buildOopMap.cpp revision 1472:c18cbe5936b8
1/* 2 * Copyright (c) 2002, 2009, 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 "incls/_precompiled.incl" 26#include "incls/_buildOopMap.cpp.incl" 27 28// The functions in this file builds OopMaps after all scheduling is done. 29// 30// OopMaps contain a list of all registers and stack-slots containing oops (so 31// they can be updated by GC). OopMaps also contain a list of derived-pointer 32// base-pointer pairs. When the base is moved, the derived pointer moves to 33// follow it. Finally, any registers holding callee-save values are also 34// recorded. These might contain oops, but only the caller knows. 35// 36// BuildOopMaps implements a simple forward reaching-defs solution. At each 37// GC point we'll have the reaching-def Nodes. If the reaching Nodes are 38// typed as pointers (no offset), then they are oops. Pointers+offsets are 39// derived pointers, and bases can be found from them. Finally, we'll also 40// track reaching callee-save values. Note that a copy of a callee-save value 41// "kills" it's source, so that only 1 copy of a callee-save value is alive at 42// a time. 43// 44// We run a simple bitvector liveness pass to help trim out dead oops. Due to 45// irreducible loops, we can have a reaching def of an oop that only reaches 46// along one path and no way to know if it's valid or not on the other path. 47// The bitvectors are quite dense and the liveness pass is fast. 48// 49// At GC points, we consult this information to build OopMaps. All reaching 50// defs typed as oops are added to the OopMap. Only 1 instance of a 51// callee-save register can be recorded. For derived pointers, we'll have to 52// find and record the register holding the base. 53// 54// The reaching def's is a simple 1-pass worklist approach. I tried a clever 55// breadth-first approach but it was worse (showed O(n^2) in the 56// pick-next-block code). 57// 58// The relevant data is kept in a struct of arrays (it could just as well be 59// an array of structs, but the struct-of-arrays is generally a little more 60// efficient). The arrays are indexed by register number (including 61// stack-slots as registers) and so is bounded by 200 to 300 elements in 62// practice. One array will map to a reaching def Node (or NULL for 63// conflict/dead). The other array will map to a callee-saved register or 64// OptoReg::Bad for not-callee-saved. 65 66 67//------------------------------OopFlow---------------------------------------- 68// Structure to pass around 69struct OopFlow : public ResourceObj { 70 short *_callees; // Array mapping register to callee-saved 71 Node **_defs; // array mapping register to reaching def 72 // or NULL if dead/conflict 73 // OopFlow structs, when not being actively modified, describe the _end_ of 74 // this block. 75 Block *_b; // Block for this struct 76 OopFlow *_next; // Next free OopFlow 77 // or NULL if dead/conflict 78 Compile* C; 79 80 OopFlow( short *callees, Node **defs, Compile* c ) : _callees(callees), _defs(defs), 81 _b(NULL), _next(NULL), C(c) { } 82 83 // Given reaching-defs for this block start, compute it for this block end 84 void compute_reach( PhaseRegAlloc *regalloc, int max_reg, Dict *safehash ); 85 86 // Merge these two OopFlows into the 'this' pointer. 87 void merge( OopFlow *flow, int max_reg ); 88 89 // Copy a 'flow' over an existing flow 90 void clone( OopFlow *flow, int max_size); 91 92 // Make a new OopFlow from scratch 93 static OopFlow *make( Arena *A, int max_size, Compile* C ); 94 95 // Build an oopmap from the current flow info 96 OopMap *build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, int* live ); 97}; 98 99//------------------------------compute_reach---------------------------------- 100// Given reaching-defs for this block start, compute it for this block end 101void OopFlow::compute_reach( PhaseRegAlloc *regalloc, int max_reg, Dict *safehash ) { 102 103 for( uint i=0; i<_b->_nodes.size(); i++ ) { 104 Node *n = _b->_nodes[i]; 105 106 if( n->jvms() ) { // Build an OopMap here? 107 JVMState *jvms = n->jvms(); 108 // no map needed for leaf calls 109 if( n->is_MachSafePoint() && !n->is_MachCallLeaf() ) { 110 int *live = (int*) (*safehash)[n]; 111 assert( live, "must find live" ); 112 n->as_MachSafePoint()->set_oop_map( build_oop_map(n,max_reg,regalloc, live) ); 113 } 114 } 115 116 // Assign new reaching def's. 117 // Note that I padded the _defs and _callees arrays so it's legal 118 // to index at _defs[OptoReg::Bad]. 119 OptoReg::Name first = regalloc->get_reg_first(n); 120 OptoReg::Name second = regalloc->get_reg_second(n); 121 _defs[first] = n; 122 _defs[second] = n; 123 124 // Pass callee-save info around copies 125 int idx = n->is_Copy(); 126 if( idx ) { // Copies move callee-save info 127 OptoReg::Name old_first = regalloc->get_reg_first(n->in(idx)); 128 OptoReg::Name old_second = regalloc->get_reg_second(n->in(idx)); 129 int tmp_first = _callees[old_first]; 130 int tmp_second = _callees[old_second]; 131 _callees[old_first] = OptoReg::Bad; // callee-save is moved, dead in old location 132 _callees[old_second] = OptoReg::Bad; 133 _callees[first] = tmp_first; 134 _callees[second] = tmp_second; 135 } else if( n->is_Phi() ) { // Phis do not mod callee-saves 136 assert( _callees[first] == _callees[regalloc->get_reg_first(n->in(1))], "" ); 137 assert( _callees[second] == _callees[regalloc->get_reg_second(n->in(1))], "" ); 138 assert( _callees[first] == _callees[regalloc->get_reg_first(n->in(n->req()-1))], "" ); 139 assert( _callees[second] == _callees[regalloc->get_reg_second(n->in(n->req()-1))], "" ); 140 } else { 141 _callees[first] = OptoReg::Bad; // No longer holding a callee-save value 142 _callees[second] = OptoReg::Bad; 143 144 // Find base case for callee saves 145 if( n->is_Proj() && n->in(0)->is_Start() ) { 146 if( OptoReg::is_reg(first) && 147 regalloc->_matcher.is_save_on_entry(first) ) 148 _callees[first] = first; 149 if( OptoReg::is_reg(second) && 150 regalloc->_matcher.is_save_on_entry(second) ) 151 _callees[second] = second; 152 } 153 } 154 } 155} 156 157//------------------------------merge------------------------------------------ 158// Merge the given flow into the 'this' flow 159void OopFlow::merge( OopFlow *flow, int max_reg ) { 160 assert( _b == NULL, "merging into a happy flow" ); 161 assert( flow->_b, "this flow is still alive" ); 162 assert( flow != this, "no self flow" ); 163 164 // Do the merge. If there are any differences, drop to 'bottom' which 165 // is OptoReg::Bad or NULL depending. 166 for( int i=0; i<max_reg; i++ ) { 167 // Merge the callee-save's 168 if( _callees[i] != flow->_callees[i] ) 169 _callees[i] = OptoReg::Bad; 170 // Merge the reaching defs 171 if( _defs[i] != flow->_defs[i] ) 172 _defs[i] = NULL; 173 } 174 175} 176 177//------------------------------clone------------------------------------------ 178void OopFlow::clone( OopFlow *flow, int max_size ) { 179 _b = flow->_b; 180 memcpy( _callees, flow->_callees, sizeof(short)*max_size); 181 memcpy( _defs , flow->_defs , sizeof(Node*)*max_size); 182} 183 184//------------------------------make------------------------------------------- 185OopFlow *OopFlow::make( Arena *A, int max_size, Compile* C ) { 186 short *callees = NEW_ARENA_ARRAY(A,short,max_size+1); 187 Node **defs = NEW_ARENA_ARRAY(A,Node*,max_size+1); 188 debug_only( memset(defs,0,(max_size+1)*sizeof(Node*)) ); 189 OopFlow *flow = new (A) OopFlow(callees+1, defs+1, C); 190 assert( &flow->_callees[OptoReg::Bad] == callees, "Ok to index at OptoReg::Bad" ); 191 assert( &flow->_defs [OptoReg::Bad] == defs , "Ok to index at OptoReg::Bad" ); 192 return flow; 193} 194 195//------------------------------bit twiddlers---------------------------------- 196static int get_live_bit( int *live, int reg ) { 197 return live[reg>>LogBitsPerInt] & (1<<(reg&(BitsPerInt-1))); } 198static void set_live_bit( int *live, int reg ) { 199 live[reg>>LogBitsPerInt] |= (1<<(reg&(BitsPerInt-1))); } 200static void clr_live_bit( int *live, int reg ) { 201 live[reg>>LogBitsPerInt] &= ~(1<<(reg&(BitsPerInt-1))); } 202 203//------------------------------build_oop_map---------------------------------- 204// Build an oopmap from the current flow info 205OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, int* live ) { 206 int framesize = regalloc->_framesize; 207 int max_inarg_slot = OptoReg::reg2stack(regalloc->_matcher._new_SP); 208 debug_only( char *dup_check = NEW_RESOURCE_ARRAY(char,OptoReg::stack0()); 209 memset(dup_check,0,OptoReg::stack0()) ); 210 211 OopMap *omap = new OopMap( framesize, max_inarg_slot ); 212 MachCallNode *mcall = n->is_MachCall() ? n->as_MachCall() : NULL; 213 JVMState* jvms = n->jvms(); 214 215 // For all registers do... 216 for( int reg=0; reg<max_reg; reg++ ) { 217 if( get_live_bit(live,reg) == 0 ) 218 continue; // Ignore if not live 219 220 // %%% C2 can use 2 OptoRegs when the physical register is only one 64bit 221 // register in that case we'll get an non-concrete register for the second 222 // half. We only need to tell the map the register once! 223 // 224 // However for the moment we disable this change and leave things as they 225 // were. 226 227 VMReg r = OptoReg::as_VMReg(OptoReg::Name(reg), framesize, max_inarg_slot); 228 229 if (false && r->is_reg() && !r->is_concrete()) { 230 continue; 231 } 232 233 // See if dead (no reaching def). 234 Node *def = _defs[reg]; // Get reaching def 235 assert( def, "since live better have reaching def" ); 236 237 // Classify the reaching def as oop, derived, callee-save, dead, or other 238 const Type *t = def->bottom_type(); 239 if( t->isa_oop_ptr() ) { // Oop or derived? 240 assert( !OptoReg::is_valid(_callees[reg]), "oop can't be callee save" ); 241#ifdef _LP64 242 // 64-bit pointers record oop-ishness on 2 aligned adjacent registers. 243 // Make sure both are record from the same reaching def, but do not 244 // put both into the oopmap. 245 if( (reg&1) == 1 ) { // High half of oop-pair? 246 assert( _defs[reg-1] == _defs[reg], "both halves from same reaching def" ); 247 continue; // Do not record high parts in oopmap 248 } 249#endif 250 251 // Check for a legal reg name in the oopMap and bailout if it is not. 252 if (!omap->legal_vm_reg_name(r)) { 253 regalloc->C->record_method_not_compilable("illegal oopMap register name"); 254 continue; 255 } 256 if( t->is_ptr()->_offset == 0 ) { // Not derived? 257 if( mcall ) { 258 // Outgoing argument GC mask responsibility belongs to the callee, 259 // not the caller. Inspect the inputs to the call, to see if 260 // this live-range is one of them. 261 uint cnt = mcall->tf()->domain()->cnt(); 262 uint j; 263 for( j = TypeFunc::Parms; j < cnt; j++) 264 if( mcall->in(j) == def ) 265 break; // reaching def is an argument oop 266 if( j < cnt ) // arg oops dont go in GC map 267 continue; // Continue on to the next register 268 } 269 omap->set_oop(r); 270 } else { // Else it's derived. 271 // Find the base of the derived value. 272 uint i; 273 // Fast, common case, scan 274 for( i = jvms->oopoff(); i < n->req(); i+=2 ) 275 if( n->in(i) == def ) break; // Common case 276 if( i == n->req() ) { // Missed, try a more generous scan 277 // Scan again, but this time peek through copies 278 for( i = jvms->oopoff(); i < n->req(); i+=2 ) { 279 Node *m = n->in(i); // Get initial derived value 280 while( 1 ) { 281 Node *d = def; // Get initial reaching def 282 while( 1 ) { // Follow copies of reaching def to end 283 if( m == d ) goto found; // breaks 3 loops 284 int idx = d->is_Copy(); 285 if( !idx ) break; 286 d = d->in(idx); // Link through copy 287 } 288 int idx = m->is_Copy(); 289 if( !idx ) break; 290 m = m->in(idx); 291 } 292 } 293 guarantee( 0, "must find derived/base pair" ); 294 } 295 found: ; 296 Node *base = n->in(i+1); // Base is other half of pair 297 int breg = regalloc->get_reg_first(base); 298 VMReg b = OptoReg::as_VMReg(OptoReg::Name(breg), framesize, max_inarg_slot); 299 300 // I record liveness at safepoints BEFORE I make the inputs 301 // live. This is because argument oops are NOT live at a 302 // safepoint (or at least they cannot appear in the oopmap). 303 // Thus bases of base/derived pairs might not be in the 304 // liveness data but they need to appear in the oopmap. 305 if( get_live_bit(live,breg) == 0 ) {// Not live? 306 // Flag it, so next derived pointer won't re-insert into oopmap 307 set_live_bit(live,breg); 308 // Already missed our turn? 309 if( breg < reg ) { 310 if (b->is_stack() || b->is_concrete() || true ) { 311 omap->set_oop( b); 312 } 313 } 314 } 315 if (b->is_stack() || b->is_concrete() || true ) { 316 omap->set_derived_oop( r, b); 317 } 318 } 319 320 } else if( t->isa_narrowoop() ) { 321 assert( !OptoReg::is_valid(_callees[reg]), "oop can't be callee save" ); 322 // Check for a legal reg name in the oopMap and bailout if it is not. 323 if (!omap->legal_vm_reg_name(r)) { 324 regalloc->C->record_method_not_compilable("illegal oopMap register name"); 325 continue; 326 } 327 if( mcall ) { 328 // Outgoing argument GC mask responsibility belongs to the callee, 329 // not the caller. Inspect the inputs to the call, to see if 330 // this live-range is one of them. 331 uint cnt = mcall->tf()->domain()->cnt(); 332 uint j; 333 for( j = TypeFunc::Parms; j < cnt; j++) 334 if( mcall->in(j) == def ) 335 break; // reaching def is an argument oop 336 if( j < cnt ) // arg oops dont go in GC map 337 continue; // Continue on to the next register 338 } 339 omap->set_narrowoop(r); 340 } else if( OptoReg::is_valid(_callees[reg])) { // callee-save? 341 // It's a callee-save value 342 assert( dup_check[_callees[reg]]==0, "trying to callee save same reg twice" ); 343 debug_only( dup_check[_callees[reg]]=1; ) 344 VMReg callee = OptoReg::as_VMReg(OptoReg::Name(_callees[reg])); 345 if ( callee->is_concrete() || true ) { 346 omap->set_callee_saved( r, callee); 347 } 348 349 } else { 350 // Other - some reaching non-oop value 351 omap->set_value( r); 352#ifdef ASSERT 353 if( t->isa_rawptr() && C->cfg()->_raw_oops.member(def) ) { 354 def->dump(); 355 n->dump(); 356 assert(false, "there should be a oop in OopMap instead of a live raw oop at safepoint"); 357 } 358#endif 359 } 360 361 } 362 363#ifdef ASSERT 364 /* Nice, Intel-only assert 365 int cnt_callee_saves=0; 366 int reg2 = 0; 367 while (OptoReg::is_reg(reg2)) { 368 if( dup_check[reg2] != 0) cnt_callee_saves++; 369 assert( cnt_callee_saves==3 || cnt_callee_saves==5, "missed some callee-save" ); 370 reg2++; 371 } 372 */ 373#endif 374 375#ifdef ASSERT 376 for( OopMapStream oms1(omap, OopMapValue::derived_oop_value); !oms1.is_done(); oms1.next()) { 377 OopMapValue omv1 = oms1.current(); 378 bool found = false; 379 for( OopMapStream oms2(omap,OopMapValue::oop_value); !oms2.is_done(); oms2.next()) { 380 if( omv1.content_reg() == oms2.current().reg() ) { 381 found = true; 382 break; 383 } 384 } 385 assert( found, "derived with no base in oopmap" ); 386 } 387#endif 388 389 return omap; 390} 391 392//------------------------------do_liveness------------------------------------ 393// Compute backwards liveness on registers 394static void do_liveness( PhaseRegAlloc *regalloc, PhaseCFG *cfg, Block_List *worklist, int max_reg_ints, Arena *A, Dict *safehash ) { 395 int *live = NEW_ARENA_ARRAY(A, int, (cfg->_num_blocks+1) * max_reg_ints); 396 int *tmp_live = &live[cfg->_num_blocks * max_reg_ints]; 397 Node *root = cfg->C->root(); 398 // On CISC platforms, get the node representing the stack pointer that regalloc 399 // used for spills 400 Node *fp = NodeSentinel; 401 if (UseCISCSpill && root->req() > 1) { 402 fp = root->in(1)->in(TypeFunc::FramePtr); 403 } 404 memset( live, 0, cfg->_num_blocks * (max_reg_ints<<LogBytesPerInt) ); 405 // Push preds onto worklist 406 for( uint i=1; i<root->req(); i++ ) 407 worklist->push(cfg->_bbs[root->in(i)->_idx]); 408 409 // ZKM.jar includes tiny infinite loops which are unreached from below. 410 // If we missed any blocks, we'll retry here after pushing all missed 411 // blocks on the worklist. Normally this outer loop never trips more 412 // than once. 413 while( 1 ) { 414 415 while( worklist->size() ) { // Standard worklist algorithm 416 Block *b = worklist->rpop(); 417 418 // Copy first successor into my tmp_live space 419 int s0num = b->_succs[0]->_pre_order; 420 int *t = &live[s0num*max_reg_ints]; 421 for( int i=0; i<max_reg_ints; i++ ) 422 tmp_live[i] = t[i]; 423 424 // OR in the remaining live registers 425 for( uint j=1; j<b->_num_succs; j++ ) { 426 uint sjnum = b->_succs[j]->_pre_order; 427 int *t = &live[sjnum*max_reg_ints]; 428 for( int i=0; i<max_reg_ints; i++ ) 429 tmp_live[i] |= t[i]; 430 } 431 432 // Now walk tmp_live up the block backwards, computing live 433 for( int k=b->_nodes.size()-1; k>=0; k-- ) { 434 Node *n = b->_nodes[k]; 435 // KILL def'd bits 436 int first = regalloc->get_reg_first(n); 437 int second = regalloc->get_reg_second(n); 438 if( OptoReg::is_valid(first) ) clr_live_bit(tmp_live,first); 439 if( OptoReg::is_valid(second) ) clr_live_bit(tmp_live,second); 440 441 MachNode *m = n->is_Mach() ? n->as_Mach() : NULL; 442 443 // Check if m is potentially a CISC alternate instruction (i.e, possibly 444 // synthesized by RegAlloc from a conventional instruction and a 445 // spilled input) 446 bool is_cisc_alternate = false; 447 if (UseCISCSpill && m) { 448 is_cisc_alternate = m->is_cisc_alternate(); 449 } 450 451 // GEN use'd bits 452 for( uint l=1; l<n->req(); l++ ) { 453 Node *def = n->in(l); 454 assert(def != 0, "input edge required"); 455 int first = regalloc->get_reg_first(def); 456 int second = regalloc->get_reg_second(def); 457 if( OptoReg::is_valid(first) ) set_live_bit(tmp_live,first); 458 if( OptoReg::is_valid(second) ) set_live_bit(tmp_live,second); 459 // If we use the stack pointer in a cisc-alternative instruction, 460 // check for use as a memory operand. Then reconstruct the RegName 461 // for this stack location, and set the appropriate bit in the 462 // live vector 4987749. 463 if (is_cisc_alternate && def == fp) { 464 const TypePtr *adr_type = NULL; 465 intptr_t offset; 466 const Node* base = m->get_base_and_disp(offset, adr_type); 467 if (base == NodeSentinel) { 468 // Machnode has multiple memory inputs. We are unable to reason 469 // with these, but are presuming (with trepidation) that not any of 470 // them are oops. This can be fixed by making get_base_and_disp() 471 // look at a specific input instead of all inputs. 472 assert(!def->bottom_type()->isa_oop_ptr(), "expecting non-oop mem input"); 473 } else if (base != fp || offset == Type::OffsetBot) { 474 // Do nothing: the fp operand is either not from a memory use 475 // (base == NULL) OR the fp is used in a non-memory context 476 // (base is some other register) OR the offset is not constant, 477 // so it is not a stack slot. 478 } else { 479 assert(offset >= 0, "unexpected negative offset"); 480 offset -= (offset % jintSize); // count the whole word 481 int stack_reg = regalloc->offset2reg(offset); 482 if (OptoReg::is_stack(stack_reg)) { 483 set_live_bit(tmp_live, stack_reg); 484 } else { 485 assert(false, "stack_reg not on stack?"); 486 } 487 } 488 } 489 } 490 491 if( n->jvms() ) { // Record liveness at safepoint 492 493 // This placement of this stanza means inputs to calls are 494 // considered live at the callsite's OopMap. Argument oops are 495 // hence live, but NOT included in the oopmap. See cutout in 496 // build_oop_map. Debug oops are live (and in OopMap). 497 int *n_live = NEW_ARENA_ARRAY(A, int, max_reg_ints); 498 for( int l=0; l<max_reg_ints; l++ ) 499 n_live[l] = tmp_live[l]; 500 safehash->Insert(n,n_live); 501 } 502 503 } 504 505 // Now at block top, see if we have any changes. If so, propagate 506 // to prior blocks. 507 int *old_live = &live[b->_pre_order*max_reg_ints]; 508 int l; 509 for( l=0; l<max_reg_ints; l++ ) 510 if( tmp_live[l] != old_live[l] ) 511 break; 512 if( l<max_reg_ints ) { // Change! 513 // Copy in new value 514 for( l=0; l<max_reg_ints; l++ ) 515 old_live[l] = tmp_live[l]; 516 // Push preds onto worklist 517 for( l=1; l<(int)b->num_preds(); l++ ) 518 worklist->push(cfg->_bbs[b->pred(l)->_idx]); 519 } 520 } 521 522 // Scan for any missing safepoints. Happens to infinite loops 523 // ala ZKM.jar 524 uint i; 525 for( i=1; i<cfg->_num_blocks; i++ ) { 526 Block *b = cfg->_blocks[i]; 527 uint j; 528 for( j=1; j<b->_nodes.size(); j++ ) 529 if( b->_nodes[j]->jvms() && 530 (*safehash)[b->_nodes[j]] == NULL ) 531 break; 532 if( j<b->_nodes.size() ) break; 533 } 534 if( i == cfg->_num_blocks ) 535 break; // Got 'em all 536#ifndef PRODUCT 537 if( PrintOpto && Verbose ) 538 tty->print_cr("retripping live calc"); 539#endif 540 // Force the issue (expensively): recheck everybody 541 for( i=1; i<cfg->_num_blocks; i++ ) 542 worklist->push(cfg->_blocks[i]); 543 } 544 545} 546 547//------------------------------BuildOopMaps----------------------------------- 548// Collect GC mask info - where are all the OOPs? 549void Compile::BuildOopMaps() { 550 NOT_PRODUCT( TracePhase t3("bldOopMaps", &_t_buildOopMaps, TimeCompiler); ) 551 // Can't resource-mark because I need to leave all those OopMaps around, 552 // or else I need to resource-mark some arena other than the default. 553 // ResourceMark rm; // Reclaim all OopFlows when done 554 int max_reg = _regalloc->_max_reg; // Current array extent 555 556 Arena *A = Thread::current()->resource_area(); 557 Block_List worklist; // Worklist of pending blocks 558 559 int max_reg_ints = round_to(max_reg, BitsPerInt)>>LogBitsPerInt; 560 Dict *safehash = NULL; // Used for assert only 561 // Compute a backwards liveness per register. Needs a bitarray of 562 // #blocks x (#registers, rounded up to ints) 563 safehash = new Dict(cmpkey,hashkey,A); 564 do_liveness( _regalloc, _cfg, &worklist, max_reg_ints, A, safehash ); 565 OopFlow *free_list = NULL; // Free, unused 566 567 // Array mapping blocks to completed oopflows 568 OopFlow **flows = NEW_ARENA_ARRAY(A, OopFlow*, _cfg->_num_blocks); 569 memset( flows, 0, _cfg->_num_blocks*sizeof(OopFlow*) ); 570 571 572 // Do the first block 'by hand' to prime the worklist 573 Block *entry = _cfg->_blocks[1]; 574 OopFlow *rootflow = OopFlow::make(A,max_reg,this); 575 // Initialize to 'bottom' (not 'top') 576 memset( rootflow->_callees, OptoReg::Bad, max_reg*sizeof(short) ); 577 memset( rootflow->_defs , 0, max_reg*sizeof(Node*) ); 578 flows[entry->_pre_order] = rootflow; 579 580 // Do the first block 'by hand' to prime the worklist 581 rootflow->_b = entry; 582 rootflow->compute_reach( _regalloc, max_reg, safehash ); 583 for( uint i=0; i<entry->_num_succs; i++ ) 584 worklist.push(entry->_succs[i]); 585 586 // Now worklist contains blocks which have some, but perhaps not all, 587 // predecessors visited. 588 while( worklist.size() ) { 589 // Scan for a block with all predecessors visited, or any randoms slob 590 // otherwise. All-preds-visited order allows me to recycle OopFlow 591 // structures rapidly and cut down on the memory footprint. 592 // Note: not all predecessors might be visited yet (must happen for 593 // irreducible loops). This is OK, since every live value must have the 594 // SAME reaching def for the block, so any reaching def is OK. 595 uint i; 596 597 Block *b = worklist.pop(); 598 // Ignore root block 599 if( b == _cfg->_broot ) continue; 600 // Block is already done? Happens if block has several predecessors, 601 // he can get on the worklist more than once. 602 if( flows[b->_pre_order] ) continue; 603 604 // If this block has a visited predecessor AND that predecessor has this 605 // last block as his only undone child, we can move the OopFlow from the 606 // pred to this block. Otherwise we have to grab a new OopFlow. 607 OopFlow *flow = NULL; // Flag for finding optimized flow 608 Block *pred = (Block*)0xdeadbeef; 609 uint j; 610 // Scan this block's preds to find a done predecessor 611 for( j=1; j<b->num_preds(); j++ ) { 612 Block *p = _cfg->_bbs[b->pred(j)->_idx]; 613 OopFlow *p_flow = flows[p->_pre_order]; 614 if( p_flow ) { // Predecessor is done 615 assert( p_flow->_b == p, "cross check" ); 616 pred = p; // Record some predecessor 617 // If all successors of p are done except for 'b', then we can carry 618 // p_flow forward to 'b' without copying, otherwise we have to draw 619 // from the free_list and clone data. 620 uint k; 621 for( k=0; k<p->_num_succs; k++ ) 622 if( !flows[p->_succs[k]->_pre_order] && 623 p->_succs[k] != b ) 624 break; 625 626 // Either carry-forward the now-unused OopFlow for b's use 627 // or draw a new one from the free list 628 if( k==p->_num_succs ) { 629 flow = p_flow; 630 break; // Found an ideal pred, use him 631 } 632 } 633 } 634 635 if( flow ) { 636 // We have an OopFlow that's the last-use of a predecessor. 637 // Carry it forward. 638 } else { // Draw a new OopFlow from the freelist 639 if( !free_list ) 640 free_list = OopFlow::make(A,max_reg,C); 641 flow = free_list; 642 assert( flow->_b == NULL, "oopFlow is not free" ); 643 free_list = flow->_next; 644 flow->_next = NULL; 645 646 // Copy/clone over the data 647 flow->clone(flows[pred->_pre_order], max_reg); 648 } 649 650 // Mark flow for block. Blocks can only be flowed over once, 651 // because after the first time they are guarded from entering 652 // this code again. 653 assert( flow->_b == pred, "have some prior flow" ); 654 flow->_b = NULL; 655 656 // Now push flow forward 657 flows[b->_pre_order] = flow;// Mark flow for this block 658 flow->_b = b; 659 flow->compute_reach( _regalloc, max_reg, safehash ); 660 661 // Now push children onto worklist 662 for( i=0; i<b->_num_succs; i++ ) 663 worklist.push(b->_succs[i]); 664 665 } 666} 667