1 /* 2 * Copyright (c) 1997, 2016, 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 "memory/resourceArea.hpp" 29 #include "compiler/compilerDirectives.hpp" 30 #include "opto/block.hpp" 31 #include "opto/cfgnode.hpp" 32 #include "opto/chaitin.hpp" 33 #include "opto/loopnode.hpp" 34 #include "opto/machnode.hpp" 35 #include "opto/matcher.hpp" 36 #include "opto/opcodes.hpp" 37 #include "opto/rootnode.hpp" 38 #include "utilities/copy.hpp" 39 40 void Block_Array::grow( uint i ) { 41 assert(i >= Max(), "must be an overflow"); 42 debug_only(_limit = i+1); 43 if( i < _size ) return; 44 if( !_size ) { 45 _size = 1; 46 _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) ); 47 _blocks[0] = NULL; 48 } 49 uint old = _size; 50 while( i >= _size ) _size <<= 1; // Double to fit 51 _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*)); 52 Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) ); 53 } 54 55 void Block_List::remove(uint i) { 56 assert(i < _cnt, "index out of bounds"); 57 Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*))); 58 pop(); // shrink list by one block 59 } 60 61 void Block_List::insert(uint i, Block *b) { 62 push(b); // grow list by one block 63 Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*))); 64 _blocks[i] = b; 65 } 66 67 #ifndef PRODUCT 68 void Block_List::print() { 69 for (uint i=0; i < size(); i++) { 70 tty->print("B%d ", _blocks[i]->_pre_order); 71 } 72 tty->print("size = %d\n", size()); 73 } 74 #endif 75 76 uint Block::code_alignment() const { 77 // Check for Root block 78 if (_pre_order == 0) return CodeEntryAlignment; 79 // Check for Start block 80 if (_pre_order == 1) return InteriorEntryAlignment; 81 // Check for loop alignment 82 if (has_loop_alignment()) return loop_alignment(); 83 84 return relocInfo::addr_unit(); // no particular alignment 85 } 86 87 uint Block::compute_loop_alignment() { 88 Node *h = head(); 89 int unit_sz = relocInfo::addr_unit(); 90 if (h->is_Loop() && h->as_Loop()->is_inner_loop()) { 91 // Pre- and post-loops have low trip count so do not bother with 92 // NOPs for align loop head. The constants are hidden from tuning 93 // but only because my "divide by 4" heuristic surely gets nearly 94 // all possible gain (a "do not align at all" heuristic has a 95 // chance of getting a really tiny gain). 96 if (h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() || 97 h->as_CountedLoop()->is_post_loop())) { 98 return (OptoLoopAlignment > 4*unit_sz) ? (OptoLoopAlignment>>2) : unit_sz; 99 } 100 // Loops with low backedge frequency should not be aligned. 101 Node *n = h->in(LoopNode::LoopBackControl)->in(0); 102 if (n->is_MachIf() && n->as_MachIf()->_prob < 0.01) { 103 return unit_sz; // Loop does not loop, more often than not! 104 } 105 return OptoLoopAlignment; // Otherwise align loop head 106 } 107 108 return unit_sz; // no particular alignment 109 } 110 111 // Compute the size of first 'inst_cnt' instructions in this block. 112 // Return the number of instructions left to compute if the block has 113 // less then 'inst_cnt' instructions. Stop, and return 0 if sum_size 114 // exceeds OptoLoopAlignment. 115 uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt, 116 PhaseRegAlloc* ra) { 117 uint last_inst = number_of_nodes(); 118 for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) { 119 uint inst_size = get_node(j)->size(ra); 120 if( inst_size > 0 ) { 121 inst_cnt--; 122 uint sz = sum_size + inst_size; 123 if( sz <= (uint)OptoLoopAlignment ) { 124 // Compute size of instructions which fit into fetch buffer only 125 // since all inst_cnt instructions will not fit even if we align them. 126 sum_size = sz; 127 } else { 128 return 0; 129 } 130 } 131 } 132 return inst_cnt; 133 } 134 135 uint Block::find_node( const Node *n ) const { 136 for( uint i = 0; i < number_of_nodes(); i++ ) { 137 if( get_node(i) == n ) 138 return i; 139 } 140 ShouldNotReachHere(); 141 return 0; 142 } 143 144 // Find and remove n from block list 145 void Block::find_remove( const Node *n ) { 146 remove_node(find_node(n)); 147 } 148 149 bool Block::contains(const Node *n) const { 150 return _nodes.contains(n); 151 } 152 153 // Return empty status of a block. Empty blocks contain only the head, other 154 // ideal nodes, and an optional trailing goto. 155 int Block::is_Empty() const { 156 157 // Root or start block is not considered empty 158 if (head()->is_Root() || head()->is_Start()) { 159 return not_empty; 160 } 161 162 int success_result = completely_empty; 163 int end_idx = number_of_nodes() - 1; 164 165 // Check for ending goto 166 if ((end_idx > 0) && (get_node(end_idx)->is_MachGoto())) { 167 success_result = empty_with_goto; 168 end_idx--; 169 } 170 171 // Unreachable blocks are considered empty 172 if (num_preds() <= 1) { 173 return success_result; 174 } 175 176 // Ideal nodes are allowable in empty blocks: skip them Only MachNodes 177 // turn directly into code, because only MachNodes have non-trivial 178 // emit() functions. 179 while ((end_idx > 0) && !get_node(end_idx)->is_Mach()) { 180 end_idx--; 181 } 182 183 // No room for any interesting instructions? 184 if (end_idx == 0) { 185 return success_result; 186 } 187 188 return not_empty; 189 } 190 191 // Return true if the block's code implies that it is likely to be 192 // executed infrequently. Check to see if the block ends in a Halt or 193 // a low probability call. 194 bool Block::has_uncommon_code() const { 195 Node* en = end(); 196 197 if (en->is_MachGoto()) 198 en = en->in(0); 199 if (en->is_Catch()) 200 en = en->in(0); 201 if (en->is_MachProj() && en->in(0)->is_MachCall()) { 202 MachCallNode* call = en->in(0)->as_MachCall(); 203 if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) { 204 // This is true for slow-path stubs like new_{instance,array}, 205 // slow_arraycopy, complete_monitor_locking, uncommon_trap. 206 // The magic number corresponds to the probability of an uncommon_trap, 207 // even though it is a count not a probability. 208 return true; 209 } 210 } 211 212 int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode(); 213 return op == Op_Halt; 214 } 215 216 // True if block is low enough frequency or guarded by a test which 217 // mostly does not go here. 218 bool PhaseCFG::is_uncommon(const Block* block) { 219 // Initial blocks must never be moved, so are never uncommon. 220 if (block->head()->is_Root() || block->head()->is_Start()) return false; 221 222 // Check for way-low freq 223 if(block->_freq < BLOCK_FREQUENCY(0.00001f) ) return true; 224 225 // Look for code shape indicating uncommon_trap or slow path 226 if (block->has_uncommon_code()) return true; 227 228 const float epsilon = 0.05f; 229 const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon); 230 uint uncommon_preds = 0; 231 uint freq_preds = 0; 232 uint uncommon_for_freq_preds = 0; 233 234 for( uint i=1; i< block->num_preds(); i++ ) { 235 Block* guard = get_block_for_node(block->pred(i)); 236 // Check to see if this block follows its guard 1 time out of 10000 237 // or less. 238 // 239 // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which 240 // we intend to be "uncommon", such as slow-path TLE allocation, 241 // predicted call failure, and uncommon trap triggers. 242 // 243 // Use an epsilon value of 5% to allow for variability in frequency 244 // predictions and floating point calculations. The net effect is 245 // that guard_factor is set to 9500. 246 // 247 // Ignore low-frequency blocks. 248 // The next check is (guard->_freq < 1.e-5 * 9500.). 249 if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) { 250 uncommon_preds++; 251 } else { 252 freq_preds++; 253 if(block->_freq < guard->_freq * guard_factor ) { 254 uncommon_for_freq_preds++; 255 } 256 } 257 } 258 if( block->num_preds() > 1 && 259 // The block is uncommon if all preds are uncommon or 260 (uncommon_preds == (block->num_preds()-1) || 261 // it is uncommon for all frequent preds. 262 uncommon_for_freq_preds == freq_preds) ) { 263 return true; 264 } 265 return false; 266 } 267 268 #ifndef PRODUCT 269 void Block::dump_bidx(const Block* orig, outputStream* st) const { 270 if (_pre_order) st->print("B%d",_pre_order); 271 else st->print("N%d", head()->_idx); 272 273 if (Verbose && orig != this) { 274 // Dump the original block's idx 275 st->print(" ("); 276 orig->dump_bidx(orig, st); 277 st->print(")"); 278 } 279 } 280 281 void Block::dump_pred(const PhaseCFG* cfg, Block* orig, outputStream* st) const { 282 if (is_connector()) { 283 for (uint i=1; i<num_preds(); i++) { 284 Block *p = cfg->get_block_for_node(pred(i)); 285 p->dump_pred(cfg, orig, st); 286 } 287 } else { 288 dump_bidx(orig, st); 289 st->print(" "); 290 } 291 } 292 293 void Block::dump_head(const PhaseCFG* cfg, outputStream* st) const { 294 // Print the basic block 295 dump_bidx(this, st); 296 st->print(": #\t"); 297 298 // Print the incoming CFG edges and the outgoing CFG edges 299 for( uint i=0; i<_num_succs; i++ ) { 300 non_connector_successor(i)->dump_bidx(_succs[i], st); 301 st->print(" "); 302 } 303 st->print("<- "); 304 if( head()->is_block_start() ) { 305 for (uint i=1; i<num_preds(); i++) { 306 Node *s = pred(i); 307 if (cfg != NULL) { 308 Block *p = cfg->get_block_for_node(s); 309 p->dump_pred(cfg, p, st); 310 } else { 311 while (!s->is_block_start()) 312 s = s->in(0); 313 st->print("N%d ", s->_idx ); 314 } 315 } 316 } else { 317 st->print("BLOCK HEAD IS JUNK "); 318 } 319 320 // Print loop, if any 321 const Block *bhead = this; // Head of self-loop 322 Node *bh = bhead->head(); 323 324 if ((cfg != NULL) && bh->is_Loop() && !head()->is_Root()) { 325 LoopNode *loop = bh->as_Loop(); 326 const Block *bx = cfg->get_block_for_node(loop->in(LoopNode::LoopBackControl)); 327 while (bx->is_connector()) { 328 bx = cfg->get_block_for_node(bx->pred(1)); 329 } 330 st->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order); 331 // Dump any loop-specific bits, especially for CountedLoops. 332 loop->dump_spec(st); 333 } else if (has_loop_alignment()) { 334 st->print(" top-of-loop"); 335 } 336 st->print(" Freq: %g",_freq); 337 if( Verbose || WizardMode ) { 338 st->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth); 339 st->print(" RegPressure: %d",_reg_pressure); 340 st->print(" IHRP Index: %d",_ihrp_index); 341 st->print(" FRegPressure: %d",_freg_pressure); 342 st->print(" FHRP Index: %d",_fhrp_index); 343 } 344 st->cr(); 345 } 346 347 void Block::dump() const { 348 dump(NULL); 349 } 350 351 void Block::dump(const PhaseCFG* cfg) const { 352 dump_head(cfg); 353 for (uint i=0; i< number_of_nodes(); i++) { 354 get_node(i)->dump(); 355 } 356 tty->print("\n"); 357 } 358 #endif 359 360 PhaseCFG::PhaseCFG(Arena* arena, RootNode* root, Matcher& matcher) 361 : Phase(CFG) 362 , _block_arena(arena) 363 , _regalloc(NULL) 364 , _scheduling_for_pressure(false) 365 , _root(root) 366 , _matcher(matcher) 367 , _node_to_block_mapping(arena) 368 , _node_latency(NULL) 369 #ifndef PRODUCT 370 , _trace_opto_pipelining(C->directive()->TraceOptoPipeliningOption) 371 #endif 372 #ifdef ASSERT 373 , _raw_oops(arena) 374 #endif 375 { 376 ResourceMark rm; 377 // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode, 378 // then Match it into a machine-specific Node. Then clone the machine 379 // Node on demand. 380 Node *x = new GotoNode(NULL); 381 x->init_req(0, x); 382 _goto = matcher.match_tree(x); 383 assert(_goto != NULL, ""); 384 _goto->set_req(0,_goto); 385 386 // Build the CFG in Reverse Post Order 387 _number_of_blocks = build_cfg(); 388 _root_block = get_block_for_node(_root); 389 } 390 391 // Build a proper looking CFG. Make every block begin with either a StartNode 392 // or a RegionNode. Make every block end with either a Goto, If or Return. 393 // The RootNode both starts and ends it's own block. Do this with a recursive 394 // backwards walk over the control edges. 395 uint PhaseCFG::build_cfg() { 396 Arena *a = Thread::current()->resource_area(); 397 VectorSet visited(a); 398 399 // Allocate stack with enough space to avoid frequent realloc 400 Node_Stack nstack(a, C->live_nodes() >> 1); 401 nstack.push(_root, 0); 402 uint sum = 0; // Counter for blocks 403 404 while (nstack.is_nonempty()) { 405 // node and in's index from stack's top 406 // 'np' is _root (see above) or RegionNode, StartNode: we push on stack 407 // only nodes which point to the start of basic block (see below). 408 Node *np = nstack.node(); 409 // idx > 0, except for the first node (_root) pushed on stack 410 // at the beginning when idx == 0. 411 // We will use the condition (idx == 0) later to end the build. 412 uint idx = nstack.index(); 413 Node *proj = np->in(idx); 414 const Node *x = proj->is_block_proj(); 415 // Does the block end with a proper block-ending Node? One of Return, 416 // If or Goto? (This check should be done for visited nodes also). 417 if (x == NULL) { // Does not end right... 418 Node *g = _goto->clone(); // Force it to end in a Goto 419 g->set_req(0, proj); 420 np->set_req(idx, g); 421 x = proj = g; 422 } 423 if (!visited.test_set(x->_idx)) { // Visit this block once 424 // Skip any control-pinned middle'in stuff 425 Node *p = proj; 426 do { 427 proj = p; // Update pointer to last Control 428 p = p->in(0); // Move control forward 429 } while( !p->is_block_proj() && 430 !p->is_block_start() ); 431 // Make the block begin with one of Region or StartNode. 432 if( !p->is_block_start() ) { 433 RegionNode *r = new RegionNode( 2 ); 434 r->init_req(1, p); // Insert RegionNode in the way 435 proj->set_req(0, r); // Insert RegionNode in the way 436 p = r; 437 } 438 // 'p' now points to the start of this basic block 439 440 // Put self in array of basic blocks 441 Block *bb = new (_block_arena) Block(_block_arena, p); 442 map_node_to_block(p, bb); 443 map_node_to_block(x, bb); 444 if( x != p ) { // Only for root is x == p 445 bb->push_node((Node*)x); 446 } 447 // Now handle predecessors 448 ++sum; // Count 1 for self block 449 uint cnt = bb->num_preds(); 450 for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors 451 Node *prevproj = p->in(i); // Get prior input 452 assert( !prevproj->is_Con(), "dead input not removed" ); 453 // Check to see if p->in(i) is a "control-dependent" CFG edge - 454 // i.e., it splits at the source (via an IF or SWITCH) and merges 455 // at the destination (via a many-input Region). 456 // This breaks critical edges. The RegionNode to start the block 457 // will be added when <p,i> is pulled off the node stack 458 if ( cnt > 2 ) { // Merging many things? 459 assert( prevproj== bb->pred(i),""); 460 if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge? 461 // Force a block on the control-dependent edge 462 Node *g = _goto->clone(); // Force it to end in a Goto 463 g->set_req(0,prevproj); 464 p->set_req(i,g); 465 } 466 } 467 nstack.push(p, i); // 'p' is RegionNode or StartNode 468 } 469 } else { // Post-processing visited nodes 470 nstack.pop(); // remove node from stack 471 // Check if it the fist node pushed on stack at the beginning. 472 if (idx == 0) break; // end of the build 473 // Find predecessor basic block 474 Block *pb = get_block_for_node(x); 475 // Insert into nodes array, if not already there 476 if (!has_block(proj)) { 477 assert( x != proj, "" ); 478 // Map basic block of projection 479 map_node_to_block(proj, pb); 480 pb->push_node(proj); 481 } 482 // Insert self as a child of my predecessor block 483 pb->_succs.map(pb->_num_succs++, get_block_for_node(np)); 484 assert( pb->get_node(pb->number_of_nodes() - pb->_num_succs)->is_block_proj(), 485 "too many control users, not a CFG?" ); 486 } 487 } 488 // Return number of basic blocks for all children and self 489 return sum; 490 } 491 492 // Inserts a goto & corresponding basic block between 493 // block[block_no] and its succ_no'th successor block 494 void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) { 495 // get block with block_no 496 assert(block_no < number_of_blocks(), "illegal block number"); 497 Block* in = get_block(block_no); 498 // get successor block succ_no 499 assert(succ_no < in->_num_succs, "illegal successor number"); 500 Block* out = in->_succs[succ_no]; 501 // Compute frequency of the new block. Do this before inserting 502 // new block in case succ_prob() needs to infer the probability from 503 // surrounding blocks. 504 float freq = in->_freq * in->succ_prob(succ_no); 505 // get ProjNode corresponding to the succ_no'th successor of the in block 506 ProjNode* proj = in->get_node(in->number_of_nodes() - in->_num_succs + succ_no)->as_Proj(); 507 // create region for basic block 508 RegionNode* region = new RegionNode(2); 509 region->init_req(1, proj); 510 // setup corresponding basic block 511 Block* block = new (_block_arena) Block(_block_arena, region); 512 map_node_to_block(region, block); 513 C->regalloc()->set_bad(region->_idx); 514 // add a goto node 515 Node* gto = _goto->clone(); // get a new goto node 516 gto->set_req(0, region); 517 // add it to the basic block 518 block->push_node(gto); 519 map_node_to_block(gto, block); 520 C->regalloc()->set_bad(gto->_idx); 521 // hook up successor block 522 block->_succs.map(block->_num_succs++, out); 523 // remap successor's predecessors if necessary 524 for (uint i = 1; i < out->num_preds(); i++) { 525 if (out->pred(i) == proj) out->head()->set_req(i, gto); 526 } 527 // remap predecessor's successor to new block 528 in->_succs.map(succ_no, block); 529 // Set the frequency of the new block 530 block->_freq = freq; 531 // add new basic block to basic block list 532 add_block_at(block_no + 1, block); 533 } 534 535 // Does this block end in a multiway branch that cannot have the default case 536 // flipped for another case? 537 static bool no_flip_branch(Block *b) { 538 int branch_idx = b->number_of_nodes() - b->_num_succs-1; 539 if (branch_idx < 1) { 540 return false; 541 } 542 Node *branch = b->get_node(branch_idx); 543 if (branch->is_Catch()) { 544 return true; 545 } 546 if (branch->is_Mach()) { 547 if (branch->is_MachNullCheck()) { 548 return true; 549 } 550 int iop = branch->as_Mach()->ideal_Opcode(); 551 if (iop == Op_FastLock || iop == Op_FastUnlock) { 552 return true; 553 } 554 // Don't flip if branch has an implicit check. 555 if (branch->as_Mach()->is_TrapBasedCheckNode()) { 556 return true; 557 } 558 } 559 return false; 560 } 561 562 // Check for NeverBranch at block end. This needs to become a GOTO to the 563 // true target. NeverBranch are treated as a conditional branch that always 564 // goes the same direction for most of the optimizer and are used to give a 565 // fake exit path to infinite loops. At this late stage they need to turn 566 // into Goto's so that when you enter the infinite loop you indeed hang. 567 void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) { 568 // Find true target 569 int end_idx = b->end_idx(); 570 int idx = b->get_node(end_idx+1)->as_Proj()->_con; 571 Block *succ = b->_succs[idx]; 572 Node* gto = _goto->clone(); // get a new goto node 573 gto->set_req(0, b->head()); 574 Node *bp = b->get_node(end_idx); 575 b->map_node(gto, end_idx); // Slam over NeverBranch 576 map_node_to_block(gto, b); 577 C->regalloc()->set_bad(gto->_idx); 578 b->pop_node(); // Yank projections 579 b->pop_node(); // Yank projections 580 b->_succs.map(0,succ); // Map only successor 581 b->_num_succs = 1; 582 // remap successor's predecessors if necessary 583 uint j; 584 for( j = 1; j < succ->num_preds(); j++) 585 if( succ->pred(j)->in(0) == bp ) 586 succ->head()->set_req(j, gto); 587 // Kill alternate exit path 588 Block *dead = b->_succs[1-idx]; 589 for( j = 1; j < dead->num_preds(); j++) 590 if( dead->pred(j)->in(0) == bp ) 591 break; 592 // Scan through block, yanking dead path from 593 // all regions and phis. 594 dead->head()->del_req(j); 595 for( int k = 1; dead->get_node(k)->is_Phi(); k++ ) 596 dead->get_node(k)->del_req(j); 597 } 598 599 // Helper function to move block bx to the slot following b_index. Return 600 // true if the move is successful, otherwise false 601 bool PhaseCFG::move_to_next(Block* bx, uint b_index) { 602 if (bx == NULL) return false; 603 604 // Return false if bx is already scheduled. 605 uint bx_index = bx->_pre_order; 606 if ((bx_index <= b_index) && (get_block(bx_index) == bx)) { 607 return false; 608 } 609 610 // Find the current index of block bx on the block list 611 bx_index = b_index + 1; 612 while (bx_index < number_of_blocks() && get_block(bx_index) != bx) { 613 bx_index++; 614 } 615 assert(get_block(bx_index) == bx, "block not found"); 616 617 // If the previous block conditionally falls into bx, return false, 618 // because moving bx will create an extra jump. 619 for(uint k = 1; k < bx->num_preds(); k++ ) { 620 Block* pred = get_block_for_node(bx->pred(k)); 621 if (pred == get_block(bx_index - 1)) { 622 if (pred->_num_succs != 1) { 623 return false; 624 } 625 } 626 } 627 628 // Reinsert bx just past block 'b' 629 _blocks.remove(bx_index); 630 _blocks.insert(b_index + 1, bx); 631 return true; 632 } 633 634 // Move empty and uncommon blocks to the end. 635 void PhaseCFG::move_to_end(Block *b, uint i) { 636 int e = b->is_Empty(); 637 if (e != Block::not_empty) { 638 if (e == Block::empty_with_goto) { 639 // Remove the goto, but leave the block. 640 b->pop_node(); 641 } 642 // Mark this block as a connector block, which will cause it to be 643 // ignored in certain functions such as non_connector_successor(). 644 b->set_connector(); 645 } 646 // Move the empty block to the end, and don't recheck. 647 _blocks.remove(i); 648 _blocks.push(b); 649 } 650 651 // Set loop alignment for every block 652 void PhaseCFG::set_loop_alignment() { 653 uint last = number_of_blocks(); 654 assert(get_block(0) == get_root_block(), ""); 655 656 for (uint i = 1; i < last; i++) { 657 Block* block = get_block(i); 658 if (block->head()->is_Loop()) { 659 block->set_loop_alignment(block); 660 } 661 } 662 } 663 664 // Make empty basic blocks to be "connector" blocks, Move uncommon blocks 665 // to the end. 666 void PhaseCFG::remove_empty_blocks() { 667 // Move uncommon blocks to the end 668 uint last = number_of_blocks(); 669 assert(get_block(0) == get_root_block(), ""); 670 671 for (uint i = 1; i < last; i++) { 672 Block* block = get_block(i); 673 if (block->is_connector()) { 674 break; 675 } 676 677 // Check for NeverBranch at block end. This needs to become a GOTO to the 678 // true target. NeverBranch are treated as a conditional branch that 679 // always goes the same direction for most of the optimizer and are used 680 // to give a fake exit path to infinite loops. At this late stage they 681 // need to turn into Goto's so that when you enter the infinite loop you 682 // indeed hang. 683 if (block->get_node(block->end_idx())->Opcode() == Op_NeverBranch) { 684 convert_NeverBranch_to_Goto(block); 685 } 686 687 // Look for uncommon blocks and move to end. 688 if (!C->do_freq_based_layout()) { 689 if (is_uncommon(block)) { 690 move_to_end(block, i); 691 last--; // No longer check for being uncommon! 692 if (no_flip_branch(block)) { // Fall-thru case must follow? 693 // Find the fall-thru block 694 block = get_block(i); 695 move_to_end(block, i); 696 last--; 697 } 698 // backup block counter post-increment 699 i--; 700 } 701 } 702 } 703 704 // Move empty blocks to the end 705 last = number_of_blocks(); 706 for (uint i = 1; i < last; i++) { 707 Block* block = get_block(i); 708 if (block->is_Empty() != Block::not_empty) { 709 move_to_end(block, i); 710 last--; 711 i--; 712 } 713 } // End of for all blocks 714 } 715 716 Block *PhaseCFG::fixup_trap_based_check(Node *branch, Block *block, int block_pos, Block *bnext) { 717 // Trap based checks must fall through to the successor with 718 // PROB_ALWAYS. 719 // They should be an If with 2 successors. 720 assert(branch->is_MachIf(), "must be If"); 721 assert(block->_num_succs == 2, "must have 2 successors"); 722 723 // Get the If node and the projection for the first successor. 724 MachIfNode *iff = block->get_node(block->number_of_nodes()-3)->as_MachIf(); 725 ProjNode *proj0 = block->get_node(block->number_of_nodes()-2)->as_Proj(); 726 ProjNode *proj1 = block->get_node(block->number_of_nodes()-1)->as_Proj(); 727 ProjNode *projt = (proj0->Opcode() == Op_IfTrue) ? proj0 : proj1; 728 ProjNode *projf = (proj0->Opcode() == Op_IfFalse) ? proj0 : proj1; 729 730 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1]. 731 assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0"); 732 assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1"); 733 734 ProjNode *proj_always; 735 ProjNode *proj_never; 736 // We must negate the branch if the implicit check doesn't follow 737 // the branch's TRUE path. Then, the new TRUE branch target will 738 // be the old FALSE branch target. 739 if (iff->_prob <= 2*PROB_NEVER) { // There are small rounding errors. 740 proj_never = projt; 741 proj_always = projf; 742 } else { 743 // We must negate the branch if the trap doesn't follow the 744 // branch's TRUE path. Then, the new TRUE branch target will 745 // be the old FALSE branch target. 746 proj_never = projf; 747 proj_always = projt; 748 iff->negate(); 749 } 750 assert(iff->_prob <= 2*PROB_NEVER, "Trap based checks are expected to trap never!"); 751 // Map the successors properly 752 block->_succs.map(0, get_block_for_node(proj_never ->raw_out(0))); // The target of the trap. 753 block->_succs.map(1, get_block_for_node(proj_always->raw_out(0))); // The fall through target. 754 755 if (block->get_node(block->number_of_nodes() - block->_num_succs + 1) != proj_always) { 756 block->map_node(proj_never, block->number_of_nodes() - block->_num_succs + 0); 757 block->map_node(proj_always, block->number_of_nodes() - block->_num_succs + 1); 758 } 759 760 // Place the fall through block after this block. 761 Block *bs1 = block->non_connector_successor(1); 762 if (bs1 != bnext && move_to_next(bs1, block_pos)) { 763 bnext = bs1; 764 } 765 // If the fall through block still is not the next block, insert a goto. 766 if (bs1 != bnext) { 767 insert_goto_at(block_pos, 1); 768 } 769 return bnext; 770 } 771 772 // Fix up the final control flow for basic blocks. 773 void PhaseCFG::fixup_flow() { 774 // Fixup final control flow for the blocks. Remove jump-to-next 775 // block. If neither arm of an IF follows the conditional branch, we 776 // have to add a second jump after the conditional. We place the 777 // TRUE branch target in succs[0] for both GOTOs and IFs. 778 for (uint i = 0; i < number_of_blocks(); i++) { 779 Block* block = get_block(i); 780 block->_pre_order = i; // turn pre-order into block-index 781 782 // Connector blocks need no further processing. 783 if (block->is_connector()) { 784 assert((i+1) == number_of_blocks() || get_block(i + 1)->is_connector(), "All connector blocks should sink to the end"); 785 continue; 786 } 787 assert(block->is_Empty() != Block::completely_empty, "Empty blocks should be connectors"); 788 789 Block* bnext = (i < number_of_blocks() - 1) ? get_block(i + 1) : NULL; 790 Block* bs0 = block->non_connector_successor(0); 791 792 // Check for multi-way branches where I cannot negate the test to 793 // exchange the true and false targets. 794 if (no_flip_branch(block)) { 795 // Find fall through case - if must fall into its target. 796 // Get the index of the branch's first successor. 797 int branch_idx = block->number_of_nodes() - block->_num_succs; 798 799 // The branch is 1 before the branch's first successor. 800 Node *branch = block->get_node(branch_idx-1); 801 802 // Handle no-flip branches which have implicit checks and which require 803 // special block ordering and individual semantics of the 'fall through 804 // case'. 805 if ((TrapBasedNullChecks || TrapBasedRangeChecks) && 806 branch->is_Mach() && branch->as_Mach()->is_TrapBasedCheckNode()) { 807 bnext = fixup_trap_based_check(branch, block, i, bnext); 808 } else { 809 // Else, default handling for no-flip branches 810 for (uint j2 = 0; j2 < block->_num_succs; j2++) { 811 const ProjNode* p = block->get_node(branch_idx + j2)->as_Proj(); 812 if (p->_con == 0) { 813 // successor j2 is fall through case 814 if (block->non_connector_successor(j2) != bnext) { 815 // but it is not the next block => insert a goto 816 insert_goto_at(i, j2); 817 } 818 // Put taken branch in slot 0 819 if (j2 == 0 && block->_num_succs == 2) { 820 // Flip targets in succs map 821 Block *tbs0 = block->_succs[0]; 822 Block *tbs1 = block->_succs[1]; 823 block->_succs.map(0, tbs1); 824 block->_succs.map(1, tbs0); 825 } 826 break; 827 } 828 } 829 } 830 831 // Remove all CatchProjs 832 for (uint j = 0; j < block->_num_succs; j++) { 833 block->pop_node(); 834 } 835 836 } else if (block->_num_succs == 1) { 837 // Block ends in a Goto? 838 if (bnext == bs0) { 839 // We fall into next block; remove the Goto 840 block->pop_node(); 841 } 842 843 } else if(block->_num_succs == 2) { // Block ends in a If? 844 // Get opcode of 1st projection (matches _succs[0]) 845 // Note: Since this basic block has 2 exits, the last 2 nodes must 846 // be projections (in any order), the 3rd last node must be 847 // the IfNode (we have excluded other 2-way exits such as 848 // CatchNodes already). 849 MachNode* iff = block->get_node(block->number_of_nodes() - 3)->as_Mach(); 850 ProjNode* proj0 = block->get_node(block->number_of_nodes() - 2)->as_Proj(); 851 ProjNode* proj1 = block->get_node(block->number_of_nodes() - 1)->as_Proj(); 852 853 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1]. 854 assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0"); 855 assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1"); 856 857 Block* bs1 = block->non_connector_successor(1); 858 859 // Check for neither successor block following the current 860 // block ending in a conditional. If so, move one of the 861 // successors after the current one, provided that the 862 // successor was previously unscheduled, but moveable 863 // (i.e., all paths to it involve a branch). 864 if (!C->do_freq_based_layout() && bnext != bs0 && bnext != bs1) { 865 // Choose the more common successor based on the probability 866 // of the conditional branch. 867 Block* bx = bs0; 868 Block* by = bs1; 869 870 // _prob is the probability of taking the true path. Make 871 // p the probability of taking successor #1. 872 float p = iff->as_MachIf()->_prob; 873 if (proj0->Opcode() == Op_IfTrue) { 874 p = 1.0 - p; 875 } 876 877 // Prefer successor #1 if p > 0.5 878 if (p > PROB_FAIR) { 879 bx = bs1; 880 by = bs0; 881 } 882 883 // Attempt the more common successor first 884 if (move_to_next(bx, i)) { 885 bnext = bx; 886 } else if (move_to_next(by, i)) { 887 bnext = by; 888 } 889 } 890 891 // Check for conditional branching the wrong way. Negate 892 // conditional, if needed, so it falls into the following block 893 // and branches to the not-following block. 894 895 // Check for the next block being in succs[0]. We are going to branch 896 // to succs[0], so we want the fall-thru case as the next block in 897 // succs[1]. 898 if (bnext == bs0) { 899 // Fall-thru case in succs[0], so flip targets in succs map 900 Block* tbs0 = block->_succs[0]; 901 Block* tbs1 = block->_succs[1]; 902 block->_succs.map(0, tbs1); 903 block->_succs.map(1, tbs0); 904 // Flip projection for each target 905 ProjNode* tmp = proj0; 906 proj0 = proj1; 907 proj1 = tmp; 908 909 } else if(bnext != bs1) { 910 // Need a double-branch 911 // The existing conditional branch need not change. 912 // Add a unconditional branch to the false target. 913 // Alas, it must appear in its own block and adding a 914 // block this late in the game is complicated. Sigh. 915 insert_goto_at(i, 1); 916 } 917 918 // Make sure we TRUE branch to the target 919 if (proj0->Opcode() == Op_IfFalse) { 920 iff->as_MachIf()->negate(); 921 } 922 923 block->pop_node(); // Remove IfFalse & IfTrue projections 924 block->pop_node(); 925 926 } else { 927 // Multi-exit block, e.g. a switch statement 928 // But we don't need to do anything here 929 } 930 } // End of for all blocks 931 } 932 933 934 // postalloc_expand: Expand nodes after register allocation. 935 // 936 // postalloc_expand has to be called after register allocation, just 937 // before output (i.e. scheduling). It only gets called if 938 // Matcher::require_postalloc_expand is true. 939 // 940 // Background: 941 // 942 // Nodes that are expandend (one compound node requiring several 943 // assembler instructions to be implemented split into two or more 944 // non-compound nodes) after register allocation are not as nice as 945 // the ones expanded before register allocation - they don't 946 // participate in optimizations as global code motion. But after 947 // register allocation we can expand nodes that use registers which 948 // are not spillable or registers that are not allocated, because the 949 // old compound node is simply replaced (in its location in the basic 950 // block) by a new subgraph which does not contain compound nodes any 951 // more. The scheduler called during output can later on process these 952 // non-compound nodes. 953 // 954 // Implementation: 955 // 956 // Nodes requiring postalloc expand are specified in the ad file by using 957 // a postalloc_expand statement instead of ins_encode. A postalloc_expand 958 // contains a single call to an encoding, as does an ins_encode 959 // statement. Instead of an emit() function a postalloc_expand() function 960 // is generated that doesn't emit assembler but creates a new 961 // subgraph. The code below calls this postalloc_expand function for each 962 // node with the appropriate attribute. This function returns the new 963 // nodes generated in an array passed in the call. The old node, 964 // potential MachTemps before and potential Projs after it then get 965 // disconnected and replaced by the new nodes. The instruction 966 // generating the result has to be the last one in the array. In 967 // general it is assumed that Projs after the node expanded are 968 // kills. These kills are not required any more after expanding as 969 // there are now explicitly visible def-use chains and the Projs are 970 // removed. This does not hold for calls: They do not only have 971 // kill-Projs but also Projs defining values. Therefore Projs after 972 // the node expanded are removed for all but for calls. If a node is 973 // to be reused, it must be added to the nodes list returned, and it 974 // will be added again. 975 // 976 // Implementing the postalloc_expand function for a node in an enc_class 977 // is rather tedious. It requires knowledge about many node details, as 978 // the nodes and the subgraph must be hand crafted. To simplify this, 979 // adlc generates some utility variables into the postalloc_expand function, 980 // e.g., holding the operands as specified by the postalloc_expand encoding 981 // specification, e.g.: 982 // * unsigned idx_<par_name> holding the index of the node in the ins 983 // * Node *n_<par_name> holding the node loaded from the ins 984 // * MachOpnd *op_<par_name> holding the corresponding operand 985 // 986 // The ordering of operands can not be determined by looking at a 987 // rule. Especially if a match rule matches several different trees, 988 // several nodes are generated from one instruct specification with 989 // different operand orderings. In this case the adlc generated 990 // variables are the only way to access the ins and operands 991 // deterministically. 992 // 993 // If assigning a register to a node that contains an oop, don't 994 // forget to call ra_->set_oop() for the node. 995 void PhaseCFG::postalloc_expand(PhaseRegAlloc* _ra) { 996 GrowableArray <Node *> new_nodes(32); // Array with new nodes filled by postalloc_expand function of node. 997 GrowableArray <Node *> remove(32); 998 GrowableArray <Node *> succs(32); 999 unsigned int max_idx = C->unique(); // Remember to distinguish new from old nodes. 1000 DEBUG_ONLY(bool foundNode = false); 1001 1002 // for all blocks 1003 for (uint i = 0; i < number_of_blocks(); i++) { 1004 Block *b = _blocks[i]; 1005 // For all instructions in the current block. 1006 for (uint j = 0; j < b->number_of_nodes(); j++) { 1007 Node *n = b->get_node(j); 1008 if (n->is_Mach() && n->as_Mach()->requires_postalloc_expand()) { 1009 #ifdef ASSERT 1010 if (TracePostallocExpand) { 1011 if (!foundNode) { 1012 foundNode = true; 1013 tty->print("POSTALLOC EXPANDING %d %s\n", C->compile_id(), 1014 C->method() ? C->method()->name()->as_utf8() : C->stub_name()); 1015 } 1016 tty->print(" postalloc expanding "); n->dump(); 1017 if (Verbose) { 1018 tty->print(" with ins:\n"); 1019 for (uint k = 0; k < n->len(); ++k) { 1020 if (n->in(k)) { tty->print(" "); n->in(k)->dump(); } 1021 } 1022 } 1023 } 1024 #endif 1025 new_nodes.clear(); 1026 // Collect nodes that have to be removed from the block later on. 1027 uint req = n->req(); 1028 remove.clear(); 1029 for (uint k = 0; k < req; ++k) { 1030 if (n->in(k) && n->in(k)->is_MachTemp()) { 1031 remove.push(n->in(k)); // MachTemps which are inputs to the old node have to be removed. 1032 n->in(k)->del_req(0); 1033 j--; 1034 } 1035 } 1036 1037 // Check whether we can allocate enough nodes. We set a fix limit for 1038 // the size of postalloc expands with this. 1039 uint unique_limit = C->unique() + 40; 1040 if (unique_limit >= _ra->node_regs_max_index()) { 1041 Compile::current()->record_failure("out of nodes in postalloc expand"); 1042 return; 1043 } 1044 1045 // Emit (i.e. generate new nodes). 1046 n->as_Mach()->postalloc_expand(&new_nodes, _ra); 1047 1048 assert(C->unique() < unique_limit, "You allocated too many nodes in your postalloc expand."); 1049 1050 // Disconnect the inputs of the old node. 1051 // 1052 // We reuse MachSpillCopy nodes. If we need to expand them, there 1053 // are many, so reusing pays off. If reused, the node already 1054 // has the new ins. n must be the last node on new_nodes list. 1055 if (!n->is_MachSpillCopy()) { 1056 for (int k = req - 1; k >= 0; --k) { 1057 n->del_req(k); 1058 } 1059 } 1060 1061 #ifdef ASSERT 1062 // Check that all nodes have proper operands. 1063 for (int k = 0; k < new_nodes.length(); ++k) { 1064 if (new_nodes.at(k)->_idx < max_idx || !new_nodes.at(k)->is_Mach()) continue; // old node, Proj ... 1065 MachNode *m = new_nodes.at(k)->as_Mach(); 1066 for (unsigned int l = 0; l < m->num_opnds(); ++l) { 1067 if (MachOper::notAnOper(m->_opnds[l])) { 1068 outputStream *os = tty; 1069 os->print("Node %s ", m->Name()); 1070 os->print("has invalid opnd %d: %p\n", l, m->_opnds[l]); 1071 assert(0, "Invalid operands, see inline trace in hs_err_pid file."); 1072 } 1073 } 1074 } 1075 #endif 1076 1077 // Collect succs of old node in remove (for projections) and in succs (for 1078 // all other nodes) do _not_ collect projections in remove (but in succs) 1079 // in case the node is a call. We need the projections for calls as they are 1080 // associated with registes (i.e. they are defs). 1081 succs.clear(); 1082 for (DUIterator k = n->outs(); n->has_out(k); k++) { 1083 if (n->out(k)->is_Proj() && !n->is_MachCall() && !n->is_MachBranch()) { 1084 remove.push(n->out(k)); 1085 } else { 1086 succs.push(n->out(k)); 1087 } 1088 } 1089 // Replace old node n as input of its succs by last of the new nodes. 1090 for (int k = 0; k < succs.length(); ++k) { 1091 Node *succ = succs.at(k); 1092 for (uint l = 0; l < succ->req(); ++l) { 1093 if (succ->in(l) == n) { 1094 succ->set_req(l, new_nodes.at(new_nodes.length() - 1)); 1095 } 1096 } 1097 for (uint l = succ->req(); l < succ->len(); ++l) { 1098 if (succ->in(l) == n) { 1099 succ->set_prec(l, new_nodes.at(new_nodes.length() - 1)); 1100 } 1101 } 1102 } 1103 1104 // Index of old node in block. 1105 uint index = b->find_node(n); 1106 // Insert new nodes into block and map them in nodes->blocks array 1107 // and remember last node in n2. 1108 Node *n2 = NULL; 1109 for (int k = 0; k < new_nodes.length(); ++k) { 1110 n2 = new_nodes.at(k); 1111 b->insert_node(n2, ++index); 1112 map_node_to_block(n2, b); 1113 } 1114 1115 // Add old node n to remove and remove them all from block. 1116 remove.push(n); 1117 j--; 1118 #ifdef ASSERT 1119 if (TracePostallocExpand && Verbose) { 1120 tty->print(" removing:\n"); 1121 for (int k = 0; k < remove.length(); ++k) { 1122 tty->print(" "); remove.at(k)->dump(); 1123 } 1124 tty->print(" inserting:\n"); 1125 for (int k = 0; k < new_nodes.length(); ++k) { 1126 tty->print(" "); new_nodes.at(k)->dump(); 1127 } 1128 } 1129 #endif 1130 for (int k = 0; k < remove.length(); ++k) { 1131 if (b->contains(remove.at(k))) { 1132 b->find_remove(remove.at(k)); 1133 } else { 1134 assert(remove.at(k)->is_Proj() && (remove.at(k)->in(0)->is_MachBranch()), ""); 1135 } 1136 } 1137 // If anything has been inserted (n2 != NULL), continue after last node inserted. 1138 // This does not always work. Some postalloc expands don't insert any nodes, if they 1139 // do optimizations (e.g., max(x,x)). In this case we decrement j accordingly. 1140 j = n2 ? b->find_node(n2) : j; 1141 } 1142 } 1143 } 1144 1145 #ifdef ASSERT 1146 if (foundNode) { 1147 tty->print("FINISHED %d %s\n", C->compile_id(), 1148 C->method() ? C->method()->name()->as_utf8() : C->stub_name()); 1149 tty->flush(); 1150 } 1151 #endif 1152 } 1153 1154 1155 //------------------------------dump------------------------------------------- 1156 #ifndef PRODUCT 1157 void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const { 1158 const Node *x = end->is_block_proj(); 1159 assert( x, "not a CFG" ); 1160 1161 // Do not visit this block again 1162 if( visited.test_set(x->_idx) ) return; 1163 1164 // Skip through this block 1165 const Node *p = x; 1166 do { 1167 p = p->in(0); // Move control forward 1168 assert( !p->is_block_proj() || p->is_Root(), "not a CFG" ); 1169 } while( !p->is_block_start() ); 1170 1171 // Recursively visit 1172 for (uint i = 1; i < p->req(); i++) { 1173 _dump_cfg(p->in(i), visited); 1174 } 1175 1176 // Dump the block 1177 get_block_for_node(p)->dump(this); 1178 } 1179 1180 void PhaseCFG::dump( ) const { 1181 tty->print("\n--- CFG --- %d BBs\n", number_of_blocks()); 1182 if (_blocks.size()) { // Did we do basic-block layout? 1183 for (uint i = 0; i < number_of_blocks(); i++) { 1184 const Block* block = get_block(i); 1185 block->dump(this); 1186 } 1187 } else { // Else do it with a DFS 1188 VectorSet visited(_block_arena); 1189 _dump_cfg(_root,visited); 1190 } 1191 } 1192 1193 void PhaseCFG::dump_headers() { 1194 for (uint i = 0; i < number_of_blocks(); i++) { 1195 Block* block = get_block(i); 1196 if (block != NULL) { 1197 block->dump_head(this); 1198 } 1199 } 1200 } 1201 1202 void PhaseCFG::verify() const { 1203 #ifdef ASSERT 1204 // Verify sane CFG 1205 for (uint i = 0; i < number_of_blocks(); i++) { 1206 Block* block = get_block(i); 1207 uint cnt = block->number_of_nodes(); 1208 uint j; 1209 for (j = 0; j < cnt; j++) { 1210 Node *n = block->get_node(j); 1211 assert(get_block_for_node(n) == block, ""); 1212 if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) { 1213 assert(j == 1 || block->get_node(j-1)->is_Phi(), "CreateEx must be first instruction in block"); 1214 } 1215 for (uint k = 0; k < n->req(); k++) { 1216 Node *def = n->in(k); 1217 if (def && def != n) { 1218 assert(get_block_for_node(def) || def->is_Con(), "must have block; constants for debug info ok"); 1219 // Verify that instructions in the block is in correct order. 1220 // Uses must follow their definition if they are at the same block. 1221 // Mostly done to check that MachSpillCopy nodes are placed correctly 1222 // when CreateEx node is moved in build_ifg_physical(). 1223 if (get_block_for_node(def) == block && !(block->head()->is_Loop() && n->is_Phi()) && 1224 // See (+++) comment in reg_split.cpp 1225 !(n->jvms() != NULL && n->jvms()->is_monitor_use(k))) { 1226 bool is_loop = false; 1227 if (n->is_Phi()) { 1228 for (uint l = 1; l < def->req(); l++) { 1229 if (n == def->in(l)) { 1230 is_loop = true; 1231 break; // Some kind of loop 1232 } 1233 } 1234 } 1235 assert(is_loop || block->find_node(def) < j, "uses must follow definitions"); 1236 } 1237 } 1238 } 1239 } 1240 1241 j = block->end_idx(); 1242 Node* bp = (Node*)block->get_node(block->number_of_nodes() - 1)->is_block_proj(); 1243 assert(bp, "last instruction must be a block proj"); 1244 assert(bp == block->get_node(j), "wrong number of successors for this block"); 1245 if (bp->is_Catch()) { 1246 while (block->get_node(--j)->is_MachProj()) { 1247 ; 1248 } 1249 assert(block->get_node(j)->is_MachCall(), "CatchProj must follow call"); 1250 } else if (bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If) { 1251 assert(block->_num_succs == 2, "Conditional branch must have two targets"); 1252 } 1253 } 1254 #endif 1255 } 1256 #endif 1257 1258 UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) { 1259 Copy::zero_to_bytes( _indices, sizeof(uint)*max ); 1260 } 1261 1262 void UnionFind::extend( uint from_idx, uint to_idx ) { 1263 _nesting.check(); 1264 if( from_idx >= _max ) { 1265 uint size = 16; 1266 while( size <= from_idx ) size <<=1; 1267 _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size ); 1268 _max = size; 1269 } 1270 while( _cnt <= from_idx ) _indices[_cnt++] = 0; 1271 _indices[from_idx] = to_idx; 1272 } 1273 1274 void UnionFind::reset( uint max ) { 1275 // Force the Union-Find mapping to be at least this large 1276 extend(max,0); 1277 // Initialize to be the ID mapping. 1278 for( uint i=0; i<max; i++ ) map(i,i); 1279 } 1280 1281 // Straight out of Tarjan's union-find algorithm 1282 uint UnionFind::Find_compress( uint idx ) { 1283 uint cur = idx; 1284 uint next = lookup(cur); 1285 while( next != cur ) { // Scan chain of equivalences 1286 assert( next < cur, "always union smaller" ); 1287 cur = next; // until find a fixed-point 1288 next = lookup(cur); 1289 } 1290 // Core of union-find algorithm: update chain of 1291 // equivalences to be equal to the root. 1292 while( idx != next ) { 1293 uint tmp = lookup(idx); 1294 map(idx, next); 1295 idx = tmp; 1296 } 1297 return idx; 1298 } 1299 1300 // Like Find above, but no path compress, so bad asymptotic behavior 1301 uint UnionFind::Find_const( uint idx ) const { 1302 if( idx == 0 ) return idx; // Ignore the zero idx 1303 // Off the end? This can happen during debugging dumps 1304 // when data structures have not finished being updated. 1305 if( idx >= _max ) return idx; 1306 uint next = lookup(idx); 1307 while( next != idx ) { // Scan chain of equivalences 1308 idx = next; // until find a fixed-point 1309 next = lookup(idx); 1310 } 1311 return next; 1312 } 1313 1314 // union 2 sets together. 1315 void UnionFind::Union( uint idx1, uint idx2 ) { 1316 uint src = Find(idx1); 1317 uint dst = Find(idx2); 1318 assert( src, "" ); 1319 assert( dst, "" ); 1320 assert( src < _max, "oob" ); 1321 assert( dst < _max, "oob" ); 1322 assert( src < dst, "always union smaller" ); 1323 map(dst,src); 1324 } 1325 1326 #ifndef PRODUCT 1327 void Trace::dump( ) const { 1328 tty->print_cr("Trace (freq %f)", first_block()->_freq); 1329 for (Block *b = first_block(); b != NULL; b = next(b)) { 1330 tty->print(" B%d", b->_pre_order); 1331 if (b->head()->is_Loop()) { 1332 tty->print(" (L%d)", b->compute_loop_alignment()); 1333 } 1334 if (b->has_loop_alignment()) { 1335 tty->print(" (T%d)", b->code_alignment()); 1336 } 1337 } 1338 tty->cr(); 1339 } 1340 1341 void CFGEdge::dump( ) const { 1342 tty->print(" B%d --> B%d Freq: %f out:%3d%% in:%3d%% State: ", 1343 from()->_pre_order, to()->_pre_order, freq(), _from_pct, _to_pct); 1344 switch(state()) { 1345 case connected: 1346 tty->print("connected"); 1347 break; 1348 case open: 1349 tty->print("open"); 1350 break; 1351 case interior: 1352 tty->print("interior"); 1353 break; 1354 } 1355 if (infrequent()) { 1356 tty->print(" infrequent"); 1357 } 1358 tty->cr(); 1359 } 1360 #endif 1361 1362 // Comparison function for edges 1363 static int edge_order(CFGEdge **e0, CFGEdge **e1) { 1364 float freq0 = (*e0)->freq(); 1365 float freq1 = (*e1)->freq(); 1366 if (freq0 != freq1) { 1367 return freq0 > freq1 ? -1 : 1; 1368 } 1369 1370 int dist0 = (*e0)->to()->_rpo - (*e0)->from()->_rpo; 1371 int dist1 = (*e1)->to()->_rpo - (*e1)->from()->_rpo; 1372 1373 return dist1 - dist0; 1374 } 1375 1376 // Comparison function for edges 1377 extern "C" int trace_frequency_order(const void *p0, const void *p1) { 1378 Trace *tr0 = *(Trace **) p0; 1379 Trace *tr1 = *(Trace **) p1; 1380 Block *b0 = tr0->first_block(); 1381 Block *b1 = tr1->first_block(); 1382 1383 // The trace of connector blocks goes at the end; 1384 // we only expect one such trace 1385 if (b0->is_connector() != b1->is_connector()) { 1386 return b1->is_connector() ? -1 : 1; 1387 } 1388 1389 // Pull more frequently executed blocks to the beginning 1390 float freq0 = b0->_freq; 1391 float freq1 = b1->_freq; 1392 if (freq0 != freq1) { 1393 return freq0 > freq1 ? -1 : 1; 1394 } 1395 1396 int diff = tr0->first_block()->_rpo - tr1->first_block()->_rpo; 1397 1398 return diff; 1399 } 1400 1401 // Find edges of interest, i.e, those which can fall through. Presumes that 1402 // edges which don't fall through are of low frequency and can be generally 1403 // ignored. Initialize the list of traces. 1404 void PhaseBlockLayout::find_edges() { 1405 // Walk the blocks, creating edges and Traces 1406 uint i; 1407 Trace *tr = NULL; 1408 for (i = 0; i < _cfg.number_of_blocks(); i++) { 1409 Block* b = _cfg.get_block(i); 1410 tr = new Trace(b, next, prev); 1411 traces[tr->id()] = tr; 1412 1413 // All connector blocks should be at the end of the list 1414 if (b->is_connector()) break; 1415 1416 // If this block and the next one have a one-to-one successor 1417 // predecessor relationship, simply append the next block 1418 int nfallthru = b->num_fall_throughs(); 1419 while (nfallthru == 1 && 1420 b->succ_fall_through(0)) { 1421 Block *n = b->_succs[0]; 1422 1423 // Skip over single-entry connector blocks, we don't want to 1424 // add them to the trace. 1425 while (n->is_connector() && n->num_preds() == 1) { 1426 n = n->_succs[0]; 1427 } 1428 1429 // We see a merge point, so stop search for the next block 1430 if (n->num_preds() != 1) break; 1431 1432 i++; 1433 assert(n == _cfg.get_block(i), "expecting next block"); 1434 tr->append(n); 1435 uf->map(n->_pre_order, tr->id()); 1436 traces[n->_pre_order] = NULL; 1437 nfallthru = b->num_fall_throughs(); 1438 b = n; 1439 } 1440 1441 if (nfallthru > 0) { 1442 // Create a CFGEdge for each outgoing 1443 // edge that could be a fall-through. 1444 for (uint j = 0; j < b->_num_succs; j++ ) { 1445 if (b->succ_fall_through(j)) { 1446 Block *target = b->non_connector_successor(j); 1447 float freq = b->_freq * b->succ_prob(j); 1448 int from_pct = (int) ((100 * freq) / b->_freq); 1449 int to_pct = (int) ((100 * freq) / target->_freq); 1450 edges->append(new CFGEdge(b, target, freq, from_pct, to_pct)); 1451 } 1452 } 1453 } 1454 } 1455 1456 // Group connector blocks into one trace 1457 for (i++; i < _cfg.number_of_blocks(); i++) { 1458 Block *b = _cfg.get_block(i); 1459 assert(b->is_connector(), "connector blocks at the end"); 1460 tr->append(b); 1461 uf->map(b->_pre_order, tr->id()); 1462 traces[b->_pre_order] = NULL; 1463 } 1464 } 1465 1466 // Union two traces together in uf, and null out the trace in the list 1467 void PhaseBlockLayout::union_traces(Trace* updated_trace, Trace* old_trace) { 1468 uint old_id = old_trace->id(); 1469 uint updated_id = updated_trace->id(); 1470 1471 uint lo_id = updated_id; 1472 uint hi_id = old_id; 1473 1474 // If from is greater than to, swap values to meet 1475 // UnionFind guarantee. 1476 if (updated_id > old_id) { 1477 lo_id = old_id; 1478 hi_id = updated_id; 1479 1480 // Fix up the trace ids 1481 traces[lo_id] = traces[updated_id]; 1482 updated_trace->set_id(lo_id); 1483 } 1484 1485 // Union the lower with the higher and remove the pointer 1486 // to the higher. 1487 uf->Union(lo_id, hi_id); 1488 traces[hi_id] = NULL; 1489 } 1490 1491 // Append traces together via the most frequently executed edges 1492 void PhaseBlockLayout::grow_traces() { 1493 // Order the edges, and drive the growth of Traces via the most 1494 // frequently executed edges. 1495 edges->sort(edge_order); 1496 for (int i = 0; i < edges->length(); i++) { 1497 CFGEdge *e = edges->at(i); 1498 1499 if (e->state() != CFGEdge::open) continue; 1500 1501 Block *src_block = e->from(); 1502 Block *targ_block = e->to(); 1503 1504 // Don't grow traces along backedges? 1505 if (!BlockLayoutRotateLoops) { 1506 if (targ_block->_rpo <= src_block->_rpo) { 1507 targ_block->set_loop_alignment(targ_block); 1508 continue; 1509 } 1510 } 1511 1512 Trace *src_trace = trace(src_block); 1513 Trace *targ_trace = trace(targ_block); 1514 1515 // If the edge in question can join two traces at their ends, 1516 // append one trace to the other. 1517 if (src_trace->last_block() == src_block) { 1518 if (src_trace == targ_trace) { 1519 e->set_state(CFGEdge::interior); 1520 if (targ_trace->backedge(e)) { 1521 // Reset i to catch any newly eligible edge 1522 // (Or we could remember the first "open" edge, and reset there) 1523 i = 0; 1524 } 1525 } else if (targ_trace->first_block() == targ_block) { 1526 e->set_state(CFGEdge::connected); 1527 src_trace->append(targ_trace); 1528 union_traces(src_trace, targ_trace); 1529 } 1530 } 1531 } 1532 } 1533 1534 // Embed one trace into another, if the fork or join points are sufficiently 1535 // balanced. 1536 void PhaseBlockLayout::merge_traces(bool fall_thru_only) { 1537 // Walk the edge list a another time, looking at unprocessed edges. 1538 // Fold in diamonds 1539 for (int i = 0; i < edges->length(); i++) { 1540 CFGEdge *e = edges->at(i); 1541 1542 if (e->state() != CFGEdge::open) continue; 1543 if (fall_thru_only) { 1544 if (e->infrequent()) continue; 1545 } 1546 1547 Block *src_block = e->from(); 1548 Trace *src_trace = trace(src_block); 1549 bool src_at_tail = src_trace->last_block() == src_block; 1550 1551 Block *targ_block = e->to(); 1552 Trace *targ_trace = trace(targ_block); 1553 bool targ_at_start = targ_trace->first_block() == targ_block; 1554 1555 if (src_trace == targ_trace) { 1556 // This may be a loop, but we can't do much about it. 1557 e->set_state(CFGEdge::interior); 1558 continue; 1559 } 1560 1561 if (fall_thru_only) { 1562 // If the edge links the middle of two traces, we can't do anything. 1563 // Mark the edge and continue. 1564 if (!src_at_tail & !targ_at_start) { 1565 continue; 1566 } 1567 1568 // Don't grow traces along backedges? 1569 if (!BlockLayoutRotateLoops && (targ_block->_rpo <= src_block->_rpo)) { 1570 continue; 1571 } 1572 1573 // If both ends of the edge are available, why didn't we handle it earlier? 1574 assert(src_at_tail ^ targ_at_start, "Should have caught this edge earlier."); 1575 1576 if (targ_at_start) { 1577 // Insert the "targ" trace in the "src" trace if the insertion point 1578 // is a two way branch. 1579 // Better profitability check possible, but may not be worth it. 1580 // Someday, see if the this "fork" has an associated "join"; 1581 // then make a policy on merging this trace at the fork or join. 1582 // For example, other things being equal, it may be better to place this 1583 // trace at the join point if the "src" trace ends in a two-way, but 1584 // the insertion point is one-way. 1585 assert(src_block->num_fall_throughs() == 2, "unexpected diamond"); 1586 e->set_state(CFGEdge::connected); 1587 src_trace->insert_after(src_block, targ_trace); 1588 union_traces(src_trace, targ_trace); 1589 } else if (src_at_tail) { 1590 if (src_trace != trace(_cfg.get_root_block())) { 1591 e->set_state(CFGEdge::connected); 1592 targ_trace->insert_before(targ_block, src_trace); 1593 union_traces(targ_trace, src_trace); 1594 } 1595 } 1596 } else if (e->state() == CFGEdge::open) { 1597 // Append traces, even without a fall-thru connection. 1598 // But leave root entry at the beginning of the block list. 1599 if (targ_trace != trace(_cfg.get_root_block())) { 1600 e->set_state(CFGEdge::connected); 1601 src_trace->append(targ_trace); 1602 union_traces(src_trace, targ_trace); 1603 } 1604 } 1605 } 1606 } 1607 1608 // Order the sequence of the traces in some desirable way, and fixup the 1609 // jumps at the end of each block. 1610 void PhaseBlockLayout::reorder_traces(int count) { 1611 ResourceArea *area = Thread::current()->resource_area(); 1612 Trace ** new_traces = NEW_ARENA_ARRAY(area, Trace *, count); 1613 Block_List worklist; 1614 int new_count = 0; 1615 1616 // Compact the traces. 1617 for (int i = 0; i < count; i++) { 1618 Trace *tr = traces[i]; 1619 if (tr != NULL) { 1620 new_traces[new_count++] = tr; 1621 } 1622 } 1623 1624 // The entry block should be first on the new trace list. 1625 Trace *tr = trace(_cfg.get_root_block()); 1626 assert(tr == new_traces[0], "entry trace misplaced"); 1627 1628 // Sort the new trace list by frequency 1629 qsort(new_traces + 1, new_count - 1, sizeof(new_traces[0]), trace_frequency_order); 1630 1631 // Patch up the successor blocks 1632 _cfg.clear_blocks(); 1633 for (int i = 0; i < new_count; i++) { 1634 Trace *tr = new_traces[i]; 1635 if (tr != NULL) { 1636 tr->fixup_blocks(_cfg); 1637 } 1638 } 1639 } 1640 1641 // Order basic blocks based on frequency 1642 PhaseBlockLayout::PhaseBlockLayout(PhaseCFG &cfg) 1643 : Phase(BlockLayout) 1644 , _cfg(cfg) { 1645 ResourceMark rm; 1646 ResourceArea *area = Thread::current()->resource_area(); 1647 1648 // List of traces 1649 int size = _cfg.number_of_blocks() + 1; 1650 traces = NEW_ARENA_ARRAY(area, Trace *, size); 1651 memset(traces, 0, size*sizeof(Trace*)); 1652 next = NEW_ARENA_ARRAY(area, Block *, size); 1653 memset(next, 0, size*sizeof(Block *)); 1654 prev = NEW_ARENA_ARRAY(area, Block *, size); 1655 memset(prev , 0, size*sizeof(Block *)); 1656 1657 // List of edges 1658 edges = new GrowableArray<CFGEdge*>; 1659 1660 // Mapping block index --> block_trace 1661 uf = new UnionFind(size); 1662 uf->reset(size); 1663 1664 // Find edges and create traces. 1665 find_edges(); 1666 1667 // Grow traces at their ends via most frequent edges. 1668 grow_traces(); 1669 1670 // Merge one trace into another, but only at fall-through points. 1671 // This may make diamonds and other related shapes in a trace. 1672 merge_traces(true); 1673 1674 // Run merge again, allowing two traces to be catenated, even if 1675 // one does not fall through into the other. This appends loosely 1676 // related traces to be near each other. 1677 merge_traces(false); 1678 1679 // Re-order all the remaining traces by frequency 1680 reorder_traces(size); 1681 1682 assert(_cfg.number_of_blocks() >= (uint) (size - 1), "number of blocks can not shrink"); 1683 } 1684 1685 1686 // Edge e completes a loop in a trace. If the target block is head of the 1687 // loop, rotate the loop block so that the loop ends in a conditional branch. 1688 bool Trace::backedge(CFGEdge *e) { 1689 bool loop_rotated = false; 1690 Block *src_block = e->from(); 1691 Block *targ_block = e->to(); 1692 1693 assert(last_block() == src_block, "loop discovery at back branch"); 1694 if (first_block() == targ_block) { 1695 if (BlockLayoutRotateLoops && last_block()->num_fall_throughs() < 2) { 1696 // Find the last block in the trace that has a conditional 1697 // branch. 1698 Block *b; 1699 for (b = last_block(); b != NULL; b = prev(b)) { 1700 if (b->num_fall_throughs() == 2) { 1701 break; 1702 } 1703 } 1704 1705 if (b != last_block() && b != NULL) { 1706 loop_rotated = true; 1707 1708 // Rotate the loop by doing two-part linked-list surgery. 1709 append(first_block()); 1710 break_loop_after(b); 1711 } 1712 } 1713 1714 // Backbranch to the top of a trace 1715 // Scroll forward through the trace from the targ_block. If we find 1716 // a loop head before another loop top, use the the loop head alignment. 1717 for (Block *b = targ_block; b != NULL; b = next(b)) { 1718 if (b->has_loop_alignment()) { 1719 break; 1720 } 1721 if (b->head()->is_Loop()) { 1722 targ_block = b; 1723 break; 1724 } 1725 } 1726 1727 first_block()->set_loop_alignment(targ_block); 1728 1729 } else { 1730 // That loop may already have a loop top (we're reaching it again 1731 // through the backedge of an outer loop) 1732 Block* b = prev(targ_block); 1733 bool has_top = targ_block->head()->is_Loop() && b->has_loop_alignment() && !b->head()->is_Loop(); 1734 if (!has_top) { 1735 // Backbranch into the middle of a trace 1736 targ_block->set_loop_alignment(targ_block); 1737 } 1738 } 1739 1740 return loop_rotated; 1741 } 1742 1743 // push blocks onto the CFG list 1744 // ensure that blocks have the correct two-way branch sense 1745 void Trace::fixup_blocks(PhaseCFG &cfg) { 1746 Block *last = last_block(); 1747 for (Block *b = first_block(); b != NULL; b = next(b)) { 1748 cfg.add_block(b); 1749 if (!b->is_connector()) { 1750 int nfallthru = b->num_fall_throughs(); 1751 if (b != last) { 1752 if (nfallthru == 2) { 1753 // Ensure that the sense of the branch is correct 1754 Block *bnext = next(b); 1755 Block *bs0 = b->non_connector_successor(0); 1756 1757 MachNode *iff = b->get_node(b->number_of_nodes() - 3)->as_Mach(); 1758 ProjNode *proj0 = b->get_node(b->number_of_nodes() - 2)->as_Proj(); 1759 ProjNode *proj1 = b->get_node(b->number_of_nodes() - 1)->as_Proj(); 1760 1761 if (bnext == bs0) { 1762 // Fall-thru case in succs[0], should be in succs[1] 1763 1764 // Flip targets in _succs map 1765 Block *tbs0 = b->_succs[0]; 1766 Block *tbs1 = b->_succs[1]; 1767 b->_succs.map( 0, tbs1 ); 1768 b->_succs.map( 1, tbs0 ); 1769 1770 // Flip projections to match targets 1771 b->map_node(proj1, b->number_of_nodes() - 2); 1772 b->map_node(proj0, b->number_of_nodes() - 1); 1773 } 1774 } 1775 } 1776 } 1777 } 1778 }