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   assert(_stack != NULL, "must be non null");
 235   assert(_bci == SynchronizationEntryBCI || Bytecodes::is_defined(scope()->method()->java_code_at_bci(_bci)), "make sure bci points at a real bytecode");
 236 }
 237 
 238 
 239 CodeEmitInfo::CodeEmitInfo(CodeEmitInfo* info, bool lock_stack_only)
 240   : _scope(info->_scope)
 241   , _exception_handlers(NULL)
 242   , _bci(info->_bci)
 243   , _scope_debug_info(NULL)
 244   , _oop_map(NULL) {

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