block.cpp revision 0:a61af66fc99e
1/* 2 * Copyright 1997-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25// Optimization - Graph Style 26 27#include "incls/_precompiled.incl" 28#include "incls/_block.cpp.incl" 29 30 31//----------------------------------------------------------------------------- 32void Block_Array::grow( uint i ) { 33 assert(i >= Max(), "must be an overflow"); 34 debug_only(_limit = i+1); 35 if( i < _size ) return; 36 if( !_size ) { 37 _size = 1; 38 _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) ); 39 _blocks[0] = NULL; 40 } 41 uint old = _size; 42 while( i >= _size ) _size <<= 1; // Double to fit 43 _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*)); 44 Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) ); 45} 46 47//============================================================================= 48void Block_List::remove(uint i) { 49 assert(i < _cnt, "index out of bounds"); 50 Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*))); 51 pop(); // shrink list by one block 52} 53 54void Block_List::insert(uint i, Block *b) { 55 push(b); // grow list by one block 56 Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*))); 57 _blocks[i] = b; 58} 59 60 61//============================================================================= 62 63uint Block::code_alignment() { 64 // Check for Root block 65 if( _pre_order == 0 ) return CodeEntryAlignment; 66 // Check for Start block 67 if( _pre_order == 1 ) return InteriorEntryAlignment; 68 // Check for loop alignment 69 Node *h = head(); 70 if( h->is_Loop() && h->as_Loop()->is_inner_loop() ) { 71 // Pre- and post-loops have low trip count so do not bother with 72 // NOPs for align loop head. The constants are hidden from tuning 73 // but only because my "divide by 4" heuristic surely gets nearly 74 // all possible gain (a "do not align at all" heuristic has a 75 // chance of getting a really tiny gain). 76 if( h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() || 77 h->as_CountedLoop()->is_post_loop()) ) 78 return (OptoLoopAlignment > 4) ? (OptoLoopAlignment>>2) : 1; 79 // Loops with low backedge frequency should not be aligned. 80 Node *n = h->in(LoopNode::LoopBackControl)->in(0); 81 if( n->is_MachIf() && n->as_MachIf()->_prob < 0.01 ) { 82 return 1; // Loop does not loop, more often than not! 83 } 84 return OptoLoopAlignment; // Otherwise align loop head 85 } 86 return 1; // no particular alignment 87} 88 89//----------------------------------------------------------------------------- 90// Compute the size of first 'inst_cnt' instructions in this block. 91// Return the number of instructions left to compute if the block has 92// less then 'inst_cnt' instructions. 93uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt, 94 PhaseRegAlloc* ra) { 95 uint last_inst = _nodes.size(); 96 for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) { 97 uint inst_size = _nodes[j]->size(ra); 98 if( inst_size > 0 ) { 99 inst_cnt--; 100 uint sz = sum_size + inst_size; 101 if( sz <= (uint)OptoLoopAlignment ) { 102 // Compute size of instructions which fit into fetch buffer only 103 // since all inst_cnt instructions will not fit even if we align them. 104 sum_size = sz; 105 } else { 106 return 0; 107 } 108 } 109 } 110 return inst_cnt; 111} 112 113//----------------------------------------------------------------------------- 114uint Block::find_node( const Node *n ) const { 115 for( uint i = 0; i < _nodes.size(); i++ ) { 116 if( _nodes[i] == n ) 117 return i; 118 } 119 ShouldNotReachHere(); 120 return 0; 121} 122 123// Find and remove n from block list 124void Block::find_remove( const Node *n ) { 125 _nodes.remove(find_node(n)); 126} 127 128//------------------------------is_Empty--------------------------------------- 129// Return empty status of a block. Empty blocks contain only the head, other 130// ideal nodes, and an optional trailing goto. 131int Block::is_Empty() const { 132 133 // Root or start block is not considered empty 134 if (head()->is_Root() || head()->is_Start()) { 135 return not_empty; 136 } 137 138 int success_result = completely_empty; 139 int end_idx = _nodes.size()-1; 140 141 // Check for ending goto 142 if ((end_idx > 0) && (_nodes[end_idx]->is_Goto())) { 143 success_result = empty_with_goto; 144 end_idx--; 145 } 146 147 // Unreachable blocks are considered empty 148 if (num_preds() <= 1) { 149 return success_result; 150 } 151 152 // Ideal nodes are allowable in empty blocks: skip them Only MachNodes 153 // turn directly into code, because only MachNodes have non-trivial 154 // emit() functions. 155 while ((end_idx > 0) && !_nodes[end_idx]->is_Mach()) { 156 end_idx--; 157 } 158 159 // No room for any interesting instructions? 160 if (end_idx == 0) { 161 return success_result; 162 } 163 164 return not_empty; 165} 166 167//------------------------------has_uncommon_code------------------------------ 168// Return true if the block's code implies that it is not likely to be 169// executed infrequently. Check to see if the block ends in a Halt or 170// a low probability call. 171bool Block::has_uncommon_code() const { 172 Node* en = end(); 173 174 if (en->is_Goto()) 175 en = en->in(0); 176 if (en->is_Catch()) 177 en = en->in(0); 178 if (en->is_Proj() && en->in(0)->is_MachCall()) { 179 MachCallNode* call = en->in(0)->as_MachCall(); 180 if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) { 181 // This is true for slow-path stubs like new_{instance,array}, 182 // slow_arraycopy, complete_monitor_locking, uncommon_trap. 183 // The magic number corresponds to the probability of an uncommon_trap, 184 // even though it is a count not a probability. 185 return true; 186 } 187 } 188 189 int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode(); 190 return op == Op_Halt; 191} 192 193//------------------------------is_uncommon------------------------------------ 194// True if block is low enough frequency or guarded by a test which 195// mostly does not go here. 196bool Block::is_uncommon( Block_Array &bbs ) const { 197 // Initial blocks must never be moved, so are never uncommon. 198 if (head()->is_Root() || head()->is_Start()) return false; 199 200 // Check for way-low freq 201 if( _freq < BLOCK_FREQUENCY(0.00001f) ) return true; 202 203 // Look for code shape indicating uncommon_trap or slow path 204 if (has_uncommon_code()) return true; 205 206 const float epsilon = 0.05f; 207 const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon); 208 uint uncommon_preds = 0; 209 uint freq_preds = 0; 210 uint uncommon_for_freq_preds = 0; 211 212 for( uint i=1; i<num_preds(); i++ ) { 213 Block* guard = bbs[pred(i)->_idx]; 214 // Check to see if this block follows its guard 1 time out of 10000 215 // or less. 216 // 217 // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which 218 // we intend to be "uncommon", such as slow-path TLE allocation, 219 // predicted call failure, and uncommon trap triggers. 220 // 221 // Use an epsilon value of 5% to allow for variability in frequency 222 // predictions and floating point calculations. The net effect is 223 // that guard_factor is set to 9500. 224 // 225 // Ignore low-frequency blocks. 226 // The next check is (guard->_freq < 1.e-5 * 9500.). 227 if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) { 228 uncommon_preds++; 229 } else { 230 freq_preds++; 231 if( _freq < guard->_freq * guard_factor ) { 232 uncommon_for_freq_preds++; 233 } 234 } 235 } 236 if( num_preds() > 1 && 237 // The block is uncommon if all preds are uncommon or 238 (uncommon_preds == (num_preds()-1) || 239 // it is uncommon for all frequent preds. 240 uncommon_for_freq_preds == freq_preds) ) { 241 return true; 242 } 243 return false; 244} 245 246//------------------------------dump------------------------------------------- 247#ifndef PRODUCT 248void Block::dump_bidx(const Block* orig) const { 249 if (_pre_order) tty->print("B%d",_pre_order); 250 else tty->print("N%d", head()->_idx); 251 252 if (Verbose && orig != this) { 253 // Dump the original block's idx 254 tty->print(" ("); 255 orig->dump_bidx(orig); 256 tty->print(")"); 257 } 258} 259 260void Block::dump_pred(const Block_Array *bbs, Block* orig) const { 261 if (is_connector()) { 262 for (uint i=1; i<num_preds(); i++) { 263 Block *p = ((*bbs)[pred(i)->_idx]); 264 p->dump_pred(bbs, orig); 265 } 266 } else { 267 dump_bidx(orig); 268 tty->print(" "); 269 } 270} 271 272void Block::dump_head( const Block_Array *bbs ) const { 273 // Print the basic block 274 dump_bidx(this); 275 tty->print(": #\t"); 276 277 // Print the incoming CFG edges and the outgoing CFG edges 278 for( uint i=0; i<_num_succs; i++ ) { 279 non_connector_successor(i)->dump_bidx(_succs[i]); 280 tty->print(" "); 281 } 282 tty->print("<- "); 283 if( head()->is_block_start() ) { 284 for (uint i=1; i<num_preds(); i++) { 285 Node *s = pred(i); 286 if (bbs) { 287 Block *p = (*bbs)[s->_idx]; 288 p->dump_pred(bbs, p); 289 } else { 290 while (!s->is_block_start()) 291 s = s->in(0); 292 tty->print("N%d ", s->_idx ); 293 } 294 } 295 } else 296 tty->print("BLOCK HEAD IS JUNK "); 297 298 // Print loop, if any 299 const Block *bhead = this; // Head of self-loop 300 Node *bh = bhead->head(); 301 if( bbs && bh->is_Loop() && !head()->is_Root() ) { 302 LoopNode *loop = bh->as_Loop(); 303 const Block *bx = (*bbs)[loop->in(LoopNode::LoopBackControl)->_idx]; 304 while (bx->is_connector()) { 305 bx = (*bbs)[bx->pred(1)->_idx]; 306 } 307 tty->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order); 308 // Dump any loop-specific bits, especially for CountedLoops. 309 loop->dump_spec(tty); 310 } 311 tty->print(" Freq: %g",_freq); 312 if( Verbose || WizardMode ) { 313 tty->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth); 314 tty->print(" RegPressure: %d",_reg_pressure); 315 tty->print(" IHRP Index: %d",_ihrp_index); 316 tty->print(" FRegPressure: %d",_freg_pressure); 317 tty->print(" FHRP Index: %d",_fhrp_index); 318 } 319 tty->print_cr(""); 320} 321 322void Block::dump() const { dump(0); } 323 324void Block::dump( const Block_Array *bbs ) const { 325 dump_head(bbs); 326 uint cnt = _nodes.size(); 327 for( uint i=0; i<cnt; i++ ) 328 _nodes[i]->dump(); 329 tty->print("\n"); 330} 331#endif 332 333//============================================================================= 334//------------------------------PhaseCFG--------------------------------------- 335PhaseCFG::PhaseCFG( Arena *a, RootNode *r, Matcher &m ) : 336 Phase(CFG), 337 _bbs(a), 338 _root(r) 339#ifndef PRODUCT 340 , _trace_opto_pipelining(TraceOptoPipelining || C->method_has_option("TraceOptoPipelining")) 341#endif 342{ 343 ResourceMark rm; 344 // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode, 345 // then Match it into a machine-specific Node. Then clone the machine 346 // Node on demand. 347 Node *x = new (C, 1) GotoNode(NULL); 348 x->init_req(0, x); 349 _goto = m.match_tree(x); 350 assert(_goto != NULL, ""); 351 _goto->set_req(0,_goto); 352 353 // Build the CFG in Reverse Post Order 354 _num_blocks = build_cfg(); 355 _broot = _bbs[_root->_idx]; 356} 357 358//------------------------------build_cfg-------------------------------------- 359// Build a proper looking CFG. Make every block begin with either a StartNode 360// or a RegionNode. Make every block end with either a Goto, If or Return. 361// The RootNode both starts and ends it's own block. Do this with a recursive 362// backwards walk over the control edges. 363uint PhaseCFG::build_cfg() { 364 Arena *a = Thread::current()->resource_area(); 365 VectorSet visited(a); 366 367 // Allocate stack with enough space to avoid frequent realloc 368 Node_Stack nstack(a, C->unique() >> 1); 369 nstack.push(_root, 0); 370 uint sum = 0; // Counter for blocks 371 372 while (nstack.is_nonempty()) { 373 // node and in's index from stack's top 374 // 'np' is _root (see above) or RegionNode, StartNode: we push on stack 375 // only nodes which point to the start of basic block (see below). 376 Node *np = nstack.node(); 377 // idx > 0, except for the first node (_root) pushed on stack 378 // at the beginning when idx == 0. 379 // We will use the condition (idx == 0) later to end the build. 380 uint idx = nstack.index(); 381 Node *proj = np->in(idx); 382 const Node *x = proj->is_block_proj(); 383 // Does the block end with a proper block-ending Node? One of Return, 384 // If or Goto? (This check should be done for visited nodes also). 385 if (x == NULL) { // Does not end right... 386 Node *g = _goto->clone(); // Force it to end in a Goto 387 g->set_req(0, proj); 388 np->set_req(idx, g); 389 x = proj = g; 390 } 391 if (!visited.test_set(x->_idx)) { // Visit this block once 392 // Skip any control-pinned middle'in stuff 393 Node *p = proj; 394 do { 395 proj = p; // Update pointer to last Control 396 p = p->in(0); // Move control forward 397 } while( !p->is_block_proj() && 398 !p->is_block_start() ); 399 // Make the block begin with one of Region or StartNode. 400 if( !p->is_block_start() ) { 401 RegionNode *r = new (C, 2) RegionNode( 2 ); 402 r->init_req(1, p); // Insert RegionNode in the way 403 proj->set_req(0, r); // Insert RegionNode in the way 404 p = r; 405 } 406 // 'p' now points to the start of this basic block 407 408 // Put self in array of basic blocks 409 Block *bb = new (_bbs._arena) Block(_bbs._arena,p); 410 _bbs.map(p->_idx,bb); 411 _bbs.map(x->_idx,bb); 412 if( x != p ) // Only for root is x == p 413 bb->_nodes.push((Node*)x); 414 415 // Now handle predecessors 416 ++sum; // Count 1 for self block 417 uint cnt = bb->num_preds(); 418 for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors 419 Node *prevproj = p->in(i); // Get prior input 420 assert( !prevproj->is_Con(), "dead input not removed" ); 421 // Check to see if p->in(i) is a "control-dependent" CFG edge - 422 // i.e., it splits at the source (via an IF or SWITCH) and merges 423 // at the destination (via a many-input Region). 424 // This breaks critical edges. The RegionNode to start the block 425 // will be added when <p,i> is pulled off the node stack 426 if ( cnt > 2 ) { // Merging many things? 427 assert( prevproj== bb->pred(i),""); 428 if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge? 429 // Force a block on the control-dependent edge 430 Node *g = _goto->clone(); // Force it to end in a Goto 431 g->set_req(0,prevproj); 432 p->set_req(i,g); 433 } 434 } 435 nstack.push(p, i); // 'p' is RegionNode or StartNode 436 } 437 } else { // Post-processing visited nodes 438 nstack.pop(); // remove node from stack 439 // Check if it the fist node pushed on stack at the beginning. 440 if (idx == 0) break; // end of the build 441 // Find predecessor basic block 442 Block *pb = _bbs[x->_idx]; 443 // Insert into nodes array, if not already there 444 if( !_bbs.lookup(proj->_idx) ) { 445 assert( x != proj, "" ); 446 // Map basic block of projection 447 _bbs.map(proj->_idx,pb); 448 pb->_nodes.push(proj); 449 } 450 // Insert self as a child of my predecessor block 451 pb->_succs.map(pb->_num_succs++, _bbs[np->_idx]); 452 assert( pb->_nodes[ pb->_nodes.size() - pb->_num_succs ]->is_block_proj(), 453 "too many control users, not a CFG?" ); 454 } 455 } 456 // Return number of basic blocks for all children and self 457 return sum; 458} 459 460//------------------------------insert_goto_at--------------------------------- 461// Inserts a goto & corresponding basic block between 462// block[block_no] and its succ_no'th successor block 463void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) { 464 // get block with block_no 465 assert(block_no < _num_blocks, "illegal block number"); 466 Block* in = _blocks[block_no]; 467 // get successor block succ_no 468 assert(succ_no < in->_num_succs, "illegal successor number"); 469 Block* out = in->_succs[succ_no]; 470 // get ProjNode corresponding to the succ_no'th successor of the in block 471 ProjNode* proj = in->_nodes[in->_nodes.size() - in->_num_succs + succ_no]->as_Proj(); 472 // create region for basic block 473 RegionNode* region = new (C, 2) RegionNode(2); 474 region->init_req(1, proj); 475 // setup corresponding basic block 476 Block* block = new (_bbs._arena) Block(_bbs._arena, region); 477 _bbs.map(region->_idx, block); 478 C->regalloc()->set_bad(region->_idx); 479 // add a goto node 480 Node* gto = _goto->clone(); // get a new goto node 481 gto->set_req(0, region); 482 // add it to the basic block 483 block->_nodes.push(gto); 484 _bbs.map(gto->_idx, block); 485 C->regalloc()->set_bad(gto->_idx); 486 // hook up successor block 487 block->_succs.map(block->_num_succs++, out); 488 // remap successor's predecessors if necessary 489 for (uint i = 1; i < out->num_preds(); i++) { 490 if (out->pred(i) == proj) out->head()->set_req(i, gto); 491 } 492 // remap predecessor's successor to new block 493 in->_succs.map(succ_no, block); 494 // add new basic block to basic block list 495 _blocks.insert(block_no + 1, block); 496 _num_blocks++; 497} 498 499//------------------------------no_flip_branch--------------------------------- 500// Does this block end in a multiway branch that cannot have the default case 501// flipped for another case? 502static bool no_flip_branch( Block *b ) { 503 int branch_idx = b->_nodes.size() - b->_num_succs-1; 504 if( branch_idx < 1 ) return false; 505 Node *bra = b->_nodes[branch_idx]; 506 if( bra->is_Catch() ) return true; 507 if( bra->is_Mach() ) { 508 if( bra->is_MachNullCheck() ) return true; 509 int iop = bra->as_Mach()->ideal_Opcode(); 510 if( iop == Op_FastLock || iop == Op_FastUnlock ) 511 return true; 512 } 513 return false; 514} 515 516//------------------------------convert_NeverBranch_to_Goto-------------------- 517// Check for NeverBranch at block end. This needs to become a GOTO to the 518// true target. NeverBranch are treated as a conditional branch that always 519// goes the same direction for most of the optimizer and are used to give a 520// fake exit path to infinite loops. At this late stage they need to turn 521// into Goto's so that when you enter the infinite loop you indeed hang. 522void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) { 523 // Find true target 524 int end_idx = b->end_idx(); 525 int idx = b->_nodes[end_idx+1]->as_Proj()->_con; 526 Block *succ = b->_succs[idx]; 527 Node* gto = _goto->clone(); // get a new goto node 528 gto->set_req(0, b->head()); 529 Node *bp = b->_nodes[end_idx]; 530 b->_nodes.map(end_idx,gto); // Slam over NeverBranch 531 _bbs.map(gto->_idx, b); 532 C->regalloc()->set_bad(gto->_idx); 533 b->_nodes.pop(); // Yank projections 534 b->_nodes.pop(); // Yank projections 535 b->_succs.map(0,succ); // Map only successor 536 b->_num_succs = 1; 537 // remap successor's predecessors if necessary 538 uint j; 539 for( j = 1; j < succ->num_preds(); j++) 540 if( succ->pred(j)->in(0) == bp ) 541 succ->head()->set_req(j, gto); 542 // Kill alternate exit path 543 Block *dead = b->_succs[1-idx]; 544 for( j = 1; j < dead->num_preds(); j++) 545 if( dead->pred(j)->in(0) == bp ) 546 break; 547 // Scan through block, yanking dead path from 548 // all regions and phis. 549 dead->head()->del_req(j); 550 for( int k = 1; dead->_nodes[k]->is_Phi(); k++ ) 551 dead->_nodes[k]->del_req(j); 552} 553 554//------------------------------MoveToNext------------------------------------- 555// Helper function to move block bx to the slot following b_index. Return 556// true if the move is successful, otherwise false 557bool PhaseCFG::MoveToNext(Block* bx, uint b_index) { 558 if (bx == NULL) return false; 559 560 // Return false if bx is already scheduled. 561 uint bx_index = bx->_pre_order; 562 if ((bx_index <= b_index) && (_blocks[bx_index] == bx)) { 563 return false; 564 } 565 566 // Find the current index of block bx on the block list 567 bx_index = b_index + 1; 568 while( bx_index < _num_blocks && _blocks[bx_index] != bx ) bx_index++; 569 assert(_blocks[bx_index] == bx, "block not found"); 570 571 // If the previous block conditionally falls into bx, return false, 572 // because moving bx will create an extra jump. 573 for(uint k = 1; k < bx->num_preds(); k++ ) { 574 Block* pred = _bbs[bx->pred(k)->_idx]; 575 if (pred == _blocks[bx_index-1]) { 576 if (pred->_num_succs != 1) { 577 return false; 578 } 579 } 580 } 581 582 // Reinsert bx just past block 'b' 583 _blocks.remove(bx_index); 584 _blocks.insert(b_index + 1, bx); 585 return true; 586} 587 588//------------------------------MoveToEnd-------------------------------------- 589// Move empty and uncommon blocks to the end. 590void PhaseCFG::MoveToEnd(Block *b, uint i) { 591 int e = b->is_Empty(); 592 if (e != Block::not_empty) { 593 if (e == Block::empty_with_goto) { 594 // Remove the goto, but leave the block. 595 b->_nodes.pop(); 596 } 597 // Mark this block as a connector block, which will cause it to be 598 // ignored in certain functions such as non_connector_successor(). 599 b->set_connector(); 600 } 601 // Move the empty block to the end, and don't recheck. 602 _blocks.remove(i); 603 _blocks.push(b); 604} 605 606//------------------------------RemoveEmpty------------------------------------ 607// Remove empty basic blocks and useless branches. 608void PhaseCFG::RemoveEmpty() { 609 // Move uncommon blocks to the end 610 uint last = _num_blocks; 611 uint i; 612 assert( _blocks[0] == _broot, "" ); 613 for( i = 1; i < last; i++ ) { 614 Block *b = _blocks[i]; 615 616 // Check for NeverBranch at block end. This needs to become a GOTO to the 617 // true target. NeverBranch are treated as a conditional branch that 618 // always goes the same direction for most of the optimizer and are used 619 // to give a fake exit path to infinite loops. At this late stage they 620 // need to turn into Goto's so that when you enter the infinite loop you 621 // indeed hang. 622 if( b->_nodes[b->end_idx()]->Opcode() == Op_NeverBranch ) 623 convert_NeverBranch_to_Goto(b); 624 625 // Look for uncommon blocks and move to end. 626 if( b->is_uncommon(_bbs) ) { 627 MoveToEnd(b, i); 628 last--; // No longer check for being uncommon! 629 if( no_flip_branch(b) ) { // Fall-thru case must follow? 630 b = _blocks[i]; // Find the fall-thru block 631 MoveToEnd(b, i); 632 last--; 633 } 634 i--; // backup block counter post-increment 635 } 636 } 637 638 // Remove empty blocks 639 uint j1; 640 last = _num_blocks; 641 for( i=0; i < last; i++ ) { 642 Block *b = _blocks[i]; 643 if (i > 0) { 644 if (b->is_Empty() != Block::not_empty) { 645 MoveToEnd(b, i); 646 last--; 647 i--; 648 } 649 } 650 } // End of for all blocks 651 652 // Fixup final control flow for the blocks. Remove jump-to-next 653 // block. If neither arm of a IF follows the conditional branch, we 654 // have to add a second jump after the conditional. We place the 655 // TRUE branch target in succs[0] for both GOTOs and IFs. 656 for( i=0; i < _num_blocks; i++ ) { 657 Block *b = _blocks[i]; 658 b->_pre_order = i; // turn pre-order into block-index 659 660 // Connector blocks need no further processing. 661 if (b->is_connector()) { 662 assert((i+1) == _num_blocks || _blocks[i+1]->is_connector(), 663 "All connector blocks should sink to the end"); 664 continue; 665 } 666 assert(b->is_Empty() != Block::completely_empty, 667 "Empty blocks should be connectors"); 668 669 Block *bnext = (i < _num_blocks-1) ? _blocks[i+1] : NULL; 670 Block *bs0 = b->non_connector_successor(0); 671 672 // Check for multi-way branches where I cannot negate the test to 673 // exchange the true and false targets. 674 if( no_flip_branch( b ) ) { 675 // Find fall through case - if must fall into its target 676 int branch_idx = b->_nodes.size() - b->_num_succs; 677 for (uint j2 = 0; j2 < b->_num_succs; j2++) { 678 const ProjNode* p = b->_nodes[branch_idx + j2]->as_Proj(); 679 if (p->_con == 0) { 680 // successor j2 is fall through case 681 if (b->non_connector_successor(j2) != bnext) { 682 // but it is not the next block => insert a goto 683 insert_goto_at(i, j2); 684 } 685 // Put taken branch in slot 0 686 if( j2 == 0 && b->_num_succs == 2) { 687 // Flip targets in succs map 688 Block *tbs0 = b->_succs[0]; 689 Block *tbs1 = b->_succs[1]; 690 b->_succs.map( 0, tbs1 ); 691 b->_succs.map( 1, tbs0 ); 692 } 693 break; 694 } 695 } 696 // Remove all CatchProjs 697 for (j1 = 0; j1 < b->_num_succs; j1++) b->_nodes.pop(); 698 699 } else if (b->_num_succs == 1) { 700 // Block ends in a Goto? 701 if (bnext == bs0) { 702 // We fall into next block; remove the Goto 703 b->_nodes.pop(); 704 } 705 706 } else if( b->_num_succs == 2 ) { // Block ends in a If? 707 // Get opcode of 1st projection (matches _succs[0]) 708 // Note: Since this basic block has 2 exits, the last 2 nodes must 709 // be projections (in any order), the 3rd last node must be 710 // the IfNode (we have excluded other 2-way exits such as 711 // CatchNodes already). 712 MachNode *iff = b->_nodes[b->_nodes.size()-3]->as_Mach(); 713 ProjNode *proj0 = b->_nodes[b->_nodes.size()-2]->as_Proj(); 714 ProjNode *proj1 = b->_nodes[b->_nodes.size()-1]->as_Proj(); 715 716 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1]. 717 assert(proj0->raw_out(0) == b->_succs[0]->head(), "Mismatch successor 0"); 718 assert(proj1->raw_out(0) == b->_succs[1]->head(), "Mismatch successor 1"); 719 720 Block *bs1 = b->non_connector_successor(1); 721 722 // Check for neither successor block following the current 723 // block ending in a conditional. If so, move one of the 724 // successors after the current one, provided that the 725 // successor was previously unscheduled, but moveable 726 // (i.e., all paths to it involve a branch). 727 if( bnext != bs0 && bnext != bs1 ) { 728 729 // Choose the more common successor based on the probability 730 // of the conditional branch. 731 Block *bx = bs0; 732 Block *by = bs1; 733 734 // _prob is the probability of taking the true path. Make 735 // p the probability of taking successor #1. 736 float p = iff->as_MachIf()->_prob; 737 if( proj0->Opcode() == Op_IfTrue ) { 738 p = 1.0 - p; 739 } 740 741 // Prefer successor #1 if p > 0.5 742 if (p > PROB_FAIR) { 743 bx = bs1; 744 by = bs0; 745 } 746 747 // Attempt the more common successor first 748 if (MoveToNext(bx, i)) { 749 bnext = bx; 750 } else if (MoveToNext(by, i)) { 751 bnext = by; 752 } 753 } 754 755 // Check for conditional branching the wrong way. Negate 756 // conditional, if needed, so it falls into the following block 757 // and branches to the not-following block. 758 759 // Check for the next block being in succs[0]. We are going to branch 760 // to succs[0], so we want the fall-thru case as the next block in 761 // succs[1]. 762 if (bnext == bs0) { 763 // Fall-thru case in succs[0], so flip targets in succs map 764 Block *tbs0 = b->_succs[0]; 765 Block *tbs1 = b->_succs[1]; 766 b->_succs.map( 0, tbs1 ); 767 b->_succs.map( 1, tbs0 ); 768 // Flip projection for each target 769 { ProjNode *tmp = proj0; proj0 = proj1; proj1 = tmp; } 770 771 } else if( bnext == bs1 ) { // Fall-thru is already in succs[1] 772 773 } else { // Else need a double-branch 774 775 // The existing conditional branch need not change. 776 // Add a unconditional branch to the false target. 777 // Alas, it must appear in its own block and adding a 778 // block this late in the game is complicated. Sigh. 779 insert_goto_at(i, 1); 780 } 781 782 // Make sure we TRUE branch to the target 783 if( proj0->Opcode() == Op_IfFalse ) 784 iff->negate(); 785 786 b->_nodes.pop(); // Remove IfFalse & IfTrue projections 787 b->_nodes.pop(); 788 789 } else { 790 // Multi-exit block, e.g. a switch statement 791 // But we don't need to do anything here 792 } 793 794 } // End of for all blocks 795 796} 797 798 799//------------------------------dump------------------------------------------- 800#ifndef PRODUCT 801void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const { 802 const Node *x = end->is_block_proj(); 803 assert( x, "not a CFG" ); 804 805 // Do not visit this block again 806 if( visited.test_set(x->_idx) ) return; 807 808 // Skip through this block 809 const Node *p = x; 810 do { 811 p = p->in(0); // Move control forward 812 assert( !p->is_block_proj() || p->is_Root(), "not a CFG" ); 813 } while( !p->is_block_start() ); 814 815 // Recursively visit 816 for( uint i=1; i<p->req(); i++ ) 817 _dump_cfg(p->in(i),visited); 818 819 // Dump the block 820 _bbs[p->_idx]->dump(&_bbs); 821} 822 823void PhaseCFG::dump( ) const { 824 tty->print("\n--- CFG --- %d BBs\n",_num_blocks); 825 if( _blocks.size() ) { // Did we do basic-block layout? 826 for( uint i=0; i<_num_blocks; i++ ) 827 _blocks[i]->dump(&_bbs); 828 } else { // Else do it with a DFS 829 VectorSet visited(_bbs._arena); 830 _dump_cfg(_root,visited); 831 } 832} 833 834void PhaseCFG::dump_headers() { 835 for( uint i = 0; i < _num_blocks; i++ ) { 836 if( _blocks[i] == NULL ) continue; 837 _blocks[i]->dump_head(&_bbs); 838 } 839} 840 841void PhaseCFG::verify( ) const { 842 // Verify sane CFG 843 for( uint i = 0; i < _num_blocks; i++ ) { 844 Block *b = _blocks[i]; 845 uint cnt = b->_nodes.size(); 846 uint j; 847 for( j = 0; j < cnt; j++ ) { 848 Node *n = b->_nodes[j]; 849 assert( _bbs[n->_idx] == b, "" ); 850 if( j >= 1 && n->is_Mach() && 851 n->as_Mach()->ideal_Opcode() == Op_CreateEx ) { 852 assert( j == 1 || b->_nodes[j-1]->is_Phi(), 853 "CreateEx must be first instruction in block" ); 854 } 855 for( uint k = 0; k < n->req(); k++ ) { 856 Node *use = n->in(k); 857 if( use && use != n ) { 858 assert( _bbs[use->_idx] || use->is_Con(), 859 "must have block; constants for debug info ok" ); 860 } 861 } 862 } 863 864 j = b->end_idx(); 865 Node *bp = (Node*)b->_nodes[b->_nodes.size()-1]->is_block_proj(); 866 assert( bp, "last instruction must be a block proj" ); 867 assert( bp == b->_nodes[j], "wrong number of successors for this block" ); 868 if( bp->is_Catch() ) { 869 while( b->_nodes[--j]->Opcode() == Op_MachProj ) ; 870 assert( b->_nodes[j]->is_Call(), "CatchProj must follow call" ); 871 } 872 else if( bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If ) { 873 assert( b->_num_succs == 2, "Conditional branch must have two targets"); 874 } 875 } 876} 877#endif 878 879//============================================================================= 880//------------------------------UnionFind-------------------------------------- 881UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) { 882 Copy::zero_to_bytes( _indices, sizeof(uint)*max ); 883} 884 885void UnionFind::extend( uint from_idx, uint to_idx ) { 886 _nesting.check(); 887 if( from_idx >= _max ) { 888 uint size = 16; 889 while( size <= from_idx ) size <<=1; 890 _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size ); 891 _max = size; 892 } 893 while( _cnt <= from_idx ) _indices[_cnt++] = 0; 894 _indices[from_idx] = to_idx; 895} 896 897void UnionFind::reset( uint max ) { 898 assert( max <= max_uint, "Must fit within uint" ); 899 // Force the Union-Find mapping to be at least this large 900 extend(max,0); 901 // Initialize to be the ID mapping. 902 for( uint i=0; i<_max; i++ ) map(i,i); 903} 904 905//------------------------------Find_compress---------------------------------- 906// Straight out of Tarjan's union-find algorithm 907uint UnionFind::Find_compress( uint idx ) { 908 uint cur = idx; 909 uint next = lookup(cur); 910 while( next != cur ) { // Scan chain of equivalences 911 assert( next < cur, "always union smaller" ); 912 cur = next; // until find a fixed-point 913 next = lookup(cur); 914 } 915 // Core of union-find algorithm: update chain of 916 // equivalences to be equal to the root. 917 while( idx != next ) { 918 uint tmp = lookup(idx); 919 map(idx, next); 920 idx = tmp; 921 } 922 return idx; 923} 924 925//------------------------------Find_const------------------------------------- 926// Like Find above, but no path compress, so bad asymptotic behavior 927uint UnionFind::Find_const( uint idx ) const { 928 if( idx == 0 ) return idx; // Ignore the zero idx 929 // Off the end? This can happen during debugging dumps 930 // when data structures have not finished being updated. 931 if( idx >= _max ) return idx; 932 uint next = lookup(idx); 933 while( next != idx ) { // Scan chain of equivalences 934 assert( next < idx, "always union smaller" ); 935 idx = next; // until find a fixed-point 936 next = lookup(idx); 937 } 938 return next; 939} 940 941//------------------------------Union------------------------------------------ 942// union 2 sets together. 943void UnionFind::Union( uint idx1, uint idx2 ) { 944 uint src = Find(idx1); 945 uint dst = Find(idx2); 946 assert( src, "" ); 947 assert( dst, "" ); 948 assert( src < _max, "oob" ); 949 assert( dst < _max, "oob" ); 950 assert( src < dst, "always union smaller" ); 951 map(dst,src); 952} 953