1 /* 2 * Copyright (c) 1997, 2011, 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_BLOCK_HPP 26 #define SHARE_VM_OPTO_BLOCK_HPP 27 28 #include "opto/multnode.hpp" 29 #include "opto/node.hpp" 30 #include "opto/phase.hpp" 31 32 // Optimization - Graph Style 33 34 class Block; 35 class CFGLoop; 36 class MachCallNode; 37 class Matcher; 38 class RootNode; 39 class VectorSet; 40 struct Tarjan; 41 42 //------------------------------Block_Array------------------------------------ 43 // Map dense integer indices to Blocks. Uses classic doubling-array trick. 44 // Abstractly provides an infinite array of Block*'s, initialized to NULL. 45 // Note that the constructor just zeros things, and since I use Arena 46 // allocation I do not need a destructor to reclaim storage. 47 class Block_Array : public ResourceObj { 48 friend class VMStructs; 49 uint _size; // allocated size, as opposed to formal limit 50 debug_only(uint _limit;) // limit to formal domain 51 protected: 52 Block **_blocks; 53 void grow( uint i ); // Grow array node to fit 54 55 public: 56 Arena *_arena; // Arena to allocate in 57 58 Block_Array(Arena *a) : _arena(a), _size(OptoBlockListSize) { 59 debug_only(_limit=0); 60 _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize ); 61 for( int i = 0; i < OptoBlockListSize; i++ ) { 62 _blocks[i] = NULL; 63 } 64 } 65 Block *lookup( uint i ) const // Lookup, or NULL for not mapped 66 { return (i<Max()) ? _blocks[i] : (Block*)NULL; } 67 Block *operator[] ( uint i ) const // Lookup, or assert for not mapped 68 { assert( i < Max(), "oob" ); return _blocks[i]; } 69 // Extend the mapping: index i maps to Block *n. 70 void map( uint i, Block *n ) { if( i>=Max() ) grow(i); _blocks[i] = n; } 71 uint Max() const { debug_only(return _limit); return _size; } 72 }; 73 74 75 class Block_List : public Block_Array { 76 friend class VMStructs; 77 public: 78 uint _cnt; 79 Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {} 80 void push( Block *b ) { map(_cnt++,b); } 81 Block *pop() { return _blocks[--_cnt]; } 82 Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;} 83 void remove( uint i ); 84 void insert( uint i, Block *n ); 85 uint size() const { return _cnt; } 86 void reset() { _cnt = 0; } 87 void print(); 88 }; 89 90 91 class CFGElement : public ResourceObj { 92 friend class VMStructs; 93 public: 94 float _freq; // Execution frequency (estimate) 95 96 CFGElement() : _freq(0.0f) {} 97 virtual bool is_block() { return false; } 98 virtual bool is_loop() { return false; } 99 Block* as_Block() { assert(is_block(), "must be block"); return (Block*)this; } 100 CFGLoop* as_CFGLoop() { assert(is_loop(), "must be loop"); return (CFGLoop*)this; } 101 }; 102 103 //------------------------------Block------------------------------------------ 104 // This class defines a Basic Block. 105 // Basic blocks are used during the output routines, and are not used during 106 // any optimization pass. They are created late in the game. 107 class Block : public CFGElement { 108 friend class VMStructs; 109 public: 110 // Nodes in this block, in order 111 Node_List _nodes; 112 113 // Basic blocks have a Node which defines Control for all Nodes pinned in 114 // this block. This Node is a RegionNode. Exception-causing Nodes 115 // (division, subroutines) and Phi functions are always pinned. Later, 116 // every Node will get pinned to some block. 117 Node *head() const { return _nodes[0]; } 118 119 // CAUTION: num_preds() is ONE based, so that predecessor numbers match 120 // input edges to Regions and Phis. 121 uint num_preds() const { return head()->req(); } 122 Node *pred(uint i) const { return head()->in(i); } 123 124 // Array of successor blocks, same size as projs array 125 Block_Array _succs; 126 127 // Basic blocks have some number of Nodes which split control to all 128 // following blocks. These Nodes are always Projections. The field in 129 // the Projection and the block-ending Node determine which Block follows. 130 uint _num_succs; 131 132 // Basic blocks also carry all sorts of good old fashioned DFS information 133 // used to find loops, loop nesting depth, dominators, etc. 134 uint _pre_order; // Pre-order DFS number 135 136 // Dominator tree 137 uint _dom_depth; // Depth in dominator tree for fast LCA 138 Block* _idom; // Immediate dominator block 139 140 CFGLoop *_loop; // Loop to which this block belongs 141 uint _rpo; // Number in reverse post order walk 142 143 virtual bool is_block() { return true; } 144 float succ_prob(uint i); // return probability of i'th successor 145 int num_fall_throughs(); // How many fall-through candidate this block has 146 void update_uncommon_branch(Block* un); // Lower branch prob to uncommon code 147 bool succ_fall_through(uint i); // Is successor "i" is a fall-through candidate 148 Block* lone_fall_through(); // Return lone fall-through Block or null 149 150 Block* dom_lca(Block* that); // Compute LCA in dominator tree. 151 #ifdef ASSERT 152 bool dominates(Block* that) { 153 int dom_diff = this->_dom_depth - that->_dom_depth; 154 if (dom_diff > 0) return false; 155 for (; dom_diff < 0; dom_diff++) that = that->_idom; 156 return this == that; 157 } 158 #endif 159 160 // Report the alignment required by this block. Must be a power of 2. 161 // The previous block will insert nops to get this alignment. 162 uint code_alignment(); 163 uint compute_loop_alignment(); 164 165 // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies. 166 // It is currently also used to scale such frequencies relative to 167 // FreqCountInvocations relative to the old value of 1500. 168 #define BLOCK_FREQUENCY(f) ((f * (float) 1500) / FreqCountInvocations) 169 170 // Register Pressure (estimate) for Splitting heuristic 171 uint _reg_pressure; 172 uint _ihrp_index; 173 uint _freg_pressure; 174 uint _fhrp_index; 175 176 // Mark and visited bits for an LCA calculation in insert_anti_dependences. 177 // Since they hold unique node indexes, they do not need reinitialization. 178 node_idx_t _raise_LCA_mark; 179 void set_raise_LCA_mark(node_idx_t x) { _raise_LCA_mark = x; } 180 node_idx_t raise_LCA_mark() const { return _raise_LCA_mark; } 181 node_idx_t _raise_LCA_visited; 182 void set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; } 183 node_idx_t raise_LCA_visited() const { return _raise_LCA_visited; } 184 185 // Estimated size in bytes of first instructions in a loop. 186 uint _first_inst_size; 187 uint first_inst_size() const { return _first_inst_size; } 188 void set_first_inst_size(uint s) { _first_inst_size = s; } 189 190 // Compute the size of first instructions in this block. 191 uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra); 192 193 // Compute alignment padding if the block needs it. 194 // Align a loop if loop's padding is less or equal to padding limit 195 // or the size of first instructions in the loop > padding. 196 uint alignment_padding(int current_offset) { 197 int block_alignment = code_alignment(); 198 int max_pad = block_alignment-relocInfo::addr_unit(); 199 if( max_pad > 0 ) { 200 assert(is_power_of_2(max_pad+relocInfo::addr_unit()), ""); 201 int current_alignment = current_offset & max_pad; 202 if( current_alignment != 0 ) { 203 uint padding = (block_alignment-current_alignment) & max_pad; 204 if( has_loop_alignment() && 205 padding > (uint)MaxLoopPad && 206 first_inst_size() <= padding ) { 207 return 0; 208 } 209 return padding; 210 } 211 } 212 return 0; 213 } 214 215 // Connector blocks. Connector blocks are basic blocks devoid of 216 // instructions, but may have relevant non-instruction Nodes, such as 217 // Phis or MergeMems. Such blocks are discovered and marked during the 218 // RemoveEmpty phase, and elided during Output. 219 bool _connector; 220 void set_connector() { _connector = true; } 221 bool is_connector() const { return _connector; }; 222 223 // Loop_alignment will be set for blocks which are at the top of loops. 224 // The block layout pass may rotate loops such that the loop head may not 225 // be the sequentially first block of the loop encountered in the linear 226 // list of blocks. If the layout pass is not run, loop alignment is set 227 // for each block which is the head of a loop. 228 uint _loop_alignment; 229 void set_loop_alignment(Block *loop_top) { 230 uint new_alignment = loop_top->compute_loop_alignment(); 231 if (new_alignment > _loop_alignment) { 232 _loop_alignment = new_alignment; 233 } 234 } 235 uint loop_alignment() const { return _loop_alignment; } 236 bool has_loop_alignment() const { return loop_alignment() > 0; } 237 238 // Create a new Block with given head Node. 239 // Creates the (empty) predecessor arrays. 240 Block( Arena *a, Node *headnode ) 241 : CFGElement(), 242 _nodes(a), 243 _succs(a), 244 _num_succs(0), 245 _pre_order(0), 246 _idom(0), 247 _loop(NULL), 248 _reg_pressure(0), 249 _ihrp_index(1), 250 _freg_pressure(0), 251 _fhrp_index(1), 252 _raise_LCA_mark(0), 253 _raise_LCA_visited(0), 254 _first_inst_size(999999), 255 _connector(false), 256 _loop_alignment(0) { 257 _nodes.push(headnode); 258 } 259 260 // Index of 'end' Node 261 uint end_idx() const { 262 // %%%%% add a proj after every goto 263 // so (last->is_block_proj() != last) always, then simplify this code 264 // This will not give correct end_idx for block 0 when it only contains root. 265 int last_idx = _nodes.size() - 1; 266 Node *last = _nodes[last_idx]; 267 assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], ""); 268 return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs); 269 } 270 271 // Basic blocks have a Node which ends them. This Node determines which 272 // basic block follows this one in the program flow. This Node is either an 273 // IfNode, a GotoNode, a JmpNode, or a ReturnNode. 274 Node *end() const { return _nodes[end_idx()]; } 275 276 // Add an instruction to an existing block. It must go after the head 277 // instruction and before the end instruction. 278 void add_inst( Node *n ) { _nodes.insert(end_idx(),n); } 279 // Find node in block 280 uint find_node( const Node *n ) const; 281 // Find and remove n from block list 282 void find_remove( const Node *n ); 283 284 // Schedule a call next in the block 285 uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, int *ready_cnt, MachCallNode *mcall, VectorSet &next_call); 286 287 // Perform basic-block local scheduling 288 Node *select(PhaseCFG *cfg, Node_List &worklist, int *ready_cnt, VectorSet &next_call, uint sched_slot); 289 void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs ); 290 void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs); 291 bool schedule_local(PhaseCFG *cfg, Matcher &m, int *ready_cnt, VectorSet &next_call); 292 // Cleanup if any code lands between a Call and his Catch 293 void call_catch_cleanup(Block_Array &bbs); 294 // Detect implicit-null-check opportunities. Basically, find NULL checks 295 // with suitable memory ops nearby. Use the memory op to do the NULL check. 296 // I can generate a memory op if there is not one nearby. 297 void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons); 298 299 // Return the empty status of a block 300 enum { not_empty, empty_with_goto, completely_empty }; 301 int is_Empty() const; 302 303 // Forward through connectors 304 Block* non_connector() { 305 Block* s = this; 306 while (s->is_connector()) { 307 s = s->_succs[0]; 308 } 309 return s; 310 } 311 312 // Return true if b is a successor of this block 313 bool has_successor(Block* b) const { 314 for (uint i = 0; i < _num_succs; i++ ) { 315 if (non_connector_successor(i) == b) { 316 return true; 317 } 318 } 319 return false; 320 } 321 322 // Successor block, after forwarding through connectors 323 Block* non_connector_successor(int i) const { 324 return _succs[i]->non_connector(); 325 } 326 327 // Examine block's code shape to predict if it is not commonly executed. 328 bool has_uncommon_code() const; 329 330 // Use frequency calculations and code shape to predict if the block 331 // is uncommon. 332 bool is_uncommon( Block_Array &bbs ) const; 333 334 #ifndef PRODUCT 335 // Debugging print of basic block 336 void dump_bidx(const Block* orig, outputStream* st = tty) const; 337 void dump_pred(const Block_Array *bbs, Block* orig, outputStream* st = tty) const; 338 void dump_head( const Block_Array *bbs, outputStream* st = tty ) const; 339 void dump() const; 340 void dump( const Block_Array *bbs ) const; 341 #endif 342 }; 343 344 345 //------------------------------PhaseCFG--------------------------------------- 346 // Build an array of Basic Block pointers, one per Node. 347 class PhaseCFG : public Phase { 348 friend class VMStructs; 349 private: 350 // Build a proper looking cfg. Return count of basic blocks 351 uint build_cfg(); 352 353 // Perform DFS search. 354 // Setup 'vertex' as DFS to vertex mapping. 355 // Setup 'semi' as vertex to DFS mapping. 356 // Set 'parent' to DFS parent. 357 uint DFS( Tarjan *tarjan ); 358 359 // Helper function to insert a node into a block 360 void schedule_node_into_block( Node *n, Block *b ); 361 362 void replace_block_proj_ctrl( Node *n ); 363 364 // Set the basic block for pinned Nodes 365 void schedule_pinned_nodes( VectorSet &visited ); 366 367 // I'll need a few machine-specific GotoNodes. Clone from this one. 368 MachNode *_goto; 369 370 Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false); 371 void verify_anti_dependences(Block* LCA, Node* load) { 372 assert(LCA == _bbs[load->_idx], "should already be scheduled"); 373 insert_anti_dependences(LCA, load, true); 374 } 375 376 public: 377 PhaseCFG( Arena *a, RootNode *r, Matcher &m ); 378 379 uint _num_blocks; // Count of basic blocks 380 Block_List _blocks; // List of basic blocks 381 RootNode *_root; // Root of whole program 382 Block_Array _bbs; // Map Nodes to owning Basic Block 383 Block *_broot; // Basic block of root 384 uint _rpo_ctr; 385 CFGLoop* _root_loop; 386 float _outer_loop_freq; // Outmost loop frequency 387 388 // Per node latency estimation, valid only during GCM 389 GrowableArray<uint> *_node_latency; 390 391 #ifndef PRODUCT 392 bool _trace_opto_pipelining; // tracing flag 393 #endif 394 395 #ifdef ASSERT 396 Unique_Node_List _raw_oops; 397 #endif 398 399 // Build dominators 400 void Dominators(); 401 402 // Estimate block frequencies based on IfNode probabilities 403 void Estimate_Block_Frequency(); 404 405 // Global Code Motion. See Click's PLDI95 paper. Place Nodes in specific 406 // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block. 407 void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list ); 408 409 // Compute the (backwards) latency of a node from the uses 410 void latency_from_uses(Node *n); 411 412 // Compute the (backwards) latency of a node from a single use 413 int latency_from_use(Node *n, const Node *def, Node *use); 414 415 // Compute the (backwards) latency of a node from the uses of this instruction 416 void partial_latency_of_defs(Node *n); 417 418 // Schedule Nodes early in their basic blocks. 419 bool schedule_early(VectorSet &visited, Node_List &roots); 420 421 // For each node, find the latest block it can be scheduled into 422 // and then select the cheapest block between the latest and earliest 423 // block to place the node. 424 void schedule_late(VectorSet &visited, Node_List &stack); 425 426 // Pick a block between early and late that is a cheaper alternative 427 // to late. Helper for schedule_late. 428 Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self); 429 430 // Compute the instruction global latency with a backwards walk 431 void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack); 432 433 // Set loop alignment 434 void set_loop_alignment(); 435 436 // Remove empty basic blocks 437 void remove_empty(); 438 void fixup_flow(); 439 bool move_to_next(Block* bx, uint b_index); 440 void move_to_end(Block* bx, uint b_index); 441 void insert_goto_at(uint block_no, uint succ_no); 442 443 // Check for NeverBranch at block end. This needs to become a GOTO to the 444 // true target. NeverBranch are treated as a conditional branch that always 445 // goes the same direction for most of the optimizer and are used to give a 446 // fake exit path to infinite loops. At this late stage they need to turn 447 // into Goto's so that when you enter the infinite loop you indeed hang. 448 void convert_NeverBranch_to_Goto(Block *b); 449 450 CFGLoop* create_loop_tree(); 451 452 // Insert a node into a block, and update the _bbs 453 void insert( Block *b, uint idx, Node *n ) { 454 b->_nodes.insert( idx, n ); 455 _bbs.map( n->_idx, b ); 456 } 457 458 #ifndef PRODUCT 459 bool trace_opto_pipelining() const { return _trace_opto_pipelining; } 460 461 // Debugging print of CFG 462 void dump( ) const; // CFG only 463 void _dump_cfg( const Node *end, VectorSet &visited ) const; 464 void verify() const; 465 void dump_headers(); 466 #else 467 bool trace_opto_pipelining() const { return false; } 468 #endif 469 }; 470 471 472 //------------------------------UnionFind-------------------------------------- 473 // Map Block indices to a block-index for a cfg-cover. 474 // Array lookup in the optimized case. 475 class UnionFind : public ResourceObj { 476 uint _cnt, _max; 477 uint* _indices; 478 ReallocMark _nesting; // assertion check for reallocations 479 public: 480 UnionFind( uint max ); 481 void reset( uint max ); // Reset to identity map for [0..max] 482 483 uint lookup( uint nidx ) const { 484 return _indices[nidx]; 485 } 486 uint operator[] (uint nidx) const { return lookup(nidx); } 487 488 void map( uint from_idx, uint to_idx ) { 489 assert( from_idx < _cnt, "oob" ); 490 _indices[from_idx] = to_idx; 491 } 492 void extend( uint from_idx, uint to_idx ); 493 494 uint Size() const { return _cnt; } 495 496 uint Find( uint idx ) { 497 assert( idx < 65536, "Must fit into uint"); 498 uint uf_idx = lookup(idx); 499 return (uf_idx == idx) ? uf_idx : Find_compress(idx); 500 } 501 uint Find_compress( uint idx ); 502 uint Find_const( uint idx ) const; 503 void Union( uint idx1, uint idx2 ); 504 505 }; 506 507 //----------------------------BlockProbPair--------------------------- 508 // Ordered pair of Node*. 509 class BlockProbPair VALUE_OBJ_CLASS_SPEC { 510 protected: 511 Block* _target; // block target 512 float _prob; // probability of edge to block 513 public: 514 BlockProbPair() : _target(NULL), _prob(0.0) {} 515 BlockProbPair(Block* b, float p) : _target(b), _prob(p) {} 516 517 Block* get_target() const { return _target; } 518 float get_prob() const { return _prob; } 519 }; 520 521 //------------------------------CFGLoop------------------------------------------- 522 class CFGLoop : public CFGElement { 523 friend class VMStructs; 524 int _id; 525 int _depth; 526 CFGLoop *_parent; // root of loop tree is the method level "pseudo" loop, it's parent is null 527 CFGLoop *_sibling; // null terminated list 528 CFGLoop *_child; // first child, use child's sibling to visit all immediately nested loops 529 GrowableArray<CFGElement*> _members; // list of members of loop 530 GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities 531 float _exit_prob; // probability any loop exit is taken on a single loop iteration 532 void update_succ_freq(Block* b, float freq); 533 534 public: 535 CFGLoop(int id) : 536 CFGElement(), 537 _id(id), 538 _depth(0), 539 _parent(NULL), 540 _sibling(NULL), 541 _child(NULL), 542 _exit_prob(1.0f) {} 543 CFGLoop* parent() { return _parent; } 544 void push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk); 545 void add_member(CFGElement *s) { _members.push(s); } 546 void add_nested_loop(CFGLoop* cl); 547 Block* head() { 548 assert(_members.at(0)->is_block(), "head must be a block"); 549 Block* hd = _members.at(0)->as_Block(); 550 assert(hd->_loop == this, "just checking"); 551 assert(hd->head()->is_Loop(), "must begin with loop head node"); 552 return hd; 553 } 554 Block* backedge_block(); // Return the block on the backedge of the loop (else NULL) 555 void compute_loop_depth(int depth); 556 void compute_freq(); // compute frequency with loop assuming head freq 1.0f 557 void scale_freq(); // scale frequency by loop trip count (including outer loops) 558 float outer_loop_freq() const; // frequency of outer loop 559 bool in_loop_nest(Block* b); 560 float trip_count() const { return 1.0f / _exit_prob; } 561 virtual bool is_loop() { return true; } 562 int id() { return _id; } 563 564 #ifndef PRODUCT 565 void dump( ) const; 566 void dump_tree() const; 567 #endif 568 }; 569 570 571 //----------------------------------CFGEdge------------------------------------ 572 // A edge between two basic blocks that will be embodied by a branch or a 573 // fall-through. 574 class CFGEdge : public ResourceObj { 575 friend class VMStructs; 576 private: 577 Block * _from; // Source basic block 578 Block * _to; // Destination basic block 579 float _freq; // Execution frequency (estimate) 580 int _state; 581 bool _infrequent; 582 int _from_pct; 583 int _to_pct; 584 585 // Private accessors 586 int from_pct() const { return _from_pct; } 587 int to_pct() const { return _to_pct; } 588 int from_infrequent() const { return from_pct() < BlockLayoutMinDiamondPercentage; } 589 int to_infrequent() const { return to_pct() < BlockLayoutMinDiamondPercentage; } 590 591 public: 592 enum { 593 open, // initial edge state; unprocessed 594 connected, // edge used to connect two traces together 595 interior // edge is interior to trace (could be backedge) 596 }; 597 598 CFGEdge(Block *from, Block *to, float freq, int from_pct, int to_pct) : 599 _from(from), _to(to), _freq(freq), 600 _from_pct(from_pct), _to_pct(to_pct), _state(open) { 601 _infrequent = from_infrequent() || to_infrequent(); 602 } 603 604 float freq() const { return _freq; } 605 Block* from() const { return _from; } 606 Block* to () const { return _to; } 607 int infrequent() const { return _infrequent; } 608 int state() const { return _state; } 609 610 void set_state(int state) { _state = state; } 611 612 #ifndef PRODUCT 613 void dump( ) const; 614 #endif 615 }; 616 617 618 //-----------------------------------Trace------------------------------------- 619 // An ordered list of basic blocks. 620 class Trace : public ResourceObj { 621 private: 622 uint _id; // Unique Trace id (derived from initial block) 623 Block ** _next_list; // Array mapping index to next block 624 Block ** _prev_list; // Array mapping index to previous block 625 Block * _first; // First block in the trace 626 Block * _last; // Last block in the trace 627 628 // Return the block that follows "b" in the trace. 629 Block * next(Block *b) const { return _next_list[b->_pre_order]; } 630 void set_next(Block *b, Block *n) const { _next_list[b->_pre_order] = n; } 631 632 // Return the block that precedes "b" in the trace. 633 Block * prev(Block *b) const { return _prev_list[b->_pre_order]; } 634 void set_prev(Block *b, Block *p) const { _prev_list[b->_pre_order] = p; } 635 636 // We've discovered a loop in this trace. Reset last to be "b", and first as 637 // the block following "b 638 void break_loop_after(Block *b) { 639 _last = b; 640 _first = next(b); 641 set_prev(_first, NULL); 642 set_next(_last, NULL); 643 } 644 645 public: 646 647 Trace(Block *b, Block **next_list, Block **prev_list) : 648 _first(b), 649 _last(b), 650 _next_list(next_list), 651 _prev_list(prev_list), 652 _id(b->_pre_order) { 653 set_next(b, NULL); 654 set_prev(b, NULL); 655 }; 656 657 // Return the id number 658 uint id() const { return _id; } 659 void set_id(uint id) { _id = id; } 660 661 // Return the first block in the trace 662 Block * first_block() const { return _first; } 663 664 // Return the last block in the trace 665 Block * last_block() const { return _last; } 666 667 // Insert a trace in the middle of this one after b 668 void insert_after(Block *b, Trace *tr) { 669 set_next(tr->last_block(), next(b)); 670 if (next(b) != NULL) { 671 set_prev(next(b), tr->last_block()); 672 } 673 674 set_next(b, tr->first_block()); 675 set_prev(tr->first_block(), b); 676 677 if (b == _last) { 678 _last = tr->last_block(); 679 } 680 } 681 682 void insert_before(Block *b, Trace *tr) { 683 Block *p = prev(b); 684 assert(p != NULL, "use append instead"); 685 insert_after(p, tr); 686 } 687 688 // Append another trace to this one. 689 void append(Trace *tr) { 690 insert_after(_last, tr); 691 } 692 693 // Append a block at the end of this trace 694 void append(Block *b) { 695 set_next(_last, b); 696 set_prev(b, _last); 697 _last = b; 698 } 699 700 // Adjust the the blocks in this trace 701 void fixup_blocks(PhaseCFG &cfg); 702 bool backedge(CFGEdge *e); 703 704 #ifndef PRODUCT 705 void dump( ) const; 706 #endif 707 }; 708 709 //------------------------------PhaseBlockLayout------------------------------- 710 // Rearrange blocks into some canonical order, based on edges and their frequencies 711 class PhaseBlockLayout : public Phase { 712 friend class VMStructs; 713 PhaseCFG &_cfg; // Control flow graph 714 715 GrowableArray<CFGEdge *> *edges; 716 Trace **traces; 717 Block **next; 718 Block **prev; 719 UnionFind *uf; 720 721 // Given a block, find its encompassing Trace 722 Trace * trace(Block *b) { 723 return traces[uf->Find_compress(b->_pre_order)]; 724 } 725 public: 726 PhaseBlockLayout(PhaseCFG &cfg); 727 728 void find_edges(); 729 void grow_traces(); 730 void merge_traces(bool loose_connections); 731 void reorder_traces(int count); 732 void union_traces(Trace* from, Trace* to); 733 }; 734 735 #endif // SHARE_VM_OPTO_BLOCK_HPP