth;              // Used for fast LCA test
 873   GrowableArray<uint>* _dom_stk; // For recomputation of dom depth
 874 
 875 public:
 876   Node* idom_no_update(Node* d) const {
 877     return idom_no_update(d->_idx);
 878   }
 879 
 880   Node* idom_no_update(uint didx) const {
 881     assert(didx < _idom_size, "oob");
 882     Node* n = _idom[didx];
 883     assert(n != NULL,"Bad immediate dominator info.");
 884     while (n->in(0) == NULL) { // Skip dead CFG nodes
 885       n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
 886       assert(n != NULL,"Bad immediate dominator info.");
 887     }
 888     return n;
 889   }
 890 
 891   Node *idom(Node* d) const {
 892     return idom(d->_idx);
 893   }
 894 
 895   Node *idom(uint didx) const {
 896     Node *n = idom_no_update(didx);
 897     _idom[didx] = n; // Lazily remove dead CFG nodes from table.
 898     return n;
 899   }
 900 
 901   uint dom_depth(Node* d) const {
 902     guarantee(d != NULL, "Null dominator info.");
 903     guarantee(d->_idx < _idom_size, "");
 904     return _dom_depth[d->_idx];
 905   }
 906   void set_idom(Node* d, Node* n, uint dom_depth);
 907   // Locally compute IDOM using dom_lca call
 908   Node *compute_idom( Node *region ) const;
 909   // Recompute dom_depth
 910   void recompute_dom_depth();
 911 
 912   // Is safept not required by an outer loop?
 913   bool is_deleteable_safept(Node* sfpt);
 914 
 915   // Replace parallel induction variable (parallel to trip counter)
 916   void replace_parallel_iv(IdealLoopTree *loop);
 917 
 918   // Perform verification that the graph is valid.
 919   PhaseIdealLoop( PhaseIterGVN &igvn) :
 920     PhaseTransform(Ideal_Loop),
 921     _igvn(igvn),
 922     _verify_me(NULL),
 923     _verify_only(true),
 924     _dom_lca_tags(arena()) { // Thread::resource_area
 925     build_and_optimize(LoopOptsVerify);
 926   }
 927 
 928   // build the loop tree and perform any requested optimizations
 929   void build_and_optimize(LoopOptsMode mode);
 930 
 931   // Dominators for the sea of nodes
 932   void Dominators();
 933   Node *dom_lca( Node *n1, Node *n2 ) const {
 934     return find_non_split_ctrl(dom_lca_internal(n1, n2));
 935   }
 936   Node *dom_lca_internal( Node *n1, Node *n2 ) const;
 937 
 938   // Compute the Ideal Node to Loop mapping
 939   PhaseIdealLoop(PhaseIterGVN &igvn, LoopOptsMode mode) :
 940     PhaseTransform(Ideal_Loop),
 941     _igvn(igvn),
 942     _verify_me(NULL),
 943     _verify_only(false),
 944     _dom_lca_tags(arena()) { // Thread::resource_area
 945     build_and_optimize(mode);
 946   }
 947 
 948   // Verify that verify_me made the same decisions as a fresh run.
 949   PhaseIdealLoop(PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me) :
 950     PhaseTransform(Ideal_Loop),
 951     _igvn(igvn),
 952     _verify_me(verify_me),
 953     _verify_only(false),
 954     _dom_lca_tags(arena()) { // Thread::resource_area
 955     build_and_optimize(LoopOptsVerify);
 956   }
 957 
 958   // Build and verify the loop tree without modifying the graph.  This
 959   // is useful to verify that all inputs properly dominate their uses.
 960   static void verify(PhaseIterGVN& igvn) {
 961 #ifdef ASSERT
 962     PhaseIdealLoop v(igvn);
 963 #endif
 964   }
 965 
 966   // True if the method has at least 1 irreducible loop
 967   bool _has_irreducible_loops;
 968 
 969   // Per-Node transform
 970   virtual Node *transform( Node *a_node ) { return 0; }
 971 
 972   bool is_counted_loop(Node* x, IdealLoopTree*& loop);
 973   IdealLoopTree* create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
 974                                                IdealLoopTree* loop, float cl_prob, float le_fcnt,
 975                                                Node*& entry_control, Node*& iffalse);
 976 
 977   Node* exact_limit( IdealLoopTree *loop );
 978 
 979   // Return a post-walked LoopNode
 980   IdealLoopTree *get_loop( Node *n ) const {
 981     // Dead nodes have no loop, so return the top level loop instead
 982     if (!has_node(n))  return _ltree_root;
 983     assert(!has_ctrl(n), "");
 984     return (IdealLoopTree*)_nodes[n->_idx];
 985   }
 986 
 987   IdealLoopTree *ltree_root() const { return _ltree_root; }
 988 
 989   // Is 'n' a (nested) member of 'loop'?
 990   int is_member( const IdealLoopTree *loop, Node *n ) const {
 991     return loop->is_member(get_loop(n)); }
 992 
 993   // This is the basic building block of the loop optimizations.  It clones an
 994   // entire loop body.  It makes an old_new loop body mapping; with this
 995   // mapping you can find the new-loop equivalent to an old-loop node.  All
 996   // new-loop nodes are exactly equal to their old-loop counterparts, all
 997   // edges are the same.  All exits from the old-loop now have a RegionNode
 998   // that merges the equivalent new-loop path.  This is true even for the
 999   // normal "loop-exit" condition.  All uses of loop-invariant old-loop values
1000   // now come from (one or more) Phis that merge their new-loop equivalents.
1001   // Parameter side_by_side_idom:
1002   //   When side_by_size_idom is NULL, the dominator tree is constructed for
1003   //      the clone loop to dominate the original.  Used in construction of
1004   //      pre-main-post loop sequence.
1005   //   When nonnull, the clone and original are side-by-side, both are
1006   //      dominated by the passed in side_by_side_idom node.  Used in
1007   //      construction of unswitched loops.
1008   enum CloneLoopMode {
1009     IgnoreStripMined = 0,        // Only clone inner strip mined loop
1010     CloneIncludesStripMined = 1, // clone both inner and outer strip mined loops
1011     ControlAroundStripMined = 2  // Only clone inner strip mined loop,
1012                                  // result control flow branches
1013                                  // either to inner clone or outer
1014                                  // strip mined loop.
1015   };
1016   void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
1017                   CloneLoopMode mode, Node* side_by_side_idom = NULL);
1018   void clone_loop_handle_data_uses(Node* old, Node_List &old_new,
1019                                    IdealLoopTree* loop, IdealLoopTree* companion_loop,
1020                                    Node_List*& split_if_set, Node_List*& split_bool_set,
1021                                    Node_List*& split_cex_set, Node_List& worklist,
1022                                    uint new_counter, CloneLoopMode mode);
1023   void clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
1024                         IdealLoopTree* outer_loop, int dd, Node_List &old_new,
1025                         Node_List& extra_data_nodes);
1026 
1027   // If we got the effect of peeling, either by actually peeling or by
1028   // making a pre-loop which must execute at least once, we can remove
1029   // all loop-invariant dominated tests in the main body.
1030   void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new );
1031 
1032   // Generate code to do a loop peel for the given loop (and body).
1033   // old_new is a temp array.
1034   void do_peeling( IdealLoopTree *loop, Node_List &old_new );
1035 
1036   // Add pre and post loops around the given loop.  These loops are used
1037   // during RCE, unrolling and aligning loops.
1038   void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only );
1039 
1040   // Add post loop after the given loop.
1041   Node *insert_post_loop(IdealLoopTree *loop, Node_List &old_new,
1042                          CountedLoopNode *main_head, CountedLoopEndNode *main_end,
1043                          Node *incr, Node *limit, CountedLoopNode *&post_head);
1044 
1045   // Add an RCE'd post loop which we will multi-version adapt for run time test path usage
1046   void insert_scalar_rced_post_loop( IdealLoopTree *loop, Node_List &old_new );
1047 
1048   // Add a vector post loop between a vector main loop and the current post loop
1049   void insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new);
1050   // If Node n lives in the back_ctrl block, we clone a private version of n
1051   // in preheader_ctrl block and return that, otherwise return n.
1052   Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones );
1053 
1054   // Take steps to maximally unroll the loop.  Peel any odd iterations, then
1055   // unroll to do double iterations.  The next round of major loop transforms
1056   // will repeat till the doubled loop body does all remaining iterations in 1
1057   // pass.
1058   void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new );
1059 
1060   // Unroll the loop body one step - make each trip do 2 iterations.
1061   void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip );
1062 
1063   // Mark vector reduction candidates before loop unrolling
1064   void mark_reductions( IdealLoopTree *loop );
1065 
1066   // Return true if exp is a constant times an induction var
1067   bool is_scaled_iv(Node* exp, Node* iv, int* p_scale);
1068 
1069   // Return true if exp is a scaled induction var plus (or minus) constant
1070   bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0);
1071 
1072   // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted
1073   ProjNode* create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
1074                                         Deoptimization::DeoptReason reason,
1075                                         int opcode);
1076   void register_control(Node* n, IdealLoopTree *loop, Node* pred);
1077 
1078   // Clone loop predicates to cloned loops (peeled, unswitched)
1079   static ProjNode* clone_predicate(ProjNode* predicate_proj, Node* new_entry,
1080                                    Deoptimization::DeoptReason reason,
1081                                    PhaseIdealLoop* loop_phase,
1082                                    PhaseIterGVN* igvn);
1083 




1084   static Node* clone_loop_predicates(Node* old_entry, Node* new_entry,
1085                                          bool clone_limit_check,
1086                                          PhaseIdealLoop* loop_phase,
1087                                          PhaseIterGVN* igvn);
1088   Node* clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check);
1089 
1090   static Node* skip_all_loop_predicates(Node* entry);
1091   static Node* skip_loop_predicates(Node* entry);
1092 
1093   // Find a good location to insert a predicate
1094   static ProjNode* find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason);
1095   // Find a predicate
1096   static Node* find_predicate(Node* entry);
1097   // Construct a range check for a predicate if
1098   BoolNode* rc_predicate(IdealLoopTree *loop, Node* ctrl,
1099                          int scale, Node* offset,
1100                          Node* init, Node* limit, jint stride,
1101                          Node* range, bool upper, bool &overflow);
1102 
1103   // Implementation of the loop predication to promote checks outside the loop
1104   bool loop_predication_impl(IdealLoopTree *loop);
1105   bool loop_predication_impl_helper(IdealLoopTree *loop, ProjNode* proj, ProjNode *predicate_proj,
1106                                     CountedLoopNode *cl, ConNode* zero, Invariance& invar,
1107                                     Deoptimization::DeoptReason reason);
1108   bool loop_predication_should_follow_branches(IdealLoopTree *loop, ProjNode *predicate_proj, float& loop_trip_cnt);
1109   void loop_predication_follow_branches(Node *c, IdealLoopTree *loop, float loop_trip_cnt,
1110                                         PathFrequency& pf, Node_Stack& stack, VectorSet& seen,
1111                                         Node_List& if_proj_list);
1112   ProjNode* insert_skeleton_predicate(IfNode* iff, IdealLoopTree *loop,
1113                                       ProjNode* proj, ProjNode *predicate_proj,
1114                                       ProjNode* upper_bound_proj,
1115                                       int scale, Node* offset,
1116                                       Node* init, Node* limit, jint stride,
1117                                       Node* rng, bool& overflow,
1118                                       Deoptimization::DeoptReason reason);
1119   Node* add_range_check_predicate(IdealLoopTree* loop, CountedLoopNode* cl,
1120                                   Node* predicate_proj, int scale_con, Node* offset,
1121                                   Node* limit, jint stride_con);
1122 
1123   // Helper function to collect predicate for eliminating the useless ones
1124   void collect_potentially_useful_predicates(IdealLoopTree *loop, Unique_Node_List &predicate_opaque1);
1125   void eliminate_useless_predicates();
1126 
1127   // Change the control input of expensive nodes to allow commoning by
1128   // IGVN when it is guaranteed to not result in a more frequent
1129   // execution of the expensive node. Return true if progress.
1130   bool process_expensive_nodes();
1131 
1132   // Check whether node has become unreachable
1133   bool is_node_unreachable(Node *n) const {
1134     return !has_node(n) || n->is_unreachable(_igvn);
1135   }
1136 
1137   // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1138   int do_range_check( IdealLoopTree *loop, Node_List &old_new );
1139 
1140   // Check to see if do_range_check(...) cleaned the main loop of range-checks
1141   void has_range_checks(IdealLoopTree *loop);
1142 
1143   // Process post loops which have range checks and try to build a multi-version
1144   // guard to safely determine if we can execute the post loop which was RCE'd.
1145   bool multi_version_post_loops(IdealLoopTree *rce_loop, IdealLoopTree *legacy_loop);
1146 
1147   // Cause the rce'd post loop to optimized away, this happens if we cannot complete multiverioning
1148   void poison_rce_post_loop(IdealLoopTree *rce_loop);
1149 
1150   // Create a slow version of the loop by cloning the loop
1151   // and inserting an if to select fast-slow versions.
1152   ProjNode* create_slow_version_of_loop(IdealLoopTree *loop,
1153                                         Node_List &old_new,
1154                                         int opcode,
1155                                         CloneLoopMode mode);
1156 
1157   // Clone a loop and return the clone head (clone_loop_head).
1158   // Added nodes include int(1), int(0) - disconnected, If, IfTrue, IfFalse,
1159   // This routine was created for usage in CountedLoopReserveKit.
1160   //
1161   //    int(1) -> If -> IfTrue -> original_loop_head
1162   //              |
1163   //              V
1164   //           IfFalse -> clone_loop_head (returned by function pointer)
1165   //
1166   LoopNode* create_reserve_version_of_loop(IdealLoopTree *loop, CountedLoopReserveKit* lk);
1167   // Clone loop with an invariant test (that does not exit) and
1168   // insert a clone of the test that selects which version to
1169   // execute.
1170   void do_unswitching (IdealLoopTree *loop, Node_List &old_new);
1171 
1172   // Find candidate "if" for unswitching
1173   IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const;
1174 
1175   // Range Check Elimination uses this function!
1176   // Constrain the main loop iterations so the affine function:
1177   //    low_limit <= scale_con * I + offset  <  upper_limit
1178   // always holds true.  That is, either increase the number of iterations in
1179   // the pre-loop or the post-loop until the condition holds true in the main
1180   // loop.  Scale_con, offset and limit are all loop invariant.
1181   void add_constraint( int stride_con, int scale_con, Node *offset, Node *low_limit, Node *upper_limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit );
1182   // Helper function for add_constraint().
1183   Node* adjust_limit( int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl );
1184 
1185   // Partially peel loop up through last_peel node.
1186   bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
1187 
1188   // Create a scheduled list of nodes control dependent on ctrl set.
1189   void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched );
1190   // Has a use in the vector set
1191   bool has_use_in_set( Node* n, VectorSet& vset );
1192   // Has use internal to the vector set (ie. not in a phi at the loop head)
1193   bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop );
1194   // clone "n" for uses that are outside of loop
1195   int  clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist );
1196   // clone "n" for special uses that are in the not_peeled region
1197   void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
1198                                           VectorSet& not_peel, Node_List& sink_list, Node_List& worklist );
1199   // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
1200   void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp );
1201 #ifdef ASSERT
1202   // Validate the loop partition sets: peel and not_peel
1203   bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel );
1204   // Ensure that uses outside of loop are of the right form
1205   bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
1206                                  uint orig_exit_idx, uint clone_exit_idx);
1207   bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx);
1208 #endif
1209 
1210   // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.)
1211   int stride_of_possible_iv( Node* iff );
1212   bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; }
1213   // Return the (unique) control output node that's in the loop (if it exists.)
1214   Node* stay_in_loop( Node* n, IdealLoopTree *loop);
1215   // Insert a signed compare loop exit cloned from an unsigned compare.
1216   IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop);
1217   void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop);
1218   // Utility to register node "n" with PhaseIdealLoop
1219   void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth);
1220   // Utility to create an if-projection
1221   ProjNode* proj_clone(ProjNode* p, IfNode* iff);
1222   // Force the iff control output to be the live_proj
1223   Node* short_circuit_if(IfNode* iff, ProjNode* live_proj);
1224   // Insert a region before an if projection
1225   RegionNode* insert_region_before_proj(ProjNode* proj);
1226   // Insert a new if before an if projection
1227   ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj);
1228 
1229   // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
1230   // "Nearly" because all Nodes have been cloned from the original in the loop,
1231   // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
1232   // through the Phi recursively, and return a Bool.
1233   Node *clone_iff( PhiNode *phi, IdealLoopTree *loop );
1234   CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop );
1235 
1236 
1237   // Rework addressing expressions to get the most loop-invariant stuff
1238   // moved out.  We'd like to do all associative operators, but it's especially
1239   // important (common) to do address expressions.
1240   Node *remix_address_expressions( Node *n );
1241 
1242   // Attempt to use a conditional move instead of a phi/branch
1243   Node *conditional_move( Node *n );
1244 
1245   // Reorganize offset computations to lower register pressure.
1246   // Mostly prevent loop-fallout uses of the pre-incremented trip counter
1247   // (which are then alive with the post-incremented trip counter
1248   // forcing an extra register move)
1249   void reorg_offsets( IdealLoopTree *loop );
1250 
1251   // Check for aggressive application of 'split-if' optimization,
1252   // using basic block level info.
1253   void  split_if_with_blocks     ( VectorSet &visited, Node_Stack &nstack, bool last_round );
1254   Node *split_if_with_blocks_pre ( Node *n );
1255   void  split_if_with_blocks_post( Node *n, bool last_round );
1256   Node *has_local_phi_input( Node *n );
1257   // Mark an IfNode as being dominated by a prior test,
1258   // without actually altering the CFG (and hence IDOM info).
1259   void dominated_by( Node *prevdom, Node *iff, bool flip = false, bool exclude_loop_predicate = false );
1260 
1261   // Split Node 'n' through merge point
1262   Node *split_thru_region( Node *n, Node *region );
1263   // Split Node 'n' through merge point if there is enough win.
1264   Node *split_thru_phi( Node *n, Node *region, int policy );
1265   // Found an If getting its condition-code input from a Phi in the
1266   // same block.  Split thru the Region.
1267   void do_split_if( Node *iff );
1268 
1269   // Conversion of fill/copy patterns into intrisic versions
1270   bool do_intrinsify_fill();
1271   bool intrinsify_fill(IdealLoopTree* lpt);
1272   bool match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
1273                        Node*& shift, Node*& offset);
1274 
1275 private:
1276   // Return a type based on condition control flow
1277   const TypeInt* filtered_type( Node *n, Node* n_ctrl);
1278   const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); }
1279  // Helpers for filtered type
1280   const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl);
1281 
1282   // Helper functions
1283   Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache );
1284   Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true );
1285   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 );
1286   bool split_up( Node *n, Node *blk1, Node *blk2 );
1287   void sink_use( Node *use, Node *post_loop );
1288   Node *place_near_use( Node *useblock ) const;
1289   Node* try_move_store_before_loop(Node* n, Node *n_ctrl);
1290   void try_move_store_after_loop(Node* n);
1291   bool identical_backtoback_ifs(Node *n);
1292   bool can_split_if(Node *n_ctrl);
1293 
1294   bool _created_loop_node;
1295 public:
1296   void set_created_loop_node() { _created_loop_node = true; }
1297   bool created_loop_node()     { return _created_loop_node; }
1298   void register_new_node( Node *n, Node *blk );
1299 
1300 #ifdef ASSERT
1301   void dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA);
1302 #endif
1303 
1304 #ifndef PRODUCT
1305   void dump( ) const;
1306   void dump( IdealLoopTree *loop, uint rpo_idx, Node_List &rpo_list ) const;
1307   void rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const;
1308   void verify() const;          // Major slow  :-)
1309   void verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const;
1310   IdealLoopTree *get_loop_idx(Node* n) const {
1311     // Dead nodes have no loop, so return the top level loop instead
1312     return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root;
1313   }
1314   // Print some stats
1315   static void print_statistics();
1316   static int _loop_invokes;     // Count of PhaseIdealLoop invokes
1317   static int _loop_work;        // Sum of PhaseIdealLoop x _unique
1318 #endif
1319 };
1320 
1321 // This kit may be used for making of a reserved copy of a loop before this loop
1322 //  goes under non-reversible changes.
1323 //
1324 // Function create_reserve() creates a reserved copy (clone) of the loop.
1325 // The reserved copy is created by calling
1326 // PhaseIdealLoop::create_reserve_version_of_loop - see there how
1327 // the original and reserved loops are connected in the outer graph.
1328 // If create_reserve succeeded, it returns 'true' and _has_reserved is set to 'true'.
1329 //
1330 // By default the reserved copy (clone) of the loop is created as dead code - it is
1331 // dominated in the outer loop by this node chain:
1332 //   intcon(1)->If->IfFalse->reserved_copy.
1333 // The original loop is dominated by the the same node chain but IfTrue projection:
1334 //   intcon(0)->If->IfTrue->original_loop.
1335 //
1336 // In this implementation of CountedLoopReserveKit the ctor includes create_reserve()
1337 // and the dtor, checks _use_new value.
1338 // If _use_new == false, it "switches" control to reserved copy of the loop
1339 // by simple replacing of node intcon(1) with node intcon(0).
1340 //
1341 // Here is a proposed example of usage (see also SuperWord::output in superword.cpp).
1342 //
1343 // void CountedLoopReserveKit_example()
1344 // {
1345 //    CountedLoopReserveKit lrk((phase, lpt, DoReserveCopy = true); // create local object
1346 //    if (DoReserveCopy && !lrk.has_reserved()) {
1347 //      return; //failed to create reserved loop copy
1348 //    }
1349 //    ...
1350 //    //something is wrong, switch to original loop
1351 ///   if(something_is_wrong) return; // ~CountedLoopReserveKit makes the switch
1352 //    ...
1353 //    //everything worked ok, return with the newly modified loop
1354 //    lrk.use_new();
1355 //    return; // ~CountedLoopReserveKit does nothing once use_new() was called
1356 //  }
1357 //
1358 // Keep in mind, that by default if create_reserve() is not followed by use_new()
1359 // the dtor will "switch to the original" loop.
1360 // NOTE. You you modify outside of the original loop this class is no help.
1361 //
1362 class CountedLoopReserveKit {
1363   private:
1364     PhaseIdealLoop* _phase;
1365     IdealLoopTree*  _lpt;
1366     LoopNode*       _lp;
1367     IfNode*         _iff;
1368     LoopNode*       _lp_reserved;
1369     bool            _has_reserved;
1370     bool            _use_new;
1371     const bool      _active; //may be set to false in ctor, then the object is dummy
1372 
1373   public:
1374     CountedLoopReserveKit(PhaseIdealLoop* phase, IdealLoopTree *loop, bool active);
1375     ~CountedLoopReserveKit();
1376     void use_new()                {_use_new = true;}
1377     void set_iff(IfNode* x)       {_iff = x;}
1378     bool has_reserved()     const { return _active && _has_reserved;}
1379   private:
1380     bool create_reserve();
1381 };// class CountedLoopReserveKit
1382 
1383 inline Node* IdealLoopTree::tail() {
1384 // Handle lazy update of _tail field
1385   Node *n = _tail;
1386   //while( !n->in(0) )  // Skip dead CFG nodes
1387     //n = n->in(1);
1388   if (n->in(0) == NULL)
1389     n = _phase->get_ctrl(n);
1390   _tail = n;
1391   return n;
1392 }
1393 
1394 
1395 // Iterate over the loop tree using a preorder, left-to-right traversal.
1396 //
1397 // Example that visits all counted loops from within PhaseIdealLoop
1398 //
1399 //  for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
1400 //   IdealLoopTree* lpt = iter.current();
1401 //   if (!lpt->is_counted()) continue;
1402 //   ...
1403 class LoopTreeIterator : public StackObj {
1404 private:
1405   IdealLoopTree* _root;
1406   IdealLoopTree* _curnt;
1407 
1408 public:
1409   LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {}
1410 
1411   bool done() { return _curnt == NULL; }       // Finished iterating?
1412 
1413   void next();                                 // Advance to next loop tree
1414 
1415   IdealLoopTree* current() { return _curnt; }  // Return current value of iterator.
1416 };
1417 
1418 #endif // SHARE_VM_OPTO_LOOPNODE_HPP
--- EOF ---