loopnode.hpp revision 1472:c18cbe5936b8
1/* 2 * Copyright (c) 1998, 2009, 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 25class CmpNode; 26class CountedLoopEndNode; 27class CountedLoopNode; 28class IdealLoopTree; 29class LoopNode; 30class Node; 31class PhaseIdealLoop; 32class VectorSet; 33class Invariance; 34struct small_cache; 35 36// 37// I D E A L I Z E D L O O P S 38// 39// Idealized loops are the set of loops I perform more interesting 40// transformations on, beyond simple hoisting. 41 42//------------------------------LoopNode--------------------------------------- 43// Simple loop header. Fall in path on left, loop-back path on right. 44class LoopNode : public RegionNode { 45 // Size is bigger to hold the flags. However, the flags do not change 46 // the semantics so it does not appear in the hash & cmp functions. 47 virtual uint size_of() const { return sizeof(*this); } 48protected: 49 short _loop_flags; 50 // Names for flag bitfields 51 enum { pre_post_main=0, inner_loop=8, partial_peel_loop=16, partial_peel_failed=32 }; 52 char _unswitch_count; 53 enum { _unswitch_max=3 }; 54 55public: 56 // Names for edge indices 57 enum { Self=0, EntryControl, LoopBackControl }; 58 59 int is_inner_loop() const { return _loop_flags & inner_loop; } 60 void set_inner_loop() { _loop_flags |= inner_loop; } 61 62 int is_partial_peel_loop() const { return _loop_flags & partial_peel_loop; } 63 void set_partial_peel_loop() { _loop_flags |= partial_peel_loop; } 64 int partial_peel_has_failed() const { return _loop_flags & partial_peel_failed; } 65 void mark_partial_peel_failed() { _loop_flags |= partial_peel_failed; } 66 67 int unswitch_max() { return _unswitch_max; } 68 int unswitch_count() { return _unswitch_count; } 69 void set_unswitch_count(int val) { 70 assert (val <= unswitch_max(), "too many unswitches"); 71 _unswitch_count = val; 72 } 73 74 LoopNode( Node *entry, Node *backedge ) : RegionNode(3), _loop_flags(0), _unswitch_count(0) { 75 init_class_id(Class_Loop); 76 init_req(EntryControl, entry); 77 init_req(LoopBackControl, backedge); 78 } 79 80 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape); 81 virtual int Opcode() const; 82 bool can_be_counted_loop(PhaseTransform* phase) const { 83 return req() == 3 && in(0) != NULL && 84 in(1) != NULL && phase->type(in(1)) != Type::TOP && 85 in(2) != NULL && phase->type(in(2)) != Type::TOP; 86 } 87#ifndef PRODUCT 88 virtual void dump_spec(outputStream *st) const; 89#endif 90}; 91 92//------------------------------Counted Loops---------------------------------- 93// Counted loops are all trip-counted loops, with exactly 1 trip-counter exit 94// path (and maybe some other exit paths). The trip-counter exit is always 95// last in the loop. The trip-counter does not have to stride by a constant, 96// but it does have to stride by a loop-invariant amount; the exit value is 97// also loop invariant. 98 99// CountedLoopNodes and CountedLoopEndNodes come in matched pairs. The 100// CountedLoopNode has the incoming loop control and the loop-back-control 101// which is always the IfTrue before the matching CountedLoopEndNode. The 102// CountedLoopEndNode has an incoming control (possibly not the 103// CountedLoopNode if there is control flow in the loop), the post-increment 104// trip-counter value, and the limit. The trip-counter value is always of 105// the form (Op old-trip-counter stride). The old-trip-counter is produced 106// by a Phi connected to the CountedLoopNode. The stride is loop invariant. 107// The Op is any commutable opcode, including Add, Mul, Xor. The 108// CountedLoopEndNode also takes in the loop-invariant limit value. 109 110// From a CountedLoopNode I can reach the matching CountedLoopEndNode via the 111// loop-back control. From CountedLoopEndNodes I can reach CountedLoopNodes 112// via the old-trip-counter from the Op node. 113 114//------------------------------CountedLoopNode-------------------------------- 115// CountedLoopNodes head simple counted loops. CountedLoopNodes have as 116// inputs the incoming loop-start control and the loop-back control, so they 117// act like RegionNodes. They also take in the initial trip counter, the 118// loop-invariant stride and the loop-invariant limit value. CountedLoopNodes 119// produce a loop-body control and the trip counter value. Since 120// CountedLoopNodes behave like RegionNodes I still have a standard CFG model. 121 122class CountedLoopNode : public LoopNode { 123 // Size is bigger to hold _main_idx. However, _main_idx does not change 124 // the semantics so it does not appear in the hash & cmp functions. 125 virtual uint size_of() const { return sizeof(*this); } 126 127 // For Pre- and Post-loops during debugging ONLY, this holds the index of 128 // the Main CountedLoop. Used to assert that we understand the graph shape. 129 node_idx_t _main_idx; 130 131 // Known trip count calculated by policy_maximally_unroll 132 int _trip_count; 133 134 // Expected trip count from profile data 135 float _profile_trip_cnt; 136 137 // Log2 of original loop bodies in unrolled loop 138 int _unrolled_count_log2; 139 140 // Node count prior to last unrolling - used to decide if 141 // unroll,optimize,unroll,optimize,... is making progress 142 int _node_count_before_unroll; 143 144public: 145 CountedLoopNode( Node *entry, Node *backedge ) 146 : LoopNode(entry, backedge), _trip_count(max_jint), 147 _profile_trip_cnt(COUNT_UNKNOWN), _unrolled_count_log2(0), 148 _node_count_before_unroll(0) { 149 init_class_id(Class_CountedLoop); 150 // Initialize _trip_count to the largest possible value. 151 // Will be reset (lower) if the loop's trip count is known. 152 } 153 154 virtual int Opcode() const; 155 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape); 156 157 Node *init_control() const { return in(EntryControl); } 158 Node *back_control() const { return in(LoopBackControl); } 159 CountedLoopEndNode *loopexit() const; 160 Node *init_trip() const; 161 Node *stride() const; 162 int stride_con() const; 163 bool stride_is_con() const; 164 Node *limit() const; 165 Node *incr() const; 166 Node *phi() const; 167 168 // Match increment with optional truncation 169 static Node* match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type); 170 171 // A 'main' loop has a pre-loop and a post-loop. The 'main' loop 172 // can run short a few iterations and may start a few iterations in. 173 // It will be RCE'd and unrolled and aligned. 174 175 // A following 'post' loop will run any remaining iterations. Used 176 // during Range Check Elimination, the 'post' loop will do any final 177 // iterations with full checks. Also used by Loop Unrolling, where 178 // the 'post' loop will do any epilog iterations needed. Basically, 179 // a 'post' loop can not profitably be further unrolled or RCE'd. 180 181 // A preceding 'pre' loop will run at least 1 iteration (to do peeling), 182 // it may do under-flow checks for RCE and may do alignment iterations 183 // so the following main loop 'knows' that it is striding down cache 184 // lines. 185 186 // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or 187 // Aligned, may be missing it's pre-loop. 188 enum { Normal=0, Pre=1, Main=2, Post=3, PrePostFlagsMask=3, Main_Has_No_Pre_Loop=4 }; 189 int is_normal_loop() const { return (_loop_flags&PrePostFlagsMask) == Normal; } 190 int is_pre_loop () const { return (_loop_flags&PrePostFlagsMask) == Pre; } 191 int is_main_loop () const { return (_loop_flags&PrePostFlagsMask) == Main; } 192 int is_post_loop () const { return (_loop_flags&PrePostFlagsMask) == Post; } 193 int is_main_no_pre_loop() const { return _loop_flags & Main_Has_No_Pre_Loop; } 194 void set_main_no_pre_loop() { _loop_flags |= Main_Has_No_Pre_Loop; } 195 196 int main_idx() const { return _main_idx; } 197 198 199 void set_pre_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; } 200 void set_main_loop ( ) { assert(is_normal_loop(),""); _loop_flags |= Main; } 201 void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; } 202 void set_normal_loop( ) { _loop_flags &= ~PrePostFlagsMask; } 203 204 void set_trip_count(int tc) { _trip_count = tc; } 205 int trip_count() { return _trip_count; } 206 207 void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; } 208 float profile_trip_cnt() { return _profile_trip_cnt; } 209 210 void double_unrolled_count() { _unrolled_count_log2++; } 211 int unrolled_count() { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); } 212 213 void set_node_count_before_unroll(int ct) { _node_count_before_unroll = ct; } 214 int node_count_before_unroll() { return _node_count_before_unroll; } 215 216#ifndef PRODUCT 217 virtual void dump_spec(outputStream *st) const; 218#endif 219}; 220 221//------------------------------CountedLoopEndNode----------------------------- 222// CountedLoopEndNodes end simple trip counted loops. They act much like 223// IfNodes. 224class CountedLoopEndNode : public IfNode { 225public: 226 enum { TestControl, TestValue }; 227 228 CountedLoopEndNode( Node *control, Node *test, float prob, float cnt ) 229 : IfNode( control, test, prob, cnt) { 230 init_class_id(Class_CountedLoopEnd); 231 } 232 virtual int Opcode() const; 233 234 Node *cmp_node() const { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; } 235 Node *incr() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; } 236 Node *limit() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; } 237 Node *stride() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; } 238 Node *phi() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; } 239 Node *init_trip() const { Node *tmp = phi (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; } 240 int stride_con() const; 241 bool stride_is_con() const { Node *tmp = stride (); return (tmp != NULL && tmp->is_Con()); } 242 BoolTest::mask test_trip() const { return in(TestValue)->as_Bool()->_test._test; } 243 CountedLoopNode *loopnode() const { 244 Node *ln = phi()->in(0); 245 assert( ln->Opcode() == Op_CountedLoop, "malformed loop" ); 246 return (CountedLoopNode*)ln; } 247 248#ifndef PRODUCT 249 virtual void dump_spec(outputStream *st) const; 250#endif 251}; 252 253 254inline CountedLoopEndNode *CountedLoopNode::loopexit() const { 255 Node *bc = back_control(); 256 if( bc == NULL ) return NULL; 257 Node *le = bc->in(0); 258 if( le->Opcode() != Op_CountedLoopEnd ) 259 return NULL; 260 return (CountedLoopEndNode*)le; 261} 262inline Node *CountedLoopNode::init_trip() const { return loopexit() ? loopexit()->init_trip() : NULL; } 263inline Node *CountedLoopNode::stride() const { return loopexit() ? loopexit()->stride() : NULL; } 264inline int CountedLoopNode::stride_con() const { return loopexit() ? loopexit()->stride_con() : 0; } 265inline bool CountedLoopNode::stride_is_con() const { return loopexit() && loopexit()->stride_is_con(); } 266inline Node *CountedLoopNode::limit() const { return loopexit() ? loopexit()->limit() : NULL; } 267inline Node *CountedLoopNode::incr() const { return loopexit() ? loopexit()->incr() : NULL; } 268inline Node *CountedLoopNode::phi() const { return loopexit() ? loopexit()->phi() : NULL; } 269 270 271// -----------------------------IdealLoopTree---------------------------------- 272class IdealLoopTree : public ResourceObj { 273public: 274 IdealLoopTree *_parent; // Parent in loop tree 275 IdealLoopTree *_next; // Next sibling in loop tree 276 IdealLoopTree *_child; // First child in loop tree 277 278 // The head-tail backedge defines the loop. 279 // If tail is NULL then this loop has multiple backedges as part of the 280 // same loop. During cleanup I'll peel off the multiple backedges; merge 281 // them at the loop bottom and flow 1 real backedge into the loop. 282 Node *_head; // Head of loop 283 Node *_tail; // Tail of loop 284 inline Node *tail(); // Handle lazy update of _tail field 285 PhaseIdealLoop* _phase; 286 287 Node_List _body; // Loop body for inner loops 288 289 uint8 _nest; // Nesting depth 290 uint8 _irreducible:1, // True if irreducible 291 _has_call:1, // True if has call safepoint 292 _has_sfpt:1, // True if has non-call safepoint 293 _rce_candidate:1; // True if candidate for range check elimination 294 295 Node_List* _required_safept; // A inner loop cannot delete these safepts; 296 bool _allow_optimizations; // Allow loop optimizations 297 298 IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail ) 299 : _parent(0), _next(0), _child(0), 300 _head(head), _tail(tail), 301 _phase(phase), 302 _required_safept(NULL), 303 _allow_optimizations(true), 304 _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0) 305 { } 306 307 // Is 'l' a member of 'this'? 308 int is_member( const IdealLoopTree *l ) const; // Test for nested membership 309 310 // Set loop nesting depth. Accumulate has_call bits. 311 int set_nest( uint depth ); 312 313 // Split out multiple fall-in edges from the loop header. Move them to a 314 // private RegionNode before the loop. This becomes the loop landing pad. 315 void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ); 316 317 // Split out the outermost loop from this shared header. 318 void split_outer_loop( PhaseIdealLoop *phase ); 319 320 // Merge all the backedges from the shared header into a private Region. 321 // Feed that region as the one backedge to this loop. 322 void merge_many_backedges( PhaseIdealLoop *phase ); 323 324 // Split shared headers and insert loop landing pads. 325 // Insert a LoopNode to replace the RegionNode. 326 // Returns TRUE if loop tree is structurally changed. 327 bool beautify_loops( PhaseIdealLoop *phase ); 328 329 // Perform optimization to use the loop predicates for null checks and range checks. 330 // Applies to any loop level (not just the innermost one) 331 bool loop_predication( PhaseIdealLoop *phase); 332 333 // Perform iteration-splitting on inner loops. Split iterations to 334 // avoid range checks or one-shot null checks. Returns false if the 335 // current round of loop opts should stop. 336 bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new ); 337 338 // Driver for various flavors of iteration splitting. Returns false 339 // if the current round of loop opts should stop. 340 bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ); 341 342 // Given dominators, try to find loops with calls that must always be 343 // executed (call dominates loop tail). These loops do not need non-call 344 // safepoints (ncsfpt). 345 void check_safepts(VectorSet &visited, Node_List &stack); 346 347 // Allpaths backwards scan from loop tail, terminating each path at first safepoint 348 // encountered. 349 void allpaths_check_safepts(VectorSet &visited, Node_List &stack); 350 351 // Convert to counted loops where possible 352 void counted_loop( PhaseIdealLoop *phase ); 353 354 // Check for Node being a loop-breaking test 355 Node *is_loop_exit(Node *iff) const; 356 357 // Returns true if ctrl is executed on every complete iteration 358 bool dominates_backedge(Node* ctrl); 359 360 // Remove simplistic dead code from loop body 361 void DCE_loop_body(); 362 363 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage. 364 // Replace with a 1-in-10 exit guess. 365 void adjust_loop_exit_prob( PhaseIdealLoop *phase ); 366 367 // Return TRUE or FALSE if the loop should never be RCE'd or aligned. 368 // Useful for unrolling loops with NO array accesses. 369 bool policy_peel_only( PhaseIdealLoop *phase ) const; 370 371 // Return TRUE or FALSE if the loop should be unswitched -- clone 372 // loop with an invariant test 373 bool policy_unswitching( PhaseIdealLoop *phase ) const; 374 375 // Micro-benchmark spamming. Remove empty loops. 376 bool policy_do_remove_empty_loop( PhaseIdealLoop *phase ); 377 378 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can 379 // make some loop-invariant test (usually a null-check) happen before the 380 // loop. 381 bool policy_peeling( PhaseIdealLoop *phase ) const; 382 383 // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any 384 // known trip count in the counted loop node. 385 bool policy_maximally_unroll( PhaseIdealLoop *phase ) const; 386 387 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if 388 // the loop is a CountedLoop and the body is small enough. 389 bool policy_unroll( PhaseIdealLoop *phase ) const; 390 391 // Return TRUE or FALSE if the loop should be range-check-eliminated. 392 // Gather a list of IF tests that are dominated by iteration splitting; 393 // also gather the end of the first split and the start of the 2nd split. 394 bool policy_range_check( PhaseIdealLoop *phase ) const; 395 396 // Return TRUE or FALSE if the loop should be cache-line aligned. 397 // Gather the expression that does the alignment. Note that only 398 // one array base can be aligned in a loop (unless the VM guarantees 399 // mutual alignment). Note that if we vectorize short memory ops 400 // into longer memory ops, we may want to increase alignment. 401 bool policy_align( PhaseIdealLoop *phase ) const; 402 403 // Return TRUE if "iff" is a range check. 404 bool is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const; 405 406 // Compute loop trip count from profile data 407 void compute_profile_trip_cnt( PhaseIdealLoop *phase ); 408 409 // Reassociate invariant expressions. 410 void reassociate_invariants(PhaseIdealLoop *phase); 411 // Reassociate invariant add and subtract expressions. 412 Node* reassociate_add_sub(Node* n1, PhaseIdealLoop *phase); 413 // Return nonzero index of invariant operand if invariant and variant 414 // are combined with an Add or Sub. Helper for reassociate_invariants. 415 int is_invariant_addition(Node* n, PhaseIdealLoop *phase); 416 417 // Return true if n is invariant 418 bool is_invariant(Node* n) const; 419 420 // Put loop body on igvn work list 421 void record_for_igvn(); 422 423 bool is_loop() { return !_irreducible && _tail && !_tail->is_top(); } 424 bool is_inner() { return is_loop() && _child == NULL; } 425 bool is_counted() { return is_loop() && _head != NULL && _head->is_CountedLoop(); } 426 427#ifndef PRODUCT 428 void dump_head( ) const; // Dump loop head only 429 void dump() const; // Dump this loop recursively 430 void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const; 431#endif 432 433}; 434 435// -----------------------------PhaseIdealLoop--------------------------------- 436// Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees into a 437// loop tree. Drives the loop-based transformations on the ideal graph. 438class PhaseIdealLoop : public PhaseTransform { 439 friend class IdealLoopTree; 440 friend class SuperWord; 441 // Pre-computed def-use info 442 PhaseIterGVN &_igvn; 443 444 // Head of loop tree 445 IdealLoopTree *_ltree_root; 446 447 // Array of pre-order numbers, plus post-visited bit. 448 // ZERO for not pre-visited. EVEN for pre-visited but not post-visited. 449 // ODD for post-visited. Other bits are the pre-order number. 450 uint *_preorders; 451 uint _max_preorder; 452 453 const PhaseIdealLoop* _verify_me; 454 bool _verify_only; 455 456 // Allocate _preorders[] array 457 void allocate_preorders() { 458 _max_preorder = C->unique()+8; 459 _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder); 460 memset(_preorders, 0, sizeof(uint) * _max_preorder); 461 } 462 463 // Allocate _preorders[] array 464 void reallocate_preorders() { 465 if ( _max_preorder < C->unique() ) { 466 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique()); 467 _max_preorder = C->unique(); 468 } 469 memset(_preorders, 0, sizeof(uint) * _max_preorder); 470 } 471 472 // Check to grow _preorders[] array for the case when build_loop_tree_impl() 473 // adds new nodes. 474 void check_grow_preorders( ) { 475 if ( _max_preorder < C->unique() ) { 476 uint newsize = _max_preorder<<1; // double size of array 477 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize); 478 memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder)); 479 _max_preorder = newsize; 480 } 481 } 482 // Check for pre-visited. Zero for NOT visited; non-zero for visited. 483 int is_visited( Node *n ) const { return _preorders[n->_idx]; } 484 // Pre-order numbers are written to the Nodes array as low-bit-set values. 485 void set_preorder_visited( Node *n, int pre_order ) { 486 assert( !is_visited( n ), "already set" ); 487 _preorders[n->_idx] = (pre_order<<1); 488 }; 489 // Return pre-order number. 490 int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; } 491 492 // Check for being post-visited. 493 // Should be previsited already (checked with assert(is_visited(n))). 494 int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; } 495 496 // Mark as post visited 497 void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; } 498 499 // Set/get control node out. Set lower bit to distinguish from IdealLoopTree 500 // Returns true if "n" is a data node, false if it's a control node. 501 bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; } 502 503 // clear out dead code after build_loop_late 504 Node_List _deadlist; 505 506 // Support for faster execution of get_late_ctrl()/dom_lca() 507 // when a node has many uses and dominator depth is deep. 508 Node_Array _dom_lca_tags; 509 void init_dom_lca_tags(); 510 void clear_dom_lca_tags(); 511 512 // Helper for debugging bad dominance relationships 513 bool verify_dominance(Node* n, Node* use, Node* LCA, Node* early); 514 515 Node* compute_lca_of_uses(Node* n, Node* early, bool verify = false); 516 517 // Inline wrapper for frequent cases: 518 // 1) only one use 519 // 2) a use is the same as the current LCA passed as 'n1' 520 Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) { 521 assert( n->is_CFG(), "" ); 522 // Fast-path NULL lca 523 if( lca != NULL && lca != n ) { 524 assert( lca->is_CFG(), "" ); 525 // find LCA of all uses 526 n = dom_lca_for_get_late_ctrl_internal( lca, n, tag ); 527 } 528 return find_non_split_ctrl(n); 529 } 530 Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag ); 531 532 // Helper function for directing control inputs away from CFG split 533 // points. 534 Node *find_non_split_ctrl( Node *ctrl ) const { 535 if (ctrl != NULL) { 536 if (ctrl->is_MultiBranch()) { 537 ctrl = ctrl->in(0); 538 } 539 assert(ctrl->is_CFG(), "CFG"); 540 } 541 return ctrl; 542 } 543 544public: 545 bool has_node( Node* n ) const { return _nodes[n->_idx] != NULL; } 546 // check if transform created new nodes that need _ctrl recorded 547 Node *get_late_ctrl( Node *n, Node *early ); 548 Node *get_early_ctrl( Node *n ); 549 void set_early_ctrl( Node *n ); 550 void set_subtree_ctrl( Node *root ); 551 void set_ctrl( Node *n, Node *ctrl ) { 552 assert( !has_node(n) || has_ctrl(n), "" ); 553 assert( ctrl->in(0), "cannot set dead control node" ); 554 assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" ); 555 _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) ); 556 } 557 // Set control and update loop membership 558 void set_ctrl_and_loop(Node* n, Node* ctrl) { 559 IdealLoopTree* old_loop = get_loop(get_ctrl(n)); 560 IdealLoopTree* new_loop = get_loop(ctrl); 561 if (old_loop != new_loop) { 562 if (old_loop->_child == NULL) old_loop->_body.yank(n); 563 if (new_loop->_child == NULL) new_loop->_body.push(n); 564 } 565 set_ctrl(n, ctrl); 566 } 567 // Control nodes can be replaced or subsumed. During this pass they 568 // get their replacement Node in slot 1. Instead of updating the block 569 // location of all Nodes in the subsumed block, we lazily do it. As we 570 // pull such a subsumed block out of the array, we write back the final 571 // correct block. 572 Node *get_ctrl( Node *i ) { 573 assert(has_node(i), ""); 574 Node *n = get_ctrl_no_update(i); 575 _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) ); 576 assert(has_node(i) && has_ctrl(i), ""); 577 assert(n == find_non_split_ctrl(n), "must return legal ctrl" ); 578 return n; 579 } 580 // true if CFG node d dominates CFG node n 581 bool is_dominator(Node *d, Node *n); 582 // return get_ctrl for a data node and self(n) for a CFG node 583 Node* ctrl_or_self(Node* n) { 584 if (has_ctrl(n)) 585 return get_ctrl(n); 586 else { 587 assert (n->is_CFG(), "must be a CFG node"); 588 return n; 589 } 590 } 591 592private: 593 Node *get_ctrl_no_update( Node *i ) const { 594 assert( has_ctrl(i), "" ); 595 Node *n = (Node*)(((intptr_t)_nodes[i->_idx]) & ~1); 596 if (!n->in(0)) { 597 // Skip dead CFG nodes 598 do { 599 n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1); 600 } while (!n->in(0)); 601 n = find_non_split_ctrl(n); 602 } 603 return n; 604 } 605 606 // Check for loop being set 607 // "n" must be a control node. Returns true if "n" is known to be in a loop. 608 bool has_loop( Node *n ) const { 609 assert(!has_node(n) || !has_ctrl(n), ""); 610 return has_node(n); 611 } 612 // Set loop 613 void set_loop( Node *n, IdealLoopTree *loop ) { 614 _nodes.map(n->_idx, (Node*)loop); 615 } 616 // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms. Replace 617 // the 'old_node' with 'new_node'. Kill old-node. Add a reference 618 // from old_node to new_node to support the lazy update. Reference 619 // replaces loop reference, since that is not needed for dead node. 620public: 621 void lazy_update( Node *old_node, Node *new_node ) { 622 assert( old_node != new_node, "no cycles please" ); 623 //old_node->set_req( 1, new_node /*NO DU INFO*/ ); 624 // Nodes always have DU info now, so re-use the side array slot 625 // for this node to provide the forwarding pointer. 626 _nodes.map( old_node->_idx, (Node*)((intptr_t)new_node + 1) ); 627 } 628 void lazy_replace( Node *old_node, Node *new_node ) { 629 _igvn.hash_delete(old_node); 630 _igvn.subsume_node( old_node, new_node ); 631 lazy_update( old_node, new_node ); 632 } 633 void lazy_replace_proj( Node *old_node, Node *new_node ) { 634 assert( old_node->req() == 1, "use this for Projs" ); 635 _igvn.hash_delete(old_node); // Must hash-delete before hacking edges 636 old_node->add_req( NULL ); 637 lazy_replace( old_node, new_node ); 638 } 639 640private: 641 642 // Place 'n' in some loop nest, where 'n' is a CFG node 643 void build_loop_tree(); 644 int build_loop_tree_impl( Node *n, int pre_order ); 645 // Insert loop into the existing loop tree. 'innermost' is a leaf of the 646 // loop tree, not the root. 647 IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost ); 648 649 // Place Data nodes in some loop nest 650 void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ); 651 void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ); 652 void build_loop_late_post ( Node* n ); 653 654 // Array of immediate dominance info for each CFG node indexed by node idx 655private: 656 uint _idom_size; 657 Node **_idom; // Array of immediate dominators 658 uint *_dom_depth; // Used for fast LCA test 659 GrowableArray<uint>* _dom_stk; // For recomputation of dom depth 660 661 Node* idom_no_update(Node* d) const { 662 assert(d->_idx < _idom_size, "oob"); 663 Node* n = _idom[d->_idx]; 664 assert(n != NULL,"Bad immediate dominator info."); 665 while (n->in(0) == NULL) { // Skip dead CFG nodes 666 //n = n->in(1); 667 n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1); 668 assert(n != NULL,"Bad immediate dominator info."); 669 } 670 return n; 671 } 672 Node *idom(Node* d) const { 673 uint didx = d->_idx; 674 Node *n = idom_no_update(d); 675 _idom[didx] = n; // Lazily remove dead CFG nodes from table. 676 return n; 677 } 678 uint dom_depth(Node* d) const { 679 assert(d->_idx < _idom_size, ""); 680 return _dom_depth[d->_idx]; 681 } 682 void set_idom(Node* d, Node* n, uint dom_depth); 683 // Locally compute IDOM using dom_lca call 684 Node *compute_idom( Node *region ) const; 685 // Recompute dom_depth 686 void recompute_dom_depth(); 687 688 // Is safept not required by an outer loop? 689 bool is_deleteable_safept(Node* sfpt); 690 691 // Perform verification that the graph is valid. 692 PhaseIdealLoop( PhaseIterGVN &igvn) : 693 PhaseTransform(Ideal_Loop), 694 _igvn(igvn), 695 _dom_lca_tags(C->comp_arena()), 696 _verify_me(NULL), 697 _verify_only(true) { 698 build_and_optimize(false, false); 699 } 700 701 // build the loop tree and perform any requested optimizations 702 void build_and_optimize(bool do_split_if, bool do_loop_pred); 703 704public: 705 // Dominators for the sea of nodes 706 void Dominators(); 707 Node *dom_lca( Node *n1, Node *n2 ) const { 708 return find_non_split_ctrl(dom_lca_internal(n1, n2)); 709 } 710 Node *dom_lca_internal( Node *n1, Node *n2 ) const; 711 712 // Compute the Ideal Node to Loop mapping 713 PhaseIdealLoop( PhaseIterGVN &igvn, bool do_split_ifs, bool do_loop_pred) : 714 PhaseTransform(Ideal_Loop), 715 _igvn(igvn), 716 _dom_lca_tags(C->comp_arena()), 717 _verify_me(NULL), 718 _verify_only(false) { 719 build_and_optimize(do_split_ifs, do_loop_pred); 720 } 721 722 // Verify that verify_me made the same decisions as a fresh run. 723 PhaseIdealLoop( PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me) : 724 PhaseTransform(Ideal_Loop), 725 _igvn(igvn), 726 _dom_lca_tags(C->comp_arena()), 727 _verify_me(verify_me), 728 _verify_only(false) { 729 build_and_optimize(false, false); 730 } 731 732 // Build and verify the loop tree without modifying the graph. This 733 // is useful to verify that all inputs properly dominate their uses. 734 static void verify(PhaseIterGVN& igvn) { 735#ifdef ASSERT 736 PhaseIdealLoop v(igvn); 737#endif 738 } 739 740 // True if the method has at least 1 irreducible loop 741 bool _has_irreducible_loops; 742 743 // Per-Node transform 744 virtual Node *transform( Node *a_node ) { return 0; } 745 746 Node *is_counted_loop( Node *x, IdealLoopTree *loop ); 747 748 // Return a post-walked LoopNode 749 IdealLoopTree *get_loop( Node *n ) const { 750 // Dead nodes have no loop, so return the top level loop instead 751 if (!has_node(n)) return _ltree_root; 752 assert(!has_ctrl(n), ""); 753 return (IdealLoopTree*)_nodes[n->_idx]; 754 } 755 756 // Is 'n' a (nested) member of 'loop'? 757 int is_member( const IdealLoopTree *loop, Node *n ) const { 758 return loop->is_member(get_loop(n)); } 759 760 // This is the basic building block of the loop optimizations. It clones an 761 // entire loop body. It makes an old_new loop body mapping; with this 762 // mapping you can find the new-loop equivalent to an old-loop node. All 763 // new-loop nodes are exactly equal to their old-loop counterparts, all 764 // edges are the same. All exits from the old-loop now have a RegionNode 765 // that merges the equivalent new-loop path. This is true even for the 766 // normal "loop-exit" condition. All uses of loop-invariant old-loop values 767 // now come from (one or more) Phis that merge their new-loop equivalents. 768 // Parameter side_by_side_idom: 769 // When side_by_size_idom is NULL, the dominator tree is constructed for 770 // the clone loop to dominate the original. Used in construction of 771 // pre-main-post loop sequence. 772 // When nonnull, the clone and original are side-by-side, both are 773 // dominated by the passed in side_by_side_idom node. Used in 774 // construction of unswitched loops. 775 void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth, 776 Node* side_by_side_idom = NULL); 777 778 // If we got the effect of peeling, either by actually peeling or by 779 // making a pre-loop which must execute at least once, we can remove 780 // all loop-invariant dominated tests in the main body. 781 void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ); 782 783 // Generate code to do a loop peel for the given loop (and body). 784 // old_new is a temp array. 785 void do_peeling( IdealLoopTree *loop, Node_List &old_new ); 786 787 // Add pre and post loops around the given loop. These loops are used 788 // during RCE, unrolling and aligning loops. 789 void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ); 790 // If Node n lives in the back_ctrl block, we clone a private version of n 791 // in preheader_ctrl block and return that, otherwise return n. 792 Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ); 793 794 // Take steps to maximally unroll the loop. Peel any odd iterations, then 795 // unroll to do double iterations. The next round of major loop transforms 796 // will repeat till the doubled loop body does all remaining iterations in 1 797 // pass. 798 void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ); 799 800 // Unroll the loop body one step - make each trip do 2 iterations. 801 void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ); 802 803 // Return true if exp is a constant times an induction var 804 bool is_scaled_iv(Node* exp, Node* iv, int* p_scale); 805 806 // Return true if exp is a scaled induction var plus (or minus) constant 807 bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0); 808 809 // Return true if proj is for "proj->[region->..]call_uct" 810 bool is_uncommon_trap_proj(ProjNode* proj, bool must_reason_predicate = false); 811 // Return true for "if(test)-> proj -> ... 812 // | 813 // V 814 // other_proj->[region->..]call_uct" 815 bool is_uncommon_trap_if_pattern(ProjNode* proj, bool must_reason_predicate = false); 816 // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted 817 ProjNode* create_new_if_for_predicate(ProjNode* cont_proj); 818 // Find a good location to insert a predicate 819 ProjNode* find_predicate_insertion_point(Node* start_c); 820 // Construct a range check for a predicate if 821 BoolNode* rc_predicate(Node* ctrl, 822 int scale, Node* offset, 823 Node* init, Node* limit, Node* stride, 824 Node* range, bool upper); 825 826 // Implementation of the loop predication to promote checks outside the loop 827 bool loop_predication_impl(IdealLoopTree *loop); 828 829 // Helper function to collect predicate for eliminating the useless ones 830 void collect_potentially_useful_predicates(IdealLoopTree *loop, Unique_Node_List &predicate_opaque1); 831 void eliminate_useless_predicates(); 832 833 // Eliminate range-checks and other trip-counter vs loop-invariant tests. 834 void do_range_check( IdealLoopTree *loop, Node_List &old_new ); 835 836 // Create a slow version of the loop by cloning the loop 837 // and inserting an if to select fast-slow versions. 838 ProjNode* create_slow_version_of_loop(IdealLoopTree *loop, 839 Node_List &old_new); 840 841 // Clone loop with an invariant test (that does not exit) and 842 // insert a clone of the test that selects which version to 843 // execute. 844 void do_unswitching (IdealLoopTree *loop, Node_List &old_new); 845 846 // Find candidate "if" for unswitching 847 IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const; 848 849 // Range Check Elimination uses this function! 850 // Constrain the main loop iterations so the affine function: 851 // scale_con * I + offset < limit 852 // always holds true. That is, either increase the number of iterations in 853 // the pre-loop or the post-loop until the condition holds true in the main 854 // loop. Scale_con, offset and limit are all loop invariant. 855 void add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ); 856 857 // Partially peel loop up through last_peel node. 858 bool partial_peel( IdealLoopTree *loop, Node_List &old_new ); 859 860 // Create a scheduled list of nodes control dependent on ctrl set. 861 void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched ); 862 // Has a use in the vector set 863 bool has_use_in_set( Node* n, VectorSet& vset ); 864 // Has use internal to the vector set (ie. not in a phi at the loop head) 865 bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ); 866 // clone "n" for uses that are outside of loop 867 void clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ); 868 // clone "n" for special uses that are in the not_peeled region 869 void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n, 870 VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ); 871 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist 872 void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ); 873#ifdef ASSERT 874 // Validate the loop partition sets: peel and not_peel 875 bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel ); 876 // Ensure that uses outside of loop are of the right form 877 bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list, 878 uint orig_exit_idx, uint clone_exit_idx); 879 bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx); 880#endif 881 882 // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.) 883 int stride_of_possible_iv( Node* iff ); 884 bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; } 885 // Return the (unique) control output node that's in the loop (if it exists.) 886 Node* stay_in_loop( Node* n, IdealLoopTree *loop); 887 // Insert a signed compare loop exit cloned from an unsigned compare. 888 IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop); 889 void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop); 890 // Utility to register node "n" with PhaseIdealLoop 891 void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth); 892 // Utility to create an if-projection 893 ProjNode* proj_clone(ProjNode* p, IfNode* iff); 894 // Force the iff control output to be the live_proj 895 Node* short_circuit_if(IfNode* iff, ProjNode* live_proj); 896 // Insert a region before an if projection 897 RegionNode* insert_region_before_proj(ProjNode* proj); 898 // Insert a new if before an if projection 899 ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj); 900 901 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps. 902 // "Nearly" because all Nodes have been cloned from the original in the loop, 903 // but the fall-in edges to the Cmp are different. Clone bool/Cmp pairs 904 // through the Phi recursively, and return a Bool. 905 BoolNode *clone_iff( PhiNode *phi, IdealLoopTree *loop ); 906 CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop ); 907 908 909 // Rework addressing expressions to get the most loop-invariant stuff 910 // moved out. We'd like to do all associative operators, but it's especially 911 // important (common) to do address expressions. 912 Node *remix_address_expressions( Node *n ); 913 914 // Attempt to use a conditional move instead of a phi/branch 915 Node *conditional_move( Node *n ); 916 917 // Reorganize offset computations to lower register pressure. 918 // Mostly prevent loop-fallout uses of the pre-incremented trip counter 919 // (which are then alive with the post-incremented trip counter 920 // forcing an extra register move) 921 void reorg_offsets( IdealLoopTree *loop ); 922 923 // Check for aggressive application of 'split-if' optimization, 924 // using basic block level info. 925 void split_if_with_blocks ( VectorSet &visited, Node_Stack &nstack ); 926 Node *split_if_with_blocks_pre ( Node *n ); 927 void split_if_with_blocks_post( Node *n ); 928 Node *has_local_phi_input( Node *n ); 929 // Mark an IfNode as being dominated by a prior test, 930 // without actually altering the CFG (and hence IDOM info). 931 void dominated_by( Node *prevdom, Node *iff ); 932 933 // Split Node 'n' through merge point 934 Node *split_thru_region( Node *n, Node *region ); 935 // Split Node 'n' through merge point if there is enough win. 936 Node *split_thru_phi( Node *n, Node *region, int policy ); 937 // Found an If getting its condition-code input from a Phi in the 938 // same block. Split thru the Region. 939 void do_split_if( Node *iff ); 940 941private: 942 // Return a type based on condition control flow 943 const TypeInt* filtered_type( Node *n, Node* n_ctrl); 944 const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); } 945 // Helpers for filtered type 946 const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl); 947 948 // Helper functions 949 Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache ); 950 Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ); 951 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 ); 952 bool split_up( Node *n, Node *blk1, Node *blk2 ); 953 void sink_use( Node *use, Node *post_loop ); 954 Node *place_near_use( Node *useblock ) const; 955 956 bool _created_loop_node; 957public: 958 void set_created_loop_node() { _created_loop_node = true; } 959 bool created_loop_node() { return _created_loop_node; } 960 void register_new_node( Node *n, Node *blk ); 961 962#ifndef PRODUCT 963 void dump( ) const; 964 void dump( IdealLoopTree *loop, uint rpo_idx, Node_List &rpo_list ) const; 965 void rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const; 966 void verify() const; // Major slow :-) 967 void verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const; 968 IdealLoopTree *get_loop_idx(Node* n) const { 969 // Dead nodes have no loop, so return the top level loop instead 970 return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root; 971 } 972 // Print some stats 973 static void print_statistics(); 974 static int _loop_invokes; // Count of PhaseIdealLoop invokes 975 static int _loop_work; // Sum of PhaseIdealLoop x _unique 976#endif 977}; 978 979inline Node* IdealLoopTree::tail() { 980// Handle lazy update of _tail field 981 Node *n = _tail; 982 //while( !n->in(0) ) // Skip dead CFG nodes 983 //n = n->in(1); 984 if (n->in(0) == NULL) 985 n = _phase->get_ctrl(n); 986 _tail = n; 987 return n; 988} 989 990 991// Iterate over the loop tree using a preorder, left-to-right traversal. 992// 993// Example that visits all counted loops from within PhaseIdealLoop 994// 995// for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { 996// IdealLoopTree* lpt = iter.current(); 997// if (!lpt->is_counted()) continue; 998// ... 999class LoopTreeIterator : public StackObj { 1000private: 1001 IdealLoopTree* _root; 1002 IdealLoopTree* _curnt; 1003 1004public: 1005 LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {} 1006 1007 bool done() { return _curnt == NULL; } // Finished iterating? 1008 1009 void next(); // Advance to next loop tree 1010 1011 IdealLoopTree* current() { return _curnt; } // Return current value of iterator. 1012}; 1013