1 #ifdef USE_PRAGMA_IDENT_HDR 2 #pragma ident "@(#)block.hpp 1.102 07/09/25 09:22:14 JVM" 3 #endif 4 /* 5 * Copyright 1997-2008 Sun Microsystems, Inc. All Rights Reserved. 6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 7 * 8 * This code is free software; you can redistribute it and/or modify it 9 * under the terms of the GNU General Public License version 2 only, as 10 * published by the Free Software Foundation. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 23 * CA 95054 USA or visit www.sun.com if you need additional information or 24 * have any questions. 25 * 26 */ 27 28 // Optimization - Graph Style 29 30 class Block; 31 class CFGLoop; 32 class MachCallNode; 33 class Matcher; 34 class RootNode; 35 class VectorSet; 36 struct Tarjan; 37 38 //------------------------------Block_Array------------------------------------ 39 // Map dense integer indices to Blocks. Uses classic doubling-array trick. 40 // Abstractly provides an infinite array of Block*'s, initialized to NULL. 41 // Note that the constructor just zeros things, and since I use Arena 42 // allocation I do not need a destructor to reclaim storage. 43 class Block_Array : public ResourceObj { 44 uint _size; // allocated size, as opposed to formal limit 45 debug_only(uint _limit;) // limit to formal domain 46 protected: 47 Block **_blocks; 48 void grow( uint i ); // Grow array node to fit 49 50 public: 51 Arena *_arena; // Arena to allocate in 52 53 Block_Array(Arena *a) : _arena(a), _size(OptoBlockListSize) { 54 debug_only(_limit=0); 55 _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize ); 56 for( int i = 0; i < OptoBlockListSize; i++ ) { 57 _blocks[i] = NULL; 58 } 59 } 60 Block *lookup( uint i ) const // Lookup, or NULL for not mapped 61 { return (i<Max()) ? _blocks[i] : (Block*)NULL; } 62 Block *operator[] ( uint i ) const // Lookup, or assert for not mapped 63 { assert( i < Max(), "oob" ); return _blocks[i]; } 64 // Extend the mapping: index i maps to Block *n. 65 void map( uint i, Block *n ) { if( i>=Max() ) grow(i); _blocks[i] = n; } 66 uint Max() const { debug_only(return _limit); return _size; } 67 }; 68 69 70 class Block_List : public Block_Array { 71 public: 72 uint _cnt; 73 Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {} 74 void push( Block *b ) { map(_cnt++,b); } 75 Block *pop() { return _blocks[--_cnt]; } 76 Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;} 77 void remove( uint i ); 78 void insert( uint i, Block *n ); 79 uint size() const { return _cnt; } 80 void reset() { _cnt = 0; } 81 void print(); 82 }; 83 84 85 class CFGElement : public ResourceObj { 86 public: 87 float _freq; // Execution frequency (estimate) 88 89 CFGElement() : _freq(0.0f) {} 90 virtual bool is_block() { return false; } 91 virtual bool is_loop() { return false; } 92 Block* as_Block() { assert(is_block(), "must be block"); return (Block*)this; } 93 CFGLoop* as_CFGLoop() { assert(is_loop(), "must be loop"); return (CFGLoop*)this; } 94 }; 95 96 //------------------------------Block------------------------------------------ 97 // This class defines a Basic Block. 98 // Basic blocks are used during the output routines, and are not used during 99 // any optimization pass. They are created late in the game. 100 class Block : public CFGElement { 101 public: 102 // Nodes in this block, in order 103 Node_List _nodes; 104 105 // Basic blocks have a Node which defines Control for all Nodes pinned in 106 // this block. This Node is a RegionNode. Exception-causing Nodes 107 // (division, subroutines) and Phi functions are always pinned. Later, 108 // every Node will get pinned to some block. 109 Node *head() const { return _nodes[0]; } 110 111 // CAUTION: num_preds() is ONE based, so that predecessor numbers match 112 // input edges to Regions and Phis. 113 uint num_preds() const { return head()->req(); } 114 Node *pred(uint i) const { return head()->in(i); } 115 116 // Array of successor blocks, same size as projs array 117 Block_Array _succs; 118 119 // Basic blocks have some number of Nodes which split control to all 120 // following blocks. These Nodes are always Projections. The field in 121 // the Projection and the block-ending Node determine which Block follows. 122 uint _num_succs; 123 124 // Basic blocks also carry all sorts of good old fashioned DFS information 125 // used to find loops, loop nesting depth, dominators, etc. 126 uint _pre_order; // Pre-order DFS number 127 128 // Dominator tree 129 uint _dom_depth; // Depth in dominator tree for fast LCA 130 Block* _idom; // Immediate dominator block 131 132 CFGLoop *_loop; // Loop to which this block belongs 133 uint _rpo; // Number in reverse post order walk 134 135 virtual bool is_block() { return true; } 136 float succ_prob(uint i); // return probability of i'th successor 137 int num_fall_throughs(); // How many fall-through candidate this block has 138 void update_uncommon_branch(Block* un); // Lower branch prob to uncommon code 139 bool succ_fall_through(uint i); // Is successor "i" is a fall-through candidate 140 Block* lone_fall_through(); // Return lone fall-through Block or null 141 142 Block* dom_lca(Block* that); // Compute LCA in dominator tree. 143 #ifdef ASSERT 144 bool dominates(Block* that) { 145 int dom_diff = this->_dom_depth - that->_dom_depth; 146 if (dom_diff > 0) return false; 147 for (; dom_diff < 0; dom_diff++) that = that->_idom; 148 return this == that; 149 } 150 #endif 151 152 // Report the alignment required by this block. Must be a power of 2. 153 // The previous block will insert nops to get this alignment. 154 uint code_alignment(); 155 uint compute_loop_alignment(); 156 157 // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies. 158 // It is currently also used to scale such frequencies relative to 159 // FreqCountInvocations relative to the old value of 1500. 160 #define BLOCK_FREQUENCY(f) ((f * (float) 1500) / FreqCountInvocations) 161 162 // Register Pressure (estimate) for Splitting heuristic 163 uint _reg_pressure; 164 uint _ihrp_index; 165 uint _freg_pressure; 166 uint _fhrp_index; 167 168 // Mark and visited bits for an LCA calculation in insert_anti_dependences. 169 // Since they hold unique node indexes, they do not need reinitialization. 170 node_idx_t _raise_LCA_mark; 171 void set_raise_LCA_mark(node_idx_t x) { _raise_LCA_mark = x; } 172 node_idx_t raise_LCA_mark() const { return _raise_LCA_mark; } 173 node_idx_t _raise_LCA_visited; 174 void set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; } 175 node_idx_t raise_LCA_visited() const { return _raise_LCA_visited; } 176 177 // Estimated size in bytes of first instructions in a loop. 178 uint _first_inst_size; 179 uint first_inst_size() const { return _first_inst_size; } 180 void set_first_inst_size(uint s) { _first_inst_size = s; } 181 182 // Compute the size of first instructions in this block. 183 uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra); 184 185 // Compute alignment padding if the block needs it. 186 // Align a loop if loop's padding is less or equal to padding limit 187 // or the size of first instructions in the loop > padding. 188 uint alignment_padding(int current_offset) { 189 int block_alignment = code_alignment(); 190 int max_pad = block_alignment-relocInfo::addr_unit(); 191 if( max_pad > 0 ) { 192 assert(is_power_of_2(max_pad+relocInfo::addr_unit()), ""); 193 int current_alignment = current_offset & max_pad; 194 if( current_alignment != 0 ) { 195 uint padding = (block_alignment-current_alignment) & max_pad; 196 if( has_loop_alignment() && 197 padding > (uint)MaxLoopPad && 198 first_inst_size() <= padding ) { 199 return 0; 200 } 201 return padding; 202 } 203 } 204 return 0; 205 } 206 207 // Connector blocks. Connector blocks are basic blocks devoid of 208 // instructions, but may have relevant non-instruction Nodes, such as 209 // Phis or MergeMems. Such blocks are discovered and marked during the 210 // RemoveEmpty phase, and elided during Output. 211 bool _connector; 212 void set_connector() { _connector = true; } 213 bool is_connector() const { return _connector; }; 214 215 // Loop_alignment will be set for blocks which are at the top of loops. 216 // The block layout pass may rotate loops such that the loop head may not 217 // be the sequentially first block of the loop encountered in the linear 218 // list of blocks. If the layout pass is not run, loop alignment is set 219 // for each block which is the head of a loop. 220 uint _loop_alignment; 221 void set_loop_alignment(Block *loop_top) { 222 uint new_alignment = loop_top->compute_loop_alignment(); 223 if (new_alignment > _loop_alignment) { 224 _loop_alignment = new_alignment; 225 } 226 } 227 uint loop_alignment() const { return _loop_alignment; } 228 bool has_loop_alignment() const { return loop_alignment() > 0; } 229 230 // Create a new Block with given head Node. 231 // Creates the (empty) predecessor arrays. 232 Block( Arena *a, Node *headnode ) 233 : CFGElement(), 234 _nodes(a), 235 _succs(a), 236 _num_succs(0), 237 _pre_order(0), 238 _idom(0), 239 _loop(NULL), 240 _reg_pressure(0), 241 _ihrp_index(1), 242 _freg_pressure(0), 243 _fhrp_index(1), 244 _raise_LCA_mark(0), 245 _raise_LCA_visited(0), 246 _first_inst_size(999999), 247 _connector(false), 248 _loop_alignment(0) { 249 _nodes.push(headnode); 250 } 251 252 // Index of 'end' Node 253 uint end_idx() const { 254 // %%%%% add a proj after every goto 255 // so (last->is_block_proj() != last) always, then simplify this code 256 // This will not give correct end_idx for block 0 when it only contains root. 257 int last_idx = _nodes.size() - 1; 258 Node *last = _nodes[last_idx]; 259 assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], ""); 260 return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs); 261 } 262 263 // Basic blocks have a Node which ends them. This Node determines which 264 // basic block follows this one in the program flow. This Node is either an 265 // IfNode, a GotoNode, a JmpNode, or a ReturnNode. 266 Node *end() const { return _nodes[end_idx()]; } 267 268 // Add an instruction to an existing block. It must go after the head 269 // instruction and before the end instruction. 270 void add_inst( Node *n ) { _nodes.insert(end_idx(),n); } 271 // Find node in block 272 uint find_node( const Node *n ) const; 273 // Find and remove n from block list 274 void find_remove( const Node *n ); 275 276 // Schedule a call next in the block 277 uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, int *ready_cnt, MachCallNode *mcall, VectorSet &next_call); 278 279 // Perform basic-block local scheduling 280 Node *select(PhaseCFG *cfg, Node_List &worklist, int *ready_cnt, VectorSet &next_call, uint sched_slot); 281 void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs ); 282 void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs); 283 bool schedule_local(PhaseCFG *cfg, Matcher &m, int *ready_cnt, VectorSet &next_call); 284 // Cleanup if any code lands between a Call and his Catch 285 void call_catch_cleanup(Block_Array &bbs); 286 // Detect implicit-null-check opportunities. Basically, find NULL checks 287 // with suitable memory ops nearby. Use the memory op to do the NULL check. 288 // I can generate a memory op if there is not one nearby. 289 void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons); 290 291 // Return the empty status of a block 292 enum { not_empty, empty_with_goto, completely_empty }; 293 int is_Empty() const; 294 295 // Forward through connectors 296 Block* non_connector() { 297 Block* s = this; 298 while (s->is_connector()) { 299 s = s->_succs[0]; 300 } 301 return s; 302 } 303 304 // Return true if b is a successor of this block 305 bool has_successor(Block* b) const { 306 for (uint i = 0; i < _num_succs; i++ ) { 307 if (non_connector_successor(i) == b) { 308 return true; 309 } 310 } 311 return false; 312 } 313 314 // Successor block, after forwarding through connectors 315 Block* non_connector_successor(int i) const { 316 return _succs[i]->non_connector(); 317 } 318 319 // Examine block's code shape to predict if it is not commonly executed. 320 bool has_uncommon_code() const; 321 322 // Use frequency calculations and code shape to predict if the block 323 // is uncommon. 324 bool is_uncommon( Block_Array &bbs ) const; 325 326 #ifndef PRODUCT 327 // Debugging print of basic block 328 void dump_bidx(const Block* orig) const; 329 void dump_pred(const Block_Array *bbs, Block* orig) const; 330 void dump_head( const Block_Array *bbs ) const; 331 void dump( ) const; 332 void dump( const Block_Array *bbs ) const; 333 #endif 334 }; 335 336 337 //------------------------------PhaseCFG--------------------------------------- 338 // Build an array of Basic Block pointers, one per Node. 339 class PhaseCFG : public Phase { 340 private: 341 // Build a proper looking cfg. Return count of basic blocks 342 uint build_cfg(); 343 344 // Perform DFS search. 345 // Setup 'vertex' as DFS to vertex mapping. 346 // Setup 'semi' as vertex to DFS mapping. 347 // Set 'parent' to DFS parent. 348 uint DFS( Tarjan *tarjan ); 349 350 // Helper function to insert a node into a block 351 void schedule_node_into_block( Node *n, Block *b ); 352 353 // Set the basic block for pinned Nodes 354 void schedule_pinned_nodes( VectorSet &visited ); 355 356 // I'll need a few machine-specific GotoNodes. Clone from this one. 357 MachNode *_goto; 358 359 Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false); 360 void verify_anti_dependences(Block* LCA, Node* load) { 361 assert(LCA == _bbs[load->_idx], "should already be scheduled"); 362 insert_anti_dependences(LCA, load, true); 363 } 364 365 public: 366 PhaseCFG( Arena *a, RootNode *r, Matcher &m ); 367 368 uint _num_blocks; // Count of basic blocks 369 Block_List _blocks; // List of basic blocks 370 RootNode *_root; // Root of whole program 371 Block_Array _bbs; // Map Nodes to owning Basic Block 372 Block *_broot; // Basic block of root 373 uint _rpo_ctr; 374 CFGLoop* _root_loop; 375 376 // Per node latency estimation, valid only during GCM 377 GrowableArray<uint> _node_latency; 378 379 #ifndef PRODUCT 380 bool _trace_opto_pipelining; // tracing flag 381 #endif 382 383 // Build dominators 384 void Dominators(); 385 386 // Estimate block frequencies based on IfNode probabilities 387 void Estimate_Block_Frequency(); 388 389 // Global Code Motion. See Click's PLDI95 paper. Place Nodes in specific 390 // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block. 391 void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list ); 392 393 // Compute the (backwards) latency of a node from the uses 394 void latency_from_uses(Node *n); 395 396 // Compute the (backwards) latency of a node from a single use 397 int latency_from_use(Node *n, const Node *def, Node *use); 398 399 // Compute the (backwards) latency of a node from the uses of this instruction 400 void partial_latency_of_defs(Node *n); 401 402 // Schedule Nodes early in their basic blocks. 403 bool schedule_early(VectorSet &visited, Node_List &roots); 404 405 // For each node, find the latest block it can be scheduled into 406 // and then select the cheapest block between the latest and earliest 407 // block to place the node. 408 void schedule_late(VectorSet &visited, Node_List &stack); 409 410 // Pick a block between early and late that is a cheaper alternative 411 // to late. Helper for schedule_late. 412 Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self); 413 414 // Compute the instruction global latency with a backwards walk 415 void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack); 416 417 // Set loop alignment 418 void set_loop_alignment(); 419 420 // Remove empty basic blocks 421 void remove_empty(); 422 void fixup_flow(); 423 bool move_to_next(Block* bx, uint b_index); 424 void move_to_end(Block* bx, uint b_index); 425 void insert_goto_at(uint block_no, uint succ_no); 426 427 // Check for NeverBranch at block end. This needs to become a GOTO to the 428 // true target. NeverBranch are treated as a conditional branch that always 429 // goes the same direction for most of the optimizer and are used to give a 430 // fake exit path to infinite loops. At this late stage they need to turn 431 // into Goto's so that when you enter the infinite loop you indeed hang. 432 void convert_NeverBranch_to_Goto(Block *b); 433 434 CFGLoop* create_loop_tree(); 435 436 // Insert a node into a block, and update the _bbs 437 void insert( Block *b, uint idx, Node *n ) { 438 b->_nodes.insert( idx, n ); 439 _bbs.map( n->_idx, b ); 440 } 441 442 #ifndef PRODUCT 443 bool trace_opto_pipelining() const { return _trace_opto_pipelining; } 444 445 // Debugging print of CFG 446 void dump( ) const; // CFG only 447 void _dump_cfg( const Node *end, VectorSet &visited ) const; 448 void verify() const; 449 void dump_headers(); 450 #else 451 bool trace_opto_pipelining() const { return false; } 452 #endif 453 }; 454 455 456 //------------------------------UnionFind-------------------------------------- 457 // Map Block indices to a block-index for a cfg-cover. 458 // Array lookup in the optimized case. 459 class UnionFind : public ResourceObj { 460 uint _cnt, _max; 461 uint* _indices; 462 ReallocMark _nesting; // assertion check for reallocations 463 public: 464 UnionFind( uint max ); 465 void reset( uint max ); // Reset to identity map for [0..max] 466 467 uint lookup( uint nidx ) const { 468 return _indices[nidx]; 469 } 470 uint operator[] (uint nidx) const { return lookup(nidx); } 471 472 void map( uint from_idx, uint to_idx ) { 473 assert( from_idx < _cnt, "oob" ); 474 _indices[from_idx] = to_idx; 475 } 476 void extend( uint from_idx, uint to_idx ); 477 478 uint Size() const { return _cnt; } 479 480 uint Find( uint idx ) { 481 assert( idx < 65536, "Must fit into uint"); 482 uint uf_idx = lookup(idx); 483 return (uf_idx == idx) ? uf_idx : Find_compress(idx); 484 } 485 uint Find_compress( uint idx ); 486 uint Find_const( uint idx ) const; 487 void Union( uint idx1, uint idx2 ); 488 489 }; 490 491 //----------------------------BlockProbPair--------------------------- 492 // Ordered pair of Node*. 493 class BlockProbPair VALUE_OBJ_CLASS_SPEC { 494 protected: 495 Block* _target; // block target 496 float _prob; // probability of edge to block 497 public: 498 BlockProbPair() : _target(NULL), _prob(0.0) {} 499 BlockProbPair(Block* b, float p) : _target(b), _prob(p) {} 500 501 Block* get_target() const { return _target; } 502 float get_prob() const { return _prob; } 503 }; 504 505 //------------------------------CFGLoop------------------------------------------- 506 class CFGLoop : public CFGElement { 507 int _id; 508 int _depth; 509 CFGLoop *_parent; // root of loop tree is the method level "pseudo" loop, it's parent is null 510 CFGLoop *_sibling; // null terminated list 511 CFGLoop *_child; // first child, use child's sibling to visit all immediately nested loops 512 GrowableArray<CFGElement*> _members; // list of members of loop 513 GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities 514 float _exit_prob; // probability any loop exit is taken on a single loop iteration 515 void update_succ_freq(Block* b, float freq); 516 517 public: 518 CFGLoop(int id) : 519 CFGElement(), 520 _id(id), 521 _depth(0), 522 _parent(NULL), 523 _sibling(NULL), 524 _child(NULL), 525 _exit_prob(1.0f) {} 526 CFGLoop* parent() { return _parent; } 527 void push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk); 528 void add_member(CFGElement *s) { _members.push(s); } 529 void add_nested_loop(CFGLoop* cl); 530 Block* head() { 531 assert(_members.at(0)->is_block(), "head must be a block"); 532 Block* hd = _members.at(0)->as_Block(); 533 assert(hd->_loop == this, "just checking"); 534 assert(hd->head()->is_Loop(), "must begin with loop head node"); 535 return hd; 536 } 537 Block* backedge_block(); // Return the block on the backedge of the loop (else NULL) 538 void compute_loop_depth(int depth); 539 void compute_freq(); // compute frequency with loop assuming head freq 1.0f 540 void scale_freq(); // scale frequency by loop trip count (including outer loops) 541 bool in_loop_nest(Block* b); 542 float trip_count() const { return 1.0f / _exit_prob; } 543 virtual bool is_loop() { return true; } 544 int id() { return _id; } 545 546 #ifndef PRODUCT 547 void dump( ) const; 548 void dump_tree() const; 549 #endif 550 }; 551 552 553 //----------------------------------CFGEdge------------------------------------ 554 // A edge between two basic blocks that will be embodied by a branch or a 555 // fall-through. 556 class CFGEdge : public ResourceObj { 557 private: 558 Block * _from; // Source basic block 559 Block * _to; // Destination basic block 560 float _freq; // Execution frequency (estimate) 561 int _state; 562 bool _infrequent; 563 int _from_pct; 564 int _to_pct; 565 566 // Private accessors 567 int from_pct() const { return _from_pct; } 568 int to_pct() const { return _to_pct; } 569 int from_infrequent() const { return from_pct() < BlockLayoutMinDiamondPercentage; } 570 int to_infrequent() const { return to_pct() < BlockLayoutMinDiamondPercentage; } 571 572 public: 573 enum { 574 open, // initial edge state; unprocessed 575 connected, // edge used to connect two traces together 576 interior // edge is interior to trace (could be backedge) 577 }; 578 579 CFGEdge(Block *from, Block *to, float freq, int from_pct, int to_pct) : 580 _from(from), _to(to), _freq(freq), 581 _from_pct(from_pct), _to_pct(to_pct), _state(open) { 582 _infrequent = from_infrequent() || to_infrequent(); 583 } 584 585 float freq() const { return _freq; } 586 Block* from() const { return _from; } 587 Block* to () const { return _to; } 588 int infrequent() const { return _infrequent; } 589 int state() const { return _state; } 590 591 void set_state(int state) { _state = state; } 592 593 #ifndef PRODUCT 594 void dump( ) const; 595 #endif 596 }; 597 598 599 //-----------------------------------Trace------------------------------------- 600 // An ordered list of basic blocks. 601 class Trace : public ResourceObj { 602 private: 603 uint _id; // Unique Trace id (derived from initial block) 604 Block ** _next_list; // Array mapping index to next block 605 Block ** _prev_list; // Array mapping index to previous block 606 Block * _first; // First block in the trace 607 Block * _last; // Last block in the trace 608 609 // Return the block that follows "b" in the trace. 610 Block * next(Block *b) const { return _next_list[b->_pre_order]; } 611 void set_next(Block *b, Block *n) const { _next_list[b->_pre_order] = n; } 612 613 // Return the block that preceeds "b" in the trace. 614 Block * prev(Block *b) const { return _prev_list[b->_pre_order]; } 615 void set_prev(Block *b, Block *p) const { _prev_list[b->_pre_order] = p; } 616 617 // We've discovered a loop in this trace. Reset last to be "b", and first as 618 // the block following "b 619 void break_loop_after(Block *b) { 620 _last = b; 621 _first = next(b); 622 set_prev(_first, NULL); 623 set_next(_last, NULL); 624 } 625 626 public: 627 628 Trace(Block *b, Block **next_list, Block **prev_list) : 629 _first(b), 630 _last(b), 631 _next_list(next_list), 632 _prev_list(prev_list), 633 _id(b->_pre_order) { 634 set_next(b, NULL); 635 set_prev(b, NULL); 636 }; 637 638 // Return the id number 639 uint id() const { return _id; } 640 void set_id(uint id) { _id = id; } 641 642 // Return the first block in the trace 643 Block * first_block() const { return _first; } 644 645 // Return the last block in the trace 646 Block * last_block() const { return _last; } 647 648 // Insert a trace in the middle of this one after b 649 void insert_after(Block *b, Trace *tr) { 650 set_next(tr->last_block(), next(b)); 651 if (next(b) != NULL) { 652 set_prev(next(b), tr->last_block()); 653 } 654 655 set_next(b, tr->first_block()); 656 set_prev(tr->first_block(), b); 657 658 if (b == _last) { 659 _last = tr->last_block(); 660 } 661 } 662 663 void insert_before(Block *b, Trace *tr) { 664 Block *p = prev(b); 665 assert(p != NULL, "use append instead"); 666 insert_after(p, tr); 667 } 668 669 // Append another trace to this one. 670 void append(Trace *tr) { 671 insert_after(_last, tr); 672 } 673 674 // Append a block at the end of this trace 675 void append(Block *b) { 676 set_next(_last, b); 677 set_prev(b, _last); 678 _last = b; 679 } 680 681 // Adjust the the blocks in this trace 682 void fixup_blocks(PhaseCFG &cfg); 683 bool backedge(CFGEdge *e); 684 685 #ifndef PRODUCT 686 void dump( ) const; 687 #endif 688 }; 689 690 //------------------------------PhaseBlockLayout------------------------------- 691 // Rearrange blocks into some canonical order, based on edges and their frequencies 692 class PhaseBlockLayout : public Phase { 693 PhaseCFG &_cfg; // Control flow graph 694 695 GrowableArray<CFGEdge *> *edges; 696 Trace **traces; 697 Block **next; 698 Block **prev; 699 UnionFind *uf; 700 701 // Given a block, find its encompassing Trace 702 Trace * trace(Block *b) { 703 return traces[uf->Find_compress(b->_pre_order)]; 704 } 705 public: 706 PhaseBlockLayout(PhaseCFG &cfg); 707 708 void find_edges(); 709 void grow_traces(); 710 void merge_traces(bool loose_connections); 711 void reorder_traces(int count); 712 void union_traces(Trace* from, Trace* to); 713 };