block.cpp revision 5776:de6a9e811145
1/* 2 * Copyright (c) 1997, 2013, 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#include "precompiled.hpp" 26#include "libadt/vectset.hpp" 27#include "memory/allocation.inline.hpp" 28#include "opto/block.hpp" 29#include "opto/cfgnode.hpp" 30#include "opto/chaitin.hpp" 31#include "opto/loopnode.hpp" 32#include "opto/machnode.hpp" 33#include "opto/matcher.hpp" 34#include "opto/opcodes.hpp" 35#include "opto/rootnode.hpp" 36#include "utilities/copy.hpp" 37 38void Block_Array::grow( uint i ) { 39 assert(i >= Max(), "must be an overflow"); 40 debug_only(_limit = i+1); 41 if( i < _size ) return; 42 if( !_size ) { 43 _size = 1; 44 _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) ); 45 _blocks[0] = NULL; 46 } 47 uint old = _size; 48 while( i >= _size ) _size <<= 1; // Double to fit 49 _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*)); 50 Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) ); 51} 52 53void Block_List::remove(uint i) { 54 assert(i < _cnt, "index out of bounds"); 55 Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*))); 56 pop(); // shrink list by one block 57} 58 59void Block_List::insert(uint i, Block *b) { 60 push(b); // grow list by one block 61 Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*))); 62 _blocks[i] = b; 63} 64 65#ifndef PRODUCT 66void Block_List::print() { 67 for (uint i=0; i < size(); i++) { 68 tty->print("B%d ", _blocks[i]->_pre_order); 69 } 70 tty->print("size = %d\n", size()); 71} 72#endif 73 74uint Block::code_alignment() { 75 // Check for Root block 76 if (_pre_order == 0) return CodeEntryAlignment; 77 // Check for Start block 78 if (_pre_order == 1) return InteriorEntryAlignment; 79 // Check for loop alignment 80 if (has_loop_alignment()) return loop_alignment(); 81 82 return relocInfo::addr_unit(); // no particular alignment 83} 84 85uint Block::compute_loop_alignment() { 86 Node *h = head(); 87 int unit_sz = relocInfo::addr_unit(); 88 if (h->is_Loop() && h->as_Loop()->is_inner_loop()) { 89 // Pre- and post-loops have low trip count so do not bother with 90 // NOPs for align loop head. The constants are hidden from tuning 91 // but only because my "divide by 4" heuristic surely gets nearly 92 // all possible gain (a "do not align at all" heuristic has a 93 // chance of getting a really tiny gain). 94 if (h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() || 95 h->as_CountedLoop()->is_post_loop())) { 96 return (OptoLoopAlignment > 4*unit_sz) ? (OptoLoopAlignment>>2) : unit_sz; 97 } 98 // Loops with low backedge frequency should not be aligned. 99 Node *n = h->in(LoopNode::LoopBackControl)->in(0); 100 if (n->is_MachIf() && n->as_MachIf()->_prob < 0.01) { 101 return unit_sz; // Loop does not loop, more often than not! 102 } 103 return OptoLoopAlignment; // Otherwise align loop head 104 } 105 106 return unit_sz; // no particular alignment 107} 108 109// Compute the size of first 'inst_cnt' instructions in this block. 110// Return the number of instructions left to compute if the block has 111// less then 'inst_cnt' instructions. Stop, and return 0 if sum_size 112// exceeds OptoLoopAlignment. 113uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt, 114 PhaseRegAlloc* ra) { 115 uint last_inst = number_of_nodes(); 116 for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) { 117 uint inst_size = get_node(j)->size(ra); 118 if( inst_size > 0 ) { 119 inst_cnt--; 120 uint sz = sum_size + inst_size; 121 if( sz <= (uint)OptoLoopAlignment ) { 122 // Compute size of instructions which fit into fetch buffer only 123 // since all inst_cnt instructions will not fit even if we align them. 124 sum_size = sz; 125 } else { 126 return 0; 127 } 128 } 129 } 130 return inst_cnt; 131} 132 133uint Block::find_node( const Node *n ) const { 134 for( uint i = 0; i < number_of_nodes(); i++ ) { 135 if( get_node(i) == n ) 136 return i; 137 } 138 ShouldNotReachHere(); 139 return 0; 140} 141 142// Find and remove n from block list 143void Block::find_remove( const Node *n ) { 144 remove_node(find_node(n)); 145} 146 147// Return empty status of a block. Empty blocks contain only the head, other 148// ideal nodes, and an optional trailing goto. 149int Block::is_Empty() const { 150 151 // Root or start block is not considered empty 152 if (head()->is_Root() || head()->is_Start()) { 153 return not_empty; 154 } 155 156 int success_result = completely_empty; 157 int end_idx = number_of_nodes() - 1; 158 159 // Check for ending goto 160 if ((end_idx > 0) && (get_node(end_idx)->is_MachGoto())) { 161 success_result = empty_with_goto; 162 end_idx--; 163 } 164 165 // Unreachable blocks are considered empty 166 if (num_preds() <= 1) { 167 return success_result; 168 } 169 170 // Ideal nodes are allowable in empty blocks: skip them Only MachNodes 171 // turn directly into code, because only MachNodes have non-trivial 172 // emit() functions. 173 while ((end_idx > 0) && !get_node(end_idx)->is_Mach()) { 174 end_idx--; 175 } 176 177 // No room for any interesting instructions? 178 if (end_idx == 0) { 179 return success_result; 180 } 181 182 return not_empty; 183} 184 185// Return true if the block's code implies that it is likely to be 186// executed infrequently. Check to see if the block ends in a Halt or 187// a low probability call. 188bool Block::has_uncommon_code() const { 189 Node* en = end(); 190 191 if (en->is_MachGoto()) 192 en = en->in(0); 193 if (en->is_Catch()) 194 en = en->in(0); 195 if (en->is_MachProj() && en->in(0)->is_MachCall()) { 196 MachCallNode* call = en->in(0)->as_MachCall(); 197 if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) { 198 // This is true for slow-path stubs like new_{instance,array}, 199 // slow_arraycopy, complete_monitor_locking, uncommon_trap. 200 // The magic number corresponds to the probability of an uncommon_trap, 201 // even though it is a count not a probability. 202 return true; 203 } 204 } 205 206 int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode(); 207 return op == Op_Halt; 208} 209 210// True if block is low enough frequency or guarded by a test which 211// mostly does not go here. 212bool PhaseCFG::is_uncommon(const Block* block) { 213 // Initial blocks must never be moved, so are never uncommon. 214 if (block->head()->is_Root() || block->head()->is_Start()) return false; 215 216 // Check for way-low freq 217 if(block->_freq < BLOCK_FREQUENCY(0.00001f) ) return true; 218 219 // Look for code shape indicating uncommon_trap or slow path 220 if (block->has_uncommon_code()) return true; 221 222 const float epsilon = 0.05f; 223 const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon); 224 uint uncommon_preds = 0; 225 uint freq_preds = 0; 226 uint uncommon_for_freq_preds = 0; 227 228 for( uint i=1; i< block->num_preds(); i++ ) { 229 Block* guard = get_block_for_node(block->pred(i)); 230 // Check to see if this block follows its guard 1 time out of 10000 231 // or less. 232 // 233 // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which 234 // we intend to be "uncommon", such as slow-path TLE allocation, 235 // predicted call failure, and uncommon trap triggers. 236 // 237 // Use an epsilon value of 5% to allow for variability in frequency 238 // predictions and floating point calculations. The net effect is 239 // that guard_factor is set to 9500. 240 // 241 // Ignore low-frequency blocks. 242 // The next check is (guard->_freq < 1.e-5 * 9500.). 243 if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) { 244 uncommon_preds++; 245 } else { 246 freq_preds++; 247 if(block->_freq < guard->_freq * guard_factor ) { 248 uncommon_for_freq_preds++; 249 } 250 } 251 } 252 if( block->num_preds() > 1 && 253 // The block is uncommon if all preds are uncommon or 254 (uncommon_preds == (block->num_preds()-1) || 255 // it is uncommon for all frequent preds. 256 uncommon_for_freq_preds == freq_preds) ) { 257 return true; 258 } 259 return false; 260} 261 262#ifndef PRODUCT 263void Block::dump_bidx(const Block* orig, outputStream* st) const { 264 if (_pre_order) st->print("B%d",_pre_order); 265 else st->print("N%d", head()->_idx); 266 267 if (Verbose && orig != this) { 268 // Dump the original block's idx 269 st->print(" ("); 270 orig->dump_bidx(orig, st); 271 st->print(")"); 272 } 273} 274 275void Block::dump_pred(const PhaseCFG* cfg, Block* orig, outputStream* st) const { 276 if (is_connector()) { 277 for (uint i=1; i<num_preds(); i++) { 278 Block *p = cfg->get_block_for_node(pred(i)); 279 p->dump_pred(cfg, orig, st); 280 } 281 } else { 282 dump_bidx(orig, st); 283 st->print(" "); 284 } 285} 286 287void Block::dump_head(const PhaseCFG* cfg, outputStream* st) const { 288 // Print the basic block 289 dump_bidx(this, st); 290 st->print(": #\t"); 291 292 // Print the incoming CFG edges and the outgoing CFG edges 293 for( uint i=0; i<_num_succs; i++ ) { 294 non_connector_successor(i)->dump_bidx(_succs[i], st); 295 st->print(" "); 296 } 297 st->print("<- "); 298 if( head()->is_block_start() ) { 299 for (uint i=1; i<num_preds(); i++) { 300 Node *s = pred(i); 301 if (cfg != NULL) { 302 Block *p = cfg->get_block_for_node(s); 303 p->dump_pred(cfg, p, st); 304 } else { 305 while (!s->is_block_start()) 306 s = s->in(0); 307 st->print("N%d ", s->_idx ); 308 } 309 } 310 } else { 311 st->print("BLOCK HEAD IS JUNK "); 312 } 313 314 // Print loop, if any 315 const Block *bhead = this; // Head of self-loop 316 Node *bh = bhead->head(); 317 318 if ((cfg != NULL) && bh->is_Loop() && !head()->is_Root()) { 319 LoopNode *loop = bh->as_Loop(); 320 const Block *bx = cfg->get_block_for_node(loop->in(LoopNode::LoopBackControl)); 321 while (bx->is_connector()) { 322 bx = cfg->get_block_for_node(bx->pred(1)); 323 } 324 st->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order); 325 // Dump any loop-specific bits, especially for CountedLoops. 326 loop->dump_spec(st); 327 } else if (has_loop_alignment()) { 328 st->print(" top-of-loop"); 329 } 330 st->print(" Freq: %g",_freq); 331 if( Verbose || WizardMode ) { 332 st->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth); 333 st->print(" RegPressure: %d",_reg_pressure); 334 st->print(" IHRP Index: %d",_ihrp_index); 335 st->print(" FRegPressure: %d",_freg_pressure); 336 st->print(" FHRP Index: %d",_fhrp_index); 337 } 338 st->print_cr(""); 339} 340 341void Block::dump() const { 342 dump(NULL); 343} 344 345void Block::dump(const PhaseCFG* cfg) const { 346 dump_head(cfg); 347 for (uint i=0; i< number_of_nodes(); i++) { 348 get_node(i)->dump(); 349 } 350 tty->print("\n"); 351} 352#endif 353 354PhaseCFG::PhaseCFG(Arena* arena, RootNode* root, Matcher& matcher) 355: Phase(CFG) 356, _block_arena(arena) 357, _root(root) 358, _matcher(matcher) 359, _node_to_block_mapping(arena) 360, _node_latency(NULL) 361#ifndef PRODUCT 362, _trace_opto_pipelining(TraceOptoPipelining || C->method_has_option("TraceOptoPipelining")) 363#endif 364#ifdef ASSERT 365, _raw_oops(arena) 366#endif 367{ 368 ResourceMark rm; 369 // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode, 370 // then Match it into a machine-specific Node. Then clone the machine 371 // Node on demand. 372 Node *x = new (C) GotoNode(NULL); 373 x->init_req(0, x); 374 _goto = matcher.match_tree(x); 375 assert(_goto != NULL, ""); 376 _goto->set_req(0,_goto); 377 378 // Build the CFG in Reverse Post Order 379 _number_of_blocks = build_cfg(); 380 _root_block = get_block_for_node(_root); 381} 382 383// Build a proper looking CFG. Make every block begin with either a StartNode 384// or a RegionNode. Make every block end with either a Goto, If or Return. 385// The RootNode both starts and ends it's own block. Do this with a recursive 386// backwards walk over the control edges. 387uint PhaseCFG::build_cfg() { 388 Arena *a = Thread::current()->resource_area(); 389 VectorSet visited(a); 390 391 // Allocate stack with enough space to avoid frequent realloc 392 Node_Stack nstack(a, C->unique() >> 1); 393 nstack.push(_root, 0); 394 uint sum = 0; // Counter for blocks 395 396 while (nstack.is_nonempty()) { 397 // node and in's index from stack's top 398 // 'np' is _root (see above) or RegionNode, StartNode: we push on stack 399 // only nodes which point to the start of basic block (see below). 400 Node *np = nstack.node(); 401 // idx > 0, except for the first node (_root) pushed on stack 402 // at the beginning when idx == 0. 403 // We will use the condition (idx == 0) later to end the build. 404 uint idx = nstack.index(); 405 Node *proj = np->in(idx); 406 const Node *x = proj->is_block_proj(); 407 // Does the block end with a proper block-ending Node? One of Return, 408 // If or Goto? (This check should be done for visited nodes also). 409 if (x == NULL) { // Does not end right... 410 Node *g = _goto->clone(); // Force it to end in a Goto 411 g->set_req(0, proj); 412 np->set_req(idx, g); 413 x = proj = g; 414 } 415 if (!visited.test_set(x->_idx)) { // Visit this block once 416 // Skip any control-pinned middle'in stuff 417 Node *p = proj; 418 do { 419 proj = p; // Update pointer to last Control 420 p = p->in(0); // Move control forward 421 } while( !p->is_block_proj() && 422 !p->is_block_start() ); 423 // Make the block begin with one of Region or StartNode. 424 if( !p->is_block_start() ) { 425 RegionNode *r = new (C) RegionNode( 2 ); 426 r->init_req(1, p); // Insert RegionNode in the way 427 proj->set_req(0, r); // Insert RegionNode in the way 428 p = r; 429 } 430 // 'p' now points to the start of this basic block 431 432 // Put self in array of basic blocks 433 Block *bb = new (_block_arena) Block(_block_arena, p); 434 map_node_to_block(p, bb); 435 map_node_to_block(x, bb); 436 if( x != p ) { // Only for root is x == p 437 bb->push_node((Node*)x); 438 } 439 // Now handle predecessors 440 ++sum; // Count 1 for self block 441 uint cnt = bb->num_preds(); 442 for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors 443 Node *prevproj = p->in(i); // Get prior input 444 assert( !prevproj->is_Con(), "dead input not removed" ); 445 // Check to see if p->in(i) is a "control-dependent" CFG edge - 446 // i.e., it splits at the source (via an IF or SWITCH) and merges 447 // at the destination (via a many-input Region). 448 // This breaks critical edges. The RegionNode to start the block 449 // will be added when <p,i> is pulled off the node stack 450 if ( cnt > 2 ) { // Merging many things? 451 assert( prevproj== bb->pred(i),""); 452 if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge? 453 // Force a block on the control-dependent edge 454 Node *g = _goto->clone(); // Force it to end in a Goto 455 g->set_req(0,prevproj); 456 p->set_req(i,g); 457 } 458 } 459 nstack.push(p, i); // 'p' is RegionNode or StartNode 460 } 461 } else { // Post-processing visited nodes 462 nstack.pop(); // remove node from stack 463 // Check if it the fist node pushed on stack at the beginning. 464 if (idx == 0) break; // end of the build 465 // Find predecessor basic block 466 Block *pb = get_block_for_node(x); 467 // Insert into nodes array, if not already there 468 if (!has_block(proj)) { 469 assert( x != proj, "" ); 470 // Map basic block of projection 471 map_node_to_block(proj, pb); 472 pb->push_node(proj); 473 } 474 // Insert self as a child of my predecessor block 475 pb->_succs.map(pb->_num_succs++, get_block_for_node(np)); 476 assert( pb->get_node(pb->number_of_nodes() - pb->_num_succs)->is_block_proj(), 477 "too many control users, not a CFG?" ); 478 } 479 } 480 // Return number of basic blocks for all children and self 481 return sum; 482} 483 484// Inserts a goto & corresponding basic block between 485// block[block_no] and its succ_no'th successor block 486void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) { 487 // get block with block_no 488 assert(block_no < number_of_blocks(), "illegal block number"); 489 Block* in = get_block(block_no); 490 // get successor block succ_no 491 assert(succ_no < in->_num_succs, "illegal successor number"); 492 Block* out = in->_succs[succ_no]; 493 // Compute frequency of the new block. Do this before inserting 494 // new block in case succ_prob() needs to infer the probability from 495 // surrounding blocks. 496 float freq = in->_freq * in->succ_prob(succ_no); 497 // get ProjNode corresponding to the succ_no'th successor of the in block 498 ProjNode* proj = in->get_node(in->number_of_nodes() - in->_num_succs + succ_no)->as_Proj(); 499 // create region for basic block 500 RegionNode* region = new (C) RegionNode(2); 501 region->init_req(1, proj); 502 // setup corresponding basic block 503 Block* block = new (_block_arena) Block(_block_arena, region); 504 map_node_to_block(region, block); 505 C->regalloc()->set_bad(region->_idx); 506 // add a goto node 507 Node* gto = _goto->clone(); // get a new goto node 508 gto->set_req(0, region); 509 // add it to the basic block 510 block->push_node(gto); 511 map_node_to_block(gto, block); 512 C->regalloc()->set_bad(gto->_idx); 513 // hook up successor block 514 block->_succs.map(block->_num_succs++, out); 515 // remap successor's predecessors if necessary 516 for (uint i = 1; i < out->num_preds(); i++) { 517 if (out->pred(i) == proj) out->head()->set_req(i, gto); 518 } 519 // remap predecessor's successor to new block 520 in->_succs.map(succ_no, block); 521 // Set the frequency of the new block 522 block->_freq = freq; 523 // add new basic block to basic block list 524 add_block_at(block_no + 1, block); 525} 526 527// Does this block end in a multiway branch that cannot have the default case 528// flipped for another case? 529static bool no_flip_branch( Block *b ) { 530 int branch_idx = b->number_of_nodes() - b->_num_succs-1; 531 if( branch_idx < 1 ) return false; 532 Node *bra = b->get_node(branch_idx); 533 if( bra->is_Catch() ) 534 return true; 535 if( bra->is_Mach() ) { 536 if( bra->is_MachNullCheck() ) 537 return true; 538 int iop = bra->as_Mach()->ideal_Opcode(); 539 if( iop == Op_FastLock || iop == Op_FastUnlock ) 540 return true; 541 } 542 return false; 543} 544 545// Check for NeverBranch at block end. This needs to become a GOTO to the 546// true target. NeverBranch are treated as a conditional branch that always 547// goes the same direction for most of the optimizer and are used to give a 548// fake exit path to infinite loops. At this late stage they need to turn 549// into Goto's so that when you enter the infinite loop you indeed hang. 550void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) { 551 // Find true target 552 int end_idx = b->end_idx(); 553 int idx = b->get_node(end_idx+1)->as_Proj()->_con; 554 Block *succ = b->_succs[idx]; 555 Node* gto = _goto->clone(); // get a new goto node 556 gto->set_req(0, b->head()); 557 Node *bp = b->get_node(end_idx); 558 b->map_node(gto, end_idx); // Slam over NeverBranch 559 map_node_to_block(gto, b); 560 C->regalloc()->set_bad(gto->_idx); 561 b->pop_node(); // Yank projections 562 b->pop_node(); // Yank projections 563 b->_succs.map(0,succ); // Map only successor 564 b->_num_succs = 1; 565 // remap successor's predecessors if necessary 566 uint j; 567 for( j = 1; j < succ->num_preds(); j++) 568 if( succ->pred(j)->in(0) == bp ) 569 succ->head()->set_req(j, gto); 570 // Kill alternate exit path 571 Block *dead = b->_succs[1-idx]; 572 for( j = 1; j < dead->num_preds(); j++) 573 if( dead->pred(j)->in(0) == bp ) 574 break; 575 // Scan through block, yanking dead path from 576 // all regions and phis. 577 dead->head()->del_req(j); 578 for( int k = 1; dead->get_node(k)->is_Phi(); k++ ) 579 dead->get_node(k)->del_req(j); 580} 581 582// Helper function to move block bx to the slot following b_index. Return 583// true if the move is successful, otherwise false 584bool PhaseCFG::move_to_next(Block* bx, uint b_index) { 585 if (bx == NULL) return false; 586 587 // Return false if bx is already scheduled. 588 uint bx_index = bx->_pre_order; 589 if ((bx_index <= b_index) && (get_block(bx_index) == bx)) { 590 return false; 591 } 592 593 // Find the current index of block bx on the block list 594 bx_index = b_index + 1; 595 while (bx_index < number_of_blocks() && get_block(bx_index) != bx) { 596 bx_index++; 597 } 598 assert(get_block(bx_index) == bx, "block not found"); 599 600 // If the previous block conditionally falls into bx, return false, 601 // because moving bx will create an extra jump. 602 for(uint k = 1; k < bx->num_preds(); k++ ) { 603 Block* pred = get_block_for_node(bx->pred(k)); 604 if (pred == get_block(bx_index - 1)) { 605 if (pred->_num_succs != 1) { 606 return false; 607 } 608 } 609 } 610 611 // Reinsert bx just past block 'b' 612 _blocks.remove(bx_index); 613 _blocks.insert(b_index + 1, bx); 614 return true; 615} 616 617// Move empty and uncommon blocks to the end. 618void PhaseCFG::move_to_end(Block *b, uint i) { 619 int e = b->is_Empty(); 620 if (e != Block::not_empty) { 621 if (e == Block::empty_with_goto) { 622 // Remove the goto, but leave the block. 623 b->pop_node(); 624 } 625 // Mark this block as a connector block, which will cause it to be 626 // ignored in certain functions such as non_connector_successor(). 627 b->set_connector(); 628 } 629 // Move the empty block to the end, and don't recheck. 630 _blocks.remove(i); 631 _blocks.push(b); 632} 633 634// Set loop alignment for every block 635void PhaseCFG::set_loop_alignment() { 636 uint last = number_of_blocks(); 637 assert(get_block(0) == get_root_block(), ""); 638 639 for (uint i = 1; i < last; i++) { 640 Block* block = get_block(i); 641 if (block->head()->is_Loop()) { 642 block->set_loop_alignment(block); 643 } 644 } 645} 646 647// Make empty basic blocks to be "connector" blocks, Move uncommon blocks 648// to the end. 649void PhaseCFG::remove_empty_blocks() { 650 // Move uncommon blocks to the end 651 uint last = number_of_blocks(); 652 assert(get_block(0) == get_root_block(), ""); 653 654 for (uint i = 1; i < last; i++) { 655 Block* block = get_block(i); 656 if (block->is_connector()) { 657 break; 658 } 659 660 // Check for NeverBranch at block end. This needs to become a GOTO to the 661 // true target. NeverBranch are treated as a conditional branch that 662 // always goes the same direction for most of the optimizer and are used 663 // to give a fake exit path to infinite loops. At this late stage they 664 // need to turn into Goto's so that when you enter the infinite loop you 665 // indeed hang. 666 if (block->get_node(block->end_idx())->Opcode() == Op_NeverBranch) { 667 convert_NeverBranch_to_Goto(block); 668 } 669 670 // Look for uncommon blocks and move to end. 671 if (!C->do_freq_based_layout()) { 672 if (is_uncommon(block)) { 673 move_to_end(block, i); 674 last--; // No longer check for being uncommon! 675 if (no_flip_branch(block)) { // Fall-thru case must follow? 676 // Find the fall-thru block 677 block = get_block(i); 678 move_to_end(block, i); 679 last--; 680 } 681 // backup block counter post-increment 682 i--; 683 } 684 } 685 } 686 687 // Move empty blocks to the end 688 last = number_of_blocks(); 689 for (uint i = 1; i < last; i++) { 690 Block* block = get_block(i); 691 if (block->is_Empty() != Block::not_empty) { 692 move_to_end(block, i); 693 last--; 694 i--; 695 } 696 } // End of for all blocks 697} 698 699// Fix up the final control flow for basic blocks. 700void PhaseCFG::fixup_flow() { 701 // Fixup final control flow for the blocks. Remove jump-to-next 702 // block. If neither arm of a IF follows the conditional branch, we 703 // have to add a second jump after the conditional. We place the 704 // TRUE branch target in succs[0] for both GOTOs and IFs. 705 for (uint i = 0; i < number_of_blocks(); i++) { 706 Block* block = get_block(i); 707 block->_pre_order = i; // turn pre-order into block-index 708 709 // Connector blocks need no further processing. 710 if (block->is_connector()) { 711 assert((i+1) == number_of_blocks() || get_block(i + 1)->is_connector(), "All connector blocks should sink to the end"); 712 continue; 713 } 714 assert(block->is_Empty() != Block::completely_empty, "Empty blocks should be connectors"); 715 716 Block* bnext = (i < number_of_blocks() - 1) ? get_block(i + 1) : NULL; 717 Block* bs0 = block->non_connector_successor(0); 718 719 // Check for multi-way branches where I cannot negate the test to 720 // exchange the true and false targets. 721 if (no_flip_branch(block)) { 722 // Find fall through case - if must fall into its target 723 int branch_idx = block->number_of_nodes() - block->_num_succs; 724 for (uint j2 = 0; j2 < block->_num_succs; j2++) { 725 const ProjNode* p = block->get_node(branch_idx + j2)->as_Proj(); 726 if (p->_con == 0) { 727 // successor j2 is fall through case 728 if (block->non_connector_successor(j2) != bnext) { 729 // but it is not the next block => insert a goto 730 insert_goto_at(i, j2); 731 } 732 // Put taken branch in slot 0 733 if (j2 == 0 && block->_num_succs == 2) { 734 // Flip targets in succs map 735 Block *tbs0 = block->_succs[0]; 736 Block *tbs1 = block->_succs[1]; 737 block->_succs.map(0, tbs1); 738 block->_succs.map(1, tbs0); 739 } 740 break; 741 } 742 } 743 744 // Remove all CatchProjs 745 for (uint j = 0; j < block->_num_succs; j++) { 746 block->pop_node(); 747 } 748 749 } else if (block->_num_succs == 1) { 750 // Block ends in a Goto? 751 if (bnext == bs0) { 752 // We fall into next block; remove the Goto 753 block->pop_node(); 754 } 755 756 } else if(block->_num_succs == 2) { // Block ends in a If? 757 // Get opcode of 1st projection (matches _succs[0]) 758 // Note: Since this basic block has 2 exits, the last 2 nodes must 759 // be projections (in any order), the 3rd last node must be 760 // the IfNode (we have excluded other 2-way exits such as 761 // CatchNodes already). 762 MachNode* iff = block->get_node(block->number_of_nodes() - 3)->as_Mach(); 763 ProjNode* proj0 = block->get_node(block->number_of_nodes() - 2)->as_Proj(); 764 ProjNode* proj1 = block->get_node(block->number_of_nodes() - 1)->as_Proj(); 765 766 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1]. 767 assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0"); 768 assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1"); 769 770 Block* bs1 = block->non_connector_successor(1); 771 772 // Check for neither successor block following the current 773 // block ending in a conditional. If so, move one of the 774 // successors after the current one, provided that the 775 // successor was previously unscheduled, but moveable 776 // (i.e., all paths to it involve a branch). 777 if (!C->do_freq_based_layout() && bnext != bs0 && bnext != bs1) { 778 // Choose the more common successor based on the probability 779 // of the conditional branch. 780 Block* bx = bs0; 781 Block* by = bs1; 782 783 // _prob is the probability of taking the true path. Make 784 // p the probability of taking successor #1. 785 float p = iff->as_MachIf()->_prob; 786 if (proj0->Opcode() == Op_IfTrue) { 787 p = 1.0 - p; 788 } 789 790 // Prefer successor #1 if p > 0.5 791 if (p > PROB_FAIR) { 792 bx = bs1; 793 by = bs0; 794 } 795 796 // Attempt the more common successor first 797 if (move_to_next(bx, i)) { 798 bnext = bx; 799 } else if (move_to_next(by, i)) { 800 bnext = by; 801 } 802 } 803 804 // Check for conditional branching the wrong way. Negate 805 // conditional, if needed, so it falls into the following block 806 // and branches to the not-following block. 807 808 // Check for the next block being in succs[0]. We are going to branch 809 // to succs[0], so we want the fall-thru case as the next block in 810 // succs[1]. 811 if (bnext == bs0) { 812 // Fall-thru case in succs[0], so flip targets in succs map 813 Block* tbs0 = block->_succs[0]; 814 Block* tbs1 = block->_succs[1]; 815 block->_succs.map(0, tbs1); 816 block->_succs.map(1, tbs0); 817 // Flip projection for each target 818 ProjNode* tmp = proj0; 819 proj0 = proj1; 820 proj1 = tmp; 821 822 } else if(bnext != bs1) { 823 // Need a double-branch 824 // The existing conditional branch need not change. 825 // Add a unconditional branch to the false target. 826 // Alas, it must appear in its own block and adding a 827 // block this late in the game is complicated. Sigh. 828 insert_goto_at(i, 1); 829 } 830 831 // Make sure we TRUE branch to the target 832 if (proj0->Opcode() == Op_IfFalse) { 833 iff->as_MachIf()->negate(); 834 } 835 836 block->pop_node(); // Remove IfFalse & IfTrue projections 837 block->pop_node(); 838 839 } else { 840 // Multi-exit block, e.g. a switch statement 841 // But we don't need to do anything here 842 } 843 } // End of for all blocks 844} 845 846 847#ifndef PRODUCT 848void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const { 849 const Node *x = end->is_block_proj(); 850 assert( x, "not a CFG" ); 851 852 // Do not visit this block again 853 if( visited.test_set(x->_idx) ) return; 854 855 // Skip through this block 856 const Node *p = x; 857 do { 858 p = p->in(0); // Move control forward 859 assert( !p->is_block_proj() || p->is_Root(), "not a CFG" ); 860 } while( !p->is_block_start() ); 861 862 // Recursively visit 863 for (uint i = 1; i < p->req(); i++) { 864 _dump_cfg(p->in(i), visited); 865 } 866 867 // Dump the block 868 get_block_for_node(p)->dump(this); 869} 870 871void PhaseCFG::dump( ) const { 872 tty->print("\n--- CFG --- %d BBs\n", number_of_blocks()); 873 if (_blocks.size()) { // Did we do basic-block layout? 874 for (uint i = 0; i < number_of_blocks(); i++) { 875 const Block* block = get_block(i); 876 block->dump(this); 877 } 878 } else { // Else do it with a DFS 879 VectorSet visited(_block_arena); 880 _dump_cfg(_root,visited); 881 } 882} 883 884void PhaseCFG::dump_headers() { 885 for (uint i = 0; i < number_of_blocks(); i++) { 886 Block* block = get_block(i); 887 if (block != NULL) { 888 block->dump_head(this); 889 } 890 } 891} 892 893void PhaseCFG::verify() const { 894#ifdef ASSERT 895 // Verify sane CFG 896 for (uint i = 0; i < number_of_blocks(); i++) { 897 Block* block = get_block(i); 898 uint cnt = block->number_of_nodes(); 899 uint j; 900 for (j = 0; j < cnt; j++) { 901 Node *n = block->get_node(j); 902 assert(get_block_for_node(n) == block, ""); 903 if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) { 904 assert(j == 1 || block->get_node(j-1)->is_Phi(), "CreateEx must be first instruction in block"); 905 } 906 for (uint k = 0; k < n->req(); k++) { 907 Node *def = n->in(k); 908 if (def && def != n) { 909 assert(get_block_for_node(def) || def->is_Con(), "must have block; constants for debug info ok"); 910 // Verify that instructions in the block is in correct order. 911 // Uses must follow their definition if they are at the same block. 912 // Mostly done to check that MachSpillCopy nodes are placed correctly 913 // when CreateEx node is moved in build_ifg_physical(). 914 if (get_block_for_node(def) == block && !(block->head()->is_Loop() && n->is_Phi()) && 915 // See (+++) comment in reg_split.cpp 916 !(n->jvms() != NULL && n->jvms()->is_monitor_use(k))) { 917 bool is_loop = false; 918 if (n->is_Phi()) { 919 for (uint l = 1; l < def->req(); l++) { 920 if (n == def->in(l)) { 921 is_loop = true; 922 break; // Some kind of loop 923 } 924 } 925 } 926 assert(is_loop || block->find_node(def) < j, "uses must follow definitions"); 927 } 928 } 929 } 930 } 931 932 j = block->end_idx(); 933 Node* bp = (Node*)block->get_node(block->number_of_nodes() - 1)->is_block_proj(); 934 assert(bp, "last instruction must be a block proj"); 935 assert(bp == block->get_node(j), "wrong number of successors for this block"); 936 if (bp->is_Catch()) { 937 while (block->get_node(--j)->is_MachProj()) { 938 ; 939 } 940 assert(block->get_node(j)->is_MachCall(), "CatchProj must follow call"); 941 } else if (bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If) { 942 assert(block->_num_succs == 2, "Conditional branch must have two targets"); 943 } 944 } 945#endif 946} 947#endif 948 949UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) { 950 Copy::zero_to_bytes( _indices, sizeof(uint)*max ); 951} 952 953void UnionFind::extend( uint from_idx, uint to_idx ) { 954 _nesting.check(); 955 if( from_idx >= _max ) { 956 uint size = 16; 957 while( size <= from_idx ) size <<=1; 958 _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size ); 959 _max = size; 960 } 961 while( _cnt <= from_idx ) _indices[_cnt++] = 0; 962 _indices[from_idx] = to_idx; 963} 964 965void UnionFind::reset( uint max ) { 966 assert( max <= max_uint, "Must fit within uint" ); 967 // Force the Union-Find mapping to be at least this large 968 extend(max,0); 969 // Initialize to be the ID mapping. 970 for( uint i=0; i<max; i++ ) map(i,i); 971} 972 973// Straight out of Tarjan's union-find algorithm 974uint UnionFind::Find_compress( uint idx ) { 975 uint cur = idx; 976 uint next = lookup(cur); 977 while( next != cur ) { // Scan chain of equivalences 978 assert( next < cur, "always union smaller" ); 979 cur = next; // until find a fixed-point 980 next = lookup(cur); 981 } 982 // Core of union-find algorithm: update chain of 983 // equivalences to be equal to the root. 984 while( idx != next ) { 985 uint tmp = lookup(idx); 986 map(idx, next); 987 idx = tmp; 988 } 989 return idx; 990} 991 992// Like Find above, but no path compress, so bad asymptotic behavior 993uint UnionFind::Find_const( uint idx ) const { 994 if( idx == 0 ) return idx; // Ignore the zero idx 995 // Off the end? This can happen during debugging dumps 996 // when data structures have not finished being updated. 997 if( idx >= _max ) return idx; 998 uint next = lookup(idx); 999 while( next != idx ) { // Scan chain of equivalences 1000 idx = next; // until find a fixed-point 1001 next = lookup(idx); 1002 } 1003 return next; 1004} 1005 1006// union 2 sets together. 1007void UnionFind::Union( uint idx1, uint idx2 ) { 1008 uint src = Find(idx1); 1009 uint dst = Find(idx2); 1010 assert( src, "" ); 1011 assert( dst, "" ); 1012 assert( src < _max, "oob" ); 1013 assert( dst < _max, "oob" ); 1014 assert( src < dst, "always union smaller" ); 1015 map(dst,src); 1016} 1017 1018#ifndef PRODUCT 1019void Trace::dump( ) const { 1020 tty->print_cr("Trace (freq %f)", first_block()->_freq); 1021 for (Block *b = first_block(); b != NULL; b = next(b)) { 1022 tty->print(" B%d", b->_pre_order); 1023 if (b->head()->is_Loop()) { 1024 tty->print(" (L%d)", b->compute_loop_alignment()); 1025 } 1026 if (b->has_loop_alignment()) { 1027 tty->print(" (T%d)", b->code_alignment()); 1028 } 1029 } 1030 tty->cr(); 1031} 1032 1033void CFGEdge::dump( ) const { 1034 tty->print(" B%d --> B%d Freq: %f out:%3d%% in:%3d%% State: ", 1035 from()->_pre_order, to()->_pre_order, freq(), _from_pct, _to_pct); 1036 switch(state()) { 1037 case connected: 1038 tty->print("connected"); 1039 break; 1040 case open: 1041 tty->print("open"); 1042 break; 1043 case interior: 1044 tty->print("interior"); 1045 break; 1046 } 1047 if (infrequent()) { 1048 tty->print(" infrequent"); 1049 } 1050 tty->cr(); 1051} 1052#endif 1053 1054// Comparison function for edges 1055static int edge_order(CFGEdge **e0, CFGEdge **e1) { 1056 float freq0 = (*e0)->freq(); 1057 float freq1 = (*e1)->freq(); 1058 if (freq0 != freq1) { 1059 return freq0 > freq1 ? -1 : 1; 1060 } 1061 1062 int dist0 = (*e0)->to()->_rpo - (*e0)->from()->_rpo; 1063 int dist1 = (*e1)->to()->_rpo - (*e1)->from()->_rpo; 1064 1065 return dist1 - dist0; 1066} 1067 1068// Comparison function for edges 1069extern "C" int trace_frequency_order(const void *p0, const void *p1) { 1070 Trace *tr0 = *(Trace **) p0; 1071 Trace *tr1 = *(Trace **) p1; 1072 Block *b0 = tr0->first_block(); 1073 Block *b1 = tr1->first_block(); 1074 1075 // The trace of connector blocks goes at the end; 1076 // we only expect one such trace 1077 if (b0->is_connector() != b1->is_connector()) { 1078 return b1->is_connector() ? -1 : 1; 1079 } 1080 1081 // Pull more frequently executed blocks to the beginning 1082 float freq0 = b0->_freq; 1083 float freq1 = b1->_freq; 1084 if (freq0 != freq1) { 1085 return freq0 > freq1 ? -1 : 1; 1086 } 1087 1088 int diff = tr0->first_block()->_rpo - tr1->first_block()->_rpo; 1089 1090 return diff; 1091} 1092 1093// Find edges of interest, i.e, those which can fall through. Presumes that 1094// edges which don't fall through are of low frequency and can be generally 1095// ignored. Initialize the list of traces. 1096void PhaseBlockLayout::find_edges() { 1097 // Walk the blocks, creating edges and Traces 1098 uint i; 1099 Trace *tr = NULL; 1100 for (i = 0; i < _cfg.number_of_blocks(); i++) { 1101 Block* b = _cfg.get_block(i); 1102 tr = new Trace(b, next, prev); 1103 traces[tr->id()] = tr; 1104 1105 // All connector blocks should be at the end of the list 1106 if (b->is_connector()) break; 1107 1108 // If this block and the next one have a one-to-one successor 1109 // predecessor relationship, simply append the next block 1110 int nfallthru = b->num_fall_throughs(); 1111 while (nfallthru == 1 && 1112 b->succ_fall_through(0)) { 1113 Block *n = b->_succs[0]; 1114 1115 // Skip over single-entry connector blocks, we don't want to 1116 // add them to the trace. 1117 while (n->is_connector() && n->num_preds() == 1) { 1118 n = n->_succs[0]; 1119 } 1120 1121 // We see a merge point, so stop search for the next block 1122 if (n->num_preds() != 1) break; 1123 1124 i++; 1125 assert(n = _cfg.get_block(i), "expecting next block"); 1126 tr->append(n); 1127 uf->map(n->_pre_order, tr->id()); 1128 traces[n->_pre_order] = NULL; 1129 nfallthru = b->num_fall_throughs(); 1130 b = n; 1131 } 1132 1133 if (nfallthru > 0) { 1134 // Create a CFGEdge for each outgoing 1135 // edge that could be a fall-through. 1136 for (uint j = 0; j < b->_num_succs; j++ ) { 1137 if (b->succ_fall_through(j)) { 1138 Block *target = b->non_connector_successor(j); 1139 float freq = b->_freq * b->succ_prob(j); 1140 int from_pct = (int) ((100 * freq) / b->_freq); 1141 int to_pct = (int) ((100 * freq) / target->_freq); 1142 edges->append(new CFGEdge(b, target, freq, from_pct, to_pct)); 1143 } 1144 } 1145 } 1146 } 1147 1148 // Group connector blocks into one trace 1149 for (i++; i < _cfg.number_of_blocks(); i++) { 1150 Block *b = _cfg.get_block(i); 1151 assert(b->is_connector(), "connector blocks at the end"); 1152 tr->append(b); 1153 uf->map(b->_pre_order, tr->id()); 1154 traces[b->_pre_order] = NULL; 1155 } 1156} 1157 1158// Union two traces together in uf, and null out the trace in the list 1159void PhaseBlockLayout::union_traces(Trace* updated_trace, Trace* old_trace) { 1160 uint old_id = old_trace->id(); 1161 uint updated_id = updated_trace->id(); 1162 1163 uint lo_id = updated_id; 1164 uint hi_id = old_id; 1165 1166 // If from is greater than to, swap values to meet 1167 // UnionFind guarantee. 1168 if (updated_id > old_id) { 1169 lo_id = old_id; 1170 hi_id = updated_id; 1171 1172 // Fix up the trace ids 1173 traces[lo_id] = traces[updated_id]; 1174 updated_trace->set_id(lo_id); 1175 } 1176 1177 // Union the lower with the higher and remove the pointer 1178 // to the higher. 1179 uf->Union(lo_id, hi_id); 1180 traces[hi_id] = NULL; 1181} 1182 1183// Append traces together via the most frequently executed edges 1184void PhaseBlockLayout::grow_traces() { 1185 // Order the edges, and drive the growth of Traces via the most 1186 // frequently executed edges. 1187 edges->sort(edge_order); 1188 for (int i = 0; i < edges->length(); i++) { 1189 CFGEdge *e = edges->at(i); 1190 1191 if (e->state() != CFGEdge::open) continue; 1192 1193 Block *src_block = e->from(); 1194 Block *targ_block = e->to(); 1195 1196 // Don't grow traces along backedges? 1197 if (!BlockLayoutRotateLoops) { 1198 if (targ_block->_rpo <= src_block->_rpo) { 1199 targ_block->set_loop_alignment(targ_block); 1200 continue; 1201 } 1202 } 1203 1204 Trace *src_trace = trace(src_block); 1205 Trace *targ_trace = trace(targ_block); 1206 1207 // If the edge in question can join two traces at their ends, 1208 // append one trace to the other. 1209 if (src_trace->last_block() == src_block) { 1210 if (src_trace == targ_trace) { 1211 e->set_state(CFGEdge::interior); 1212 if (targ_trace->backedge(e)) { 1213 // Reset i to catch any newly eligible edge 1214 // (Or we could remember the first "open" edge, and reset there) 1215 i = 0; 1216 } 1217 } else if (targ_trace->first_block() == targ_block) { 1218 e->set_state(CFGEdge::connected); 1219 src_trace->append(targ_trace); 1220 union_traces(src_trace, targ_trace); 1221 } 1222 } 1223 } 1224} 1225 1226// Embed one trace into another, if the fork or join points are sufficiently 1227// balanced. 1228void PhaseBlockLayout::merge_traces(bool fall_thru_only) { 1229 // Walk the edge list a another time, looking at unprocessed edges. 1230 // Fold in diamonds 1231 for (int i = 0; i < edges->length(); i++) { 1232 CFGEdge *e = edges->at(i); 1233 1234 if (e->state() != CFGEdge::open) continue; 1235 if (fall_thru_only) { 1236 if (e->infrequent()) continue; 1237 } 1238 1239 Block *src_block = e->from(); 1240 Trace *src_trace = trace(src_block); 1241 bool src_at_tail = src_trace->last_block() == src_block; 1242 1243 Block *targ_block = e->to(); 1244 Trace *targ_trace = trace(targ_block); 1245 bool targ_at_start = targ_trace->first_block() == targ_block; 1246 1247 if (src_trace == targ_trace) { 1248 // This may be a loop, but we can't do much about it. 1249 e->set_state(CFGEdge::interior); 1250 continue; 1251 } 1252 1253 if (fall_thru_only) { 1254 // If the edge links the middle of two traces, we can't do anything. 1255 // Mark the edge and continue. 1256 if (!src_at_tail & !targ_at_start) { 1257 continue; 1258 } 1259 1260 // Don't grow traces along backedges? 1261 if (!BlockLayoutRotateLoops && (targ_block->_rpo <= src_block->_rpo)) { 1262 continue; 1263 } 1264 1265 // If both ends of the edge are available, why didn't we handle it earlier? 1266 assert(src_at_tail ^ targ_at_start, "Should have caught this edge earlier."); 1267 1268 if (targ_at_start) { 1269 // Insert the "targ" trace in the "src" trace if the insertion point 1270 // is a two way branch. 1271 // Better profitability check possible, but may not be worth it. 1272 // Someday, see if the this "fork" has an associated "join"; 1273 // then make a policy on merging this trace at the fork or join. 1274 // For example, other things being equal, it may be better to place this 1275 // trace at the join point if the "src" trace ends in a two-way, but 1276 // the insertion point is one-way. 1277 assert(src_block->num_fall_throughs() == 2, "unexpected diamond"); 1278 e->set_state(CFGEdge::connected); 1279 src_trace->insert_after(src_block, targ_trace); 1280 union_traces(src_trace, targ_trace); 1281 } else if (src_at_tail) { 1282 if (src_trace != trace(_cfg.get_root_block())) { 1283 e->set_state(CFGEdge::connected); 1284 targ_trace->insert_before(targ_block, src_trace); 1285 union_traces(targ_trace, src_trace); 1286 } 1287 } 1288 } else if (e->state() == CFGEdge::open) { 1289 // Append traces, even without a fall-thru connection. 1290 // But leave root entry at the beginning of the block list. 1291 if (targ_trace != trace(_cfg.get_root_block())) { 1292 e->set_state(CFGEdge::connected); 1293 src_trace->append(targ_trace); 1294 union_traces(src_trace, targ_trace); 1295 } 1296 } 1297 } 1298} 1299 1300// Order the sequence of the traces in some desirable way, and fixup the 1301// jumps at the end of each block. 1302void PhaseBlockLayout::reorder_traces(int count) { 1303 ResourceArea *area = Thread::current()->resource_area(); 1304 Trace ** new_traces = NEW_ARENA_ARRAY(area, Trace *, count); 1305 Block_List worklist; 1306 int new_count = 0; 1307 1308 // Compact the traces. 1309 for (int i = 0; i < count; i++) { 1310 Trace *tr = traces[i]; 1311 if (tr != NULL) { 1312 new_traces[new_count++] = tr; 1313 } 1314 } 1315 1316 // The entry block should be first on the new trace list. 1317 Trace *tr = trace(_cfg.get_root_block()); 1318 assert(tr == new_traces[0], "entry trace misplaced"); 1319 1320 // Sort the new trace list by frequency 1321 qsort(new_traces + 1, new_count - 1, sizeof(new_traces[0]), trace_frequency_order); 1322 1323 // Patch up the successor blocks 1324 _cfg.clear_blocks(); 1325 for (int i = 0; i < new_count; i++) { 1326 Trace *tr = new_traces[i]; 1327 if (tr != NULL) { 1328 tr->fixup_blocks(_cfg); 1329 } 1330 } 1331} 1332 1333// Order basic blocks based on frequency 1334PhaseBlockLayout::PhaseBlockLayout(PhaseCFG &cfg) 1335: Phase(BlockLayout) 1336, _cfg(cfg) { 1337 ResourceMark rm; 1338 ResourceArea *area = Thread::current()->resource_area(); 1339 1340 // List of traces 1341 int size = _cfg.number_of_blocks() + 1; 1342 traces = NEW_ARENA_ARRAY(area, Trace *, size); 1343 memset(traces, 0, size*sizeof(Trace*)); 1344 next = NEW_ARENA_ARRAY(area, Block *, size); 1345 memset(next, 0, size*sizeof(Block *)); 1346 prev = NEW_ARENA_ARRAY(area, Block *, size); 1347 memset(prev , 0, size*sizeof(Block *)); 1348 1349 // List of edges 1350 edges = new GrowableArray<CFGEdge*>; 1351 1352 // Mapping block index --> block_trace 1353 uf = new UnionFind(size); 1354 uf->reset(size); 1355 1356 // Find edges and create traces. 1357 find_edges(); 1358 1359 // Grow traces at their ends via most frequent edges. 1360 grow_traces(); 1361 1362 // Merge one trace into another, but only at fall-through points. 1363 // This may make diamonds and other related shapes in a trace. 1364 merge_traces(true); 1365 1366 // Run merge again, allowing two traces to be catenated, even if 1367 // one does not fall through into the other. This appends loosely 1368 // related traces to be near each other. 1369 merge_traces(false); 1370 1371 // Re-order all the remaining traces by frequency 1372 reorder_traces(size); 1373 1374 assert(_cfg.number_of_blocks() >= (uint) (size - 1), "number of blocks can not shrink"); 1375} 1376 1377 1378// Edge e completes a loop in a trace. If the target block is head of the 1379// loop, rotate the loop block so that the loop ends in a conditional branch. 1380bool Trace::backedge(CFGEdge *e) { 1381 bool loop_rotated = false; 1382 Block *src_block = e->from(); 1383 Block *targ_block = e->to(); 1384 1385 assert(last_block() == src_block, "loop discovery at back branch"); 1386 if (first_block() == targ_block) { 1387 if (BlockLayoutRotateLoops && last_block()->num_fall_throughs() < 2) { 1388 // Find the last block in the trace that has a conditional 1389 // branch. 1390 Block *b; 1391 for (b = last_block(); b != NULL; b = prev(b)) { 1392 if (b->num_fall_throughs() == 2) { 1393 break; 1394 } 1395 } 1396 1397 if (b != last_block() && b != NULL) { 1398 loop_rotated = true; 1399 1400 // Rotate the loop by doing two-part linked-list surgery. 1401 append(first_block()); 1402 break_loop_after(b); 1403 } 1404 } 1405 1406 // Backbranch to the top of a trace 1407 // Scroll forward through the trace from the targ_block. If we find 1408 // a loop head before another loop top, use the the loop head alignment. 1409 for (Block *b = targ_block; b != NULL; b = next(b)) { 1410 if (b->has_loop_alignment()) { 1411 break; 1412 } 1413 if (b->head()->is_Loop()) { 1414 targ_block = b; 1415 break; 1416 } 1417 } 1418 1419 first_block()->set_loop_alignment(targ_block); 1420 1421 } else { 1422 // Backbranch into the middle of a trace 1423 targ_block->set_loop_alignment(targ_block); 1424 } 1425 1426 return loop_rotated; 1427} 1428 1429// push blocks onto the CFG list 1430// ensure that blocks have the correct two-way branch sense 1431void Trace::fixup_blocks(PhaseCFG &cfg) { 1432 Block *last = last_block(); 1433 for (Block *b = first_block(); b != NULL; b = next(b)) { 1434 cfg.add_block(b); 1435 if (!b->is_connector()) { 1436 int nfallthru = b->num_fall_throughs(); 1437 if (b != last) { 1438 if (nfallthru == 2) { 1439 // Ensure that the sense of the branch is correct 1440 Block *bnext = next(b); 1441 Block *bs0 = b->non_connector_successor(0); 1442 1443 MachNode *iff = b->get_node(b->number_of_nodes() - 3)->as_Mach(); 1444 ProjNode *proj0 = b->get_node(b->number_of_nodes() - 2)->as_Proj(); 1445 ProjNode *proj1 = b->get_node(b->number_of_nodes() - 1)->as_Proj(); 1446 1447 if (bnext == bs0) { 1448 // Fall-thru case in succs[0], should be in succs[1] 1449 1450 // Flip targets in _succs map 1451 Block *tbs0 = b->_succs[0]; 1452 Block *tbs1 = b->_succs[1]; 1453 b->_succs.map( 0, tbs1 ); 1454 b->_succs.map( 1, tbs0 ); 1455 1456 // Flip projections to match targets 1457 b->map_node(proj1, b->number_of_nodes() - 2); 1458 b->map_node(proj0, b->number_of_nodes() - 1); 1459 } 1460 } 1461 } 1462 } 1463 } 1464} 1465