1 /*
   2  * Copyright 1999-2010 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 # include "incls/_precompiled.incl"
  26 # include "incls/_c1_IR.cpp.incl"
  27 
  28 
  29 // Implementation of XHandlers
  30 //
  31 // Note: This code could eventually go away if we are
  32 //       just using the ciExceptionHandlerStream.
  33 
  34 XHandlers::XHandlers(ciMethod* method) : _list(method->exception_table_length()) {
  35   ciExceptionHandlerStream s(method);
  36   while (!s.is_done()) {
  37     _list.append(new XHandler(s.handler()));
  38     s.next();
  39   }
  40   assert(s.count() == method->exception_table_length(), "exception table lengths inconsistent");
  41 }
  42 
  43 // deep copy of all XHandler contained in list
  44 XHandlers::XHandlers(XHandlers* other) :
  45   _list(other->length())
  46 {
  47   for (int i = 0; i < other->length(); i++) {
  48     _list.append(new XHandler(other->handler_at(i)));
  49   }
  50 }
  51 
  52 // Returns whether a particular exception type can be caught.  Also
  53 // returns true if klass is unloaded or any exception handler
  54 // classes are unloaded.  type_is_exact indicates whether the throw
  55 // is known to be exactly that class or it might throw a subtype.
  56 bool XHandlers::could_catch(ciInstanceKlass* klass, bool type_is_exact) const {
  57   // the type is unknown so be conservative
  58   if (!klass->is_loaded()) {
  59     return true;
  60   }
  61 
  62   for (int i = 0; i < length(); i++) {
  63     XHandler* handler = handler_at(i);
  64     if (handler->is_catch_all()) {
  65       // catch of ANY
  66       return true;
  67     }
  68     ciInstanceKlass* handler_klass = handler->catch_klass();
  69     // if it's unknown it might be catchable
  70     if (!handler_klass->is_loaded()) {
  71       return true;
  72     }
  73     // if the throw type is definitely a subtype of the catch type
  74     // then it can be caught.
  75     if (klass->is_subtype_of(handler_klass)) {
  76       return true;
  77     }
  78     if (!type_is_exact) {
  79       // If the type isn't exactly known then it can also be caught by
  80       // catch statements where the inexact type is a subtype of the
  81       // catch type.
  82       // given: foo extends bar extends Exception
  83       // throw bar can be caught by catch foo, catch bar, and catch
  84       // Exception, however it can't be caught by any handlers without
  85       // bar in its type hierarchy.
  86       if (handler_klass->is_subtype_of(klass)) {
  87         return true;
  88       }
  89     }
  90   }
  91 
  92   return false;
  93 }
  94 
  95 
  96 bool XHandlers::equals(XHandlers* others) const {
  97   if (others == NULL) return false;
  98   if (length() != others->length()) return false;
  99 
 100   for (int i = 0; i < length(); i++) {
 101     if (!handler_at(i)->equals(others->handler_at(i))) return false;
 102   }
 103   return true;
 104 }
 105 
 106 bool XHandler::equals(XHandler* other) const {
 107   assert(entry_pco() != -1 && other->entry_pco() != -1, "must have entry_pco");
 108 
 109   if (entry_pco() != other->entry_pco()) return false;
 110   if (scope_count() != other->scope_count()) return false;
 111   if (_desc != other->_desc) return false;
 112 
 113   assert(entry_block() == other->entry_block(), "entry_block must be equal when entry_pco is equal");
 114   return true;
 115 }
 116 
 117 
 118 // Implementation of IRScope
 119 
 120 BlockBegin* IRScope::header_block(BlockBegin* entry, BlockBegin::Flag f, ValueStack* state) {
 121   if (entry == NULL) return NULL;
 122   assert(entry->is_set(f), "entry/flag mismatch");
 123   // create header block
 124   BlockBegin* h = new BlockBegin(entry->bci());
 125   BlockEnd* g = new Goto(entry, false);
 126   h->set_next(g, entry->bci());
 127   h->set_end(g);
 128   h->set(f);
 129   // setup header block end state
 130   ValueStack* s = state->copy(); // can use copy since stack is empty (=> no phis)
 131   assert(s->stack_is_empty(), "must have empty stack at entry point");
 132   g->set_state(s);
 133   return h;
 134 }
 135 
 136 
 137 BlockBegin* IRScope::build_graph(Compilation* compilation, int osr_bci) {
 138   GraphBuilder gm(compilation, this);
 139   NOT_PRODUCT(if (PrintValueNumbering && Verbose) gm.print_stats());
 140   if (compilation->bailed_out()) return NULL;
 141   return gm.start();
 142 }
 143 
 144 
 145 IRScope::IRScope(Compilation* compilation, IRScope* caller, int caller_bci, ciMethod* method, int osr_bci, bool create_graph)
 146 : _callees(2)
 147 , _compilation(compilation)
 148 , _lock_stack_size(-1)
 149 , _requires_phi_function(method->max_locals())
 150 {
 151   _caller             = caller;
 152   _caller_bci         = caller == NULL ? -1 : caller_bci;
 153   _caller_state       = NULL; // Must be set later if needed
 154   _level              = caller == NULL ?  0 : caller->level() + 1;
 155   _method             = method;
 156   _xhandlers          = new XHandlers(method);
 157   _number_of_locks    = 0;
 158   _monitor_pairing_ok = method->has_balanced_monitors();
 159   _start              = NULL;
 160 
 161   if (osr_bci == -1) {
 162     _requires_phi_function.clear();
 163   } else {
 164         // selective creation of phi functions is not possibel in osr-methods
 165     _requires_phi_function.set_range(0, method->max_locals());
 166   }
 167 
 168   assert(method->holder()->is_loaded() , "method holder must be loaded");
 169 
 170   // build graph if monitor pairing is ok
 171   if (create_graph && monitor_pairing_ok()) _start = build_graph(compilation, osr_bci);
 172 }
 173 
 174 
 175 int IRScope::max_stack() const {
 176   int my_max = method()->max_stack();
 177   int callee_max = 0;
 178   for (int i = 0; i < number_of_callees(); i++) {
 179     callee_max = MAX2(callee_max, callee_no(i)->max_stack());
 180   }
 181   return my_max + callee_max;
 182 }
 183 
 184 
 185 void IRScope::compute_lock_stack_size() {
 186   if (!InlineMethodsWithExceptionHandlers) {
 187     _lock_stack_size = 0;
 188     return;
 189   }
 190 
 191   // Figure out whether we have to preserve expression stack elements
 192   // for parent scopes, and if so, how many
 193   IRScope* cur_scope = this;
 194   while (cur_scope != NULL && !cur_scope->xhandlers()->has_handlers()) {
 195     cur_scope = cur_scope->caller();
 196   }
 197   _lock_stack_size = (cur_scope == NULL ? 0 :
 198                       (cur_scope->caller_state() == NULL ? 0 :
 199                        cur_scope->caller_state()->stack_size()));
 200 }
 201 
 202 int IRScope::top_scope_bci() const {
 203   assert(!is_top_scope(), "no correct answer for top scope possible");
 204   const IRScope* scope = this;
 205   while (!scope->caller()->is_top_scope()) {
 206     scope = scope->caller();
 207   }
 208   return scope->caller_bci();
 209 }
 210 
 211 bool IRScopeDebugInfo::should_reexecute() {
 212   ciMethod* cur_method = scope()->method();
 213   int       cur_bci    = bci();
 214   if (cur_method != NULL && cur_bci != SynchronizationEntryBCI) {
 215     Bytecodes::Code code = cur_method->java_code_at_bci(cur_bci);
 216     return Interpreter::bytecode_should_reexecute(code);
 217   } else
 218     return false;
 219 }
 220 
 221 
 222 // Implementation of CodeEmitInfo
 223 
 224 // Stack must be NON-null
 225 CodeEmitInfo::CodeEmitInfo(int bci, ValueStack* stack, XHandlers* exception_handlers)
 226   : _scope(stack->scope())
 227   , _bci(bci)
 228   , _scope_debug_info(NULL)
 229   , _oop_map(NULL)
 230   , _stack(stack)
 231   , _exception_handlers(exception_handlers)
 232   , _next(NULL)
 233   , _id(-1)
 234   , _is_method_handle_invoke(false) {
 235   assert(_stack != NULL, "must be non null");
 236   assert(_bci == SynchronizationEntryBCI || Bytecodes::is_defined(scope()->method()->java_code_at_bci(_bci)), "make sure bci points at a real bytecode");
 237 }
 238 
 239 
 240 CodeEmitInfo::CodeEmitInfo(CodeEmitInfo* info, bool lock_stack_only)
 241   : _scope(info->_scope)
 242   , _exception_handlers(NULL)
 243   , _bci(info->_bci)
 244   , _scope_debug_info(NULL)
 245   , _oop_map(NULL)
 246   , _is_method_handle_invoke(info->_is_method_handle_invoke) {
 247   if (lock_stack_only) {
 248     if (info->_stack != NULL) {
 249       _stack = info->_stack->copy_locks();
 250     } else {
 251       _stack = NULL;
 252     }
 253   } else {
 254     _stack = info->_stack;
 255   }
 256 
 257   // deep copy of exception handlers
 258   if (info->_exception_handlers != NULL) {
 259     _exception_handlers = new XHandlers(info->_exception_handlers);
 260   }
 261 }
 262 
 263 
 264 void CodeEmitInfo::record_debug_info(DebugInformationRecorder* recorder, int pc_offset) {
 265   // record the safepoint before recording the debug info for enclosing scopes
 266   recorder->add_safepoint(pc_offset, _oop_map->deep_copy());
 267   _scope_debug_info->record_debug_info(recorder, pc_offset, true/*topmost*/, _is_method_handle_invoke);
 268   recorder->end_safepoint(pc_offset);
 269 }
 270 
 271 
 272 void CodeEmitInfo::add_register_oop(LIR_Opr opr) {
 273   assert(_oop_map != NULL, "oop map must already exist");
 274   assert(opr->is_single_cpu(), "should not call otherwise");
 275 
 276   int frame_size = frame_map()->framesize();
 277   int arg_count = frame_map()->oop_map_arg_count();
 278   VMReg name = frame_map()->regname(opr);
 279   _oop_map->set_oop(name);
 280 }
 281 
 282 
 283 
 284 
 285 // Implementation of IR
 286 
 287 IR::IR(Compilation* compilation, ciMethod* method, int osr_bci) :
 288     _locals_size(in_WordSize(-1))
 289   , _num_loops(0) {
 290   // initialize data structures
 291   ValueType::initialize();
 292   Instruction::initialize();
 293   BlockBegin::initialize();
 294   GraphBuilder::initialize();
 295   // setup IR fields
 296   _compilation = compilation;
 297   _top_scope   = new IRScope(compilation, NULL, -1, method, osr_bci, true);
 298   _code        = NULL;
 299 }
 300 
 301 
 302 void IR::optimize() {
 303   Optimizer opt(this);
 304   if (DoCEE) {
 305     opt.eliminate_conditional_expressions();
 306 #ifndef PRODUCT
 307     if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after CEE"); print(true); }
 308     if (PrintIR  || PrintIR1 ) { tty->print_cr("IR after CEE"); print(false); }
 309 #endif
 310   }
 311   if (EliminateBlocks) {
 312     opt.eliminate_blocks();
 313 #ifndef PRODUCT
 314     if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after block elimination"); print(true); }
 315     if (PrintIR  || PrintIR1 ) { tty->print_cr("IR after block elimination"); print(false); }
 316 #endif
 317   }
 318   if (EliminateNullChecks) {
 319     opt.eliminate_null_checks();
 320 #ifndef PRODUCT
 321     if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after null check elimination"); print(true); }
 322     if (PrintIR  || PrintIR1 ) { tty->print_cr("IR after null check elimination"); print(false); }
 323 #endif
 324   }
 325 }
 326 
 327 
 328 static int sort_pairs(BlockPair** a, BlockPair** b) {
 329   if ((*a)->from() == (*b)->from()) {
 330     return (*a)->to()->block_id() - (*b)->to()->block_id();
 331   } else {
 332     return (*a)->from()->block_id() - (*b)->from()->block_id();
 333   }
 334 }
 335 
 336 
 337 class CriticalEdgeFinder: public BlockClosure {
 338   BlockPairList blocks;
 339   IR*       _ir;
 340 
 341  public:
 342   CriticalEdgeFinder(IR* ir): _ir(ir) {}
 343   void block_do(BlockBegin* bb) {
 344     BlockEnd* be = bb->end();
 345     int nos = be->number_of_sux();
 346     if (nos >= 2) {
 347       for (int i = 0; i < nos; i++) {
 348         BlockBegin* sux = be->sux_at(i);
 349         if (sux->number_of_preds() >= 2) {
 350           blocks.append(new BlockPair(bb, sux));
 351         }
 352       }
 353     }
 354   }
 355 
 356   void split_edges() {
 357     BlockPair* last_pair = NULL;
 358     blocks.sort(sort_pairs);
 359     for (int i = 0; i < blocks.length(); i++) {
 360       BlockPair* pair = blocks.at(i);
 361       if (last_pair != NULL && pair->is_same(last_pair)) continue;
 362       BlockBegin* from = pair->from();
 363       BlockBegin* to = pair->to();
 364       BlockBegin* split = from->insert_block_between(to);
 365 #ifndef PRODUCT
 366       if ((PrintIR || PrintIR1) && Verbose) {
 367         tty->print_cr("Split critical edge B%d -> B%d (new block B%d)",
 368                       from->block_id(), to->block_id(), split->block_id());
 369       }
 370 #endif
 371       last_pair = pair;
 372     }
 373   }
 374 };
 375 
 376 void IR::split_critical_edges() {
 377   CriticalEdgeFinder cef(this);
 378 
 379   iterate_preorder(&cef);
 380   cef.split_edges();
 381 }
 382 
 383 
 384 class UseCountComputer: public AllStatic {
 385  private:
 386   static void update_use_count(Value* n) {
 387     // Local instructions and Phis for expression stack values at the
 388     // start of basic blocks are not added to the instruction list
 389     if ((*n)->bci() == -99 && (*n)->as_Local() == NULL &&
 390         (*n)->as_Phi() == NULL) {
 391       assert(false, "a node was not appended to the graph");
 392       Compilation::current_compilation()->bailout("a node was not appended to the graph");
 393     }
 394     // use n's input if not visited before
 395     if (!(*n)->is_pinned() && !(*n)->has_uses()) {
 396       // note: a) if the instruction is pinned, it will be handled by compute_use_count
 397       //       b) if the instruction has uses, it was touched before
 398       //       => in both cases we don't need to update n's values
 399       uses_do(n);
 400     }
 401     // use n
 402     (*n)->_use_count++;
 403   }
 404 
 405   static Values* worklist;
 406   static int depth;
 407   enum {
 408     max_recurse_depth = 20
 409   };
 410 
 411   static void uses_do(Value* n) {
 412     depth++;
 413     if (depth > max_recurse_depth) {
 414       // don't allow the traversal to recurse too deeply
 415       worklist->push(*n);
 416     } else {
 417       (*n)->input_values_do(update_use_count);
 418       // special handling for some instructions
 419       if ((*n)->as_BlockEnd() != NULL) {
 420         // note on BlockEnd:
 421         //   must 'use' the stack only if the method doesn't
 422         //   terminate, however, in those cases stack is empty
 423         (*n)->state_values_do(update_use_count);
 424       }
 425     }
 426     depth--;
 427   }
 428 
 429   static void basic_compute_use_count(BlockBegin* b) {
 430     depth = 0;
 431     // process all pinned nodes as the roots of expression trees
 432     for (Instruction* n = b; n != NULL; n = n->next()) {
 433       if (n->is_pinned()) uses_do(&n);
 434     }
 435     assert(depth == 0, "should have counted back down");
 436 
 437     // now process any unpinned nodes which recursed too deeply
 438     while (worklist->length() > 0) {
 439       Value t = worklist->pop();
 440       if (!t->is_pinned()) {
 441         // compute the use count
 442         uses_do(&t);
 443 
 444         // pin the instruction so that LIRGenerator doesn't recurse
 445         // too deeply during it's evaluation.
 446         t->pin();
 447       }
 448     }
 449     assert(depth == 0, "should have counted back down");
 450   }
 451 
 452  public:
 453   static void compute(BlockList* blocks) {
 454     worklist = new Values();
 455     blocks->blocks_do(basic_compute_use_count);
 456     worklist = NULL;
 457   }
 458 };
 459 
 460 
 461 Values* UseCountComputer::worklist = NULL;
 462 int UseCountComputer::depth = 0;
 463 
 464 // helper macro for short definition of trace-output inside code
 465 #ifndef PRODUCT
 466   #define TRACE_LINEAR_SCAN(level, code)       \
 467     if (TraceLinearScanLevel >= level) {       \
 468       code;                                    \
 469     }
 470 #else
 471   #define TRACE_LINEAR_SCAN(level, code)
 472 #endif
 473 
 474 class ComputeLinearScanOrder : public StackObj {
 475  private:
 476   int        _max_block_id;        // the highest block_id of a block
 477   int        _num_blocks;          // total number of blocks (smaller than _max_block_id)
 478   int        _num_loops;           // total number of loops
 479   bool       _iterative_dominators;// method requires iterative computation of dominatiors
 480 
 481   BlockList* _linear_scan_order;   // the resulting list of blocks in correct order
 482 
 483   BitMap     _visited_blocks;      // used for recursive processing of blocks
 484   BitMap     _active_blocks;       // used for recursive processing of blocks
 485   BitMap     _dominator_blocks;    // temproary BitMap used for computation of dominator
 486   intArray   _forward_branches;    // number of incoming forward branches for each block
 487   BlockList  _loop_end_blocks;     // list of all loop end blocks collected during count_edges
 488   BitMap2D   _loop_map;            // two-dimensional bit set: a bit is set if a block is contained in a loop
 489   BlockList  _work_list;           // temporary list (used in mark_loops and compute_order)
 490 
 491   // accessors for _visited_blocks and _active_blocks
 492   void init_visited()                     { _active_blocks.clear(); _visited_blocks.clear(); }
 493   bool is_visited(BlockBegin* b) const    { return _visited_blocks.at(b->block_id()); }
 494   bool is_active(BlockBegin* b) const     { return _active_blocks.at(b->block_id()); }
 495   void set_visited(BlockBegin* b)         { assert(!is_visited(b), "already set"); _visited_blocks.set_bit(b->block_id()); }
 496   void set_active(BlockBegin* b)          { assert(!is_active(b), "already set");  _active_blocks.set_bit(b->block_id()); }
 497   void clear_active(BlockBegin* b)        { assert(is_active(b), "not already");   _active_blocks.clear_bit(b->block_id()); }
 498 
 499   // accessors for _forward_branches
 500   void inc_forward_branches(BlockBegin* b) { _forward_branches.at_put(b->block_id(), _forward_branches.at(b->block_id()) + 1); }
 501   int  dec_forward_branches(BlockBegin* b) { _forward_branches.at_put(b->block_id(), _forward_branches.at(b->block_id()) - 1); return _forward_branches.at(b->block_id()); }
 502 
 503   // accessors for _loop_map
 504   bool is_block_in_loop   (int loop_idx, BlockBegin* b) const { return _loop_map.at(loop_idx, b->block_id()); }
 505   void set_block_in_loop  (int loop_idx, BlockBegin* b)       { _loop_map.set_bit(loop_idx, b->block_id()); }
 506   void clear_block_in_loop(int loop_idx, int block_id)        { _loop_map.clear_bit(loop_idx, block_id); }
 507 
 508   // count edges between blocks
 509   void count_edges(BlockBegin* cur, BlockBegin* parent);
 510 
 511   // loop detection
 512   void mark_loops();
 513   void clear_non_natural_loops(BlockBegin* start_block);
 514   void assign_loop_depth(BlockBegin* start_block);
 515 
 516   // computation of final block order
 517   BlockBegin* common_dominator(BlockBegin* a, BlockBegin* b);
 518   void compute_dominator(BlockBegin* cur, BlockBegin* parent);
 519   int  compute_weight(BlockBegin* cur);
 520   bool ready_for_processing(BlockBegin* cur);
 521   void sort_into_work_list(BlockBegin* b);
 522   void append_block(BlockBegin* cur);
 523   void compute_order(BlockBegin* start_block);
 524 
 525   // fixup of dominators for non-natural loops
 526   bool compute_dominators_iter();
 527   void compute_dominators();
 528 
 529   // debug functions
 530   NOT_PRODUCT(void print_blocks();)
 531   DEBUG_ONLY(void verify();)
 532 
 533  public:
 534   ComputeLinearScanOrder(BlockBegin* start_block);
 535 
 536   // accessors for final result
 537   BlockList* linear_scan_order() const    { return _linear_scan_order; }
 538   int        num_loops() const            { return _num_loops; }
 539 };
 540 
 541 
 542 ComputeLinearScanOrder::ComputeLinearScanOrder(BlockBegin* start_block) :
 543   _max_block_id(BlockBegin::number_of_blocks()),
 544   _num_blocks(0),
 545   _num_loops(0),
 546   _iterative_dominators(false),
 547   _visited_blocks(_max_block_id),
 548   _active_blocks(_max_block_id),
 549   _dominator_blocks(_max_block_id),
 550   _forward_branches(_max_block_id, 0),
 551   _loop_end_blocks(8),
 552   _work_list(8),
 553   _linear_scan_order(NULL), // initialized later with correct size
 554   _loop_map(0, 0)           // initialized later with correct size
 555 {
 556   TRACE_LINEAR_SCAN(2, "***** computing linear-scan block order");
 557 
 558   init_visited();
 559   count_edges(start_block, NULL);
 560 
 561   if (_num_loops > 0) {
 562     mark_loops();
 563     clear_non_natural_loops(start_block);
 564     assign_loop_depth(start_block);
 565   }
 566 
 567   compute_order(start_block);
 568   compute_dominators();
 569 
 570   NOT_PRODUCT(print_blocks());
 571   DEBUG_ONLY(verify());
 572 }
 573 
 574 
 575 // Traverse the CFG:
 576 // * count total number of blocks
 577 // * count all incoming edges and backward incoming edges
 578 // * number loop header blocks
 579 // * create a list with all loop end blocks
 580 void ComputeLinearScanOrder::count_edges(BlockBegin* cur, BlockBegin* parent) {
 581   TRACE_LINEAR_SCAN(3, tty->print_cr("Enter count_edges for block B%d coming from B%d", cur->block_id(), parent != NULL ? parent->block_id() : -1));
 582   assert(cur->dominator() == NULL, "dominator already initialized");
 583 
 584   if (is_active(cur)) {
 585     TRACE_LINEAR_SCAN(3, tty->print_cr("backward branch"));
 586     assert(is_visited(cur), "block must be visisted when block is active");
 587     assert(parent != NULL, "must have parent");
 588 
 589     cur->set(BlockBegin::linear_scan_loop_header_flag);
 590     cur->set(BlockBegin::backward_branch_target_flag);
 591 
 592     parent->set(BlockBegin::linear_scan_loop_end_flag);
 593 
 594     // When a loop header is also the start of an exception handler, then the backward branch is
 595     // an exception edge. Because such edges are usually critical edges which cannot be split, the
 596     // loop must be excluded here from processing.
 597     if (cur->is_set(BlockBegin::exception_entry_flag)) {
 598       // Make sure that dominators are correct in this weird situation
 599       _iterative_dominators = true;
 600       return;
 601     }
 602     assert(parent->number_of_sux() == 1 && parent->sux_at(0) == cur,
 603            "loop end blocks must have one successor (critical edges are split)");
 604 
 605     _loop_end_blocks.append(parent);
 606     return;
 607   }
 608 
 609   // increment number of incoming forward branches
 610   inc_forward_branches(cur);
 611 
 612   if (is_visited(cur)) {
 613     TRACE_LINEAR_SCAN(3, tty->print_cr("block already visited"));
 614     return;
 615   }
 616 
 617   _num_blocks++;
 618   set_visited(cur);
 619   set_active(cur);
 620 
 621   // recursive call for all successors
 622   int i;
 623   for (i = cur->number_of_sux() - 1; i >= 0; i--) {
 624     count_edges(cur->sux_at(i), cur);
 625   }
 626   for (i = cur->number_of_exception_handlers() - 1; i >= 0; i--) {
 627     count_edges(cur->exception_handler_at(i), cur);
 628   }
 629 
 630   clear_active(cur);
 631 
 632   // Each loop has a unique number.
 633   // When multiple loops are nested, assign_loop_depth assumes that the
 634   // innermost loop has the lowest number. This is guaranteed by setting
 635   // the loop number after the recursive calls for the successors above
 636   // have returned.
 637   if (cur->is_set(BlockBegin::linear_scan_loop_header_flag)) {
 638     assert(cur->loop_index() == -1, "cannot set loop-index twice");
 639     TRACE_LINEAR_SCAN(3, tty->print_cr("Block B%d is loop header of loop %d", cur->block_id(), _num_loops));
 640 
 641     cur->set_loop_index(_num_loops);
 642     _num_loops++;
 643   }
 644 
 645   TRACE_LINEAR_SCAN(3, tty->print_cr("Finished count_edges for block B%d", cur->block_id()));
 646 }
 647 
 648 
 649 void ComputeLinearScanOrder::mark_loops() {
 650   TRACE_LINEAR_SCAN(3, tty->print_cr("----- marking loops"));
 651 
 652   _loop_map = BitMap2D(_num_loops, _max_block_id);
 653   _loop_map.clear();
 654 
 655   for (int i = _loop_end_blocks.length() - 1; i >= 0; i--) {
 656     BlockBegin* loop_end   = _loop_end_blocks.at(i);
 657     BlockBegin* loop_start = loop_end->sux_at(0);
 658     int         loop_idx   = loop_start->loop_index();
 659 
 660     TRACE_LINEAR_SCAN(3, tty->print_cr("Processing loop from B%d to B%d (loop %d):", loop_start->block_id(), loop_end->block_id(), loop_idx));
 661     assert(loop_end->is_set(BlockBegin::linear_scan_loop_end_flag), "loop end flag must be set");
 662     assert(loop_end->number_of_sux() == 1, "incorrect number of successors");
 663     assert(loop_start->is_set(BlockBegin::linear_scan_loop_header_flag), "loop header flag must be set");
 664     assert(loop_idx >= 0 && loop_idx < _num_loops, "loop index not set");
 665     assert(_work_list.is_empty(), "work list must be empty before processing");
 666 
 667     // add the end-block of the loop to the working list
 668     _work_list.push(loop_end);
 669     set_block_in_loop(loop_idx, loop_end);
 670     do {
 671       BlockBegin* cur = _work_list.pop();
 672 
 673       TRACE_LINEAR_SCAN(3, tty->print_cr("    processing B%d", cur->block_id()));
 674       assert(is_block_in_loop(loop_idx, cur), "bit in loop map must be set when block is in work list");
 675 
 676       // recursive processing of all predecessors ends when start block of loop is reached
 677       if (cur != loop_start && !cur->is_set(BlockBegin::osr_entry_flag)) {
 678         for (int j = cur->number_of_preds() - 1; j >= 0; j--) {
 679           BlockBegin* pred = cur->pred_at(j);
 680 
 681           if (!is_block_in_loop(loop_idx, pred) /*&& !pred->is_set(BlockBeginosr_entry_flag)*/) {
 682             // this predecessor has not been processed yet, so add it to work list
 683             TRACE_LINEAR_SCAN(3, tty->print_cr("    pushing B%d", pred->block_id()));
 684             _work_list.push(pred);
 685             set_block_in_loop(loop_idx, pred);
 686           }
 687         }
 688       }
 689     } while (!_work_list.is_empty());
 690   }
 691 }
 692 
 693 
 694 // check for non-natural loops (loops where the loop header does not dominate
 695 // all other loop blocks = loops with mulitple entries).
 696 // such loops are ignored
 697 void ComputeLinearScanOrder::clear_non_natural_loops(BlockBegin* start_block) {
 698   for (int i = _num_loops - 1; i >= 0; i--) {
 699     if (is_block_in_loop(i, start_block)) {
 700       // loop i contains the entry block of the method
 701       // -> this is not a natural loop, so ignore it
 702       TRACE_LINEAR_SCAN(2, tty->print_cr("Loop %d is non-natural, so it is ignored", i));
 703 
 704       for (int block_id = _max_block_id - 1; block_id >= 0; block_id--) {
 705         clear_block_in_loop(i, block_id);
 706       }
 707       _iterative_dominators = true;
 708     }
 709   }
 710 }
 711 
 712 void ComputeLinearScanOrder::assign_loop_depth(BlockBegin* start_block) {
 713   TRACE_LINEAR_SCAN(3, "----- computing loop-depth and weight");
 714   init_visited();
 715 
 716   assert(_work_list.is_empty(), "work list must be empty before processing");
 717   _work_list.append(start_block);
 718 
 719   do {
 720     BlockBegin* cur = _work_list.pop();
 721 
 722     if (!is_visited(cur)) {
 723       set_visited(cur);
 724       TRACE_LINEAR_SCAN(4, tty->print_cr("Computing loop depth for block B%d", cur->block_id()));
 725 
 726       // compute loop-depth and loop-index for the block
 727       assert(cur->loop_depth() == 0, "cannot set loop-depth twice");
 728       int i;
 729       int loop_depth = 0;
 730       int min_loop_idx = -1;
 731       for (i = _num_loops - 1; i >= 0; i--) {
 732         if (is_block_in_loop(i, cur)) {
 733           loop_depth++;
 734           min_loop_idx = i;
 735         }
 736       }
 737       cur->set_loop_depth(loop_depth);
 738       cur->set_loop_index(min_loop_idx);
 739 
 740       // append all unvisited successors to work list
 741       for (i = cur->number_of_sux() - 1; i >= 0; i--) {
 742         _work_list.append(cur->sux_at(i));
 743       }
 744       for (i = cur->number_of_exception_handlers() - 1; i >= 0; i--) {
 745         _work_list.append(cur->exception_handler_at(i));
 746       }
 747     }
 748   } while (!_work_list.is_empty());
 749 }
 750 
 751 
 752 BlockBegin* ComputeLinearScanOrder::common_dominator(BlockBegin* a, BlockBegin* b) {
 753   assert(a != NULL && b != NULL, "must have input blocks");
 754 
 755   _dominator_blocks.clear();
 756   while (a != NULL) {
 757     _dominator_blocks.set_bit(a->block_id());
 758     assert(a->dominator() != NULL || a == _linear_scan_order->at(0), "dominator must be initialized");
 759     a = a->dominator();
 760   }
 761   while (b != NULL && !_dominator_blocks.at(b->block_id())) {
 762     assert(b->dominator() != NULL || b == _linear_scan_order->at(0), "dominator must be initialized");
 763     b = b->dominator();
 764   }
 765 
 766   assert(b != NULL, "could not find dominator");
 767   return b;
 768 }
 769 
 770 void ComputeLinearScanOrder::compute_dominator(BlockBegin* cur, BlockBegin* parent) {
 771   if (cur->dominator() == NULL) {
 772     TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: initializing dominator of B%d to B%d", cur->block_id(), parent->block_id()));
 773     cur->set_dominator(parent);
 774 
 775   } else if (!(cur->is_set(BlockBegin::linear_scan_loop_header_flag) && parent->is_set(BlockBegin::linear_scan_loop_end_flag))) {
 776     TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: computing dominator of B%d: common dominator of B%d and B%d is B%d", cur->block_id(), parent->block_id(), cur->dominator()->block_id(), common_dominator(cur->dominator(), parent)->block_id()));
 777     assert(cur->number_of_preds() > 1, "");
 778     cur->set_dominator(common_dominator(cur->dominator(), parent));
 779   }
 780 }
 781 
 782 
 783 int ComputeLinearScanOrder::compute_weight(BlockBegin* cur) {
 784   BlockBegin* single_sux = NULL;
 785   if (cur->number_of_sux() == 1) {
 786     single_sux = cur->sux_at(0);
 787   }
 788 
 789   // limit loop-depth to 15 bit (only for security reason, it will never be so big)
 790   int weight = (cur->loop_depth() & 0x7FFF) << 16;
 791 
 792   // general macro for short definition of weight flags
 793   // the first instance of INC_WEIGHT_IF has the highest priority
 794   int cur_bit = 15;
 795   #define INC_WEIGHT_IF(condition) if ((condition)) { weight |= (1 << cur_bit); } cur_bit--;
 796 
 797   // this is necessery for the (very rare) case that two successing blocks have
 798   // the same loop depth, but a different loop index (can happen for endless loops
 799   // with exception handlers)
 800   INC_WEIGHT_IF(!cur->is_set(BlockBegin::linear_scan_loop_header_flag));
 801 
 802   // loop end blocks (blocks that end with a backward branch) are added
 803   // after all other blocks of the loop.
 804   INC_WEIGHT_IF(!cur->is_set(BlockBegin::linear_scan_loop_end_flag));
 805 
 806   // critical edge split blocks are prefered because than they have a bigger
 807   // proability to be completely empty
 808   INC_WEIGHT_IF(cur->is_set(BlockBegin::critical_edge_split_flag));
 809 
 810   // exceptions should not be thrown in normal control flow, so these blocks
 811   // are added as late as possible
 812   INC_WEIGHT_IF(cur->end()->as_Throw() == NULL  && (single_sux == NULL || single_sux->end()->as_Throw()  == NULL));
 813   INC_WEIGHT_IF(cur->end()->as_Return() == NULL && (single_sux == NULL || single_sux->end()->as_Return() == NULL));
 814 
 815   // exceptions handlers are added as late as possible
 816   INC_WEIGHT_IF(!cur->is_set(BlockBegin::exception_entry_flag));
 817 
 818   // guarantee that weight is > 0
 819   weight |= 1;
 820 
 821   #undef INC_WEIGHT_IF
 822   assert(cur_bit >= 0, "too many flags");
 823   assert(weight > 0, "weight cannot become negative");
 824 
 825   return weight;
 826 }
 827 
 828 bool ComputeLinearScanOrder::ready_for_processing(BlockBegin* cur) {
 829   // Discount the edge just traveled.
 830   // When the number drops to zero, all forward branches were processed
 831   if (dec_forward_branches(cur) != 0) {
 832     return false;
 833   }
 834 
 835   assert(_linear_scan_order->index_of(cur) == -1, "block already processed (block can be ready only once)");
 836   assert(_work_list.index_of(cur) == -1, "block already in work-list (block can be ready only once)");
 837   return true;
 838 }
 839 
 840 void ComputeLinearScanOrder::sort_into_work_list(BlockBegin* cur) {
 841   assert(_work_list.index_of(cur) == -1, "block already in work list");
 842 
 843   int cur_weight = compute_weight(cur);
 844 
 845   // the linear_scan_number is used to cache the weight of a block
 846   cur->set_linear_scan_number(cur_weight);
 847 
 848 #ifndef PRODUCT
 849   if (StressLinearScan) {
 850     _work_list.insert_before(0, cur);
 851     return;
 852   }
 853 #endif
 854 
 855   _work_list.append(NULL); // provide space for new element
 856 
 857   int insert_idx = _work_list.length() - 1;
 858   while (insert_idx > 0 && _work_list.at(insert_idx - 1)->linear_scan_number() > cur_weight) {
 859     _work_list.at_put(insert_idx, _work_list.at(insert_idx - 1));
 860     insert_idx--;
 861   }
 862   _work_list.at_put(insert_idx, cur);
 863 
 864   TRACE_LINEAR_SCAN(3, tty->print_cr("Sorted B%d into worklist. new worklist:", cur->block_id()));
 865   TRACE_LINEAR_SCAN(3, for (int i = 0; i < _work_list.length(); i++) tty->print_cr("%8d B%2d  weight:%6x", i, _work_list.at(i)->block_id(), _work_list.at(i)->linear_scan_number()));
 866 
 867 #ifdef ASSERT
 868   for (int i = 0; i < _work_list.length(); i++) {
 869     assert(_work_list.at(i)->linear_scan_number() > 0, "weight not set");
 870     assert(i == 0 || _work_list.at(i - 1)->linear_scan_number() <= _work_list.at(i)->linear_scan_number(), "incorrect order in worklist");
 871   }
 872 #endif
 873 }
 874 
 875 void ComputeLinearScanOrder::append_block(BlockBegin* cur) {
 876   TRACE_LINEAR_SCAN(3, tty->print_cr("appending block B%d (weight 0x%6x) to linear-scan order", cur->block_id(), cur->linear_scan_number()));
 877   assert(_linear_scan_order->index_of(cur) == -1, "cannot add the same block twice");
 878 
 879   // currently, the linear scan order and code emit order are equal.
 880   // therefore the linear_scan_number and the weight of a block must also
 881   // be equal.
 882   cur->set_linear_scan_number(_linear_scan_order->length());
 883   _linear_scan_order->append(cur);
 884 }
 885 
 886 void ComputeLinearScanOrder::compute_order(BlockBegin* start_block) {
 887   TRACE_LINEAR_SCAN(3, "----- computing final block order");
 888 
 889   // the start block is always the first block in the linear scan order
 890   _linear_scan_order = new BlockList(_num_blocks);
 891   append_block(start_block);
 892 
 893   assert(start_block->end()->as_Base() != NULL, "start block must end with Base-instruction");
 894   BlockBegin* std_entry = ((Base*)start_block->end())->std_entry();
 895   BlockBegin* osr_entry = ((Base*)start_block->end())->osr_entry();
 896 
 897   BlockBegin* sux_of_osr_entry = NULL;
 898   if (osr_entry != NULL) {
 899     // special handling for osr entry:
 900     // ignore the edge between the osr entry and its successor for processing
 901     // the osr entry block is added manually below
 902     assert(osr_entry->number_of_sux() == 1, "osr entry must have exactly one successor");
 903     assert(osr_entry->sux_at(0)->number_of_preds() >= 2, "sucessor of osr entry must have two predecessors (otherwise it is not present in normal control flow");
 904 
 905     sux_of_osr_entry = osr_entry->sux_at(0);
 906     dec_forward_branches(sux_of_osr_entry);
 907 
 908     compute_dominator(osr_entry, start_block);
 909     _iterative_dominators = true;
 910   }
 911   compute_dominator(std_entry, start_block);
 912 
 913   // start processing with standard entry block
 914   assert(_work_list.is_empty(), "list must be empty before processing");
 915 
 916   if (ready_for_processing(std_entry)) {
 917     sort_into_work_list(std_entry);
 918   } else {
 919     assert(false, "the std_entry must be ready for processing (otherwise, the method has no start block)");
 920   }
 921 
 922   do {
 923     BlockBegin* cur = _work_list.pop();
 924 
 925     if (cur == sux_of_osr_entry) {
 926       // the osr entry block is ignored in normal processing, it is never added to the
 927       // work list. Instead, it is added as late as possible manually here.
 928       append_block(osr_entry);
 929       compute_dominator(cur, osr_entry);
 930     }
 931     append_block(cur);
 932 
 933     int i;
 934     int num_sux = cur->number_of_sux();
 935     // changed loop order to get "intuitive" order of if- and else-blocks
 936     for (i = 0; i < num_sux; i++) {
 937       BlockBegin* sux = cur->sux_at(i);
 938       compute_dominator(sux, cur);
 939       if (ready_for_processing(sux)) {
 940         sort_into_work_list(sux);
 941       }
 942     }
 943     num_sux = cur->number_of_exception_handlers();
 944     for (i = 0; i < num_sux; i++) {
 945       BlockBegin* sux = cur->exception_handler_at(i);
 946       compute_dominator(sux, cur);
 947       if (ready_for_processing(sux)) {
 948         sort_into_work_list(sux);
 949       }
 950     }
 951   } while (_work_list.length() > 0);
 952 }
 953 
 954 
 955 bool ComputeLinearScanOrder::compute_dominators_iter() {
 956   bool changed = false;
 957   int num_blocks = _linear_scan_order->length();
 958 
 959   assert(_linear_scan_order->at(0)->dominator() == NULL, "must not have dominator");
 960   assert(_linear_scan_order->at(0)->number_of_preds() == 0, "must not have predecessors");
 961   for (int i = 1; i < num_blocks; i++) {
 962     BlockBegin* block = _linear_scan_order->at(i);
 963 
 964     BlockBegin* dominator = block->pred_at(0);
 965     int num_preds = block->number_of_preds();
 966     for (int i = 1; i < num_preds; i++) {
 967       dominator = common_dominator(dominator, block->pred_at(i));
 968     }
 969 
 970     if (dominator != block->dominator()) {
 971       TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: updating dominator of B%d from B%d to B%d", block->block_id(), block->dominator()->block_id(), dominator->block_id()));
 972 
 973       block->set_dominator(dominator);
 974       changed = true;
 975     }
 976   }
 977   return changed;
 978 }
 979 
 980 void ComputeLinearScanOrder::compute_dominators() {
 981   TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing dominators (iterative computation reqired: %d)", _iterative_dominators));
 982 
 983   // iterative computation of dominators is only required for methods with non-natural loops
 984   // and OSR-methods. For all other methods, the dominators computed when generating the
 985   // linear scan block order are correct.
 986   if (_iterative_dominators) {
 987     do {
 988       TRACE_LINEAR_SCAN(1, tty->print_cr("DOM: next iteration of fix-point calculation"));
 989     } while (compute_dominators_iter());
 990   }
 991 
 992   // check that dominators are correct
 993   assert(!compute_dominators_iter(), "fix point not reached");
 994 }
 995 
 996 
 997 #ifndef PRODUCT
 998 void ComputeLinearScanOrder::print_blocks() {
 999   if (TraceLinearScanLevel >= 2) {
1000     tty->print_cr("----- loop information:");
1001     for (int block_idx = 0; block_idx < _linear_scan_order->length(); block_idx++) {
1002       BlockBegin* cur = _linear_scan_order->at(block_idx);
1003 
1004       tty->print("%4d: B%2d: ", cur->linear_scan_number(), cur->block_id());
1005       for (int loop_idx = 0; loop_idx < _num_loops; loop_idx++) {
1006         tty->print ("%d ", is_block_in_loop(loop_idx, cur));
1007       }
1008       tty->print_cr(" -> loop_index: %2d, loop_depth: %2d", cur->loop_index(), cur->loop_depth());
1009     }
1010   }
1011 
1012   if (TraceLinearScanLevel >= 1) {
1013     tty->print_cr("----- linear-scan block order:");
1014     for (int block_idx = 0; block_idx < _linear_scan_order->length(); block_idx++) {
1015       BlockBegin* cur = _linear_scan_order->at(block_idx);
1016       tty->print("%4d: B%2d    loop: %2d  depth: %2d", cur->linear_scan_number(), cur->block_id(), cur->loop_index(), cur->loop_depth());
1017 
1018       tty->print(cur->is_set(BlockBegin::exception_entry_flag)         ? " ex" : "   ");
1019       tty->print(cur->is_set(BlockBegin::critical_edge_split_flag)     ? " ce" : "   ");
1020       tty->print(cur->is_set(BlockBegin::linear_scan_loop_header_flag) ? " lh" : "   ");
1021       tty->print(cur->is_set(BlockBegin::linear_scan_loop_end_flag)    ? " le" : "   ");
1022 
1023       if (cur->dominator() != NULL) {
1024         tty->print("    dom: B%d ", cur->dominator()->block_id());
1025       } else {
1026         tty->print("    dom: NULL ");
1027       }
1028 
1029       if (cur->number_of_preds() > 0) {
1030         tty->print("    preds: ");
1031         for (int j = 0; j < cur->number_of_preds(); j++) {
1032           BlockBegin* pred = cur->pred_at(j);
1033           tty->print("B%d ", pred->block_id());
1034         }
1035       }
1036       if (cur->number_of_sux() > 0) {
1037         tty->print("    sux: ");
1038         for (int j = 0; j < cur->number_of_sux(); j++) {
1039           BlockBegin* sux = cur->sux_at(j);
1040           tty->print("B%d ", sux->block_id());
1041         }
1042       }
1043       if (cur->number_of_exception_handlers() > 0) {
1044         tty->print("    ex: ");
1045         for (int j = 0; j < cur->number_of_exception_handlers(); j++) {
1046           BlockBegin* ex = cur->exception_handler_at(j);
1047           tty->print("B%d ", ex->block_id());
1048         }
1049       }
1050       tty->cr();
1051     }
1052   }
1053 }
1054 #endif
1055 
1056 #ifdef ASSERT
1057 void ComputeLinearScanOrder::verify() {
1058   assert(_linear_scan_order->length() == _num_blocks, "wrong number of blocks in list");
1059 
1060   if (StressLinearScan) {
1061     // blocks are scrambled when StressLinearScan is used
1062     return;
1063   }
1064 
1065   // check that all successors of a block have a higher linear-scan-number
1066   // and that all predecessors of a block have a lower linear-scan-number
1067   // (only backward branches of loops are ignored)
1068   int i;
1069   for (i = 0; i < _linear_scan_order->length(); i++) {
1070     BlockBegin* cur = _linear_scan_order->at(i);
1071 
1072     assert(cur->linear_scan_number() == i, "incorrect linear_scan_number");
1073     assert(cur->linear_scan_number() >= 0 && cur->linear_scan_number() == _linear_scan_order->index_of(cur), "incorrect linear_scan_number");
1074 
1075     int j;
1076     for (j = cur->number_of_sux() - 1; j >= 0; j--) {
1077       BlockBegin* sux = cur->sux_at(j);
1078 
1079       assert(sux->linear_scan_number() >= 0 && sux->linear_scan_number() == _linear_scan_order->index_of(sux), "incorrect linear_scan_number");
1080       if (!cur->is_set(BlockBegin::linear_scan_loop_end_flag)) {
1081         assert(cur->linear_scan_number() < sux->linear_scan_number(), "invalid order");
1082       }
1083       if (cur->loop_depth() == sux->loop_depth()) {
1084         assert(cur->loop_index() == sux->loop_index() || sux->is_set(BlockBegin::linear_scan_loop_header_flag), "successing blocks with same loop depth must have same loop index");
1085       }
1086     }
1087 
1088     for (j = cur->number_of_preds() - 1; j >= 0; j--) {
1089       BlockBegin* pred = cur->pred_at(j);
1090 
1091       assert(pred->linear_scan_number() >= 0 && pred->linear_scan_number() == _linear_scan_order->index_of(pred), "incorrect linear_scan_number");
1092       if (!cur->is_set(BlockBegin::linear_scan_loop_header_flag)) {
1093         assert(cur->linear_scan_number() > pred->linear_scan_number(), "invalid order");
1094       }
1095       if (cur->loop_depth() == pred->loop_depth()) {
1096         assert(cur->loop_index() == pred->loop_index() || cur->is_set(BlockBegin::linear_scan_loop_header_flag), "successing blocks with same loop depth must have same loop index");
1097       }
1098 
1099       assert(cur->dominator()->linear_scan_number() <= cur->pred_at(j)->linear_scan_number(), "dominator must be before predecessors");
1100     }
1101 
1102     // check dominator
1103     if (i == 0) {
1104       assert(cur->dominator() == NULL, "first block has no dominator");
1105     } else {
1106       assert(cur->dominator() != NULL, "all but first block must have dominator");
1107     }
1108     assert(cur->number_of_preds() != 1 || cur->dominator() == cur->pred_at(0), "Single predecessor must also be dominator");
1109   }
1110 
1111   // check that all loops are continuous
1112   for (int loop_idx = 0; loop_idx < _num_loops; loop_idx++) {
1113     int block_idx = 0;
1114     assert(!is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx)), "the first block must not be present in any loop");
1115 
1116     // skip blocks before the loop
1117     while (block_idx < _num_blocks && !is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx))) {
1118       block_idx++;
1119     }
1120     // skip blocks of loop
1121     while (block_idx < _num_blocks && is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx))) {
1122       block_idx++;
1123     }
1124     // after the first non-loop block, there must not be another loop-block
1125     while (block_idx < _num_blocks) {
1126       assert(!is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx)), "loop not continuous in linear-scan order");
1127       block_idx++;
1128     }
1129   }
1130 }
1131 #endif
1132 
1133 
1134 void IR::compute_code() {
1135   assert(is_valid(), "IR must be valid");
1136 
1137   ComputeLinearScanOrder compute_order(start());
1138   _num_loops = compute_order.num_loops();
1139   _code = compute_order.linear_scan_order();
1140 }
1141 
1142 
1143 void IR::compute_use_counts() {
1144   // make sure all values coming out of this block get evaluated.
1145   int num_blocks = _code->length();
1146   for (int i = 0; i < num_blocks; i++) {
1147     _code->at(i)->end()->state()->pin_stack_for_linear_scan();
1148   }
1149 
1150   // compute use counts
1151   UseCountComputer::compute(_code);
1152 }
1153 
1154 
1155 void IR::iterate_preorder(BlockClosure* closure) {
1156   assert(is_valid(), "IR must be valid");
1157   start()->iterate_preorder(closure);
1158 }
1159 
1160 
1161 void IR::iterate_postorder(BlockClosure* closure) {
1162   assert(is_valid(), "IR must be valid");
1163   start()->iterate_postorder(closure);
1164 }
1165 
1166 void IR::iterate_linear_scan_order(BlockClosure* closure) {
1167   linear_scan_order()->iterate_forward(closure);
1168 }
1169 
1170 
1171 #ifndef PRODUCT
1172 class BlockPrinter: public BlockClosure {
1173  private:
1174   InstructionPrinter* _ip;
1175   bool                _cfg_only;
1176   bool                _live_only;
1177 
1178  public:
1179   BlockPrinter(InstructionPrinter* ip, bool cfg_only, bool live_only = false) {
1180     _ip       = ip;
1181     _cfg_only = cfg_only;
1182     _live_only = live_only;
1183   }
1184 
1185   virtual void block_do(BlockBegin* block) {
1186     if (_cfg_only) {
1187       _ip->print_instr(block); tty->cr();
1188     } else {
1189       block->print_block(*_ip, _live_only);
1190     }
1191   }
1192 };
1193 
1194 
1195 void IR::print(BlockBegin* start, bool cfg_only, bool live_only) {
1196   ttyLocker ttyl;
1197   InstructionPrinter ip(!cfg_only);
1198   BlockPrinter bp(&ip, cfg_only, live_only);
1199   start->iterate_preorder(&bp);
1200   tty->cr();
1201 }
1202 
1203 void IR::print(bool cfg_only, bool live_only) {
1204   if (is_valid()) {
1205     print(start(), cfg_only, live_only);
1206   } else {
1207     tty->print_cr("invalid IR");
1208   }
1209 }
1210 
1211 
1212 define_array(BlockListArray, BlockList*)
1213 define_stack(BlockListList, BlockListArray)
1214 
1215 class PredecessorValidator : public BlockClosure {
1216  private:
1217   BlockListList* _predecessors;
1218   BlockList*     _blocks;
1219 
1220   static int cmp(BlockBegin** a, BlockBegin** b) {
1221     return (*a)->block_id() - (*b)->block_id();
1222   }
1223 
1224  public:
1225   PredecessorValidator(IR* hir) {
1226     ResourceMark rm;
1227     _predecessors = new BlockListList(BlockBegin::number_of_blocks(), NULL);
1228     _blocks = new BlockList();
1229 
1230     int i;
1231     hir->start()->iterate_preorder(this);
1232     if (hir->code() != NULL) {
1233       assert(hir->code()->length() == _blocks->length(), "must match");
1234       for (i = 0; i < _blocks->length(); i++) {
1235         assert(hir->code()->contains(_blocks->at(i)), "should be in both lists");
1236       }
1237     }
1238 
1239     for (i = 0; i < _blocks->length(); i++) {
1240       BlockBegin* block = _blocks->at(i);
1241       BlockList* preds = _predecessors->at(block->block_id());
1242       if (preds == NULL) {
1243         assert(block->number_of_preds() == 0, "should be the same");
1244         continue;
1245       }
1246 
1247       // clone the pred list so we can mutate it
1248       BlockList* pred_copy = new BlockList();
1249       int j;
1250       for (j = 0; j < block->number_of_preds(); j++) {
1251         pred_copy->append(block->pred_at(j));
1252       }
1253       // sort them in the same order
1254       preds->sort(cmp);
1255       pred_copy->sort(cmp);
1256       int length = MIN2(preds->length(), block->number_of_preds());
1257       for (j = 0; j < block->number_of_preds(); j++) {
1258         assert(preds->at(j) == pred_copy->at(j), "must match");
1259       }
1260 
1261       assert(preds->length() == block->number_of_preds(), "should be the same");
1262     }
1263   }
1264 
1265   virtual void block_do(BlockBegin* block) {
1266     _blocks->append(block);
1267     BlockEnd* be = block->end();
1268     int n = be->number_of_sux();
1269     int i;
1270     for (i = 0; i < n; i++) {
1271       BlockBegin* sux = be->sux_at(i);
1272       assert(!sux->is_set(BlockBegin::exception_entry_flag), "must not be xhandler");
1273 
1274       BlockList* preds = _predecessors->at_grow(sux->block_id(), NULL);
1275       if (preds == NULL) {
1276         preds = new BlockList();
1277         _predecessors->at_put(sux->block_id(), preds);
1278       }
1279       preds->append(block);
1280     }
1281 
1282     n = block->number_of_exception_handlers();
1283     for (i = 0; i < n; i++) {
1284       BlockBegin* sux = block->exception_handler_at(i);
1285       assert(sux->is_set(BlockBegin::exception_entry_flag), "must be xhandler");
1286 
1287       BlockList* preds = _predecessors->at_grow(sux->block_id(), NULL);
1288       if (preds == NULL) {
1289         preds = new BlockList();
1290         _predecessors->at_put(sux->block_id(), preds);
1291       }
1292       preds->append(block);
1293     }
1294   }
1295 };
1296 
1297 void IR::verify() {
1298 #ifdef ASSERT
1299   PredecessorValidator pv(this);
1300 #endif
1301 }
1302 
1303 #endif // PRODUCT
1304 
1305 void SubstitutionResolver::substitute(Value* v) {
1306   Value v0 = *v;
1307   if (v0) {
1308     Value vs = v0->subst();
1309     if (vs != v0) {
1310       *v = v0->subst();
1311     }
1312   }
1313 }
1314 
1315 #ifdef ASSERT
1316 void check_substitute(Value* v) {
1317   Value v0 = *v;
1318   if (v0) {
1319     Value vs = v0->subst();
1320     assert(vs == v0, "missed substitution");
1321   }
1322 }
1323 #endif
1324 
1325 
1326 void SubstitutionResolver::block_do(BlockBegin* block) {
1327   Instruction* last = NULL;
1328   for (Instruction* n = block; n != NULL;) {
1329     n->values_do(substitute);
1330     // need to remove this instruction from the instruction stream
1331     if (n->subst() != n) {
1332       assert(last != NULL, "must have last");
1333       last->set_next(n->next(), n->next()->bci());
1334     } else {
1335       last = n;
1336     }
1337     n = last->next();
1338   }
1339 
1340 #ifdef ASSERT
1341   if (block->state()) block->state()->values_do(check_substitute);
1342   block->block_values_do(check_substitute);
1343   if (block->end() && block->end()->state()) block->end()->state()->values_do(check_substitute);
1344 #endif
1345 }
--- EOF ---