1 /*
   2  * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "asm/macroAssembler.hpp"
  27 #include "asm/macroAssembler.inline.hpp"
  28 #include "ci/ciReplay.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "code/exceptionHandlerTable.hpp"
  31 #include "code/nmethod.hpp"
  32 #include "compiler/compileLog.hpp"
  33 #include "compiler/disassembler.hpp"
  34 #include "compiler/oopMap.hpp"
  35 #include "opto/addnode.hpp"
  36 #include "opto/block.hpp"
  37 #include "opto/c2compiler.hpp"
  38 #include "opto/callGenerator.hpp"
  39 #include "opto/callnode.hpp"
  40 #include "opto/cfgnode.hpp"
  41 #include "opto/chaitin.hpp"
  42 #include "opto/compile.hpp"
  43 #include "opto/connode.hpp"
  44 #include "opto/divnode.hpp"
  45 #include "opto/escape.hpp"
  46 #include "opto/idealGraphPrinter.hpp"
  47 #include "opto/loopnode.hpp"
  48 #include "opto/machnode.hpp"
  49 #include "opto/macro.hpp"
  50 #include "opto/matcher.hpp"
  51 #include "opto/mathexactnode.hpp"
  52 #include "opto/memnode.hpp"
  53 #include "opto/mulnode.hpp"
  54 #include "opto/node.hpp"
  55 #include "opto/opcodes.hpp"
  56 #include "opto/output.hpp"
  57 #include "opto/parse.hpp"
  58 #include "opto/phaseX.hpp"
  59 #include "opto/rootnode.hpp"
  60 #include "opto/runtime.hpp"
  61 #include "opto/stringopts.hpp"
  62 #include "opto/type.hpp"
  63 #include "opto/vectornode.hpp"
  64 #include "runtime/arguments.hpp"
  65 #include "runtime/signature.hpp"
  66 #include "runtime/stubRoutines.hpp"
  67 #include "runtime/timer.hpp"
  68 #include "trace/tracing.hpp"
  69 #include "utilities/copy.hpp"
  70 #if defined AD_MD_HPP
  71 # include AD_MD_HPP
  72 #elif defined TARGET_ARCH_MODEL_x86_32
  73 # include "adfiles/ad_x86_32.hpp"
  74 #elif defined TARGET_ARCH_MODEL_x86_64
  75 # include "adfiles/ad_x86_64.hpp"
  76 #elif defined TARGET_ARCH_MODEL_sparc
  77 # include "adfiles/ad_sparc.hpp"
  78 #elif defined TARGET_ARCH_MODEL_zero
  79 # include "adfiles/ad_zero.hpp"
  80 #elif defined TARGET_ARCH_MODEL_ppc_64
  81 # include "adfiles/ad_ppc_64.hpp"
  82 #endif
  83 
  84 
  85 // -------------------- Compile::mach_constant_base_node -----------------------
  86 // Constant table base node singleton.
  87 MachConstantBaseNode* Compile::mach_constant_base_node() {
  88   if (_mach_constant_base_node == NULL) {
  89     _mach_constant_base_node = new (C) MachConstantBaseNode();
  90     _mach_constant_base_node->add_req(C->root());
  91   }
  92   return _mach_constant_base_node;
  93 }
  94 
  95 
  96 /// Support for intrinsics.
  97 
  98 // Return the index at which m must be inserted (or already exists).
  99 // The sort order is by the address of the ciMethod, with is_virtual as minor key.
 100 int Compile::intrinsic_insertion_index(ciMethod* m, bool is_virtual) {
 101 #ifdef ASSERT
 102   for (int i = 1; i < _intrinsics->length(); i++) {
 103     CallGenerator* cg1 = _intrinsics->at(i-1);
 104     CallGenerator* cg2 = _intrinsics->at(i);
 105     assert(cg1->method() != cg2->method()
 106            ? cg1->method()     < cg2->method()
 107            : cg1->is_virtual() < cg2->is_virtual(),
 108            "compiler intrinsics list must stay sorted");
 109   }
 110 #endif
 111   // Binary search sorted list, in decreasing intervals [lo, hi].
 112   int lo = 0, hi = _intrinsics->length()-1;
 113   while (lo <= hi) {
 114     int mid = (uint)(hi + lo) / 2;
 115     ciMethod* mid_m = _intrinsics->at(mid)->method();
 116     if (m < mid_m) {
 117       hi = mid-1;
 118     } else if (m > mid_m) {
 119       lo = mid+1;
 120     } else {
 121       // look at minor sort key
 122       bool mid_virt = _intrinsics->at(mid)->is_virtual();
 123       if (is_virtual < mid_virt) {
 124         hi = mid-1;
 125       } else if (is_virtual > mid_virt) {
 126         lo = mid+1;
 127       } else {
 128         return mid;  // exact match
 129       }
 130     }
 131   }
 132   return lo;  // inexact match
 133 }
 134 
 135 void Compile::register_intrinsic(CallGenerator* cg) {
 136   if (_intrinsics == NULL) {
 137     _intrinsics = new (comp_arena())GrowableArray<CallGenerator*>(comp_arena(), 60, 0, NULL);
 138   }
 139   // This code is stolen from ciObjectFactory::insert.
 140   // Really, GrowableArray should have methods for
 141   // insert_at, remove_at, and binary_search.
 142   int len = _intrinsics->length();
 143   int index = intrinsic_insertion_index(cg->method(), cg->is_virtual());
 144   if (index == len) {
 145     _intrinsics->append(cg);
 146   } else {
 147 #ifdef ASSERT
 148     CallGenerator* oldcg = _intrinsics->at(index);
 149     assert(oldcg->method() != cg->method() || oldcg->is_virtual() != cg->is_virtual(), "don't register twice");
 150 #endif
 151     _intrinsics->append(_intrinsics->at(len-1));
 152     int pos;
 153     for (pos = len-2; pos >= index; pos--) {
 154       _intrinsics->at_put(pos+1,_intrinsics->at(pos));
 155     }
 156     _intrinsics->at_put(index, cg);
 157   }
 158   assert(find_intrinsic(cg->method(), cg->is_virtual()) == cg, "registration worked");
 159 }
 160 
 161 CallGenerator* Compile::find_intrinsic(ciMethod* m, bool is_virtual) {
 162   assert(m->is_loaded(), "don't try this on unloaded methods");
 163   if (_intrinsics != NULL) {
 164     int index = intrinsic_insertion_index(m, is_virtual);
 165     if (index < _intrinsics->length()
 166         && _intrinsics->at(index)->method() == m
 167         && _intrinsics->at(index)->is_virtual() == is_virtual) {
 168       return _intrinsics->at(index);
 169     }
 170   }
 171   // Lazily create intrinsics for intrinsic IDs well-known in the runtime.
 172   if (m->intrinsic_id() != vmIntrinsics::_none &&
 173       m->intrinsic_id() <= vmIntrinsics::LAST_COMPILER_INLINE) {
 174     CallGenerator* cg = make_vm_intrinsic(m, is_virtual);
 175     if (cg != NULL) {
 176       // Save it for next time:
 177       register_intrinsic(cg);
 178       return cg;
 179     } else {
 180       gather_intrinsic_statistics(m->intrinsic_id(), is_virtual, _intrinsic_disabled);
 181     }
 182   }
 183   return NULL;
 184 }
 185 
 186 // Compile:: register_library_intrinsics and make_vm_intrinsic are defined
 187 // in library_call.cpp.
 188 
 189 
 190 #ifndef PRODUCT
 191 // statistics gathering...
 192 
 193 juint  Compile::_intrinsic_hist_count[vmIntrinsics::ID_LIMIT] = {0};
 194 jubyte Compile::_intrinsic_hist_flags[vmIntrinsics::ID_LIMIT] = {0};
 195 
 196 bool Compile::gather_intrinsic_statistics(vmIntrinsics::ID id, bool is_virtual, int flags) {
 197   assert(id > vmIntrinsics::_none && id < vmIntrinsics::ID_LIMIT, "oob");
 198   int oflags = _intrinsic_hist_flags[id];
 199   assert(flags != 0, "what happened?");
 200   if (is_virtual) {
 201     flags |= _intrinsic_virtual;
 202   }
 203   bool changed = (flags != oflags);
 204   if ((flags & _intrinsic_worked) != 0) {
 205     juint count = (_intrinsic_hist_count[id] += 1);
 206     if (count == 1) {
 207       changed = true;           // first time
 208     }
 209     // increment the overall count also:
 210     _intrinsic_hist_count[vmIntrinsics::_none] += 1;
 211   }
 212   if (changed) {
 213     if (((oflags ^ flags) & _intrinsic_virtual) != 0) {
 214       // Something changed about the intrinsic's virtuality.
 215       if ((flags & _intrinsic_virtual) != 0) {
 216         // This is the first use of this intrinsic as a virtual call.
 217         if (oflags != 0) {
 218           // We already saw it as a non-virtual, so note both cases.
 219           flags |= _intrinsic_both;
 220         }
 221       } else if ((oflags & _intrinsic_both) == 0) {
 222         // This is the first use of this intrinsic as a non-virtual
 223         flags |= _intrinsic_both;
 224       }
 225     }
 226     _intrinsic_hist_flags[id] = (jubyte) (oflags | flags);
 227   }
 228   // update the overall flags also:
 229   _intrinsic_hist_flags[vmIntrinsics::_none] |= (jubyte) flags;
 230   return changed;
 231 }
 232 
 233 static char* format_flags(int flags, char* buf) {
 234   buf[0] = 0;
 235   if ((flags & Compile::_intrinsic_worked) != 0)    strcat(buf, ",worked");
 236   if ((flags & Compile::_intrinsic_failed) != 0)    strcat(buf, ",failed");
 237   if ((flags & Compile::_intrinsic_disabled) != 0)  strcat(buf, ",disabled");
 238   if ((flags & Compile::_intrinsic_virtual) != 0)   strcat(buf, ",virtual");
 239   if ((flags & Compile::_intrinsic_both) != 0)      strcat(buf, ",nonvirtual");
 240   if (buf[0] == 0)  strcat(buf, ",");
 241   assert(buf[0] == ',', "must be");
 242   return &buf[1];
 243 }
 244 
 245 void Compile::print_intrinsic_statistics() {
 246   char flagsbuf[100];
 247   ttyLocker ttyl;
 248   if (xtty != NULL)  xtty->head("statistics type='intrinsic'");
 249   tty->print_cr("Compiler intrinsic usage:");
 250   juint total = _intrinsic_hist_count[vmIntrinsics::_none];
 251   if (total == 0)  total = 1;  // avoid div0 in case of no successes
 252   #define PRINT_STAT_LINE(name, c, f) \
 253     tty->print_cr("  %4d (%4.1f%%) %s (%s)", (int)(c), ((c) * 100.0) / total, name, f);
 254   for (int index = 1 + (int)vmIntrinsics::_none; index < (int)vmIntrinsics::ID_LIMIT; index++) {
 255     vmIntrinsics::ID id = (vmIntrinsics::ID) index;
 256     int   flags = _intrinsic_hist_flags[id];
 257     juint count = _intrinsic_hist_count[id];
 258     if ((flags | count) != 0) {
 259       PRINT_STAT_LINE(vmIntrinsics::name_at(id), count, format_flags(flags, flagsbuf));
 260     }
 261   }
 262   PRINT_STAT_LINE("total", total, format_flags(_intrinsic_hist_flags[vmIntrinsics::_none], flagsbuf));
 263   if (xtty != NULL)  xtty->tail("statistics");
 264 }
 265 
 266 void Compile::print_statistics() {
 267   { ttyLocker ttyl;
 268     if (xtty != NULL)  xtty->head("statistics type='opto'");
 269     Parse::print_statistics();
 270     PhaseCCP::print_statistics();
 271     PhaseRegAlloc::print_statistics();
 272     Scheduling::print_statistics();
 273     PhasePeephole::print_statistics();
 274     PhaseIdealLoop::print_statistics();
 275     if (xtty != NULL)  xtty->tail("statistics");
 276   }
 277   if (_intrinsic_hist_flags[vmIntrinsics::_none] != 0) {
 278     // put this under its own <statistics> element.
 279     print_intrinsic_statistics();
 280   }
 281 }
 282 #endif //PRODUCT
 283 
 284 // Support for bundling info
 285 Bundle* Compile::node_bundling(const Node *n) {
 286   assert(valid_bundle_info(n), "oob");
 287   return &_node_bundling_base[n->_idx];
 288 }
 289 
 290 bool Compile::valid_bundle_info(const Node *n) {
 291   return (_node_bundling_limit > n->_idx);
 292 }
 293 
 294 
 295 void Compile::gvn_replace_by(Node* n, Node* nn) {
 296   for (DUIterator_Last imin, i = n->last_outs(imin); i >= imin; ) {
 297     Node* use = n->last_out(i);
 298     bool is_in_table = initial_gvn()->hash_delete(use);
 299     uint uses_found = 0;
 300     for (uint j = 0; j < use->len(); j++) {
 301       if (use->in(j) == n) {
 302         if (j < use->req())
 303           use->set_req(j, nn);
 304         else
 305           use->set_prec(j, nn);
 306         uses_found++;
 307       }
 308     }
 309     if (is_in_table) {
 310       // reinsert into table
 311       initial_gvn()->hash_find_insert(use);
 312     }
 313     record_for_igvn(use);
 314     i -= uses_found;    // we deleted 1 or more copies of this edge
 315   }
 316 }
 317 
 318 
 319 static inline bool not_a_node(const Node* n) {
 320   if (n == NULL)                   return true;
 321   if (((intptr_t)n & 1) != 0)      return true;  // uninitialized, etc.
 322   if (*(address*)n == badAddress)  return true;  // kill by Node::destruct
 323   return false;
 324 }
 325 
 326 // Identify all nodes that are reachable from below, useful.
 327 // Use breadth-first pass that records state in a Unique_Node_List,
 328 // recursive traversal is slower.
 329 void Compile::identify_useful_nodes(Unique_Node_List &useful) {
 330   int estimated_worklist_size = unique();
 331   useful.map( estimated_worklist_size, NULL );  // preallocate space
 332 
 333   // Initialize worklist
 334   if (root() != NULL)     { useful.push(root()); }
 335   // If 'top' is cached, declare it useful to preserve cached node
 336   if( cached_top_node() ) { useful.push(cached_top_node()); }
 337 
 338   // Push all useful nodes onto the list, breadthfirst
 339   for( uint next = 0; next < useful.size(); ++next ) {
 340     assert( next < unique(), "Unique useful nodes < total nodes");
 341     Node *n  = useful.at(next);
 342     uint max = n->len();
 343     for( uint i = 0; i < max; ++i ) {
 344       Node *m = n->in(i);
 345       if (not_a_node(m))  continue;
 346       useful.push(m);
 347     }
 348   }
 349 }
 350 
 351 // Update dead_node_list with any missing dead nodes using useful
 352 // list. Consider all non-useful nodes to be useless i.e., dead nodes.
 353 void Compile::update_dead_node_list(Unique_Node_List &useful) {
 354   uint max_idx = unique();
 355   VectorSet& useful_node_set = useful.member_set();
 356 
 357   for (uint node_idx = 0; node_idx < max_idx; node_idx++) {
 358     // If node with index node_idx is not in useful set,
 359     // mark it as dead in dead node list.
 360     if (! useful_node_set.test(node_idx) ) {
 361       record_dead_node(node_idx);
 362     }
 363   }
 364 }
 365 
 366 void Compile::remove_useless_late_inlines(GrowableArray<CallGenerator*>* inlines, Unique_Node_List &useful) {
 367   int shift = 0;
 368   for (int i = 0; i < inlines->length(); i++) {
 369     CallGenerator* cg = inlines->at(i);
 370     CallNode* call = cg->call_node();
 371     if (shift > 0) {
 372       inlines->at_put(i-shift, cg);
 373     }
 374     if (!useful.member(call)) {
 375       shift++;
 376     }
 377   }
 378   inlines->trunc_to(inlines->length()-shift);
 379 }
 380 
 381 // Disconnect all useless nodes by disconnecting those at the boundary.
 382 void Compile::remove_useless_nodes(Unique_Node_List &useful) {
 383   uint next = 0;
 384   while (next < useful.size()) {
 385     Node *n = useful.at(next++);
 386     if (n->is_SafePoint()) {
 387       // We're done with a parsing phase. Replaced nodes are not valid
 388       // beyond that point.
 389       n->as_SafePoint()->delete_replaced_nodes();
 390     }
 391     // Use raw traversal of out edges since this code removes out edges
 392     int max = n->outcnt();
 393     for (int j = 0; j < max; ++j) {
 394       Node* child = n->raw_out(j);
 395       if (! useful.member(child)) {
 396         assert(!child->is_top() || child != top(),
 397                "If top is cached in Compile object it is in useful list");
 398         // Only need to remove this out-edge to the useless node
 399         n->raw_del_out(j);
 400         --j;
 401         --max;
 402       }
 403     }
 404     if (n->outcnt() == 1 && n->has_special_unique_user()) {
 405       record_for_igvn(n->unique_out());
 406     }
 407   }
 408   // Remove useless macro and predicate opaq nodes
 409   for (int i = C->macro_count()-1; i >= 0; i--) {
 410     Node* n = C->macro_node(i);
 411     if (!useful.member(n)) {
 412       remove_macro_node(n);
 413     }
 414   }
 415   // Remove useless expensive node
 416   for (int i = C->expensive_count()-1; i >= 0; i--) {
 417     Node* n = C->expensive_node(i);
 418     if (!useful.member(n)) {
 419       remove_expensive_node(n);
 420     }
 421   }
 422   // clean up the late inline lists
 423   remove_useless_late_inlines(&_string_late_inlines, useful);
 424   remove_useless_late_inlines(&_boxing_late_inlines, useful);
 425   remove_useless_late_inlines(&_late_inlines, useful);
 426   debug_only(verify_graph_edges(true/*check for no_dead_code*/);)
 427 }
 428 
 429 //------------------------------frame_size_in_words-----------------------------
 430 // frame_slots in units of words
 431 int Compile::frame_size_in_words() const {
 432   // shift is 0 in LP32 and 1 in LP64
 433   const int shift = (LogBytesPerWord - LogBytesPerInt);
 434   int words = _frame_slots >> shift;
 435   assert( words << shift == _frame_slots, "frame size must be properly aligned in LP64" );
 436   return words;
 437 }
 438 
 439 // To bang the stack of this compiled method we use the stack size
 440 // that the interpreter would need in case of a deoptimization. This
 441 // removes the need to bang the stack in the deoptimization blob which
 442 // in turn simplifies stack overflow handling.
 443 int Compile::bang_size_in_bytes() const {
 444   return MAX2(_interpreter_frame_size, frame_size_in_bytes());
 445 }
 446 
 447 // ============================================================================
 448 //------------------------------CompileWrapper---------------------------------
 449 class CompileWrapper : public StackObj {
 450   Compile *const _compile;
 451  public:
 452   CompileWrapper(Compile* compile);
 453 
 454   ~CompileWrapper();
 455 };
 456 
 457 CompileWrapper::CompileWrapper(Compile* compile) : _compile(compile) {
 458   // the Compile* pointer is stored in the current ciEnv:
 459   ciEnv* env = compile->env();
 460   assert(env == ciEnv::current(), "must already be a ciEnv active");
 461   assert(env->compiler_data() == NULL, "compile already active?");
 462   env->set_compiler_data(compile);
 463   assert(compile == Compile::current(), "sanity");
 464 
 465   compile->set_type_dict(NULL);
 466   compile->set_type_hwm(NULL);
 467   compile->set_type_last_size(0);
 468   compile->set_last_tf(NULL, NULL);
 469   compile->set_indexSet_arena(NULL);
 470   compile->set_indexSet_free_block_list(NULL);
 471   compile->init_type_arena();
 472   Type::Initialize(compile);
 473   _compile->set_scratch_buffer_blob(NULL);
 474   _compile->begin_method();
 475 }
 476 CompileWrapper::~CompileWrapper() {
 477   _compile->end_method();
 478   if (_compile->scratch_buffer_blob() != NULL)
 479     BufferBlob::free(_compile->scratch_buffer_blob());
 480   _compile->env()->set_compiler_data(NULL);
 481 }
 482 
 483 
 484 //----------------------------print_compile_messages---------------------------
 485 void Compile::print_compile_messages() {
 486 #ifndef PRODUCT
 487   // Check if recompiling
 488   if (_subsume_loads == false && PrintOpto) {
 489     // Recompiling without allowing machine instructions to subsume loads
 490     tty->print_cr("*********************************************************");
 491     tty->print_cr("** Bailout: Recompile without subsuming loads          **");
 492     tty->print_cr("*********************************************************");
 493   }
 494   if (_do_escape_analysis != DoEscapeAnalysis && PrintOpto) {
 495     // Recompiling without escape analysis
 496     tty->print_cr("*********************************************************");
 497     tty->print_cr("** Bailout: Recompile without escape analysis          **");
 498     tty->print_cr("*********************************************************");
 499   }
 500   if (_eliminate_boxing != EliminateAutoBox && PrintOpto) {
 501     // Recompiling without boxing elimination
 502     tty->print_cr("*********************************************************");
 503     tty->print_cr("** Bailout: Recompile without boxing elimination       **");
 504     tty->print_cr("*********************************************************");
 505   }
 506   if (env()->break_at_compile()) {
 507     // Open the debugger when compiling this method.
 508     tty->print("### Breaking when compiling: ");
 509     method()->print_short_name();
 510     tty->cr();
 511     BREAKPOINT;
 512   }
 513 
 514   if( PrintOpto ) {
 515     if (is_osr_compilation()) {
 516       tty->print("[OSR]%3d", _compile_id);
 517     } else {
 518       tty->print("%3d", _compile_id);
 519     }
 520   }
 521 #endif
 522 }
 523 
 524 
 525 //-----------------------init_scratch_buffer_blob------------------------------
 526 // Construct a temporary BufferBlob and cache it for this compile.
 527 void Compile::init_scratch_buffer_blob(int const_size) {
 528   // If there is already a scratch buffer blob allocated and the
 529   // constant section is big enough, use it.  Otherwise free the
 530   // current and allocate a new one.
 531   BufferBlob* blob = scratch_buffer_blob();
 532   if ((blob != NULL) && (const_size <= _scratch_const_size)) {
 533     // Use the current blob.
 534   } else {
 535     if (blob != NULL) {
 536       BufferBlob::free(blob);
 537     }
 538 
 539     ResourceMark rm;
 540     _scratch_const_size = const_size;
 541     int size = (MAX_inst_size + MAX_stubs_size + _scratch_const_size);
 542     blob = BufferBlob::create("Compile::scratch_buffer", size);
 543     // Record the buffer blob for next time.
 544     set_scratch_buffer_blob(blob);
 545     // Have we run out of code space?
 546     if (scratch_buffer_blob() == NULL) {
 547       // Let CompilerBroker disable further compilations.
 548       record_failure("Not enough space for scratch buffer in CodeCache");
 549       return;
 550     }
 551   }
 552 
 553   // Initialize the relocation buffers
 554   relocInfo* locs_buf = (relocInfo*) blob->content_end() - MAX_locs_size;
 555   set_scratch_locs_memory(locs_buf);
 556 }
 557 
 558 
 559 //-----------------------scratch_emit_size-------------------------------------
 560 // Helper function that computes size by emitting code
 561 uint Compile::scratch_emit_size(const Node* n) {
 562   // Start scratch_emit_size section.
 563   set_in_scratch_emit_size(true);
 564 
 565   // Emit into a trash buffer and count bytes emitted.
 566   // This is a pretty expensive way to compute a size,
 567   // but it works well enough if seldom used.
 568   // All common fixed-size instructions are given a size
 569   // method by the AD file.
 570   // Note that the scratch buffer blob and locs memory are
 571   // allocated at the beginning of the compile task, and
 572   // may be shared by several calls to scratch_emit_size.
 573   // The allocation of the scratch buffer blob is particularly
 574   // expensive, since it has to grab the code cache lock.
 575   BufferBlob* blob = this->scratch_buffer_blob();
 576   assert(blob != NULL, "Initialize BufferBlob at start");
 577   assert(blob->size() > MAX_inst_size, "sanity");
 578   relocInfo* locs_buf = scratch_locs_memory();
 579   address blob_begin = blob->content_begin();
 580   address blob_end   = (address)locs_buf;
 581   assert(blob->content_contains(blob_end), "sanity");
 582   CodeBuffer buf(blob_begin, blob_end - blob_begin);
 583   buf.initialize_consts_size(_scratch_const_size);
 584   buf.initialize_stubs_size(MAX_stubs_size);
 585   assert(locs_buf != NULL, "sanity");
 586   int lsize = MAX_locs_size / 3;
 587   buf.consts()->initialize_shared_locs(&locs_buf[lsize * 0], lsize);
 588   buf.insts()->initialize_shared_locs( &locs_buf[lsize * 1], lsize);
 589   buf.stubs()->initialize_shared_locs( &locs_buf[lsize * 2], lsize);
 590 
 591   // Do the emission.
 592 
 593   Label fakeL; // Fake label for branch instructions.
 594   Label*   saveL = NULL;
 595   uint save_bnum = 0;
 596   bool is_branch = n->is_MachBranch();
 597   if (is_branch) {
 598     MacroAssembler masm(&buf);
 599     masm.bind(fakeL);
 600     n->as_MachBranch()->save_label(&saveL, &save_bnum);
 601     n->as_MachBranch()->label_set(&fakeL, 0);
 602   }
 603   n->emit(buf, this->regalloc());
 604   if (is_branch) // Restore label.
 605     n->as_MachBranch()->label_set(saveL, save_bnum);
 606 
 607   // End scratch_emit_size section.
 608   set_in_scratch_emit_size(false);
 609 
 610   return buf.insts_size();
 611 }
 612 
 613 
 614 // ============================================================================
 615 //------------------------------Compile standard-------------------------------
 616 debug_only( int Compile::_debug_idx = 100000; )
 617 
 618 // Compile a method.  entry_bci is -1 for normal compilations and indicates
 619 // the continuation bci for on stack replacement.
 620 
 621 
 622 Compile::Compile( ciEnv* ci_env, C2Compiler* compiler, ciMethod* target, int osr_bci,
 623                   bool subsume_loads, bool do_escape_analysis, bool eliminate_boxing )
 624                 : Phase(Compiler),
 625                   _env(ci_env),
 626                   _log(ci_env->log()),
 627                   _compile_id(ci_env->compile_id()),
 628                   _save_argument_registers(false),
 629                   _stub_name(NULL),
 630                   _stub_function(NULL),
 631                   _stub_entry_point(NULL),
 632                   _method(target),
 633                   _entry_bci(osr_bci),
 634                   _initial_gvn(NULL),
 635                   _for_igvn(NULL),
 636                   _warm_calls(NULL),
 637                   _subsume_loads(subsume_loads),
 638                   _do_escape_analysis(do_escape_analysis),
 639                   _eliminate_boxing(eliminate_boxing),
 640                   _failure_reason(NULL),
 641                   _code_buffer("Compile::Fill_buffer"),
 642                   _orig_pc_slot(0),
 643                   _orig_pc_slot_offset_in_bytes(0),
 644                   _has_method_handle_invokes(false),
 645                   _mach_constant_base_node(NULL),
 646                   _node_bundling_limit(0),
 647                   _node_bundling_base(NULL),
 648                   _java_calls(0),
 649                   _inner_loops(0),
 650                   _scratch_const_size(-1),
 651                   _in_scratch_emit_size(false),
 652                   _dead_node_list(comp_arena()),
 653                   _dead_node_count(0),
 654 #ifndef PRODUCT
 655                   _trace_opto_output(TraceOptoOutput || method()->has_option("TraceOptoOutput")),
 656                   _in_dump_cnt(0),
 657                   _printer(IdealGraphPrinter::printer()),
 658 #endif
 659                   _congraph(NULL),
 660                   _comp_arena(mtCompiler),
 661                   _node_arena(mtCompiler),
 662                   _old_arena(mtCompiler),
 663                   _Compile_types(mtCompiler),
 664                   _replay_inline_data(NULL),
 665                   _late_inlines(comp_arena(), 2, 0, NULL),
 666                   _string_late_inlines(comp_arena(), 2, 0, NULL),
 667                   _boxing_late_inlines(comp_arena(), 2, 0, NULL),
 668                   _late_inlines_pos(0),
 669                   _number_of_mh_late_inlines(0),
 670                   _inlining_progress(false),
 671                   _inlining_incrementally(false),
 672                   _print_inlining_list(NULL),
 673                   _print_inlining_idx(0),
 674                   _interpreter_frame_size(0),
 675                   _max_node_limit(MaxNodeLimit) {
 676   C = this;
 677 
 678   CompileWrapper cw(this);
 679 #ifndef PRODUCT
 680   if (TimeCompiler2) {
 681     tty->print(" ");
 682     target->holder()->name()->print();
 683     tty->print(".");
 684     target->print_short_name();
 685     tty->print("  ");
 686   }
 687   TraceTime t1("Total compilation time", &_t_totalCompilation, TimeCompiler, TimeCompiler2);
 688   TraceTime t2(NULL, &_t_methodCompilation, TimeCompiler, false);
 689   bool print_opto_assembly = PrintOptoAssembly || _method->has_option("PrintOptoAssembly");
 690   if (!print_opto_assembly) {
 691     bool print_assembly = (PrintAssembly || _method->should_print_assembly());
 692     if (print_assembly && !Disassembler::can_decode()) {
 693       tty->print_cr("PrintAssembly request changed to PrintOptoAssembly");
 694       print_opto_assembly = true;
 695     }
 696   }
 697   set_print_assembly(print_opto_assembly);
 698   set_parsed_irreducible_loop(false);
 699 
 700   if (method()->has_option("ReplayInline")) {
 701     _replay_inline_data = ciReplay::load_inline_data(method(), entry_bci(), ci_env->comp_level());
 702   }
 703 #endif
 704   set_print_inlining(PrintInlining || method()->has_option("PrintInlining") NOT_PRODUCT( || PrintOptoInlining));
 705   set_print_intrinsics(PrintIntrinsics || method()->has_option("PrintIntrinsics"));
 706   set_has_irreducible_loop(true); // conservative until build_loop_tree() reset it
 707 
 708   if (ProfileTraps RTM_OPT_ONLY( || UseRTMLocking )) {
 709     // Make sure the method being compiled gets its own MDO,
 710     // so we can at least track the decompile_count().
 711     // Need MDO to record RTM code generation state.
 712     method()->ensure_method_data();
 713   }
 714 
 715   Init(::AliasLevel);
 716 
 717 
 718   print_compile_messages();
 719 
 720   _ilt = InlineTree::build_inline_tree_root();
 721 
 722   // Even if NO memory addresses are used, MergeMem nodes must have at least 1 slice
 723   assert(num_alias_types() >= AliasIdxRaw, "");
 724 
 725 #define MINIMUM_NODE_HASH  1023
 726   // Node list that Iterative GVN will start with
 727   Unique_Node_List for_igvn(comp_arena());
 728   set_for_igvn(&for_igvn);
 729 
 730   // GVN that will be run immediately on new nodes
 731   uint estimated_size = method()->code_size()*4+64;
 732   estimated_size = (estimated_size < MINIMUM_NODE_HASH ? MINIMUM_NODE_HASH : estimated_size);
 733   PhaseGVN gvn(node_arena(), estimated_size);
 734   set_initial_gvn(&gvn);
 735 
 736   if (print_inlining() || print_intrinsics()) {
 737     _print_inlining_list = new (comp_arena())GrowableArray<PrintInliningBuffer>(comp_arena(), 1, 1, PrintInliningBuffer());
 738   }
 739   { // Scope for timing the parser
 740     TracePhase t3("parse", &_t_parser, true);
 741 
 742     // Put top into the hash table ASAP.
 743     initial_gvn()->transform_no_reclaim(top());
 744 
 745     // Set up tf(), start(), and find a CallGenerator.
 746     CallGenerator* cg = NULL;
 747     if (is_osr_compilation()) {
 748       const TypeTuple *domain = StartOSRNode::osr_domain();
 749       const TypeTuple *range = TypeTuple::make_range(method()->signature());
 750       init_tf(TypeFunc::make(domain, range));
 751       StartNode* s = new (this) StartOSRNode(root(), domain);
 752       initial_gvn()->set_type_bottom(s);
 753       init_start(s);
 754       cg = CallGenerator::for_osr(method(), entry_bci());
 755     } else {
 756       // Normal case.
 757       init_tf(TypeFunc::make(method()));
 758       StartNode* s = new (this) StartNode(root(), tf()->domain());
 759       initial_gvn()->set_type_bottom(s);
 760       init_start(s);
 761       if (method()->intrinsic_id() == vmIntrinsics::_Reference_get && UseG1GC) {
 762         // With java.lang.ref.reference.get() we must go through the
 763         // intrinsic when G1 is enabled - even when get() is the root
 764         // method of the compile - so that, if necessary, the value in
 765         // the referent field of the reference object gets recorded by
 766         // the pre-barrier code.
 767         // Specifically, if G1 is enabled, the value in the referent
 768         // field is recorded by the G1 SATB pre barrier. This will
 769         // result in the referent being marked live and the reference
 770         // object removed from the list of discovered references during
 771         // reference processing.
 772         cg = find_intrinsic(method(), false);
 773       }
 774       if (cg == NULL) {
 775         float past_uses = method()->interpreter_invocation_count();
 776         float expected_uses = past_uses;
 777         cg = CallGenerator::for_inline(method(), expected_uses);
 778       }
 779     }
 780     if (failing())  return;
 781     if (cg == NULL) {
 782       record_method_not_compilable_all_tiers("cannot parse method");
 783       return;
 784     }
 785     JVMState* jvms = build_start_state(start(), tf());
 786     if ((jvms = cg->generate(jvms)) == NULL) {
 787       record_method_not_compilable("method parse failed");
 788       return;
 789     }
 790     GraphKit kit(jvms);
 791 
 792     if (!kit.stopped()) {
 793       // Accept return values, and transfer control we know not where.
 794       // This is done by a special, unique ReturnNode bound to root.
 795       return_values(kit.jvms());
 796     }
 797 
 798     if (kit.has_exceptions()) {
 799       // Any exceptions that escape from this call must be rethrown
 800       // to whatever caller is dynamically above us on the stack.
 801       // This is done by a special, unique RethrowNode bound to root.
 802       rethrow_exceptions(kit.transfer_exceptions_into_jvms());
 803     }
 804 
 805     assert(IncrementalInline || (_late_inlines.length() == 0 && !has_mh_late_inlines()), "incremental inlining is off");
 806 
 807     if (_late_inlines.length() == 0 && !has_mh_late_inlines() && !failing() && has_stringbuilder()) {
 808       inline_string_calls(true);
 809     }
 810 
 811     if (failing())  return;
 812 
 813     print_method(PHASE_BEFORE_REMOVEUSELESS, 3);
 814 
 815     // Remove clutter produced by parsing.
 816     if (!failing()) {
 817       ResourceMark rm;
 818       PhaseRemoveUseless pru(initial_gvn(), &for_igvn);
 819     }
 820   }
 821 
 822   // Note:  Large methods are capped off in do_one_bytecode().
 823   if (failing())  return;
 824 
 825   // After parsing, node notes are no longer automagic.
 826   // They must be propagated by register_new_node_with_optimizer(),
 827   // clone(), or the like.
 828   set_default_node_notes(NULL);
 829 
 830   for (;;) {
 831     int successes = Inline_Warm();
 832     if (failing())  return;
 833     if (successes == 0)  break;
 834   }
 835 
 836   // Drain the list.
 837   Finish_Warm();
 838 #ifndef PRODUCT
 839   if (_printer) {
 840     _printer->print_inlining(this);
 841   }
 842 #endif
 843 
 844   if (failing())  return;
 845   NOT_PRODUCT( verify_graph_edges(); )
 846 
 847   // Now optimize
 848   Optimize();
 849   if (failing())  return;
 850   NOT_PRODUCT( verify_graph_edges(); )
 851 
 852 #ifndef PRODUCT
 853   if (PrintIdeal) {
 854     ttyLocker ttyl;  // keep the following output all in one block
 855     // This output goes directly to the tty, not the compiler log.
 856     // To enable tools to match it up with the compilation activity,
 857     // be sure to tag this tty output with the compile ID.
 858     if (xtty != NULL) {
 859       xtty->head("ideal compile_id='%d'%s", compile_id(),
 860                  is_osr_compilation()    ? " compile_kind='osr'" :
 861                  "");
 862     }
 863     root()->dump(9999);
 864     if (xtty != NULL) {
 865       xtty->tail("ideal");
 866     }
 867   }
 868 #endif
 869 
 870   NOT_PRODUCT( verify_barriers(); )
 871 
 872   // Dump compilation data to replay it.
 873   if (method()->has_option("DumpReplay")) {
 874     env()->dump_replay_data(_compile_id);
 875   }
 876   if (method()->has_option("DumpInline") && (ilt() != NULL)) {
 877     env()->dump_inline_data(_compile_id);
 878   }
 879 
 880   // Now that we know the size of all the monitors we can add a fixed slot
 881   // for the original deopt pc.
 882 
 883   _orig_pc_slot =  fixed_slots();
 884   int next_slot = _orig_pc_slot + (sizeof(address) / VMRegImpl::stack_slot_size);
 885   set_fixed_slots(next_slot);
 886 
 887   // Compute when to use implicit null checks. Used by matching trap based
 888   // nodes and NullCheck optimization.
 889   set_allowed_deopt_reasons();
 890 
 891   // Now generate code
 892   Code_Gen();
 893   if (failing())  return;
 894 
 895   // Check if we want to skip execution of all compiled code.
 896   {
 897 #ifndef PRODUCT
 898     if (OptoNoExecute) {
 899       record_method_not_compilable("+OptoNoExecute");  // Flag as failed
 900       return;
 901     }
 902     TracePhase t2("install_code", &_t_registerMethod, TimeCompiler);
 903 #endif
 904 
 905     if (is_osr_compilation()) {
 906       _code_offsets.set_value(CodeOffsets::Verified_Entry, 0);
 907       _code_offsets.set_value(CodeOffsets::OSR_Entry, _first_block_size);
 908     } else {
 909       _code_offsets.set_value(CodeOffsets::Verified_Entry, _first_block_size);
 910       _code_offsets.set_value(CodeOffsets::OSR_Entry, 0);
 911     }
 912 
 913     env()->register_method(_method, _entry_bci,
 914                            &_code_offsets,
 915                            _orig_pc_slot_offset_in_bytes,
 916                            code_buffer(),
 917                            frame_size_in_words(), _oop_map_set,
 918                            &_handler_table, &_inc_table,
 919                            compiler,
 920                            env()->comp_level(),
 921                            has_unsafe_access(),
 922                            SharedRuntime::is_wide_vector(max_vector_size()),
 923                            rtm_state()
 924                            );
 925 
 926     if (log() != NULL) // Print code cache state into compiler log
 927       log()->code_cache_state();
 928   }
 929 }
 930 
 931 //------------------------------Compile----------------------------------------
 932 // Compile a runtime stub
 933 Compile::Compile( ciEnv* ci_env,
 934                   TypeFunc_generator generator,
 935                   address stub_function,
 936                   const char *stub_name,
 937                   int is_fancy_jump,
 938                   bool pass_tls,
 939                   bool save_arg_registers,
 940                   bool return_pc )
 941   : Phase(Compiler),
 942     _env(ci_env),
 943     _log(ci_env->log()),
 944     _compile_id(0),
 945     _save_argument_registers(save_arg_registers),
 946     _method(NULL),
 947     _stub_name(stub_name),
 948     _stub_function(stub_function),
 949     _stub_entry_point(NULL),
 950     _entry_bci(InvocationEntryBci),
 951     _initial_gvn(NULL),
 952     _for_igvn(NULL),
 953     _warm_calls(NULL),
 954     _orig_pc_slot(0),
 955     _orig_pc_slot_offset_in_bytes(0),
 956     _subsume_loads(true),
 957     _do_escape_analysis(false),
 958     _eliminate_boxing(false),
 959     _failure_reason(NULL),
 960     _code_buffer("Compile::Fill_buffer"),
 961     _has_method_handle_invokes(false),
 962     _mach_constant_base_node(NULL),
 963     _node_bundling_limit(0),
 964     _node_bundling_base(NULL),
 965     _java_calls(0),
 966     _inner_loops(0),
 967 #ifndef PRODUCT
 968     _trace_opto_output(TraceOptoOutput),
 969     _in_dump_cnt(0),
 970     _printer(NULL),
 971 #endif
 972     _comp_arena(mtCompiler),
 973     _node_arena(mtCompiler),
 974     _old_arena(mtCompiler),
 975     _Compile_types(mtCompiler),
 976     _dead_node_list(comp_arena()),
 977     _dead_node_count(0),
 978     _congraph(NULL),
 979     _replay_inline_data(NULL),
 980     _number_of_mh_late_inlines(0),
 981     _inlining_progress(false),
 982     _inlining_incrementally(false),
 983     _print_inlining_list(NULL),
 984     _print_inlining_idx(0),
 985     _allowed_reasons(0),
 986     _interpreter_frame_size(0),
 987     _max_node_limit(MaxNodeLimit) {
 988   C = this;
 989 
 990 #ifndef PRODUCT
 991   TraceTime t1(NULL, &_t_totalCompilation, TimeCompiler, false);
 992   TraceTime t2(NULL, &_t_stubCompilation, TimeCompiler, false);
 993   set_print_assembly(PrintFrameConverterAssembly);
 994   set_parsed_irreducible_loop(false);
 995 #endif
 996   set_has_irreducible_loop(false); // no loops
 997 
 998   CompileWrapper cw(this);
 999   Init(/*AliasLevel=*/ 0);
1000   init_tf((*generator)());
1001 
1002   {
1003     // The following is a dummy for the sake of GraphKit::gen_stub
1004     Unique_Node_List for_igvn(comp_arena());
1005     set_for_igvn(&for_igvn);  // not used, but some GraphKit guys push on this
1006     PhaseGVN gvn(Thread::current()->resource_area(),255);
1007     set_initial_gvn(&gvn);    // not significant, but GraphKit guys use it pervasively
1008     gvn.transform_no_reclaim(top());
1009 
1010     GraphKit kit;
1011     kit.gen_stub(stub_function, stub_name, is_fancy_jump, pass_tls, return_pc);
1012   }
1013 
1014   NOT_PRODUCT( verify_graph_edges(); )
1015   Code_Gen();
1016   if (failing())  return;
1017 
1018 
1019   // Entry point will be accessed using compile->stub_entry_point();
1020   if (code_buffer() == NULL) {
1021     Matcher::soft_match_failure();
1022   } else {
1023     if (PrintAssembly && (WizardMode || Verbose))
1024       tty->print_cr("### Stub::%s", stub_name);
1025 
1026     if (!failing()) {
1027       assert(_fixed_slots == 0, "no fixed slots used for runtime stubs");
1028 
1029       // Make the NMethod
1030       // For now we mark the frame as never safe for profile stackwalking
1031       RuntimeStub *rs = RuntimeStub::new_runtime_stub(stub_name,
1032                                                       code_buffer(),
1033                                                       CodeOffsets::frame_never_safe,
1034                                                       // _code_offsets.value(CodeOffsets::Frame_Complete),
1035                                                       frame_size_in_words(),
1036                                                       _oop_map_set,
1037                                                       save_arg_registers);
1038       assert(rs != NULL && rs->is_runtime_stub(), "sanity check");
1039 
1040       _stub_entry_point = rs->entry_point();
1041     }
1042   }
1043 }
1044 
1045 //------------------------------Init-------------------------------------------
1046 // Prepare for a single compilation
1047 void Compile::Init(int aliaslevel) {
1048   _unique  = 0;
1049   _regalloc = NULL;
1050 
1051   _tf      = NULL;  // filled in later
1052   _top     = NULL;  // cached later
1053   _matcher = NULL;  // filled in later
1054   _cfg     = NULL;  // filled in later
1055 
1056   set_24_bit_selection_and_mode(Use24BitFP, false);
1057 
1058   _node_note_array = NULL;
1059   _default_node_notes = NULL;
1060 
1061   _immutable_memory = NULL; // filled in at first inquiry
1062 
1063   // Globally visible Nodes
1064   // First set TOP to NULL to give safe behavior during creation of RootNode
1065   set_cached_top_node(NULL);
1066   set_root(new (this) RootNode());
1067   // Now that you have a Root to point to, create the real TOP
1068   set_cached_top_node( new (this) ConNode(Type::TOP) );
1069   set_recent_alloc(NULL, NULL);
1070 
1071   // Create Debug Information Recorder to record scopes, oopmaps, etc.
1072   env()->set_oop_recorder(new OopRecorder(env()->arena()));
1073   env()->set_debug_info(new DebugInformationRecorder(env()->oop_recorder()));
1074   env()->set_dependencies(new Dependencies(env()));
1075 
1076   _fixed_slots = 0;
1077   set_has_split_ifs(false);
1078   set_has_loops(has_method() && method()->has_loops()); // first approximation
1079   set_has_stringbuilder(false);
1080   set_has_boxed_value(false);
1081   _trap_can_recompile = false;  // no traps emitted yet
1082   _major_progress = true; // start out assuming good things will happen
1083   set_has_unsafe_access(false);
1084   set_max_vector_size(0);
1085   Copy::zero_to_bytes(_trap_hist, sizeof(_trap_hist));
1086   set_decompile_count(0);
1087 
1088   set_do_freq_based_layout(BlockLayoutByFrequency || method_has_option("BlockLayoutByFrequency"));
1089   set_num_loop_opts(LoopOptsCount);
1090   set_do_inlining(Inline);
1091   set_max_inline_size(MaxInlineSize);
1092   set_freq_inline_size(FreqInlineSize);
1093   set_do_scheduling(OptoScheduling);
1094   set_do_count_invocations(false);
1095   set_do_method_data_update(false);
1096   set_rtm_state(NoRTM); // No RTM lock eliding by default
1097   method_has_option_value("MaxNodeLimit", _max_node_limit);
1098 #if INCLUDE_RTM_OPT
1099   if (UseRTMLocking && has_method() && (method()->method_data_or_null() != NULL)) {
1100     int rtm_state = method()->method_data()->rtm_state();
1101     if (method_has_option("NoRTMLockEliding") || ((rtm_state & NoRTM) != 0)) {
1102       // Don't generate RTM lock eliding code.
1103       set_rtm_state(NoRTM);
1104     } else if (method_has_option("UseRTMLockEliding") || ((rtm_state & UseRTM) != 0) || !UseRTMDeopt) {
1105       // Generate RTM lock eliding code without abort ratio calculation code.
1106       set_rtm_state(UseRTM);
1107     } else if (UseRTMDeopt) {
1108       // Generate RTM lock eliding code and include abort ratio calculation
1109       // code if UseRTMDeopt is on.
1110       set_rtm_state(ProfileRTM);
1111     }
1112   }
1113 #endif
1114   if (debug_info()->recording_non_safepoints()) {
1115     set_node_note_array(new(comp_arena()) GrowableArray<Node_Notes*>
1116                         (comp_arena(), 8, 0, NULL));
1117     set_default_node_notes(Node_Notes::make(this));
1118   }
1119 
1120   // // -- Initialize types before each compile --
1121   // // Update cached type information
1122   // if( _method && _method->constants() )
1123   //   Type::update_loaded_types(_method, _method->constants());
1124 
1125   // Init alias_type map.
1126   if (!_do_escape_analysis && aliaslevel == 3)
1127     aliaslevel = 2;  // No unique types without escape analysis
1128   _AliasLevel = aliaslevel;
1129   const int grow_ats = 16;
1130   _max_alias_types = grow_ats;
1131   _alias_types   = NEW_ARENA_ARRAY(comp_arena(), AliasType*, grow_ats);
1132   AliasType* ats = NEW_ARENA_ARRAY(comp_arena(), AliasType,  grow_ats);
1133   Copy::zero_to_bytes(ats, sizeof(AliasType)*grow_ats);
1134   {
1135     for (int i = 0; i < grow_ats; i++)  _alias_types[i] = &ats[i];
1136   }
1137   // Initialize the first few types.
1138   _alias_types[AliasIdxTop]->Init(AliasIdxTop, NULL);
1139   _alias_types[AliasIdxBot]->Init(AliasIdxBot, TypePtr::BOTTOM);
1140   _alias_types[AliasIdxRaw]->Init(AliasIdxRaw, TypeRawPtr::BOTTOM);
1141   _num_alias_types = AliasIdxRaw+1;
1142   // Zero out the alias type cache.
1143   Copy::zero_to_bytes(_alias_cache, sizeof(_alias_cache));
1144   // A NULL adr_type hits in the cache right away.  Preload the right answer.
1145   probe_alias_cache(NULL)->_index = AliasIdxTop;
1146 
1147   _intrinsics = NULL;
1148   _macro_nodes = new(comp_arena()) GrowableArray<Node*>(comp_arena(), 8,  0, NULL);
1149   _predicate_opaqs = new(comp_arena()) GrowableArray<Node*>(comp_arena(), 8,  0, NULL);
1150   _expensive_nodes = new(comp_arena()) GrowableArray<Node*>(comp_arena(), 8,  0, NULL);
1151   register_library_intrinsics();
1152 }
1153 
1154 //---------------------------init_start----------------------------------------
1155 // Install the StartNode on this compile object.
1156 void Compile::init_start(StartNode* s) {
1157   if (failing())
1158     return; // already failing
1159   assert(s == start(), "");
1160 }
1161 
1162 StartNode* Compile::start() const {
1163   assert(!failing(), "");
1164   for (DUIterator_Fast imax, i = root()->fast_outs(imax); i < imax; i++) {
1165     Node* start = root()->fast_out(i);
1166     if( start->is_Start() )
1167       return start->as_Start();
1168   }
1169   fatal("Did not find Start node!");
1170   return NULL;
1171 }
1172 
1173 //-------------------------------immutable_memory-------------------------------------
1174 // Access immutable memory
1175 Node* Compile::immutable_memory() {
1176   if (_immutable_memory != NULL) {
1177     return _immutable_memory;
1178   }
1179   StartNode* s = start();
1180   for (DUIterator_Fast imax, i = s->fast_outs(imax); true; i++) {
1181     Node *p = s->fast_out(i);
1182     if (p != s && p->as_Proj()->_con == TypeFunc::Memory) {
1183       _immutable_memory = p;
1184       return _immutable_memory;
1185     }
1186   }
1187   ShouldNotReachHere();
1188   return NULL;
1189 }
1190 
1191 //----------------------set_cached_top_node------------------------------------
1192 // Install the cached top node, and make sure Node::is_top works correctly.
1193 void Compile::set_cached_top_node(Node* tn) {
1194   if (tn != NULL)  verify_top(tn);
1195   Node* old_top = _top;
1196   _top = tn;
1197   // Calling Node::setup_is_top allows the nodes the chance to adjust
1198   // their _out arrays.
1199   if (_top != NULL)     _top->setup_is_top();
1200   if (old_top != NULL)  old_top->setup_is_top();
1201   assert(_top == NULL || top()->is_top(), "");
1202 }
1203 
1204 #ifdef ASSERT
1205 uint Compile::count_live_nodes_by_graph_walk() {
1206   Unique_Node_List useful(comp_arena());
1207   // Get useful node list by walking the graph.
1208   identify_useful_nodes(useful);
1209   return useful.size();
1210 }
1211 
1212 void Compile::print_missing_nodes() {
1213 
1214   // Return if CompileLog is NULL and PrintIdealNodeCount is false.
1215   if ((_log == NULL) && (! PrintIdealNodeCount)) {
1216     return;
1217   }
1218 
1219   // This is an expensive function. It is executed only when the user
1220   // specifies VerifyIdealNodeCount option or otherwise knows the
1221   // additional work that needs to be done to identify reachable nodes
1222   // by walking the flow graph and find the missing ones using
1223   // _dead_node_list.
1224 
1225   Unique_Node_List useful(comp_arena());
1226   // Get useful node list by walking the graph.
1227   identify_useful_nodes(useful);
1228 
1229   uint l_nodes = C->live_nodes();
1230   uint l_nodes_by_walk = useful.size();
1231 
1232   if (l_nodes != l_nodes_by_walk) {
1233     if (_log != NULL) {
1234       _log->begin_head("mismatched_nodes count='%d'", abs((int) (l_nodes - l_nodes_by_walk)));
1235       _log->stamp();
1236       _log->end_head();
1237     }
1238     VectorSet& useful_member_set = useful.member_set();
1239     int last_idx = l_nodes_by_walk;
1240     for (int i = 0; i < last_idx; i++) {
1241       if (useful_member_set.test(i)) {
1242         if (_dead_node_list.test(i)) {
1243           if (_log != NULL) {
1244             _log->elem("mismatched_node_info node_idx='%d' type='both live and dead'", i);
1245           }
1246           if (PrintIdealNodeCount) {
1247             // Print the log message to tty
1248               tty->print_cr("mismatched_node idx='%d' both live and dead'", i);
1249               useful.at(i)->dump();
1250           }
1251         }
1252       }
1253       else if (! _dead_node_list.test(i)) {
1254         if (_log != NULL) {
1255           _log->elem("mismatched_node_info node_idx='%d' type='neither live nor dead'", i);
1256         }
1257         if (PrintIdealNodeCount) {
1258           // Print the log message to tty
1259           tty->print_cr("mismatched_node idx='%d' type='neither live nor dead'", i);
1260         }
1261       }
1262     }
1263     if (_log != NULL) {
1264       _log->tail("mismatched_nodes");
1265     }
1266   }
1267 }
1268 #endif
1269 
1270 #ifndef PRODUCT
1271 void Compile::verify_top(Node* tn) const {
1272   if (tn != NULL) {
1273     assert(tn->is_Con(), "top node must be a constant");
1274     assert(((ConNode*)tn)->type() == Type::TOP, "top node must have correct type");
1275     assert(tn->in(0) != NULL, "must have live top node");
1276   }
1277 }
1278 #endif
1279 
1280 
1281 ///-------------------Managing Per-Node Debug & Profile Info-------------------
1282 
1283 void Compile::grow_node_notes(GrowableArray<Node_Notes*>* arr, int grow_by) {
1284   guarantee(arr != NULL, "");
1285   int num_blocks = arr->length();
1286   if (grow_by < num_blocks)  grow_by = num_blocks;
1287   int num_notes = grow_by * _node_notes_block_size;
1288   Node_Notes* notes = NEW_ARENA_ARRAY(node_arena(), Node_Notes, num_notes);
1289   Copy::zero_to_bytes(notes, num_notes * sizeof(Node_Notes));
1290   while (num_notes > 0) {
1291     arr->append(notes);
1292     notes     += _node_notes_block_size;
1293     num_notes -= _node_notes_block_size;
1294   }
1295   assert(num_notes == 0, "exact multiple, please");
1296 }
1297 
1298 bool Compile::copy_node_notes_to(Node* dest, Node* source) {
1299   if (source == NULL || dest == NULL)  return false;
1300 
1301   if (dest->is_Con())
1302     return false;               // Do not push debug info onto constants.
1303 
1304 #ifdef ASSERT
1305   // Leave a bread crumb trail pointing to the original node:
1306   if (dest != NULL && dest != source && dest->debug_orig() == NULL) {
1307     dest->set_debug_orig(source);
1308   }
1309 #endif
1310 
1311   if (node_note_array() == NULL)
1312     return false;               // Not collecting any notes now.
1313 
1314   // This is a copy onto a pre-existing node, which may already have notes.
1315   // If both nodes have notes, do not overwrite any pre-existing notes.
1316   Node_Notes* source_notes = node_notes_at(source->_idx);
1317   if (source_notes == NULL || source_notes->is_clear())  return false;
1318   Node_Notes* dest_notes   = node_notes_at(dest->_idx);
1319   if (dest_notes == NULL || dest_notes->is_clear()) {
1320     return set_node_notes_at(dest->_idx, source_notes);
1321   }
1322 
1323   Node_Notes merged_notes = (*source_notes);
1324   // The order of operations here ensures that dest notes will win...
1325   merged_notes.update_from(dest_notes);
1326   return set_node_notes_at(dest->_idx, &merged_notes);
1327 }
1328 
1329 
1330 //--------------------------allow_range_check_smearing-------------------------
1331 // Gating condition for coalescing similar range checks.
1332 // Sometimes we try 'speculatively' replacing a series of a range checks by a
1333 // single covering check that is at least as strong as any of them.
1334 // If the optimization succeeds, the simplified (strengthened) range check
1335 // will always succeed.  If it fails, we will deopt, and then give up
1336 // on the optimization.
1337 bool Compile::allow_range_check_smearing() const {
1338   // If this method has already thrown a range-check,
1339   // assume it was because we already tried range smearing
1340   // and it failed.
1341   uint already_trapped = trap_count(Deoptimization::Reason_range_check);
1342   return !already_trapped;
1343 }
1344 
1345 
1346 //------------------------------flatten_alias_type-----------------------------
1347 const TypePtr *Compile::flatten_alias_type( const TypePtr *tj ) const {
1348   int offset = tj->offset();
1349   TypePtr::PTR ptr = tj->ptr();
1350 
1351   // Known instance (scalarizable allocation) alias only with itself.
1352   bool is_known_inst = tj->isa_oopptr() != NULL &&
1353                        tj->is_oopptr()->is_known_instance();
1354 
1355   // Process weird unsafe references.
1356   if (offset == Type::OffsetBot && (tj->isa_instptr() /*|| tj->isa_klassptr()*/)) {
1357     assert(InlineUnsafeOps, "indeterminate pointers come only from unsafe ops");
1358     assert(!is_known_inst, "scalarizable allocation should not have unsafe references");
1359     tj = TypeOopPtr::BOTTOM;
1360     ptr = tj->ptr();
1361     offset = tj->offset();
1362   }
1363 
1364   // Array pointers need some flattening
1365   const TypeAryPtr *ta = tj->isa_aryptr();
1366   if (ta && ta->is_stable()) {
1367     // Erase stability property for alias analysis.
1368     tj = ta = ta->cast_to_stable(false);
1369   }
1370   if( ta && is_known_inst ) {
1371     if ( offset != Type::OffsetBot &&
1372          offset > arrayOopDesc::length_offset_in_bytes() ) {
1373       offset = Type::OffsetBot; // Flatten constant access into array body only
1374       tj = ta = TypeAryPtr::make(ptr, ta->ary(), ta->klass(), true, offset, ta->instance_id());
1375     }
1376   } else if( ta && _AliasLevel >= 2 ) {
1377     // For arrays indexed by constant indices, we flatten the alias
1378     // space to include all of the array body.  Only the header, klass
1379     // and array length can be accessed un-aliased.
1380     if( offset != Type::OffsetBot ) {
1381       if( ta->const_oop() ) { // MethodData* or Method*
1382         offset = Type::OffsetBot;   // Flatten constant access into array body
1383         tj = ta = TypeAryPtr::make(ptr,ta->const_oop(),ta->ary(),ta->klass(),false,offset);
1384       } else if( offset == arrayOopDesc::length_offset_in_bytes() ) {
1385         // range is OK as-is.
1386         tj = ta = TypeAryPtr::RANGE;
1387       } else if( offset == oopDesc::klass_offset_in_bytes() ) {
1388         tj = TypeInstPtr::KLASS; // all klass loads look alike
1389         ta = TypeAryPtr::RANGE; // generic ignored junk
1390         ptr = TypePtr::BotPTR;
1391       } else if( offset == oopDesc::mark_offset_in_bytes() ) {
1392         tj = TypeInstPtr::MARK;
1393         ta = TypeAryPtr::RANGE; // generic ignored junk
1394         ptr = TypePtr::BotPTR;
1395       } else {                  // Random constant offset into array body
1396         offset = Type::OffsetBot;   // Flatten constant access into array body
1397         tj = ta = TypeAryPtr::make(ptr,ta->ary(),ta->klass(),false,offset);
1398       }
1399     }
1400     // Arrays of fixed size alias with arrays of unknown size.
1401     if (ta->size() != TypeInt::POS) {
1402       const TypeAry *tary = TypeAry::make(ta->elem(), TypeInt::POS);
1403       tj = ta = TypeAryPtr::make(ptr,ta->const_oop(),tary,ta->klass(),false,offset);
1404     }
1405     // Arrays of known objects become arrays of unknown objects.
1406     if (ta->elem()->isa_narrowoop() && ta->elem() != TypeNarrowOop::BOTTOM) {
1407       const TypeAry *tary = TypeAry::make(TypeNarrowOop::BOTTOM, ta->size());
1408       tj = ta = TypeAryPtr::make(ptr,ta->const_oop(),tary,NULL,false,offset);
1409     }
1410     if (ta->elem()->isa_oopptr() && ta->elem() != TypeInstPtr::BOTTOM) {
1411       const TypeAry *tary = TypeAry::make(TypeInstPtr::BOTTOM, ta->size());
1412       tj = ta = TypeAryPtr::make(ptr,ta->const_oop(),tary,NULL,false,offset);
1413     }
1414     // Arrays of bytes and of booleans both use 'bastore' and 'baload' so
1415     // cannot be distinguished by bytecode alone.
1416     if (ta->elem() == TypeInt::BOOL) {
1417       const TypeAry *tary = TypeAry::make(TypeInt::BYTE, ta->size());
1418       ciKlass* aklass = ciTypeArrayKlass::make(T_BYTE);
1419       tj = ta = TypeAryPtr::make(ptr,ta->const_oop(),tary,aklass,false,offset);
1420     }
1421     // During the 2nd round of IterGVN, NotNull castings are removed.
1422     // Make sure the Bottom and NotNull variants alias the same.
1423     // Also, make sure exact and non-exact variants alias the same.
1424     if (ptr == TypePtr::NotNull || ta->klass_is_exact() || ta->speculative() != NULL) {
1425       tj = ta = TypeAryPtr::make(TypePtr::BotPTR,ta->ary(),ta->klass(),false,offset);
1426     }
1427   }
1428 
1429   // Oop pointers need some flattening
1430   const TypeInstPtr *to = tj->isa_instptr();
1431   if( to && _AliasLevel >= 2 && to != TypeOopPtr::BOTTOM ) {
1432     ciInstanceKlass *k = to->klass()->as_instance_klass();
1433     if( ptr == TypePtr::Constant ) {
1434       if (to->klass() != ciEnv::current()->Class_klass() ||
1435           offset < k->size_helper() * wordSize) {
1436         // No constant oop pointers (such as Strings); they alias with
1437         // unknown strings.
1438         assert(!is_known_inst, "not scalarizable allocation");
1439         tj = to = TypeInstPtr::make(TypePtr::BotPTR,to->klass(),false,0,offset);
1440       }
1441     } else if( is_known_inst ) {
1442       tj = to; // Keep NotNull and klass_is_exact for instance type
1443     } else if( ptr == TypePtr::NotNull || to->klass_is_exact() ) {
1444       // During the 2nd round of IterGVN, NotNull castings are removed.
1445       // Make sure the Bottom and NotNull variants alias the same.
1446       // Also, make sure exact and non-exact variants alias the same.
1447       tj = to = TypeInstPtr::make(TypePtr::BotPTR,to->klass(),false,0,offset);
1448     }
1449     if (to->speculative() != NULL) {
1450       tj = to = TypeInstPtr::make(to->ptr(),to->klass(),to->klass_is_exact(),to->const_oop(),to->offset(), to->instance_id());
1451     }
1452     // Canonicalize the holder of this field
1453     if (offset >= 0 && offset < instanceOopDesc::base_offset_in_bytes()) {
1454       // First handle header references such as a LoadKlassNode, even if the
1455       // object's klass is unloaded at compile time (4965979).
1456       if (!is_known_inst) { // Do it only for non-instance types
1457         tj = to = TypeInstPtr::make(TypePtr::BotPTR, env()->Object_klass(), false, NULL, offset);
1458       }
1459     } else if (offset < 0 || offset >= k->size_helper() * wordSize) {
1460       // Static fields are in the space above the normal instance
1461       // fields in the java.lang.Class instance.
1462       if (to->klass() != ciEnv::current()->Class_klass()) {
1463         to = NULL;
1464         tj = TypeOopPtr::BOTTOM;
1465         offset = tj->offset();
1466       }
1467     } else {
1468       ciInstanceKlass *canonical_holder = k->get_canonical_holder(offset);
1469       if (!k->equals(canonical_holder) || tj->offset() != offset) {
1470         if( is_known_inst ) {
1471           tj = to = TypeInstPtr::make(to->ptr(), canonical_holder, true, NULL, offset, to->instance_id());
1472         } else {
1473           tj = to = TypeInstPtr::make(to->ptr(), canonical_holder, false, NULL, offset);
1474         }
1475       }
1476     }
1477   }
1478 
1479   // Klass pointers to object array klasses need some flattening
1480   const TypeKlassPtr *tk = tj->isa_klassptr();
1481   if( tk ) {
1482     // If we are referencing a field within a Klass, we need
1483     // to assume the worst case of an Object.  Both exact and
1484     // inexact types must flatten to the same alias class so
1485     // use NotNull as the PTR.
1486     if ( offset == Type::OffsetBot || (offset >= 0 && (size_t)offset < sizeof(Klass)) ) {
1487 
1488       tj = tk = TypeKlassPtr::make(TypePtr::NotNull,
1489                                    TypeKlassPtr::OBJECT->klass(),
1490                                    offset);
1491     }
1492 
1493     ciKlass* klass = tk->klass();
1494     if( klass->is_obj_array_klass() ) {
1495       ciKlass* k = TypeAryPtr::OOPS->klass();
1496       if( !k || !k->is_loaded() )                  // Only fails for some -Xcomp runs
1497         k = TypeInstPtr::BOTTOM->klass();
1498       tj = tk = TypeKlassPtr::make( TypePtr::NotNull, k, offset );
1499     }
1500 
1501     // Check for precise loads from the primary supertype array and force them
1502     // to the supertype cache alias index.  Check for generic array loads from
1503     // the primary supertype array and also force them to the supertype cache
1504     // alias index.  Since the same load can reach both, we need to merge
1505     // these 2 disparate memories into the same alias class.  Since the
1506     // primary supertype array is read-only, there's no chance of confusion
1507     // where we bypass an array load and an array store.
1508     int primary_supers_offset = in_bytes(Klass::primary_supers_offset());
1509     if (offset == Type::OffsetBot ||
1510         (offset >= primary_supers_offset &&
1511          offset < (int)(primary_supers_offset + Klass::primary_super_limit() * wordSize)) ||
1512         offset == (int)in_bytes(Klass::secondary_super_cache_offset())) {
1513       offset = in_bytes(Klass::secondary_super_cache_offset());
1514       tj = tk = TypeKlassPtr::make( TypePtr::NotNull, tk->klass(), offset );
1515     }
1516   }
1517 
1518   // Flatten all Raw pointers together.
1519   if (tj->base() == Type::RawPtr)
1520     tj = TypeRawPtr::BOTTOM;
1521 
1522   if (tj->base() == Type::AnyPtr)
1523     tj = TypePtr::BOTTOM;      // An error, which the caller must check for.
1524 
1525   // Flatten all to bottom for now
1526   switch( _AliasLevel ) {
1527   case 0:
1528     tj = TypePtr::BOTTOM;
1529     break;
1530   case 1:                       // Flatten to: oop, static, field or array
1531     switch (tj->base()) {
1532     //case Type::AryPtr: tj = TypeAryPtr::RANGE;    break;
1533     case Type::RawPtr:   tj = TypeRawPtr::BOTTOM;   break;
1534     case Type::AryPtr:   // do not distinguish arrays at all
1535     case Type::InstPtr:  tj = TypeInstPtr::BOTTOM;  break;
1536     case Type::KlassPtr: tj = TypeKlassPtr::OBJECT; break;
1537     case Type::AnyPtr:   tj = TypePtr::BOTTOM;      break;  // caller checks it
1538     default: ShouldNotReachHere();
1539     }
1540     break;
1541   case 2:                       // No collapsing at level 2; keep all splits
1542   case 3:                       // No collapsing at level 3; keep all splits
1543     break;
1544   default:
1545     Unimplemented();
1546   }
1547 
1548   offset = tj->offset();
1549   assert( offset != Type::OffsetTop, "Offset has fallen from constant" );
1550 
1551   assert( (offset != Type::OffsetBot && tj->base() != Type::AryPtr) ||
1552           (offset == Type::OffsetBot && tj->base() == Type::AryPtr) ||
1553           (offset == Type::OffsetBot && tj == TypeOopPtr::BOTTOM) ||
1554           (offset == Type::OffsetBot && tj == TypePtr::BOTTOM) ||
1555           (offset == oopDesc::mark_offset_in_bytes() && tj->base() == Type::AryPtr) ||
1556           (offset == oopDesc::klass_offset_in_bytes() && tj->base() == Type::AryPtr) ||
1557           (offset == arrayOopDesc::length_offset_in_bytes() && tj->base() == Type::AryPtr)  ,
1558           "For oops, klasses, raw offset must be constant; for arrays the offset is never known" );
1559   assert( tj->ptr() != TypePtr::TopPTR &&
1560           tj->ptr() != TypePtr::AnyNull &&
1561           tj->ptr() != TypePtr::Null, "No imprecise addresses" );
1562 //    assert( tj->ptr() != TypePtr::Constant ||
1563 //            tj->base() == Type::RawPtr ||
1564 //            tj->base() == Type::KlassPtr, "No constant oop addresses" );
1565 
1566   return tj;
1567 }
1568 
1569 void Compile::AliasType::Init(int i, const TypePtr* at) {
1570   _index = i;
1571   _adr_type = at;
1572   _field = NULL;
1573   _element = NULL;
1574   _is_rewritable = true; // default
1575   const TypeOopPtr *atoop = (at != NULL) ? at->isa_oopptr() : NULL;
1576   if (atoop != NULL && atoop->is_known_instance()) {
1577     const TypeOopPtr *gt = atoop->cast_to_instance_id(TypeOopPtr::InstanceBot);
1578     _general_index = Compile::current()->get_alias_index(gt);
1579   } else {
1580     _general_index = 0;
1581   }
1582 }
1583 
1584 //---------------------------------print_on------------------------------------
1585 #ifndef PRODUCT
1586 void Compile::AliasType::print_on(outputStream* st) {
1587   if (index() < 10)
1588         st->print("@ <%d> ", index());
1589   else  st->print("@ <%d>",  index());
1590   st->print(is_rewritable() ? "   " : " RO");
1591   int offset = adr_type()->offset();
1592   if (offset == Type::OffsetBot)
1593         st->print(" +any");
1594   else  st->print(" +%-3d", offset);
1595   st->print(" in ");
1596   adr_type()->dump_on(st);
1597   const TypeOopPtr* tjp = adr_type()->isa_oopptr();
1598   if (field() != NULL && tjp) {
1599     if (tjp->klass()  != field()->holder() ||
1600         tjp->offset() != field()->offset_in_bytes()) {
1601       st->print(" != ");
1602       field()->print();
1603       st->print(" ***");
1604     }
1605   }
1606 }
1607 
1608 void print_alias_types() {
1609   Compile* C = Compile::current();
1610   tty->print_cr("--- Alias types, AliasIdxBot .. %d", C->num_alias_types()-1);
1611   for (int idx = Compile::AliasIdxBot; idx < C->num_alias_types(); idx++) {
1612     C->alias_type(idx)->print_on(tty);
1613     tty->cr();
1614   }
1615 }
1616 #endif
1617 
1618 
1619 //----------------------------probe_alias_cache--------------------------------
1620 Compile::AliasCacheEntry* Compile::probe_alias_cache(const TypePtr* adr_type) {
1621   intptr_t key = (intptr_t) adr_type;
1622   key ^= key >> logAliasCacheSize;
1623   return &_alias_cache[key & right_n_bits(logAliasCacheSize)];
1624 }
1625 
1626 
1627 //-----------------------------grow_alias_types--------------------------------
1628 void Compile::grow_alias_types() {
1629   const int old_ats  = _max_alias_types; // how many before?
1630   const int new_ats  = old_ats;          // how many more?
1631   const int grow_ats = old_ats+new_ats;  // how many now?
1632   _max_alias_types = grow_ats;
1633   _alias_types =  REALLOC_ARENA_ARRAY(comp_arena(), AliasType*, _alias_types, old_ats, grow_ats);
1634   AliasType* ats =    NEW_ARENA_ARRAY(comp_arena(), AliasType, new_ats);
1635   Copy::zero_to_bytes(ats, sizeof(AliasType)*new_ats);
1636   for (int i = 0; i < new_ats; i++)  _alias_types[old_ats+i] = &ats[i];
1637 }
1638 
1639 
1640 //--------------------------------find_alias_type------------------------------
1641 Compile::AliasType* Compile::find_alias_type(const TypePtr* adr_type, bool no_create, ciField* original_field) {
1642   if (_AliasLevel == 0)
1643     return alias_type(AliasIdxBot);
1644 
1645   AliasCacheEntry* ace = probe_alias_cache(adr_type);
1646   if (ace->_adr_type == adr_type) {
1647     return alias_type(ace->_index);
1648   }
1649 
1650   // Handle special cases.
1651   if (adr_type == NULL)             return alias_type(AliasIdxTop);
1652   if (adr_type == TypePtr::BOTTOM)  return alias_type(AliasIdxBot);
1653 
1654   // Do it the slow way.
1655   const TypePtr* flat = flatten_alias_type(adr_type);
1656 
1657 #ifdef ASSERT
1658   assert(flat == flatten_alias_type(flat), "idempotent");
1659   assert(flat != TypePtr::BOTTOM,     "cannot alias-analyze an untyped ptr");
1660   if (flat->isa_oopptr() && !flat->isa_klassptr()) {
1661     const TypeOopPtr* foop = flat->is_oopptr();
1662     // Scalarizable allocations have exact klass always.
1663     bool exact = !foop->klass_is_exact() || foop->is_known_instance();
1664     const TypePtr* xoop = foop->cast_to_exactness(exact)->is_ptr();
1665     assert(foop == flatten_alias_type(xoop), "exactness must not affect alias type");
1666   }
1667   assert(flat == flatten_alias_type(flat), "exact bit doesn't matter");
1668 #endif
1669 
1670   int idx = AliasIdxTop;
1671   for (int i = 0; i < num_alias_types(); i++) {
1672     if (alias_type(i)->adr_type() == flat) {
1673       idx = i;
1674       break;
1675     }
1676   }
1677 
1678   if (idx == AliasIdxTop) {
1679     if (no_create)  return NULL;
1680     // Grow the array if necessary.
1681     if (_num_alias_types == _max_alias_types)  grow_alias_types();
1682     // Add a new alias type.
1683     idx = _num_alias_types++;
1684     _alias_types[idx]->Init(idx, flat);
1685     if (flat == TypeInstPtr::KLASS)  alias_type(idx)->set_rewritable(false);
1686     if (flat == TypeAryPtr::RANGE)   alias_type(idx)->set_rewritable(false);
1687     if (flat->isa_instptr()) {
1688       if (flat->offset() == java_lang_Class::klass_offset_in_bytes()
1689           && flat->is_instptr()->klass() == env()->Class_klass())
1690         alias_type(idx)->set_rewritable(false);
1691     }
1692     if (flat->isa_aryptr()) {
1693 #ifdef ASSERT
1694       const int header_size_min  = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1695       // (T_BYTE has the weakest alignment and size restrictions...)
1696       assert(flat->offset() < header_size_min, "array body reference must be OffsetBot");
1697 #endif
1698       if (flat->offset() == TypePtr::OffsetBot) {
1699         alias_type(idx)->set_element(flat->is_aryptr()->elem());
1700       }
1701     }
1702     if (flat->isa_klassptr()) {
1703       if (flat->offset() == in_bytes(Klass::super_check_offset_offset()))
1704         alias_type(idx)->set_rewritable(false);
1705       if (flat->offset() == in_bytes(Klass::modifier_flags_offset()))
1706         alias_type(idx)->set_rewritable(false);
1707       if (flat->offset() == in_bytes(Klass::access_flags_offset()))
1708         alias_type(idx)->set_rewritable(false);
1709       if (flat->offset() == in_bytes(Klass::java_mirror_offset()))
1710         alias_type(idx)->set_rewritable(false);
1711     }
1712     // %%% (We would like to finalize JavaThread::threadObj_offset(),
1713     // but the base pointer type is not distinctive enough to identify
1714     // references into JavaThread.)
1715 
1716     // Check for final fields.
1717     const TypeInstPtr* tinst = flat->isa_instptr();
1718     if (tinst && tinst->offset() >= instanceOopDesc::base_offset_in_bytes()) {
1719       ciField* field;
1720       if (tinst->const_oop() != NULL &&
1721           tinst->klass() == ciEnv::current()->Class_klass() &&
1722           tinst->offset() >= (tinst->klass()->as_instance_klass()->size_helper() * wordSize)) {
1723         // static field
1724         ciInstanceKlass* k = tinst->const_oop()->as_instance()->java_lang_Class_klass()->as_instance_klass();
1725         field = k->get_field_by_offset(tinst->offset(), true);
1726       } else {
1727         ciInstanceKlass *k = tinst->klass()->as_instance_klass();
1728         field = k->get_field_by_offset(tinst->offset(), false);
1729       }
1730       assert(field == NULL ||
1731              original_field == NULL ||
1732              (field->holder() == original_field->holder() &&
1733               field->offset() == original_field->offset() &&
1734               field->is_static() == original_field->is_static()), "wrong field?");
1735       // Set field() and is_rewritable() attributes.
1736       if (field != NULL)  alias_type(idx)->set_field(field);
1737     }
1738   }
1739 
1740   // Fill the cache for next time.
1741   ace->_adr_type = adr_type;
1742   ace->_index    = idx;
1743   assert(alias_type(adr_type) == alias_type(idx),  "type must be installed");
1744 
1745   // Might as well try to fill the cache for the flattened version, too.
1746   AliasCacheEntry* face = probe_alias_cache(flat);
1747   if (face->_adr_type == NULL) {
1748     face->_adr_type = flat;
1749     face->_index    = idx;
1750     assert(alias_type(flat) == alias_type(idx), "flat type must work too");
1751   }
1752 
1753   return alias_type(idx);
1754 }
1755 
1756 
1757 Compile::AliasType* Compile::alias_type(ciField* field) {
1758   const TypeOopPtr* t;
1759   if (field->is_static())
1760     t = TypeInstPtr::make(field->holder()->java_mirror());
1761   else
1762     t = TypeOopPtr::make_from_klass_raw(field->holder());
1763   AliasType* atp = alias_type(t->add_offset(field->offset_in_bytes()), field);
1764   assert((field->is_final() || field->is_stable()) == !atp->is_rewritable(), "must get the rewritable bits correct");
1765   return atp;
1766 }
1767 
1768 
1769 //------------------------------have_alias_type--------------------------------
1770 bool Compile::have_alias_type(const TypePtr* adr_type) {
1771   AliasCacheEntry* ace = probe_alias_cache(adr_type);
1772   if (ace->_adr_type == adr_type) {
1773     return true;
1774   }
1775 
1776   // Handle special cases.
1777   if (adr_type == NULL)             return true;
1778   if (adr_type == TypePtr::BOTTOM)  return true;
1779 
1780   return find_alias_type(adr_type, true, NULL) != NULL;
1781 }
1782 
1783 //-----------------------------must_alias--------------------------------------
1784 // True if all values of the given address type are in the given alias category.
1785 bool Compile::must_alias(const TypePtr* adr_type, int alias_idx) {
1786   if (alias_idx == AliasIdxBot)         return true;  // the universal category
1787   if (adr_type == NULL)                 return true;  // NULL serves as TypePtr::TOP
1788   if (alias_idx == AliasIdxTop)         return false; // the empty category
1789   if (adr_type->base() == Type::AnyPtr) return false; // TypePtr::BOTTOM or its twins
1790 
1791   // the only remaining possible overlap is identity
1792   int adr_idx = get_alias_index(adr_type);
1793   assert(adr_idx != AliasIdxBot && adr_idx != AliasIdxTop, "");
1794   assert(adr_idx == alias_idx ||
1795          (alias_type(alias_idx)->adr_type() != TypeOopPtr::BOTTOM
1796           && adr_type                       != TypeOopPtr::BOTTOM),
1797          "should not be testing for overlap with an unsafe pointer");
1798   return adr_idx == alias_idx;
1799 }
1800 
1801 //------------------------------can_alias--------------------------------------
1802 // True if any values of the given address type are in the given alias category.
1803 bool Compile::can_alias(const TypePtr* adr_type, int alias_idx) {
1804   if (alias_idx == AliasIdxTop)         return false; // the empty category
1805   if (adr_type == NULL)                 return false; // NULL serves as TypePtr::TOP
1806   if (alias_idx == AliasIdxBot)         return true;  // the universal category
1807   if (adr_type->base() == Type::AnyPtr) return true;  // TypePtr::BOTTOM or its twins
1808 
1809   // the only remaining possible overlap is identity
1810   int adr_idx = get_alias_index(adr_type);
1811   assert(adr_idx != AliasIdxBot && adr_idx != AliasIdxTop, "");
1812   return adr_idx == alias_idx;
1813 }
1814 
1815 
1816 
1817 //---------------------------pop_warm_call-------------------------------------
1818 WarmCallInfo* Compile::pop_warm_call() {
1819   WarmCallInfo* wci = _warm_calls;
1820   if (wci != NULL)  _warm_calls = wci->remove_from(wci);
1821   return wci;
1822 }
1823 
1824 //----------------------------Inline_Warm--------------------------------------
1825 int Compile::Inline_Warm() {
1826   // If there is room, try to inline some more warm call sites.
1827   // %%% Do a graph index compaction pass when we think we're out of space?
1828   if (!InlineWarmCalls)  return 0;
1829 
1830   int calls_made_hot = 0;
1831   int room_to_grow   = NodeCountInliningCutoff - unique();
1832   int amount_to_grow = MIN2(room_to_grow, (int)NodeCountInliningStep);
1833   int amount_grown   = 0;
1834   WarmCallInfo* call;
1835   while (amount_to_grow > 0 && (call = pop_warm_call()) != NULL) {
1836     int est_size = (int)call->size();
1837     if (est_size > (room_to_grow - amount_grown)) {
1838       // This one won't fit anyway.  Get rid of it.
1839       call->make_cold();
1840       continue;
1841     }
1842     call->make_hot();
1843     calls_made_hot++;
1844     amount_grown   += est_size;
1845     amount_to_grow -= est_size;
1846   }
1847 
1848   if (calls_made_hot > 0)  set_major_progress();
1849   return calls_made_hot;
1850 }
1851 
1852 
1853 //----------------------------Finish_Warm--------------------------------------
1854 void Compile::Finish_Warm() {
1855   if (!InlineWarmCalls)  return;
1856   if (failing())  return;
1857   if (warm_calls() == NULL)  return;
1858 
1859   // Clean up loose ends, if we are out of space for inlining.
1860   WarmCallInfo* call;
1861   while ((call = pop_warm_call()) != NULL) {
1862     call->make_cold();
1863   }
1864 }
1865 
1866 //---------------------cleanup_loop_predicates-----------------------
1867 // Remove the opaque nodes that protect the predicates so that all unused
1868 // checks and uncommon_traps will be eliminated from the ideal graph
1869 void Compile::cleanup_loop_predicates(PhaseIterGVN &igvn) {
1870   if (predicate_count()==0) return;
1871   for (int i = predicate_count(); i > 0; i--) {
1872     Node * n = predicate_opaque1_node(i-1);
1873     assert(n->Opcode() == Op_Opaque1, "must be");
1874     igvn.replace_node(n, n->in(1));
1875   }
1876   assert(predicate_count()==0, "should be clean!");
1877 }
1878 
1879 // StringOpts and late inlining of string methods
1880 void Compile::inline_string_calls(bool parse_time) {
1881   {
1882     // remove useless nodes to make the usage analysis simpler
1883     ResourceMark rm;
1884     PhaseRemoveUseless pru(initial_gvn(), for_igvn());
1885   }
1886 
1887   {
1888     ResourceMark rm;
1889     print_method(PHASE_BEFORE_STRINGOPTS, 3);
1890     PhaseStringOpts pso(initial_gvn(), for_igvn());
1891     print_method(PHASE_AFTER_STRINGOPTS, 3);
1892   }
1893 
1894   // now inline anything that we skipped the first time around
1895   if (!parse_time) {
1896     _late_inlines_pos = _late_inlines.length();
1897   }
1898 
1899   while (_string_late_inlines.length() > 0) {
1900     CallGenerator* cg = _string_late_inlines.pop();
1901     cg->do_late_inline();
1902     if (failing())  return;
1903   }
1904   _string_late_inlines.trunc_to(0);
1905 }
1906 
1907 // Late inlining of boxing methods
1908 void Compile::inline_boxing_calls(PhaseIterGVN& igvn) {
1909   if (_boxing_late_inlines.length() > 0) {
1910     assert(has_boxed_value(), "inconsistent");
1911 
1912     PhaseGVN* gvn = initial_gvn();
1913     set_inlining_incrementally(true);
1914 
1915     assert( igvn._worklist.size() == 0, "should be done with igvn" );
1916     for_igvn()->clear();
1917     gvn->replace_with(&igvn);
1918 
1919     _late_inlines_pos = _late_inlines.length();
1920 
1921     while (_boxing_late_inlines.length() > 0) {
1922       CallGenerator* cg = _boxing_late_inlines.pop();
1923       cg->do_late_inline();
1924       if (failing())  return;
1925     }
1926     _boxing_late_inlines.trunc_to(0);
1927 
1928     {
1929       ResourceMark rm;
1930       PhaseRemoveUseless pru(gvn, for_igvn());
1931     }
1932 
1933     igvn = PhaseIterGVN(gvn);
1934     igvn.optimize();
1935 
1936     set_inlining_progress(false);
1937     set_inlining_incrementally(false);
1938   }
1939 }
1940 
1941 void Compile::inline_incrementally_one(PhaseIterGVN& igvn) {
1942   assert(IncrementalInline, "incremental inlining should be on");
1943   PhaseGVN* gvn = initial_gvn();
1944 
1945   set_inlining_progress(false);
1946   for_igvn()->clear();
1947   gvn->replace_with(&igvn);
1948 
1949   int i = 0;
1950 
1951   for (; i <_late_inlines.length() && !inlining_progress(); i++) {
1952     CallGenerator* cg = _late_inlines.at(i);
1953     _late_inlines_pos = i+1;
1954     cg->do_late_inline();
1955     if (failing())  return;
1956   }
1957   int j = 0;
1958   for (; i < _late_inlines.length(); i++, j++) {
1959     _late_inlines.at_put(j, _late_inlines.at(i));
1960   }
1961   _late_inlines.trunc_to(j);
1962 
1963   {
1964     ResourceMark rm;
1965     PhaseRemoveUseless pru(gvn, for_igvn());
1966   }
1967 
1968   igvn = PhaseIterGVN(gvn);
1969 }
1970 
1971 // Perform incremental inlining until bound on number of live nodes is reached
1972 void Compile::inline_incrementally(PhaseIterGVN& igvn) {
1973   PhaseGVN* gvn = initial_gvn();
1974 
1975   set_inlining_incrementally(true);
1976   set_inlining_progress(true);
1977   uint low_live_nodes = 0;
1978 
1979   while(inlining_progress() && _late_inlines.length() > 0) {
1980 
1981     if (live_nodes() > (uint)LiveNodeCountInliningCutoff) {
1982       if (low_live_nodes < (uint)LiveNodeCountInliningCutoff * 8 / 10) {
1983         // PhaseIdealLoop is expensive so we only try it once we are
1984         // out of live nodes and we only try it again if the previous
1985         // helped got the number of nodes down significantly
1986         PhaseIdealLoop ideal_loop( igvn, false, true );
1987         if (failing())  return;
1988         low_live_nodes = live_nodes();
1989         _major_progress = true;
1990       }
1991 
1992       if (live_nodes() > (uint)LiveNodeCountInliningCutoff) {
1993         break;
1994       }
1995     }
1996 
1997     inline_incrementally_one(igvn);
1998 
1999     if (failing())  return;
2000 
2001     igvn.optimize();
2002 
2003     if (failing())  return;
2004   }
2005 
2006   assert( igvn._worklist.size() == 0, "should be done with igvn" );
2007 
2008   if (_string_late_inlines.length() > 0) {
2009     assert(has_stringbuilder(), "inconsistent");
2010     for_igvn()->clear();
2011     initial_gvn()->replace_with(&igvn);
2012 
2013     inline_string_calls(false);
2014 
2015     if (failing())  return;
2016 
2017     {
2018       ResourceMark rm;
2019       PhaseRemoveUseless pru(initial_gvn(), for_igvn());
2020     }
2021 
2022     igvn = PhaseIterGVN(gvn);
2023 
2024     igvn.optimize();
2025   }
2026 
2027   set_inlining_incrementally(false);
2028 }
2029 
2030 
2031 //------------------------------Optimize---------------------------------------
2032 // Given a graph, optimize it.
2033 void Compile::Optimize() {
2034   TracePhase t1("optimizer", &_t_optimizer, true);
2035 
2036 #ifndef PRODUCT
2037   if (env()->break_at_compile()) {
2038     BREAKPOINT;
2039   }
2040 
2041 #endif
2042 
2043   ResourceMark rm;
2044   int          loop_opts_cnt;
2045 
2046   NOT_PRODUCT( verify_graph_edges(); )
2047 
2048   print_method(PHASE_AFTER_PARSING);
2049 
2050  {
2051   // Iterative Global Value Numbering, including ideal transforms
2052   // Initialize IterGVN with types and values from parse-time GVN
2053   PhaseIterGVN igvn(initial_gvn());
2054   {
2055     NOT_PRODUCT( TracePhase t2("iterGVN", &_t_iterGVN, TimeCompiler); )
2056     igvn.optimize();
2057   }
2058 
2059   print_method(PHASE_ITER_GVN1, 2);
2060 
2061   if (failing())  return;
2062 
2063   {
2064     NOT_PRODUCT( TracePhase t2("incrementalInline", &_t_incrInline, TimeCompiler); )
2065     inline_incrementally(igvn);
2066   }
2067 
2068   print_method(PHASE_INCREMENTAL_INLINE, 2);
2069 
2070   if (failing())  return;
2071 
2072   if (eliminate_boxing()) {
2073     NOT_PRODUCT( TracePhase t2("incrementalInline", &_t_incrInline, TimeCompiler); )
2074     // Inline valueOf() methods now.
2075     inline_boxing_calls(igvn);
2076 
2077     if (AlwaysIncrementalInline) {
2078       inline_incrementally(igvn);
2079     }
2080 
2081     print_method(PHASE_INCREMENTAL_BOXING_INLINE, 2);
2082 
2083     if (failing())  return;
2084   }
2085 
2086   // Remove the speculative part of types and clean up the graph from
2087   // the extra CastPP nodes whose only purpose is to carry them. Do
2088   // that early so that optimizations are not disrupted by the extra
2089   // CastPP nodes.
2090   remove_speculative_types(igvn);
2091 
2092   // No more new expensive nodes will be added to the list from here
2093   // so keep only the actual candidates for optimizations.
2094   cleanup_expensive_nodes(igvn);
2095 
2096   // Perform escape analysis
2097   if (_do_escape_analysis && ConnectionGraph::has_candidates(this)) {
2098     if (has_loops()) {
2099       // Cleanup graph (remove dead nodes).
2100       TracePhase t2("idealLoop", &_t_idealLoop, true);
2101       PhaseIdealLoop ideal_loop( igvn, false, true );
2102       if (major_progress()) print_method(PHASE_PHASEIDEAL_BEFORE_EA, 2);
2103       if (failing())  return;
2104     }
2105     ConnectionGraph::do_analysis(this, &igvn);
2106 
2107     if (failing())  return;
2108 
2109     // Optimize out fields loads from scalar replaceable allocations.
2110     igvn.optimize();
2111     print_method(PHASE_ITER_GVN_AFTER_EA, 2);
2112 
2113     if (failing())  return;
2114 
2115     if (congraph() != NULL && macro_count() > 0) {
2116       NOT_PRODUCT( TracePhase t2("macroEliminate", &_t_macroEliminate, TimeCompiler); )
2117       PhaseMacroExpand mexp(igvn);
2118       mexp.eliminate_macro_nodes();
2119       igvn.set_delay_transform(false);
2120 
2121       igvn.optimize();
2122       print_method(PHASE_ITER_GVN_AFTER_ELIMINATION, 2);
2123 
2124       if (failing())  return;
2125     }
2126   }
2127 
2128   // Loop transforms on the ideal graph.  Range Check Elimination,
2129   // peeling, unrolling, etc.
2130 
2131   // Set loop opts counter
2132   loop_opts_cnt = num_loop_opts();
2133   if((loop_opts_cnt > 0) && (has_loops() || has_split_ifs())) {
2134     {
2135       TracePhase t2("idealLoop", &_t_idealLoop, true);
2136       PhaseIdealLoop ideal_loop( igvn, true );
2137       loop_opts_cnt--;
2138       if (major_progress()) print_method(PHASE_PHASEIDEALLOOP1, 2);
2139       if (failing())  return;
2140     }
2141     // Loop opts pass if partial peeling occurred in previous pass
2142     if(PartialPeelLoop && major_progress() && (loop_opts_cnt > 0)) {
2143       TracePhase t3("idealLoop", &_t_idealLoop, true);
2144       PhaseIdealLoop ideal_loop( igvn, false );
2145       loop_opts_cnt--;
2146       if (major_progress()) print_method(PHASE_PHASEIDEALLOOP2, 2);
2147       if (failing())  return;
2148     }
2149     // Loop opts pass for loop-unrolling before CCP
2150     if(major_progress() && (loop_opts_cnt > 0)) {
2151       TracePhase t4("idealLoop", &_t_idealLoop, true);
2152       PhaseIdealLoop ideal_loop( igvn, false );
2153       loop_opts_cnt--;
2154       if (major_progress()) print_method(PHASE_PHASEIDEALLOOP3, 2);
2155     }
2156     if (!failing()) {
2157       // Verify that last round of loop opts produced a valid graph
2158       NOT_PRODUCT( TracePhase t2("idealLoopVerify", &_t_idealLoopVerify, TimeCompiler); )
2159       PhaseIdealLoop::verify(igvn);
2160     }
2161   }
2162   if (failing())  return;
2163 
2164   // Conditional Constant Propagation;
2165   PhaseCCP ccp( &igvn );
2166   assert( true, "Break here to ccp.dump_nodes_and_types(_root,999,1)");
2167   {
2168     TracePhase t2("ccp", &_t_ccp, true);
2169     ccp.do_transform();
2170   }
2171   print_method(PHASE_CPP1, 2);
2172 
2173   assert( true, "Break here to ccp.dump_old2new_map()");
2174 
2175   // Iterative Global Value Numbering, including ideal transforms
2176   {
2177     NOT_PRODUCT( TracePhase t2("iterGVN2", &_t_iterGVN2, TimeCompiler); )
2178     igvn = ccp;
2179     igvn.optimize();
2180   }
2181 
2182   print_method(PHASE_ITER_GVN2, 2);
2183 
2184   if (failing())  return;
2185 
2186   // Loop transforms on the ideal graph.  Range Check Elimination,
2187   // peeling, unrolling, etc.
2188   if(loop_opts_cnt > 0) {
2189     debug_only( int cnt = 0; );
2190     while(major_progress() && (loop_opts_cnt > 0)) {
2191       TracePhase t2("idealLoop", &_t_idealLoop, true);
2192       assert( cnt++ < 40, "infinite cycle in loop optimization" );
2193       PhaseIdealLoop ideal_loop( igvn, true);
2194       loop_opts_cnt--;
2195       if (major_progress()) print_method(PHASE_PHASEIDEALLOOP_ITERATIONS, 2);
2196       if (failing())  return;
2197     }
2198   }
2199 
2200   {
2201     // Verify that all previous optimizations produced a valid graph
2202     // at least to this point, even if no loop optimizations were done.
2203     NOT_PRODUCT( TracePhase t2("idealLoopVerify", &_t_idealLoopVerify, TimeCompiler); )
2204     PhaseIdealLoop::verify(igvn);
2205   }
2206 
2207   {
2208     NOT_PRODUCT( TracePhase t2("macroExpand", &_t_macroExpand, TimeCompiler); )
2209     PhaseMacroExpand  mex(igvn);
2210     if (mex.expand_macro_nodes()) {
2211       assert(failing(), "must bail out w/ explicit message");
2212       return;
2213     }
2214   }
2215 
2216  } // (End scope of igvn; run destructor if necessary for asserts.)
2217 
2218   dump_inlining();
2219   // A method with only infinite loops has no edges entering loops from root
2220   {
2221     NOT_PRODUCT( TracePhase t2("graphReshape", &_t_graphReshaping, TimeCompiler); )
2222     if (final_graph_reshaping()) {
2223       assert(failing(), "must bail out w/ explicit message");
2224       return;
2225     }
2226   }
2227 
2228   print_method(PHASE_OPTIMIZE_FINISHED, 2);
2229 }
2230 
2231 
2232 //------------------------------Code_Gen---------------------------------------
2233 // Given a graph, generate code for it
2234 void Compile::Code_Gen() {
2235   if (failing()) {
2236     return;
2237   }
2238 
2239   // Perform instruction selection.  You might think we could reclaim Matcher
2240   // memory PDQ, but actually the Matcher is used in generating spill code.
2241   // Internals of the Matcher (including some VectorSets) must remain live
2242   // for awhile - thus I cannot reclaim Matcher memory lest a VectorSet usage
2243   // set a bit in reclaimed memory.
2244 
2245   // In debug mode can dump m._nodes.dump() for mapping of ideal to machine
2246   // nodes.  Mapping is only valid at the root of each matched subtree.
2247   NOT_PRODUCT( verify_graph_edges(); )
2248 
2249   Matcher matcher;
2250   _matcher = &matcher;
2251   {
2252     TracePhase t2("matcher", &_t_matcher, true);
2253     matcher.match();
2254   }
2255   // In debug mode can dump m._nodes.dump() for mapping of ideal to machine
2256   // nodes.  Mapping is only valid at the root of each matched subtree.
2257   NOT_PRODUCT( verify_graph_edges(); )
2258 
2259   // If you have too many nodes, or if matching has failed, bail out
2260   check_node_count(0, "out of nodes matching instructions");
2261   if (failing()) {
2262     return;
2263   }
2264 
2265   // Build a proper-looking CFG
2266   PhaseCFG cfg(node_arena(), root(), matcher);
2267   _cfg = &cfg;
2268   {
2269     NOT_PRODUCT( TracePhase t2("scheduler", &_t_scheduler, TimeCompiler); )
2270     bool success = cfg.do_global_code_motion();
2271     if (!success) {
2272       return;
2273     }
2274 
2275     print_method(PHASE_GLOBAL_CODE_MOTION, 2);
2276     NOT_PRODUCT( verify_graph_edges(); )
2277     debug_only( cfg.verify(); )
2278   }
2279 
2280   PhaseChaitin regalloc(unique(), cfg, matcher);
2281   _regalloc = &regalloc;
2282   {
2283     TracePhase t2("regalloc", &_t_registerAllocation, true);
2284     // Perform register allocation.  After Chaitin, use-def chains are
2285     // no longer accurate (at spill code) and so must be ignored.
2286     // Node->LRG->reg mappings are still accurate.
2287     _regalloc->Register_Allocate();
2288 
2289     // Bail out if the allocator builds too many nodes
2290     if (failing()) {
2291       return;
2292     }
2293   }
2294 
2295   // Prior to register allocation we kept empty basic blocks in case the
2296   // the allocator needed a place to spill.  After register allocation we
2297   // are not adding any new instructions.  If any basic block is empty, we
2298   // can now safely remove it.
2299   {
2300     NOT_PRODUCT( TracePhase t2("blockOrdering", &_t_blockOrdering, TimeCompiler); )
2301     cfg.remove_empty_blocks();
2302     if (do_freq_based_layout()) {
2303       PhaseBlockLayout layout(cfg);
2304     } else {
2305       cfg.set_loop_alignment();
2306     }
2307     cfg.fixup_flow();
2308   }
2309 
2310   // Apply peephole optimizations
2311   if( OptoPeephole ) {
2312     NOT_PRODUCT( TracePhase t2("peephole", &_t_peephole, TimeCompiler); )
2313     PhasePeephole peep( _regalloc, cfg);
2314     peep.do_transform();
2315   }
2316 
2317   // Do late expand if CPU requires this.
2318   if (Matcher::require_postalloc_expand) {
2319     NOT_PRODUCT(TracePhase t2c("postalloc_expand", &_t_postalloc_expand, true));
2320     cfg.postalloc_expand(_regalloc);
2321   }
2322 
2323   // Convert Nodes to instruction bits in a buffer
2324   {
2325     // %%%% workspace merge brought two timers together for one job
2326     TracePhase t2a("output", &_t_output, true);
2327     NOT_PRODUCT( TraceTime t2b(NULL, &_t_codeGeneration, TimeCompiler, false); )
2328     Output();
2329   }
2330 
2331   print_method(PHASE_FINAL_CODE);
2332 
2333   // He's dead, Jim.
2334   _cfg     = (PhaseCFG*)0xdeadbeef;
2335   _regalloc = (PhaseChaitin*)0xdeadbeef;
2336 }
2337 
2338 
2339 //------------------------------dump_asm---------------------------------------
2340 // Dump formatted assembly
2341 #ifndef PRODUCT
2342 void Compile::dump_asm(int *pcs, uint pc_limit) {
2343   bool cut_short = false;
2344   tty->print_cr("#");
2345   tty->print("#  ");  _tf->dump();  tty->cr();
2346   tty->print_cr("#");
2347 
2348   // For all blocks
2349   int pc = 0x0;                 // Program counter
2350   char starts_bundle = ' ';
2351   _regalloc->dump_frame();
2352 
2353   Node *n = NULL;
2354   for (uint i = 0; i < _cfg->number_of_blocks(); i++) {
2355     if (VMThread::should_terminate()) {
2356       cut_short = true;
2357       break;
2358     }
2359     Block* block = _cfg->get_block(i);
2360     if (block->is_connector() && !Verbose) {
2361       continue;
2362     }
2363     n = block->head();
2364     if (pcs && n->_idx < pc_limit) {
2365       tty->print("%3.3x   ", pcs[n->_idx]);
2366     } else {
2367       tty->print("      ");
2368     }
2369     block->dump_head(_cfg);
2370     if (block->is_connector()) {
2371       tty->print_cr("        # Empty connector block");
2372     } else if (block->num_preds() == 2 && block->pred(1)->is_CatchProj() && block->pred(1)->as_CatchProj()->_con == CatchProjNode::fall_through_index) {
2373       tty->print_cr("        # Block is sole successor of call");
2374     }
2375 
2376     // For all instructions
2377     Node *delay = NULL;
2378     for (uint j = 0; j < block->number_of_nodes(); j++) {
2379       if (VMThread::should_terminate()) {
2380         cut_short = true;
2381         break;
2382       }
2383       n = block->get_node(j);
2384       if (valid_bundle_info(n)) {
2385         Bundle* bundle = node_bundling(n);
2386         if (bundle->used_in_unconditional_delay()) {
2387           delay = n;
2388           continue;
2389         }
2390         if (bundle->starts_bundle()) {
2391           starts_bundle = '+';
2392         }
2393       }
2394 
2395       if (WizardMode) {
2396         n->dump();
2397       }
2398 
2399       if( !n->is_Region() &&    // Dont print in the Assembly
2400           !n->is_Phi() &&       // a few noisely useless nodes
2401           !n->is_Proj() &&
2402           !n->is_MachTemp() &&
2403           !n->is_SafePointScalarObject() &&
2404           !n->is_Catch() &&     // Would be nice to print exception table targets
2405           !n->is_MergeMem() &&  // Not very interesting
2406           !n->is_top() &&       // Debug info table constants
2407           !(n->is_Con() && !n->is_Mach())// Debug info table constants
2408           ) {
2409         if (pcs && n->_idx < pc_limit)
2410           tty->print("%3.3x", pcs[n->_idx]);
2411         else
2412           tty->print("   ");
2413         tty->print(" %c ", starts_bundle);
2414         starts_bundle = ' ';
2415         tty->print("\t");
2416         n->format(_regalloc, tty);
2417         tty->cr();
2418       }
2419 
2420       // If we have an instruction with a delay slot, and have seen a delay,
2421       // then back up and print it
2422       if (valid_bundle_info(n) && node_bundling(n)->use_unconditional_delay()) {
2423         assert(delay != NULL, "no unconditional delay instruction");
2424         if (WizardMode) delay->dump();
2425 
2426         if (node_bundling(delay)->starts_bundle())
2427           starts_bundle = '+';
2428         if (pcs && n->_idx < pc_limit)
2429           tty->print("%3.3x", pcs[n->_idx]);
2430         else
2431           tty->print("   ");
2432         tty->print(" %c ", starts_bundle);
2433         starts_bundle = ' ';
2434         tty->print("\t");
2435         delay->format(_regalloc, tty);
2436         tty->cr();
2437         delay = NULL;
2438       }
2439 
2440       // Dump the exception table as well
2441       if( n->is_Catch() && (Verbose || WizardMode) ) {
2442         // Print the exception table for this offset
2443         _handler_table.print_subtable_for(pc);
2444       }
2445     }
2446 
2447     if (pcs && n->_idx < pc_limit)
2448       tty->print_cr("%3.3x", pcs[n->_idx]);
2449     else
2450       tty->cr();
2451 
2452     assert(cut_short || delay == NULL, "no unconditional delay branch");
2453 
2454   } // End of per-block dump
2455   tty->cr();
2456 
2457   if (cut_short)  tty->print_cr("*** disassembly is cut short ***");
2458 }
2459 #endif
2460 
2461 //------------------------------Final_Reshape_Counts---------------------------
2462 // This class defines counters to help identify when a method
2463 // may/must be executed using hardware with only 24-bit precision.
2464 struct Final_Reshape_Counts : public StackObj {
2465   int  _call_count;             // count non-inlined 'common' calls
2466   int  _float_count;            // count float ops requiring 24-bit precision
2467   int  _double_count;           // count double ops requiring more precision
2468   int  _java_call_count;        // count non-inlined 'java' calls
2469   int  _inner_loop_count;       // count loops which need alignment
2470   VectorSet _visited;           // Visitation flags
2471   Node_List _tests;             // Set of IfNodes & PCTableNodes
2472 
2473   Final_Reshape_Counts() :
2474     _call_count(0), _float_count(0), _double_count(0),
2475     _java_call_count(0), _inner_loop_count(0),
2476     _visited( Thread::current()->resource_area() ) { }
2477 
2478   void inc_call_count  () { _call_count  ++; }
2479   void inc_float_count () { _float_count ++; }
2480   void inc_double_count() { _double_count++; }
2481   void inc_java_call_count() { _java_call_count++; }
2482   void inc_inner_loop_count() { _inner_loop_count++; }
2483 
2484   int  get_call_count  () const { return _call_count  ; }
2485   int  get_float_count () const { return _float_count ; }
2486   int  get_double_count() const { return _double_count; }
2487   int  get_java_call_count() const { return _java_call_count; }
2488   int  get_inner_loop_count() const { return _inner_loop_count; }
2489 };
2490 
2491 #ifdef ASSERT
2492 static bool oop_offset_is_sane(const TypeInstPtr* tp) {
2493   ciInstanceKlass *k = tp->klass()->as_instance_klass();
2494   // Make sure the offset goes inside the instance layout.
2495   return k->contains_field_offset(tp->offset());
2496   // Note that OffsetBot and OffsetTop are very negative.
2497 }
2498 #endif
2499 
2500 // Eliminate trivially redundant StoreCMs and accumulate their
2501 // precedence edges.
2502 void Compile::eliminate_redundant_card_marks(Node* n) {
2503   assert(n->Opcode() == Op_StoreCM, "expected StoreCM");
2504   if (n->in(MemNode::Address)->outcnt() > 1) {
2505     // There are multiple users of the same address so it might be
2506     // possible to eliminate some of the StoreCMs
2507     Node* mem = n->in(MemNode::Memory);
2508     Node* adr = n->in(MemNode::Address);
2509     Node* val = n->in(MemNode::ValueIn);
2510     Node* prev = n;
2511     bool done = false;
2512     // Walk the chain of StoreCMs eliminating ones that match.  As
2513     // long as it's a chain of single users then the optimization is
2514     // safe.  Eliminating partially redundant StoreCMs would require
2515     // cloning copies down the other paths.
2516     while (mem->Opcode() == Op_StoreCM && mem->outcnt() == 1 && !done) {
2517       if (adr == mem->in(MemNode::Address) &&
2518           val == mem->in(MemNode::ValueIn)) {
2519         // redundant StoreCM
2520         if (mem->req() > MemNode::OopStore) {
2521           // Hasn't been processed by this code yet.
2522           n->add_prec(mem->in(MemNode::OopStore));
2523         } else {
2524           // Already converted to precedence edge
2525           for (uint i = mem->req(); i < mem->len(); i++) {
2526             // Accumulate any precedence edges
2527             if (mem->in(i) != NULL) {
2528               n->add_prec(mem->in(i));
2529             }
2530           }
2531           // Everything above this point has been processed.
2532           done = true;
2533         }
2534         // Eliminate the previous StoreCM
2535         prev->set_req(MemNode::Memory, mem->in(MemNode::Memory));
2536         assert(mem->outcnt() == 0, "should be dead");
2537         mem->disconnect_inputs(NULL, this);
2538       } else {
2539         prev = mem;
2540       }
2541       mem = prev->in(MemNode::Memory);
2542     }
2543   }
2544 }
2545 
2546 //------------------------------final_graph_reshaping_impl----------------------
2547 // Implement items 1-5 from final_graph_reshaping below.
2548 void Compile::final_graph_reshaping_impl( Node *n, Final_Reshape_Counts &frc) {
2549 
2550   if ( n->outcnt() == 0 ) return; // dead node
2551   uint nop = n->Opcode();
2552 
2553   // Check for 2-input instruction with "last use" on right input.
2554   // Swap to left input.  Implements item (2).
2555   if( n->req() == 3 &&          // two-input instruction
2556       n->in(1)->outcnt() > 1 && // left use is NOT a last use
2557       (!n->in(1)->is_Phi() || n->in(1)->in(2) != n) && // it is not data loop
2558       n->in(2)->outcnt() == 1 &&// right use IS a last use
2559       !n->in(2)->is_Con() ) {   // right use is not a constant
2560     // Check for commutative opcode
2561     switch( nop ) {
2562     case Op_AddI:  case Op_AddF:  case Op_AddD:  case Op_AddL:
2563     case Op_MaxI:  case Op_MinI:
2564     case Op_MulI:  case Op_MulF:  case Op_MulD:  case Op_MulL:
2565     case Op_AndL:  case Op_XorL:  case Op_OrL:
2566     case Op_AndI:  case Op_XorI:  case Op_OrI: {
2567       // Move "last use" input to left by swapping inputs
2568       n->swap_edges(1, 2);
2569       break;
2570     }
2571     default:
2572       break;
2573     }
2574   }
2575 
2576 #ifdef ASSERT
2577   if( n->is_Mem() ) {
2578     int alias_idx = get_alias_index(n->as_Mem()->adr_type());
2579     assert( n->in(0) != NULL || alias_idx != Compile::AliasIdxRaw ||
2580             // oop will be recorded in oop map if load crosses safepoint
2581             n->is_Load() && (n->as_Load()->bottom_type()->isa_oopptr() ||
2582                              LoadNode::is_immutable_value(n->in(MemNode::Address))),
2583             "raw memory operations should have control edge");
2584   }
2585 #endif
2586   // Count FPU ops and common calls, implements item (3)
2587   switch( nop ) {
2588   // Count all float operations that may use FPU
2589   case Op_AddF:
2590   case Op_SubF:
2591   case Op_MulF:
2592   case Op_DivF:
2593   case Op_NegF:
2594   case Op_ModF:
2595   case Op_ConvI2F:
2596   case Op_ConF:
2597   case Op_CmpF:
2598   case Op_CmpF3:
2599   // case Op_ConvL2F: // longs are split into 32-bit halves
2600     frc.inc_float_count();
2601     break;
2602 
2603   case Op_ConvF2D:
2604   case Op_ConvD2F:
2605     frc.inc_float_count();
2606     frc.inc_double_count();
2607     break;
2608 
2609   // Count all double operations that may use FPU
2610   case Op_AddD:
2611   case Op_SubD:
2612   case Op_MulD:
2613   case Op_DivD:
2614   case Op_NegD:
2615   case Op_ModD:
2616   case Op_ConvI2D:
2617   case Op_ConvD2I:
2618   // case Op_ConvL2D: // handled by leaf call
2619   // case Op_ConvD2L: // handled by leaf call
2620   case Op_ConD:
2621   case Op_CmpD:
2622   case Op_CmpD3:
2623     frc.inc_double_count();
2624     break;
2625   case Op_Opaque1:              // Remove Opaque Nodes before matching
2626   case Op_Opaque2:              // Remove Opaque Nodes before matching
2627   case Op_Opaque3:
2628     n->subsume_by(n->in(1), this);
2629     break;
2630   case Op_CallStaticJava:
2631   case Op_CallJava:
2632   case Op_CallDynamicJava:
2633     frc.inc_java_call_count(); // Count java call site;
2634   case Op_CallRuntime:
2635   case Op_CallLeaf:
2636   case Op_CallLeafNoFP: {
2637     assert( n->is_Call(), "" );
2638     CallNode *call = n->as_Call();
2639     // Count call sites where the FP mode bit would have to be flipped.
2640     // Do not count uncommon runtime calls:
2641     // uncommon_trap, _complete_monitor_locking, _complete_monitor_unlocking,
2642     // _new_Java, _new_typeArray, _new_objArray, _rethrow_Java, ...
2643     if( !call->is_CallStaticJava() || !call->as_CallStaticJava()->_name ) {
2644       frc.inc_call_count();   // Count the call site
2645     } else {                  // See if uncommon argument is shared
2646       Node *n = call->in(TypeFunc::Parms);
2647       int nop = n->Opcode();
2648       // Clone shared simple arguments to uncommon calls, item (1).
2649       if( n->outcnt() > 1 &&
2650           !n->is_Proj() &&
2651           nop != Op_CreateEx &&
2652           nop != Op_CheckCastPP &&
2653           nop != Op_DecodeN &&
2654           nop != Op_DecodeNKlass &&
2655           !n->is_Mem() ) {
2656         Node *x = n->clone();
2657         call->set_req( TypeFunc::Parms, x );
2658       }
2659     }
2660     break;
2661   }
2662 
2663   case Op_StoreD:
2664   case Op_LoadD:
2665   case Op_LoadD_unaligned:
2666     frc.inc_double_count();
2667     goto handle_mem;
2668   case Op_StoreF:
2669   case Op_LoadF:
2670     frc.inc_float_count();
2671     goto handle_mem;
2672 
2673   case Op_StoreCM:
2674     {
2675       // Convert OopStore dependence into precedence edge
2676       Node* prec = n->in(MemNode::OopStore);
2677       n->del_req(MemNode::OopStore);
2678       n->add_prec(prec);
2679       eliminate_redundant_card_marks(n);
2680     }
2681 
2682     // fall through
2683 
2684   case Op_StoreB:
2685   case Op_StoreC:
2686   case Op_StorePConditional:
2687   case Op_StoreI:
2688   case Op_StoreL:
2689   case Op_StoreIConditional:
2690   case Op_StoreLConditional:
2691   case Op_CompareAndSwapI:
2692   case Op_CompareAndSwapL:
2693   case Op_CompareAndSwapP:
2694   case Op_CompareAndSwapN:
2695   case Op_GetAndAddI:
2696   case Op_GetAndAddL:
2697   case Op_GetAndSetI:
2698   case Op_GetAndSetL:
2699   case Op_GetAndSetP:
2700   case Op_GetAndSetN:
2701   case Op_StoreP:
2702   case Op_StoreN:
2703   case Op_StoreNKlass:
2704   case Op_LoadB:
2705   case Op_LoadUB:
2706   case Op_LoadUS:
2707   case Op_LoadI:
2708   case Op_LoadKlass:
2709   case Op_LoadNKlass:
2710   case Op_LoadL:
2711   case Op_LoadL_unaligned:
2712   case Op_LoadPLocked:
2713   case Op_LoadP:
2714   case Op_LoadN:
2715   case Op_LoadRange:
2716   case Op_LoadS: {
2717   handle_mem:
2718 #ifdef ASSERT
2719     if( VerifyOptoOopOffsets ) {
2720       assert( n->is_Mem(), "" );
2721       MemNode *mem  = (MemNode*)n;
2722       // Check to see if address types have grounded out somehow.
2723       const TypeInstPtr *tp = mem->in(MemNode::Address)->bottom_type()->isa_instptr();
2724       assert( !tp || oop_offset_is_sane(tp), "" );
2725     }
2726 #endif
2727     break;
2728   }
2729 
2730   case Op_AddP: {               // Assert sane base pointers
2731     Node *addp = n->in(AddPNode::Address);
2732     assert( !addp->is_AddP() ||
2733             addp->in(AddPNode::Base)->is_top() || // Top OK for allocation
2734             addp->in(AddPNode::Base) == n->in(AddPNode::Base),
2735             "Base pointers must match" );
2736 #ifdef _LP64
2737     if ((UseCompressedOops || UseCompressedClassPointers) &&
2738         addp->Opcode() == Op_ConP &&
2739         addp == n->in(AddPNode::Base) &&
2740         n->in(AddPNode::Offset)->is_Con()) {
2741       // Use addressing with narrow klass to load with offset on x86.
2742       // On sparc loading 32-bits constant and decoding it have less
2743       // instructions (4) then load 64-bits constant (7).
2744       // Do this transformation here since IGVN will convert ConN back to ConP.
2745       const Type* t = addp->bottom_type();
2746       if (t->isa_oopptr() || t->isa_klassptr()) {
2747         Node* nn = NULL;
2748 
2749         int op = t->isa_oopptr() ? Op_ConN : Op_ConNKlass;
2750 
2751         // Look for existing ConN node of the same exact type.
2752         Node* r  = root();
2753         uint cnt = r->outcnt();
2754         for (uint i = 0; i < cnt; i++) {
2755           Node* m = r->raw_out(i);
2756           if (m!= NULL && m->Opcode() == op &&
2757               m->bottom_type()->make_ptr() == t) {
2758             nn = m;
2759             break;
2760           }
2761         }
2762         if (nn != NULL) {
2763           // Decode a narrow oop to match address
2764           // [R12 + narrow_oop_reg<<3 + offset]
2765           if (t->isa_oopptr()) {
2766             nn = new (this) DecodeNNode(nn, t);
2767           } else {
2768             nn = new (this) DecodeNKlassNode(nn, t);
2769           }
2770           n->set_req(AddPNode::Base, nn);
2771           n->set_req(AddPNode::Address, nn);
2772           if (addp->outcnt() == 0) {
2773             addp->disconnect_inputs(NULL, this);
2774           }
2775         }
2776       }
2777     }
2778 #endif
2779     break;
2780   }
2781 
2782 #ifdef _LP64
2783   case Op_CastPP:
2784     if (n->in(1)->is_DecodeN() && Matcher::gen_narrow_oop_implicit_null_checks()) {
2785       Node* in1 = n->in(1);
2786       const Type* t = n->bottom_type();
2787       Node* new_in1 = in1->clone();
2788       new_in1->as_DecodeN()->set_type(t);
2789 
2790       if (!Matcher::narrow_oop_use_complex_address()) {
2791         //
2792         // x86, ARM and friends can handle 2 adds in addressing mode
2793         // and Matcher can fold a DecodeN node into address by using
2794         // a narrow oop directly and do implicit NULL check in address:
2795         //
2796         // [R12 + narrow_oop_reg<<3 + offset]
2797         // NullCheck narrow_oop_reg
2798         //
2799         // On other platforms (Sparc) we have to keep new DecodeN node and
2800         // use it to do implicit NULL check in address:
2801         //
2802         // decode_not_null narrow_oop_reg, base_reg
2803         // [base_reg + offset]
2804         // NullCheck base_reg
2805         //
2806         // Pin the new DecodeN node to non-null path on these platform (Sparc)
2807         // to keep the information to which NULL check the new DecodeN node
2808         // corresponds to use it as value in implicit_null_check().
2809         //
2810         new_in1->set_req(0, n->in(0));
2811       }
2812 
2813       n->subsume_by(new_in1, this);
2814       if (in1->outcnt() == 0) {
2815         in1->disconnect_inputs(NULL, this);
2816       }
2817     }
2818     break;
2819 
2820   case Op_CmpP:
2821     // Do this transformation here to preserve CmpPNode::sub() and
2822     // other TypePtr related Ideal optimizations (for example, ptr nullness).
2823     if (n->in(1)->is_DecodeNarrowPtr() || n->in(2)->is_DecodeNarrowPtr()) {
2824       Node* in1 = n->in(1);
2825       Node* in2 = n->in(2);
2826       if (!in1->is_DecodeNarrowPtr()) {
2827         in2 = in1;
2828         in1 = n->in(2);
2829       }
2830       assert(in1->is_DecodeNarrowPtr(), "sanity");
2831 
2832       Node* new_in2 = NULL;
2833       if (in2->is_DecodeNarrowPtr()) {
2834         assert(in2->Opcode() == in1->Opcode(), "must be same node type");
2835         new_in2 = in2->in(1);
2836       } else if (in2->Opcode() == Op_ConP) {
2837         const Type* t = in2->bottom_type();
2838         if (t == TypePtr::NULL_PTR) {
2839           assert(in1->is_DecodeN(), "compare klass to null?");
2840           // Don't convert CmpP null check into CmpN if compressed
2841           // oops implicit null check is not generated.
2842           // This will allow to generate normal oop implicit null check.
2843           if (Matcher::gen_narrow_oop_implicit_null_checks())
2844             new_in2 = ConNode::make(this, TypeNarrowOop::NULL_PTR);
2845           //
2846           // This transformation together with CastPP transformation above
2847           // will generated code for implicit NULL checks for compressed oops.
2848           //
2849           // The original code after Optimize()
2850           //
2851           //    LoadN memory, narrow_oop_reg
2852           //    decode narrow_oop_reg, base_reg
2853           //    CmpP base_reg, NULL
2854           //    CastPP base_reg // NotNull
2855           //    Load [base_reg + offset], val_reg
2856           //
2857           // after these transformations will be
2858           //
2859           //    LoadN memory, narrow_oop_reg
2860           //    CmpN narrow_oop_reg, NULL
2861           //    decode_not_null narrow_oop_reg, base_reg
2862           //    Load [base_reg + offset], val_reg
2863           //
2864           // and the uncommon path (== NULL) will use narrow_oop_reg directly
2865           // since narrow oops can be used in debug info now (see the code in
2866           // final_graph_reshaping_walk()).
2867           //
2868           // At the end the code will be matched to
2869           // on x86:
2870           //
2871           //    Load_narrow_oop memory, narrow_oop_reg
2872           //    Load [R12 + narrow_oop_reg<<3 + offset], val_reg
2873           //    NullCheck narrow_oop_reg
2874           //
2875           // and on sparc:
2876           //
2877           //    Load_narrow_oop memory, narrow_oop_reg
2878           //    decode_not_null narrow_oop_reg, base_reg
2879           //    Load [base_reg + offset], val_reg
2880           //    NullCheck base_reg
2881           //
2882         } else if (t->isa_oopptr()) {
2883           new_in2 = ConNode::make(this, t->make_narrowoop());
2884         } else if (t->isa_klassptr()) {
2885           new_in2 = ConNode::make(this, t->make_narrowklass());
2886         }
2887       }
2888       if (new_in2 != NULL) {
2889         Node* cmpN = new (this) CmpNNode(in1->in(1), new_in2);
2890         n->subsume_by(cmpN, this);
2891         if (in1->outcnt() == 0) {
2892           in1->disconnect_inputs(NULL, this);
2893         }
2894         if (in2->outcnt() == 0) {
2895           in2->disconnect_inputs(NULL, this);
2896         }
2897       }
2898     }
2899     break;
2900 
2901   case Op_DecodeN:
2902   case Op_DecodeNKlass:
2903     assert(!n->in(1)->is_EncodeNarrowPtr(), "should be optimized out");
2904     // DecodeN could be pinned when it can't be fold into
2905     // an address expression, see the code for Op_CastPP above.
2906     assert(n->in(0) == NULL || (UseCompressedOops && !Matcher::narrow_oop_use_complex_address()), "no control");
2907     break;
2908 
2909   case Op_EncodeP:
2910   case Op_EncodePKlass: {
2911     Node* in1 = n->in(1);
2912     if (in1->is_DecodeNarrowPtr()) {
2913       n->subsume_by(in1->in(1), this);
2914     } else if (in1->Opcode() == Op_ConP) {
2915       const Type* t = in1->bottom_type();
2916       if (t == TypePtr::NULL_PTR) {
2917         assert(t->isa_oopptr(), "null klass?");
2918         n->subsume_by(ConNode::make(this, TypeNarrowOop::NULL_PTR), this);
2919       } else if (t->isa_oopptr()) {
2920         n->subsume_by(ConNode::make(this, t->make_narrowoop()), this);
2921       } else if (t->isa_klassptr()) {
2922         n->subsume_by(ConNode::make(this, t->make_narrowklass()), this);
2923       }
2924     }
2925     if (in1->outcnt() == 0) {
2926       in1->disconnect_inputs(NULL, this);
2927     }
2928     break;
2929   }
2930 
2931   case Op_Proj: {
2932     if (OptimizeStringConcat) {
2933       ProjNode* p = n->as_Proj();
2934       if (p->_is_io_use) {
2935         // Separate projections were used for the exception path which
2936         // are normally removed by a late inline.  If it wasn't inlined
2937         // then they will hang around and should just be replaced with
2938         // the original one.
2939         Node* proj = NULL;
2940         // Replace with just one
2941         for (SimpleDUIterator i(p->in(0)); i.has_next(); i.next()) {
2942           Node *use = i.get();
2943           if (use->is_Proj() && p != use && use->as_Proj()->_con == p->_con) {
2944             proj = use;
2945             break;
2946           }
2947         }
2948         assert(proj != NULL, "must be found");
2949         p->subsume_by(proj, this);
2950       }
2951     }
2952     break;
2953   }
2954 
2955   case Op_Phi:
2956     if (n->as_Phi()->bottom_type()->isa_narrowoop() || n->as_Phi()->bottom_type()->isa_narrowklass()) {
2957       // The EncodeP optimization may create Phi with the same edges
2958       // for all paths. It is not handled well by Register Allocator.
2959       Node* unique_in = n->in(1);
2960       assert(unique_in != NULL, "");
2961       uint cnt = n->req();
2962       for (uint i = 2; i < cnt; i++) {
2963         Node* m = n->in(i);
2964         assert(m != NULL, "");
2965         if (unique_in != m)
2966           unique_in = NULL;
2967       }
2968       if (unique_in != NULL) {
2969         n->subsume_by(unique_in, this);
2970       }
2971     }
2972     break;
2973 
2974 #endif
2975 
2976   case Op_ModI:
2977     if (UseDivMod) {
2978       // Check if a%b and a/b both exist
2979       Node* d = n->find_similar(Op_DivI);
2980       if (d) {
2981         // Replace them with a fused divmod if supported
2982         if (Matcher::has_match_rule(Op_DivModI)) {
2983           DivModINode* divmod = DivModINode::make(this, n);
2984           d->subsume_by(divmod->div_proj(), this);
2985           n->subsume_by(divmod->mod_proj(), this);
2986         } else {
2987           // replace a%b with a-((a/b)*b)
2988           Node* mult = new (this) MulINode(d, d->in(2));
2989           Node* sub  = new (this) SubINode(d->in(1), mult);
2990           n->subsume_by(sub, this);
2991         }
2992       }
2993     }
2994     break;
2995 
2996   case Op_ModL:
2997     if (UseDivMod) {
2998       // Check if a%b and a/b both exist
2999       Node* d = n->find_similar(Op_DivL);
3000       if (d) {
3001         // Replace them with a fused divmod if supported
3002         if (Matcher::has_match_rule(Op_DivModL)) {
3003           DivModLNode* divmod = DivModLNode::make(this, n);
3004           d->subsume_by(divmod->div_proj(), this);
3005           n->subsume_by(divmod->mod_proj(), this);
3006         } else {
3007           // replace a%b with a-((a/b)*b)
3008           Node* mult = new (this) MulLNode(d, d->in(2));
3009           Node* sub  = new (this) SubLNode(d->in(1), mult);
3010           n->subsume_by(sub, this);
3011         }
3012       }
3013     }
3014     break;
3015 
3016   case Op_LoadVector:
3017   case Op_StoreVector:
3018     break;
3019 
3020   case Op_PackB:
3021   case Op_PackS:
3022   case Op_PackI:
3023   case Op_PackF:
3024   case Op_PackL:
3025   case Op_PackD:
3026     if (n->req()-1 > 2) {
3027       // Replace many operand PackNodes with a binary tree for matching
3028       PackNode* p = (PackNode*) n;
3029       Node* btp = p->binary_tree_pack(this, 1, n->req());
3030       n->subsume_by(btp, this);
3031     }
3032     break;
3033   case Op_Loop:
3034   case Op_CountedLoop:
3035     if (n->as_Loop()->is_inner_loop()) {
3036       frc.inc_inner_loop_count();
3037     }
3038     break;
3039   case Op_LShiftI:
3040   case Op_RShiftI:
3041   case Op_URShiftI:
3042   case Op_LShiftL:
3043   case Op_RShiftL:
3044   case Op_URShiftL:
3045     if (Matcher::need_masked_shift_count) {
3046       // The cpu's shift instructions don't restrict the count to the
3047       // lower 5/6 bits. We need to do the masking ourselves.
3048       Node* in2 = n->in(2);
3049       juint mask = (n->bottom_type() == TypeInt::INT) ? (BitsPerInt - 1) : (BitsPerLong - 1);
3050       const TypeInt* t = in2->find_int_type();
3051       if (t != NULL && t->is_con()) {
3052         juint shift = t->get_con();
3053         if (shift > mask) { // Unsigned cmp
3054           n->set_req(2, ConNode::make(this, TypeInt::make(shift & mask)));
3055         }
3056       } else {
3057         if (t == NULL || t->_lo < 0 || t->_hi > (int)mask) {
3058           Node* shift = new (this) AndINode(in2, ConNode::make(this, TypeInt::make(mask)));
3059           n->set_req(2, shift);
3060         }
3061       }
3062       if (in2->outcnt() == 0) { // Remove dead node
3063         in2->disconnect_inputs(NULL, this);
3064       }
3065     }
3066     break;
3067   case Op_MemBarStoreStore:
3068   case Op_MemBarRelease:
3069     // Break the link with AllocateNode: it is no longer useful and
3070     // confuses register allocation.
3071     if (n->req() > MemBarNode::Precedent) {
3072       n->set_req(MemBarNode::Precedent, top());
3073     }
3074     break;
3075   default:
3076     assert( !n->is_Call(), "" );
3077     assert( !n->is_Mem(), "" );
3078     assert( nop != Op_ProfileBoolean, "should be eliminated during IGVN");
3079     break;
3080   }
3081 
3082   // Collect CFG split points
3083   if (n->is_MultiBranch())
3084     frc._tests.push(n);
3085 }
3086 
3087 //------------------------------final_graph_reshaping_walk---------------------
3088 // Replacing Opaque nodes with their input in final_graph_reshaping_impl(),
3089 // requires that the walk visits a node's inputs before visiting the node.
3090 void Compile::final_graph_reshaping_walk( Node_Stack &nstack, Node *root, Final_Reshape_Counts &frc ) {
3091   ResourceArea *area = Thread::current()->resource_area();
3092   Unique_Node_List sfpt(area);
3093 
3094   frc._visited.set(root->_idx); // first, mark node as visited
3095   uint cnt = root->req();
3096   Node *n = root;
3097   uint  i = 0;
3098   while (true) {
3099     if (i < cnt) {
3100       // Place all non-visited non-null inputs onto stack
3101       Node* m = n->in(i);
3102       ++i;
3103       if (m != NULL && !frc._visited.test_set(m->_idx)) {
3104         if (m->is_SafePoint() && m->as_SafePoint()->jvms() != NULL) {
3105           // compute worst case interpreter size in case of a deoptimization
3106           update_interpreter_frame_size(m->as_SafePoint()->jvms()->interpreter_frame_size());
3107 
3108           sfpt.push(m);
3109         }
3110         cnt = m->req();
3111         nstack.push(n, i); // put on stack parent and next input's index
3112         n = m;
3113         i = 0;
3114       }
3115     } else {
3116       // Now do post-visit work
3117       final_graph_reshaping_impl( n, frc );
3118       if (nstack.is_empty())
3119         break;             // finished
3120       n = nstack.node();   // Get node from stack
3121       cnt = n->req();
3122       i = nstack.index();
3123       nstack.pop();        // Shift to the next node on stack
3124     }
3125   }
3126 
3127   // Skip next transformation if compressed oops are not used.
3128   if ((UseCompressedOops && !Matcher::gen_narrow_oop_implicit_null_checks()) ||
3129       (!UseCompressedOops && !UseCompressedClassPointers))
3130     return;
3131 
3132   // Go over safepoints nodes to skip DecodeN/DecodeNKlass nodes for debug edges.
3133   // It could be done for an uncommon traps or any safepoints/calls
3134   // if the DecodeN/DecodeNKlass node is referenced only in a debug info.
3135   while (sfpt.size() > 0) {
3136     n = sfpt.pop();
3137     JVMState *jvms = n->as_SafePoint()->jvms();
3138     assert(jvms != NULL, "sanity");
3139     int start = jvms->debug_start();
3140     int end   = n->req();
3141     bool is_uncommon = (n->is_CallStaticJava() &&
3142                         n->as_CallStaticJava()->uncommon_trap_request() != 0);
3143     for (int j = start; j < end; j++) {
3144       Node* in = n->in(j);
3145       if (in->is_DecodeNarrowPtr()) {
3146         bool safe_to_skip = true;
3147         if (!is_uncommon ) {
3148           // Is it safe to skip?
3149           for (uint i = 0; i < in->outcnt(); i++) {
3150             Node* u = in->raw_out(i);
3151             if (!u->is_SafePoint() ||
3152                  u->is_Call() && u->as_Call()->has_non_debug_use(n)) {
3153               safe_to_skip = false;
3154             }
3155           }
3156         }
3157         if (safe_to_skip) {
3158           n->set_req(j, in->in(1));
3159         }
3160         if (in->outcnt() == 0) {
3161           in->disconnect_inputs(NULL, this);
3162         }
3163       }
3164     }
3165   }
3166 }
3167 
3168 //------------------------------final_graph_reshaping--------------------------
3169 // Final Graph Reshaping.
3170 //
3171 // (1) Clone simple inputs to uncommon calls, so they can be scheduled late
3172 //     and not commoned up and forced early.  Must come after regular
3173 //     optimizations to avoid GVN undoing the cloning.  Clone constant
3174 //     inputs to Loop Phis; these will be split by the allocator anyways.
3175 //     Remove Opaque nodes.
3176 // (2) Move last-uses by commutative operations to the left input to encourage
3177 //     Intel update-in-place two-address operations and better register usage
3178 //     on RISCs.  Must come after regular optimizations to avoid GVN Ideal
3179 //     calls canonicalizing them back.
3180 // (3) Count the number of double-precision FP ops, single-precision FP ops
3181 //     and call sites.  On Intel, we can get correct rounding either by
3182 //     forcing singles to memory (requires extra stores and loads after each
3183 //     FP bytecode) or we can set a rounding mode bit (requires setting and
3184 //     clearing the mode bit around call sites).  The mode bit is only used
3185 //     if the relative frequency of single FP ops to calls is low enough.
3186 //     This is a key transform for SPEC mpeg_audio.
3187 // (4) Detect infinite loops; blobs of code reachable from above but not
3188 //     below.  Several of the Code_Gen algorithms fail on such code shapes,
3189 //     so we simply bail out.  Happens a lot in ZKM.jar, but also happens
3190 //     from time to time in other codes (such as -Xcomp finalizer loops, etc).
3191 //     Detection is by looking for IfNodes where only 1 projection is
3192 //     reachable from below or CatchNodes missing some targets.
3193 // (5) Assert for insane oop offsets in debug mode.
3194 
3195 bool Compile::final_graph_reshaping() {
3196   // an infinite loop may have been eliminated by the optimizer,
3197   // in which case the graph will be empty.
3198   if (root()->req() == 1) {
3199     record_method_not_compilable("trivial infinite loop");
3200     return true;
3201   }
3202 
3203   // Expensive nodes have their control input set to prevent the GVN
3204   // from freely commoning them. There's no GVN beyond this point so
3205   // no need to keep the control input. We want the expensive nodes to
3206   // be freely moved to the least frequent code path by gcm.
3207   assert(OptimizeExpensiveOps || expensive_count() == 0, "optimization off but list non empty?");
3208   for (int i = 0; i < expensive_count(); i++) {
3209     _expensive_nodes->at(i)->set_req(0, NULL);
3210   }
3211 
3212   Final_Reshape_Counts frc;
3213 
3214   // Visit everybody reachable!
3215   // Allocate stack of size C->unique()/2 to avoid frequent realloc
3216   Node_Stack nstack(live_nodes() >> 1);
3217   final_graph_reshaping_walk(nstack, root(), frc);
3218 
3219   // Check for unreachable (from below) code (i.e., infinite loops).
3220   for( uint i = 0; i < frc._tests.size(); i++ ) {
3221     MultiBranchNode *n = frc._tests[i]->as_MultiBranch();
3222     // Get number of CFG targets.
3223     // Note that PCTables include exception targets after calls.
3224     uint required_outcnt = n->required_outcnt();
3225     if (n->outcnt() != required_outcnt) {
3226       // Check for a few special cases.  Rethrow Nodes never take the
3227       // 'fall-thru' path, so expected kids is 1 less.
3228       if (n->is_PCTable() && n->in(0) && n->in(0)->in(0)) {
3229         if (n->in(0)->in(0)->is_Call()) {
3230           CallNode *call = n->in(0)->in(0)->as_Call();
3231           if (call->entry_point() == OptoRuntime::rethrow_stub()) {
3232             required_outcnt--;      // Rethrow always has 1 less kid
3233           } else if (call->req() > TypeFunc::Parms &&
3234                      call->is_CallDynamicJava()) {
3235             // Check for null receiver. In such case, the optimizer has
3236             // detected that the virtual call will always result in a null
3237             // pointer exception. The fall-through projection of this CatchNode
3238             // will not be populated.
3239             Node *arg0 = call->in(TypeFunc::Parms);
3240             if (arg0->is_Type() &&
3241                 arg0->as_Type()->type()->higher_equal(TypePtr::NULL_PTR)) {
3242               required_outcnt--;
3243             }
3244           } else if (call->entry_point() == OptoRuntime::new_array_Java() &&
3245                      call->req() > TypeFunc::Parms+1 &&
3246                      call->is_CallStaticJava()) {
3247             // Check for negative array length. In such case, the optimizer has
3248             // detected that the allocation attempt will always result in an
3249             // exception. There is no fall-through projection of this CatchNode .
3250             Node *arg1 = call->in(TypeFunc::Parms+1);
3251             if (arg1->is_Type() &&
3252                 arg1->as_Type()->type()->join(TypeInt::POS)->empty()) {
3253               required_outcnt--;
3254             }
3255           }
3256         }
3257       }
3258       // Recheck with a better notion of 'required_outcnt'
3259       if (n->outcnt() != required_outcnt) {
3260         record_method_not_compilable("malformed control flow");
3261         return true;            // Not all targets reachable!
3262       }
3263     }
3264     // Check that I actually visited all kids.  Unreached kids
3265     // must be infinite loops.
3266     for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++)
3267       if (!frc._visited.test(n->fast_out(j)->_idx)) {
3268         record_method_not_compilable("infinite loop");
3269         return true;            // Found unvisited kid; must be unreach
3270       }
3271   }
3272 
3273   // If original bytecodes contained a mixture of floats and doubles
3274   // check if the optimizer has made it homogenous, item (3).
3275   if( Use24BitFPMode && Use24BitFP && UseSSE == 0 &&
3276       frc.get_float_count() > 32 &&
3277       frc.get_double_count() == 0 &&
3278       (10 * frc.get_call_count() < frc.get_float_count()) ) {
3279     set_24_bit_selection_and_mode( false,  true );
3280   }
3281 
3282   set_java_calls(frc.get_java_call_count());
3283   set_inner_loops(frc.get_inner_loop_count());
3284 
3285   // No infinite loops, no reason to bail out.
3286   return false;
3287 }
3288 
3289 //-----------------------------too_many_traps----------------------------------
3290 // Report if there are too many traps at the current method and bci.
3291 // Return true if there was a trap, and/or PerMethodTrapLimit is exceeded.
3292 bool Compile::too_many_traps(ciMethod* method,
3293                              int bci,
3294                              Deoptimization::DeoptReason reason) {
3295   ciMethodData* md = method->method_data();
3296   if (md->is_empty()) {
3297     // Assume the trap has not occurred, or that it occurred only
3298     // because of a transient condition during start-up in the interpreter.
3299     return false;
3300   }
3301   ciMethod* m = Deoptimization::reason_is_speculate(reason) ? this->method() : NULL;
3302   if (md->has_trap_at(bci, m, reason) != 0) {
3303     // Assume PerBytecodeTrapLimit==0, for a more conservative heuristic.
3304     // Also, if there are multiple reasons, or if there is no per-BCI record,
3305     // assume the worst.
3306     if (log())
3307       log()->elem("observe trap='%s' count='%d'",
3308                   Deoptimization::trap_reason_name(reason),
3309                   md->trap_count(reason));
3310     return true;
3311   } else {
3312     // Ignore method/bci and see if there have been too many globally.
3313     return too_many_traps(reason, md);
3314   }
3315 }
3316 
3317 // Less-accurate variant which does not require a method and bci.
3318 bool Compile::too_many_traps(Deoptimization::DeoptReason reason,
3319                              ciMethodData* logmd) {
3320   if (trap_count(reason) >= Deoptimization::per_method_trap_limit(reason)) {
3321     // Too many traps globally.
3322     // Note that we use cumulative trap_count, not just md->trap_count.
3323     if (log()) {
3324       int mcount = (logmd == NULL)? -1: (int)logmd->trap_count(reason);
3325       log()->elem("observe trap='%s' count='0' mcount='%d' ccount='%d'",
3326                   Deoptimization::trap_reason_name(reason),
3327                   mcount, trap_count(reason));
3328     }
3329     return true;
3330   } else {
3331     // The coast is clear.
3332     return false;
3333   }
3334 }
3335 
3336 //--------------------------too_many_recompiles--------------------------------
3337 // Report if there are too many recompiles at the current method and bci.
3338 // Consults PerBytecodeRecompilationCutoff and PerMethodRecompilationCutoff.
3339 // Is not eager to return true, since this will cause the compiler to use
3340 // Action_none for a trap point, to avoid too many recompilations.
3341 bool Compile::too_many_recompiles(ciMethod* method,
3342                                   int bci,
3343                                   Deoptimization::DeoptReason reason) {
3344   ciMethodData* md = method->method_data();
3345   if (md->is_empty()) {
3346     // Assume the trap has not occurred, or that it occurred only
3347     // because of a transient condition during start-up in the interpreter.
3348     return false;
3349   }
3350   // Pick a cutoff point well within PerBytecodeRecompilationCutoff.
3351   uint bc_cutoff = (uint) PerBytecodeRecompilationCutoff / 8;
3352   uint m_cutoff  = (uint) PerMethodRecompilationCutoff / 2 + 1;  // not zero
3353   Deoptimization::DeoptReason per_bc_reason
3354     = Deoptimization::reason_recorded_per_bytecode_if_any(reason);
3355   ciMethod* m = Deoptimization::reason_is_speculate(reason) ? this->method() : NULL;
3356   if ((per_bc_reason == Deoptimization::Reason_none
3357        || md->has_trap_at(bci, m, reason) != 0)
3358       // The trap frequency measure we care about is the recompile count:
3359       && md->trap_recompiled_at(bci, m)
3360       && md->overflow_recompile_count() >= bc_cutoff) {
3361     // Do not emit a trap here if it has already caused recompilations.
3362     // Also, if there are multiple reasons, or if there is no per-BCI record,
3363     // assume the worst.
3364     if (log())
3365       log()->elem("observe trap='%s recompiled' count='%d' recompiles2='%d'",
3366                   Deoptimization::trap_reason_name(reason),
3367                   md->trap_count(reason),
3368                   md->overflow_recompile_count());
3369     return true;
3370   } else if (trap_count(reason) != 0
3371              && decompile_count() >= m_cutoff) {
3372     // Too many recompiles globally, and we have seen this sort of trap.
3373     // Use cumulative decompile_count, not just md->decompile_count.
3374     if (log())
3375       log()->elem("observe trap='%s' count='%d' mcount='%d' decompiles='%d' mdecompiles='%d'",
3376                   Deoptimization::trap_reason_name(reason),
3377                   md->trap_count(reason), trap_count(reason),
3378                   md->decompile_count(), decompile_count());
3379     return true;
3380   } else {
3381     // The coast is clear.
3382     return false;
3383   }
3384 }
3385 
3386 // Compute when not to trap. Used by matching trap based nodes and
3387 // NullCheck optimization.
3388 void Compile::set_allowed_deopt_reasons() {
3389   _allowed_reasons = 0;
3390   if (is_method_compilation()) {
3391     for (int rs = (int)Deoptimization::Reason_none+1; rs < Compile::trapHistLength; rs++) {
3392       assert(rs < BitsPerInt, "recode bit map");
3393       if (!too_many_traps((Deoptimization::DeoptReason) rs)) {
3394         _allowed_reasons |= nth_bit(rs);
3395       }
3396     }
3397   }
3398 }
3399 
3400 #ifndef PRODUCT
3401 //------------------------------verify_graph_edges---------------------------
3402 // Walk the Graph and verify that there is a one-to-one correspondence
3403 // between Use-Def edges and Def-Use edges in the graph.
3404 void Compile::verify_graph_edges(bool no_dead_code) {
3405   if (VerifyGraphEdges) {
3406     ResourceArea *area = Thread::current()->resource_area();
3407     Unique_Node_List visited(area);
3408     // Call recursive graph walk to check edges
3409     _root->verify_edges(visited);
3410     if (no_dead_code) {
3411       // Now make sure that no visited node is used by an unvisited node.
3412       bool dead_nodes = 0;
3413       Unique_Node_List checked(area);
3414       while (visited.size() > 0) {
3415         Node* n = visited.pop();
3416         checked.push(n);
3417         for (uint i = 0; i < n->outcnt(); i++) {
3418           Node* use = n->raw_out(i);
3419           if (checked.member(use))  continue;  // already checked
3420           if (visited.member(use))  continue;  // already in the graph
3421           if (use->is_Con())        continue;  // a dead ConNode is OK
3422           // At this point, we have found a dead node which is DU-reachable.
3423           if (dead_nodes++ == 0)
3424             tty->print_cr("*** Dead nodes reachable via DU edges:");
3425           use->dump(2);
3426           tty->print_cr("---");
3427           checked.push(use);  // No repeats; pretend it is now checked.
3428         }
3429       }
3430       assert(dead_nodes == 0, "using nodes must be reachable from root");
3431     }
3432   }
3433 }
3434 
3435 // Verify GC barriers consistency
3436 // Currently supported:
3437 // - G1 pre-barriers (see GraphKit::g1_write_barrier_pre())
3438 void Compile::verify_barriers() {
3439   if (UseG1GC) {
3440     // Verify G1 pre-barriers
3441     const int marking_offset = in_bytes(JavaThread::satb_mark_queue_offset() + PtrQueue::byte_offset_of_active());
3442 
3443     ResourceArea *area = Thread::current()->resource_area();
3444     Unique_Node_List visited(area);
3445     Node_List worklist(area);
3446     // We're going to walk control flow backwards starting from the Root
3447     worklist.push(_root);
3448     while (worklist.size() > 0) {
3449       Node* x = worklist.pop();
3450       if (x == NULL || x == top()) continue;
3451       if (visited.member(x)) {
3452         continue;
3453       } else {
3454         visited.push(x);
3455       }
3456 
3457       if (x->is_Region()) {
3458         for (uint i = 1; i < x->req(); i++) {
3459           worklist.push(x->in(i));
3460         }
3461       } else {
3462         worklist.push(x->in(0));
3463         // We are looking for the pattern:
3464         //                            /->ThreadLocal
3465         // If->Bool->CmpI->LoadB->AddP->ConL(marking_offset)
3466         //              \->ConI(0)
3467         // We want to verify that the If and the LoadB have the same control
3468         // See GraphKit::g1_write_barrier_pre()
3469         if (x->is_If()) {
3470           IfNode *iff = x->as_If();
3471           if (iff->in(1)->is_Bool() && iff->in(1)->in(1)->is_Cmp()) {
3472             CmpNode *cmp = iff->in(1)->in(1)->as_Cmp();
3473             if (cmp->Opcode() == Op_CmpI && cmp->in(2)->is_Con() && cmp->in(2)->bottom_type()->is_int()->get_con() == 0
3474                 && cmp->in(1)->is_Load()) {
3475               LoadNode* load = cmp->in(1)->as_Load();
3476               if (load->Opcode() == Op_LoadB && load->in(2)->is_AddP() && load->in(2)->in(2)->Opcode() == Op_ThreadLocal
3477                   && load->in(2)->in(3)->is_Con()
3478                   && load->in(2)->in(3)->bottom_type()->is_intptr_t()->get_con() == marking_offset) {
3479 
3480                 Node* if_ctrl = iff->in(0);
3481                 Node* load_ctrl = load->in(0);
3482 
3483                 if (if_ctrl != load_ctrl) {
3484                   // Skip possible CProj->NeverBranch in infinite loops
3485                   if ((if_ctrl->is_Proj() && if_ctrl->Opcode() == Op_CProj)
3486                       && (if_ctrl->in(0)->is_MultiBranch() && if_ctrl->in(0)->Opcode() == Op_NeverBranch)) {
3487                     if_ctrl = if_ctrl->in(0)->in(0);
3488                   }
3489                 }
3490                 assert(load_ctrl != NULL && if_ctrl == load_ctrl, "controls must match");
3491               }
3492             }
3493           }
3494         }
3495       }
3496     }
3497   }
3498 }
3499 
3500 #endif
3501 
3502 // The Compile object keeps track of failure reasons separately from the ciEnv.
3503 // This is required because there is not quite a 1-1 relation between the
3504 // ciEnv and its compilation task and the Compile object.  Note that one
3505 // ciEnv might use two Compile objects, if C2Compiler::compile_method decides
3506 // to backtrack and retry without subsuming loads.  Other than this backtracking
3507 // behavior, the Compile's failure reason is quietly copied up to the ciEnv
3508 // by the logic in C2Compiler.
3509 void Compile::record_failure(const char* reason) {
3510   if (log() != NULL) {
3511     log()->elem("failure reason='%s' phase='compile'", reason);
3512   }
3513   if (_failure_reason == NULL) {
3514     // Record the first failure reason.
3515     _failure_reason = reason;
3516   }
3517 
3518   EventCompilerFailure event;
3519   if (event.should_commit()) {
3520     event.set_compileID(Compile::compile_id());
3521     event.set_failure(reason);
3522     event.commit();
3523   }
3524 
3525   if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
3526     C->print_method(PHASE_FAILURE);
3527   }
3528   _root = NULL;  // flush the graph, too
3529 }
3530 
3531 Compile::TracePhase::TracePhase(const char* name, elapsedTimer* accumulator, bool dolog)
3532   : TraceTime(NULL, accumulator, false NOT_PRODUCT( || TimeCompiler ), false),
3533     _phase_name(name), _dolog(dolog)
3534 {
3535   if (dolog) {
3536     C = Compile::current();
3537     _log = C->log();
3538   } else {
3539     C = NULL;
3540     _log = NULL;
3541   }
3542   if (_log != NULL) {
3543     _log->begin_head("phase name='%s' nodes='%d' live='%d'", _phase_name, C->unique(), C->live_nodes());
3544     _log->stamp();
3545     _log->end_head();
3546   }
3547 }
3548 
3549 Compile::TracePhase::~TracePhase() {
3550 
3551   C = Compile::current();
3552   if (_dolog) {
3553     _log = C->log();
3554   } else {
3555     _log = NULL;
3556   }
3557 
3558 #ifdef ASSERT
3559   if (PrintIdealNodeCount) {
3560     tty->print_cr("phase name='%s' nodes='%d' live='%d' live_graph_walk='%d'",
3561                   _phase_name, C->unique(), C->live_nodes(), C->count_live_nodes_by_graph_walk());
3562   }
3563 
3564   if (VerifyIdealNodeCount) {
3565     Compile::current()->print_missing_nodes();
3566   }
3567 #endif
3568 
3569   if (_log != NULL) {
3570     _log->done("phase name='%s' nodes='%d' live='%d'", _phase_name, C->unique(), C->live_nodes());
3571   }
3572 }
3573 
3574 //=============================================================================
3575 // Two Constant's are equal when the type and the value are equal.
3576 bool Compile::Constant::operator==(const Constant& other) {
3577   if (type()          != other.type()         )  return false;
3578   if (can_be_reused() != other.can_be_reused())  return false;
3579   // For floating point values we compare the bit pattern.
3580   switch (type()) {
3581   case T_FLOAT:   return (_v._value.i == other._v._value.i);
3582   case T_LONG:
3583   case T_DOUBLE:  return (_v._value.j == other._v._value.j);
3584   case T_OBJECT:
3585   case T_ADDRESS: return (_v._value.l == other._v._value.l);
3586   case T_VOID:    return (_v._value.l == other._v._value.l);  // jump-table entries
3587   case T_METADATA: return (_v._metadata == other._v._metadata);
3588   default: ShouldNotReachHere();
3589   }
3590   return false;
3591 }
3592 
3593 static int type_to_size_in_bytes(BasicType t) {
3594   switch (t) {
3595   case T_LONG:    return sizeof(jlong  );
3596   case T_FLOAT:   return sizeof(jfloat );
3597   case T_DOUBLE:  return sizeof(jdouble);
3598   case T_METADATA: return sizeof(Metadata*);
3599     // We use T_VOID as marker for jump-table entries (labels) which
3600     // need an internal word relocation.
3601   case T_VOID:
3602   case T_ADDRESS:
3603   case T_OBJECT:  return sizeof(jobject);
3604   }
3605 
3606   ShouldNotReachHere();
3607   return -1;
3608 }
3609 
3610 int Compile::ConstantTable::qsort_comparator(Constant* a, Constant* b) {
3611   // sort descending
3612   if (a->freq() > b->freq())  return -1;
3613   if (a->freq() < b->freq())  return  1;
3614   return 0;
3615 }
3616 
3617 void Compile::ConstantTable::calculate_offsets_and_size() {
3618   // First, sort the array by frequencies.
3619   _constants.sort(qsort_comparator);
3620 
3621 #ifdef ASSERT
3622   // Make sure all jump-table entries were sorted to the end of the
3623   // array (they have a negative frequency).
3624   bool found_void = false;
3625   for (int i = 0; i < _constants.length(); i++) {
3626     Constant con = _constants.at(i);
3627     if (con.type() == T_VOID)
3628       found_void = true;  // jump-tables
3629     else
3630       assert(!found_void, "wrong sorting");
3631   }
3632 #endif
3633 
3634   int offset = 0;
3635   for (int i = 0; i < _constants.length(); i++) {
3636     Constant* con = _constants.adr_at(i);
3637 
3638     // Align offset for type.
3639     int typesize = type_to_size_in_bytes(con->type());
3640     offset = align_size_up(offset, typesize);
3641     con->set_offset(offset);   // set constant's offset
3642 
3643     if (con->type() == T_VOID) {
3644       MachConstantNode* n = (MachConstantNode*) con->get_jobject();
3645       offset = offset + typesize * n->outcnt();  // expand jump-table
3646     } else {
3647       offset = offset + typesize;
3648     }
3649   }
3650 
3651   // Align size up to the next section start (which is insts; see
3652   // CodeBuffer::align_at_start).
3653   assert(_size == -1, "already set?");
3654   _size = align_size_up(offset, CodeEntryAlignment);
3655 }
3656 
3657 void Compile::ConstantTable::emit(CodeBuffer& cb) {
3658   MacroAssembler _masm(&cb);
3659   for (int i = 0; i < _constants.length(); i++) {
3660     Constant con = _constants.at(i);
3661     address constant_addr;
3662     switch (con.type()) {
3663     case T_LONG:   constant_addr = _masm.long_constant(  con.get_jlong()  ); break;
3664     case T_FLOAT:  constant_addr = _masm.float_constant( con.get_jfloat() ); break;
3665     case T_DOUBLE: constant_addr = _masm.double_constant(con.get_jdouble()); break;
3666     case T_OBJECT: {
3667       jobject obj = con.get_jobject();
3668       int oop_index = _masm.oop_recorder()->find_index(obj);
3669       constant_addr = _masm.address_constant((address) obj, oop_Relocation::spec(oop_index));
3670       break;
3671     }
3672     case T_ADDRESS: {
3673       address addr = (address) con.get_jobject();
3674       constant_addr = _masm.address_constant(addr);
3675       break;
3676     }
3677     // We use T_VOID as marker for jump-table entries (labels) which
3678     // need an internal word relocation.
3679     case T_VOID: {
3680       MachConstantNode* n = (MachConstantNode*) con.get_jobject();
3681       // Fill the jump-table with a dummy word.  The real value is
3682       // filled in later in fill_jump_table.
3683       address dummy = (address) n;
3684       constant_addr = _masm.address_constant(dummy);
3685       // Expand jump-table
3686       for (uint i = 1; i < n->outcnt(); i++) {
3687         address temp_addr = _masm.address_constant(dummy + i);
3688         assert(temp_addr, "consts section too small");
3689       }
3690       break;
3691     }
3692     case T_METADATA: {
3693       Metadata* obj = con.get_metadata();
3694       int metadata_index = _masm.oop_recorder()->find_index(obj);
3695       constant_addr = _masm.address_constant((address) obj, metadata_Relocation::spec(metadata_index));
3696       break;
3697     }
3698     default: ShouldNotReachHere();
3699     }
3700     assert(constant_addr, "consts section too small");
3701     assert((constant_addr - _masm.code()->consts()->start()) == con.offset(),
3702             err_msg_res("must be: %d == %d", (int) (constant_addr - _masm.code()->consts()->start()), (int)(con.offset())));
3703   }
3704 }
3705 
3706 int Compile::ConstantTable::find_offset(Constant& con) const {
3707   int idx = _constants.find(con);
3708   assert(idx != -1, "constant must be in constant table");
3709   int offset = _constants.at(idx).offset();
3710   assert(offset != -1, "constant table not emitted yet?");
3711   return offset;
3712 }
3713 
3714 void Compile::ConstantTable::add(Constant& con) {
3715   if (con.can_be_reused()) {
3716     int idx = _constants.find(con);
3717     if (idx != -1 && _constants.at(idx).can_be_reused()) {
3718       _constants.adr_at(idx)->inc_freq(con.freq());  // increase the frequency by the current value
3719       return;
3720     }
3721   }
3722   (void) _constants.append(con);
3723 }
3724 
3725 Compile::Constant Compile::ConstantTable::add(MachConstantNode* n, BasicType type, jvalue value) {
3726   Block* b = Compile::current()->cfg()->get_block_for_node(n);
3727   Constant con(type, value, b->_freq);
3728   add(con);
3729   return con;
3730 }
3731 
3732 Compile::Constant Compile::ConstantTable::add(Metadata* metadata) {
3733   Constant con(metadata);
3734   add(con);
3735   return con;
3736 }
3737 
3738 Compile::Constant Compile::ConstantTable::add(MachConstantNode* n, MachOper* oper) {
3739   jvalue value;
3740   BasicType type = oper->type()->basic_type();
3741   switch (type) {
3742   case T_LONG:    value.j = oper->constantL(); break;
3743   case T_FLOAT:   value.f = oper->constantF(); break;
3744   case T_DOUBLE:  value.d = oper->constantD(); break;
3745   case T_OBJECT:
3746   case T_ADDRESS: value.l = (jobject) oper->constant(); break;
3747   case T_METADATA: return add((Metadata*)oper->constant()); break;
3748   default: guarantee(false, err_msg_res("unhandled type: %s", type2name(type)));
3749   }
3750   return add(n, type, value);
3751 }
3752 
3753 Compile::Constant Compile::ConstantTable::add_jump_table(MachConstantNode* n) {
3754   jvalue value;
3755   // We can use the node pointer here to identify the right jump-table
3756   // as this method is called from Compile::Fill_buffer right before
3757   // the MachNodes are emitted and the jump-table is filled (means the
3758   // MachNode pointers do not change anymore).
3759   value.l = (jobject) n;
3760   Constant con(T_VOID, value, next_jump_table_freq(), false);  // Labels of a jump-table cannot be reused.
3761   add(con);
3762   return con;
3763 }
3764 
3765 void Compile::ConstantTable::fill_jump_table(CodeBuffer& cb, MachConstantNode* n, GrowableArray<Label*> labels) const {
3766   // If called from Compile::scratch_emit_size do nothing.
3767   if (Compile::current()->in_scratch_emit_size())  return;
3768 
3769   assert(labels.is_nonempty(), "must be");
3770   assert((uint) labels.length() == n->outcnt(), err_msg_res("must be equal: %d == %d", labels.length(), n->outcnt()));
3771 
3772   // Since MachConstantNode::constant_offset() also contains
3773   // table_base_offset() we need to subtract the table_base_offset()
3774   // to get the plain offset into the constant table.
3775   int offset = n->constant_offset() - table_base_offset();
3776 
3777   MacroAssembler _masm(&cb);
3778   address* jump_table_base = (address*) (_masm.code()->consts()->start() + offset);
3779 
3780   for (uint i = 0; i < n->outcnt(); i++) {
3781     address* constant_addr = &jump_table_base[i];
3782     assert(*constant_addr == (((address) n) + i), err_msg_res("all jump-table entries must contain adjusted node pointer: " INTPTR_FORMAT " == " INTPTR_FORMAT, p2i(*constant_addr), p2i(((address) n) + i)));
3783     *constant_addr = cb.consts()->target(*labels.at(i), (address) constant_addr);
3784     cb.consts()->relocate((address) constant_addr, relocInfo::internal_word_type);
3785   }
3786 }
3787 
3788 void Compile::dump_inlining() {
3789   if (print_inlining() || print_intrinsics()) {
3790     // Print inlining message for candidates that we couldn't inline
3791     // for lack of space or non constant receiver
3792     for (int i = 0; i < _late_inlines.length(); i++) {
3793       CallGenerator* cg = _late_inlines.at(i);
3794       cg->print_inlining_late("live nodes > LiveNodeCountInliningCutoff");
3795     }
3796     Unique_Node_List useful;
3797     useful.push(root());
3798     for (uint next = 0; next < useful.size(); ++next) {
3799       Node* n  = useful.at(next);
3800       if (n->is_Call() && n->as_Call()->generator() != NULL && n->as_Call()->generator()->call_node() == n) {
3801         CallNode* call = n->as_Call();
3802         CallGenerator* cg = call->generator();
3803         cg->print_inlining_late("receiver not constant");
3804       }
3805       uint max = n->len();
3806       for ( uint i = 0; i < max; ++i ) {
3807         Node *m = n->in(i);
3808         if ( m == NULL ) continue;
3809         useful.push(m);
3810       }
3811     }
3812     for (int i = 0; i < _print_inlining_list->length(); i++) {
3813       tty->print("%s", _print_inlining_list->adr_at(i)->ss()->as_string());
3814     }
3815   }
3816 }
3817 
3818 // Dump inlining replay data to the stream.
3819 // Don't change thread state and acquire any locks.
3820 void Compile::dump_inline_data(outputStream* out) {
3821   InlineTree* inl_tree = ilt();
3822   if (inl_tree != NULL) {
3823     out->print(" inline %d", inl_tree->count());
3824     inl_tree->dump_replay_data(out);
3825   }
3826 }
3827 
3828 int Compile::cmp_expensive_nodes(Node* n1, Node* n2) {
3829   if (n1->Opcode() < n2->Opcode())      return -1;
3830   else if (n1->Opcode() > n2->Opcode()) return 1;
3831 
3832   assert(n1->req() == n2->req(), err_msg_res("can't compare %s nodes: n1->req() = %d, n2->req() = %d", NodeClassNames[n1->Opcode()], n1->req(), n2->req()));
3833   for (uint i = 1; i < n1->req(); i++) {
3834     if (n1->in(i) < n2->in(i))      return -1;
3835     else if (n1->in(i) > n2->in(i)) return 1;
3836   }
3837 
3838   return 0;
3839 }
3840 
3841 int Compile::cmp_expensive_nodes(Node** n1p, Node** n2p) {
3842   Node* n1 = *n1p;
3843   Node* n2 = *n2p;
3844 
3845   return cmp_expensive_nodes(n1, n2);
3846 }
3847 
3848 void Compile::sort_expensive_nodes() {
3849   if (!expensive_nodes_sorted()) {
3850     _expensive_nodes->sort(cmp_expensive_nodes);
3851   }
3852 }
3853 
3854 bool Compile::expensive_nodes_sorted() const {
3855   for (int i = 1; i < _expensive_nodes->length(); i++) {
3856     if (cmp_expensive_nodes(_expensive_nodes->adr_at(i), _expensive_nodes->adr_at(i-1)) < 0) {
3857       return false;
3858     }
3859   }
3860   return true;
3861 }
3862 
3863 bool Compile::should_optimize_expensive_nodes(PhaseIterGVN &igvn) {
3864   if (_expensive_nodes->length() == 0) {
3865     return false;
3866   }
3867 
3868   assert(OptimizeExpensiveOps, "optimization off?");
3869 
3870   // Take this opportunity to remove dead nodes from the list
3871   int j = 0;
3872   for (int i = 0; i < _expensive_nodes->length(); i++) {
3873     Node* n = _expensive_nodes->at(i);
3874     if (!n->is_unreachable(igvn)) {
3875       assert(n->is_expensive(), "should be expensive");
3876       _expensive_nodes->at_put(j, n);
3877       j++;
3878     }
3879   }
3880   _expensive_nodes->trunc_to(j);
3881 
3882   // Then sort the list so that similar nodes are next to each other
3883   // and check for at least two nodes of identical kind with same data
3884   // inputs.
3885   sort_expensive_nodes();
3886 
3887   for (int i = 0; i < _expensive_nodes->length()-1; i++) {
3888     if (cmp_expensive_nodes(_expensive_nodes->adr_at(i), _expensive_nodes->adr_at(i+1)) == 0) {
3889       return true;
3890     }
3891   }
3892 
3893   return false;
3894 }
3895 
3896 void Compile::cleanup_expensive_nodes(PhaseIterGVN &igvn) {
3897   if (_expensive_nodes->length() == 0) {
3898     return;
3899   }
3900 
3901   assert(OptimizeExpensiveOps, "optimization off?");
3902 
3903   // Sort to bring similar nodes next to each other and clear the
3904   // control input of nodes for which there's only a single copy.
3905   sort_expensive_nodes();
3906 
3907   int j = 0;
3908   int identical = 0;
3909   int i = 0;
3910   for (; i < _expensive_nodes->length()-1; i++) {
3911     assert(j <= i, "can't write beyond current index");
3912     if (_expensive_nodes->at(i)->Opcode() == _expensive_nodes->at(i+1)->Opcode()) {
3913       identical++;
3914       _expensive_nodes->at_put(j++, _expensive_nodes->at(i));
3915       continue;
3916     }
3917     if (identical > 0) {
3918       _expensive_nodes->at_put(j++, _expensive_nodes->at(i));
3919       identical = 0;
3920     } else {
3921       Node* n = _expensive_nodes->at(i);
3922       igvn.hash_delete(n);
3923       n->set_req(0, NULL);
3924       igvn.hash_insert(n);
3925     }
3926   }
3927   if (identical > 0) {
3928     _expensive_nodes->at_put(j++, _expensive_nodes->at(i));
3929   } else if (_expensive_nodes->length() >= 1) {
3930     Node* n = _expensive_nodes->at(i);
3931     igvn.hash_delete(n);
3932     n->set_req(0, NULL);
3933     igvn.hash_insert(n);
3934   }
3935   _expensive_nodes->trunc_to(j);
3936 }
3937 
3938 void Compile::add_expensive_node(Node * n) {
3939   assert(!_expensive_nodes->contains(n), "duplicate entry in expensive list");
3940   assert(n->is_expensive(), "expensive nodes with non-null control here only");
3941   assert(!n->is_CFG() && !n->is_Mem(), "no cfg or memory nodes here");
3942   if (OptimizeExpensiveOps) {
3943     _expensive_nodes->append(n);
3944   } else {
3945     // Clear control input and let IGVN optimize expensive nodes if
3946     // OptimizeExpensiveOps is off.
3947     n->set_req(0, NULL);
3948   }
3949 }
3950 
3951 /**
3952  * Remove the speculative part of types and clean up the graph
3953  */
3954 void Compile::remove_speculative_types(PhaseIterGVN &igvn) {
3955   if (UseTypeSpeculation) {
3956     Unique_Node_List worklist;
3957     worklist.push(root());
3958     int modified = 0;
3959     // Go over all type nodes that carry a speculative type, drop the
3960     // speculative part of the type and enqueue the node for an igvn
3961     // which may optimize it out.
3962     for (uint next = 0; next < worklist.size(); ++next) {
3963       Node *n  = worklist.at(next);
3964       if (n->is_Type()) {
3965         TypeNode* tn = n->as_Type();
3966         const Type* t = tn->type();
3967         const Type* t_no_spec = t->remove_speculative();
3968         if (t_no_spec != t) {
3969           bool in_hash = igvn.hash_delete(n);
3970           assert(in_hash, "node should be in igvn hash table");
3971           tn->set_type(t_no_spec);
3972           igvn.hash_insert(n);
3973           igvn._worklist.push(n); // give it a chance to go away
3974           modified++;
3975         }
3976       }
3977       uint max = n->len();
3978       for( uint i = 0; i < max; ++i ) {
3979         Node *m = n->in(i);
3980         if (not_a_node(m))  continue;
3981         worklist.push(m);
3982       }
3983     }
3984     // Drop the speculative part of all types in the igvn's type table
3985     igvn.remove_speculative_types();
3986     if (modified > 0) {
3987       igvn.optimize();
3988     }
3989 #ifdef ASSERT
3990     // Verify that after the IGVN is over no speculative type has resurfaced
3991     worklist.clear();
3992     worklist.push(root());
3993     for (uint next = 0; next < worklist.size(); ++next) {
3994       Node *n  = worklist.at(next);
3995       const Type* t = igvn.type_or_null(n);
3996       assert((t == NULL) || (t == t->remove_speculative()), "no more speculative types");
3997       if (n->is_Type()) {
3998         t = n->as_Type()->type();
3999         assert(t == t->remove_speculative(), "no more speculative types");
4000       }
4001       uint max = n->len();
4002       for( uint i = 0; i < max; ++i ) {
4003         Node *m = n->in(i);
4004         if (not_a_node(m))  continue;
4005         worklist.push(m);
4006       }
4007     }
4008     igvn.check_no_speculative_types();
4009 #endif
4010   }
4011 }
4012 
4013 // Auxiliary method to support randomized stressing/fuzzing.
4014 //
4015 // This method can be called the arbitrary number of times, with current count
4016 // as the argument. The logic allows selecting a single candidate from the
4017 // running list of candidates as follows:
4018 //    int count = 0;
4019 //    Cand* selected = null;
4020 //    while(cand = cand->next()) {
4021 //      if (randomized_select(++count)) {
4022 //        selected = cand;
4023 //      }
4024 //    }
4025 //
4026 // Including count equalizes the chances any candidate is "selected".
4027 // This is useful when we don't have the complete list of candidates to choose
4028 // from uniformly. In this case, we need to adjust the randomicity of the
4029 // selection, or else we will end up biasing the selection towards the latter
4030 // candidates.
4031 //
4032 // Quick back-envelope calculation shows that for the list of n candidates
4033 // the equal probability for the candidate to persist as "best" can be
4034 // achieved by replacing it with "next" k-th candidate with the probability
4035 // of 1/k. It can be easily shown that by the end of the run, the
4036 // probability for any candidate is converged to 1/n, thus giving the
4037 // uniform distribution among all the candidates.
4038 //
4039 // We don't care about the domain size as long as (RANDOMIZED_DOMAIN / count) is large.
4040 #define RANDOMIZED_DOMAIN_POW 29
4041 #define RANDOMIZED_DOMAIN (1 << RANDOMIZED_DOMAIN_POW)
4042 #define RANDOMIZED_DOMAIN_MASK ((1 << (RANDOMIZED_DOMAIN_POW + 1)) - 1)
4043 bool Compile::randomized_select(int count) {
4044   assert(count > 0, "only positive");
4045   return (os::random() & RANDOMIZED_DOMAIN_MASK) < (RANDOMIZED_DOMAIN / count);
4046 }