1 /*
   2  * Copyright (c) 2009, 2018, 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 "compiler/compileLog.hpp"
  27 #include "opto/addnode.hpp"
  28 #include "opto/callGenerator.hpp"
  29 #include "opto/callnode.hpp"
  30 #include "opto/divnode.hpp"
  31 #include "opto/graphKit.hpp"
  32 #include "opto/idealKit.hpp"
  33 #include "opto/rootnode.hpp"
  34 #include "opto/runtime.hpp"
  35 #include "opto/stringopts.hpp"
  36 #include "opto/subnode.hpp"
  37 #include "runtime/sharedRuntime.hpp"
  38 
  39 #define __ kit.
  40 
  41 class StringConcat : public ResourceObj {
  42  private:
  43   PhaseStringOpts*    _stringopts;
  44   Node*               _string_alloc;
  45   AllocateNode*       _begin;          // The allocation the begins the pattern
  46   CallStaticJavaNode* _end;            // The final call of the pattern.  Will either be
  47                                        // SB.toString or or String.<init>(SB.toString)
  48   bool                _multiple;       // indicates this is a fusion of two or more
  49                                        // separate StringBuilders
  50 
  51   Node*               _arguments;      // The list of arguments to be concatenated
  52   GrowableArray<int>  _mode;           // into a String along with a mode flag
  53                                        // indicating how to treat the value.
  54   Node_List           _constructors;   // List of constructors (many in case of stacked concat)
  55   Node_List           _control;        // List of control nodes that will be deleted
  56   Node_List           _uncommon_traps; // Uncommon traps that needs to be rewritten
  57                                        // to restart at the initial JVMState.
  58 
  59  public:
  60   // Mode for converting arguments to Strings
  61   enum {
  62     StringMode,
  63     IntMode,
  64     CharMode,
  65     StringNullCheckMode
  66   };
  67 
  68   StringConcat(PhaseStringOpts* stringopts, CallStaticJavaNode* end):
  69     _stringopts(stringopts),
  70     _string_alloc(NULL),
  71     _begin(NULL),
  72     _end(end),
  73     _multiple(false) {
  74     _arguments = new Node(1);
  75     _arguments->del_req(0);
  76   }
  77 
  78   bool validate_mem_flow();
  79   bool validate_control_flow();
  80 
  81   void merge_add() {
  82 #if 0
  83     // XXX This is place holder code for reusing an existing String
  84     // allocation but the logic for checking the state safety is
  85     // probably inadequate at the moment.
  86     CallProjections endprojs;
  87     sc->end()->extract_projections(&endprojs, false);
  88     if (endprojs.resproj != NULL) {
  89       for (SimpleDUIterator i(endprojs.resproj); i.has_next(); i.next()) {
  90         CallStaticJavaNode *use = i.get()->isa_CallStaticJava();
  91         if (use != NULL && use->method() != NULL &&
  92             use->method()->intrinsic_id() == vmIntrinsics::_String_String &&
  93             use->in(TypeFunc::Parms + 1) == endprojs.resproj) {
  94           // Found useless new String(sb.toString()) so reuse the newly allocated String
  95           // when creating the result instead of allocating a new one.
  96           sc->set_string_alloc(use->in(TypeFunc::Parms));
  97           sc->set_end(use);
  98         }
  99       }
 100     }
 101 #endif
 102   }
 103 
 104   StringConcat* merge(StringConcat* other, Node* arg);
 105 
 106   void set_allocation(AllocateNode* alloc) {
 107     _begin = alloc;
 108   }
 109 
 110   void append(Node* value, int mode) {
 111     _arguments->add_req(value);
 112     _mode.append(mode);
 113   }
 114   void push(Node* value, int mode) {
 115     _arguments->ins_req(0, value);
 116     _mode.insert_before(0, mode);
 117   }
 118 
 119   void push_string(Node* value) {
 120     push(value, StringMode);
 121   }
 122   void push_string_null_check(Node* value) {
 123     push(value, StringNullCheckMode);
 124   }
 125   void push_int(Node* value) {
 126     push(value, IntMode);
 127   }
 128   void push_char(Node* value) {
 129     push(value, CharMode);
 130   }
 131 
 132   static bool is_SB_toString(Node* call) {
 133     if (call->is_CallStaticJava()) {
 134       CallStaticJavaNode* csj = call->as_CallStaticJava();
 135       ciMethod* m = csj->method();
 136       if (m != NULL &&
 137           (m->intrinsic_id() == vmIntrinsics::_StringBuilder_toString ||
 138            m->intrinsic_id() == vmIntrinsics::_StringBuffer_toString)) {
 139         return true;
 140       }
 141     }
 142     return false;
 143   }
 144 
 145   static Node* skip_string_null_check(Node* value) {
 146     // Look for a diamond shaped Null check of toString() result
 147     // (could be code from String.valueOf()):
 148     // (Proj == NULL) ? "null":"CastPP(Proj)#NotNULL
 149     if (value->is_Phi()) {
 150       int true_path = value->as_Phi()->is_diamond_phi();
 151       if (true_path != 0) {
 152         // phi->region->if_proj->ifnode->bool
 153         BoolNode* b = value->in(0)->in(1)->in(0)->in(1)->as_Bool();
 154         Node* cmp = b->in(1);
 155         Node* v1 = cmp->in(1);
 156         Node* v2 = cmp->in(2);
 157         // Null check of the return of toString which can simply be skipped.
 158         if (b->_test._test == BoolTest::ne &&
 159             v2->bottom_type() == TypePtr::NULL_PTR &&
 160             value->in(true_path)->Opcode() == Op_CastPP &&
 161             value->in(true_path)->in(1) == v1 &&
 162             v1->is_Proj() && is_SB_toString(v1->in(0))) {
 163           return v1;
 164         }
 165       }
 166     }
 167     return value;
 168   }
 169 
 170   Node* argument(int i) {
 171     return _arguments->in(i);
 172   }
 173   Node* argument_uncast(int i) {
 174     Node* arg = argument(i);
 175     int amode = mode(i);
 176     if (amode == StringConcat::StringMode ||
 177         amode == StringConcat::StringNullCheckMode) {
 178       arg = skip_string_null_check(arg);
 179     }
 180     return arg;
 181   }
 182   void set_argument(int i, Node* value) {
 183     _arguments->set_req(i, value);
 184   }
 185   int num_arguments() {
 186     return _mode.length();
 187   }
 188   int mode(int i) {
 189     return _mode.at(i);
 190   }
 191   void add_control(Node* ctrl) {
 192     assert(!_control.contains(ctrl), "only push once");
 193     _control.push(ctrl);
 194   }
 195   void add_constructor(Node* init) {
 196     assert(!_constructors.contains(init), "only push once");
 197     _constructors.push(init);
 198   }
 199   CallStaticJavaNode* end() { return _end; }
 200   AllocateNode* begin() { return _begin; }
 201   Node* string_alloc() { return _string_alloc; }
 202 
 203   void eliminate_unneeded_control();
 204   void eliminate_initialize(InitializeNode* init);
 205   void eliminate_call(CallNode* call);
 206 
 207   void maybe_log_transform() {
 208     CompileLog* log = _stringopts->C->log();
 209     if (log != NULL) {
 210       log->head("replace_string_concat arguments='%d' string_alloc='%d' multiple='%d'",
 211                 num_arguments(),
 212                 _string_alloc != NULL,
 213                 _multiple);
 214       JVMState* p = _begin->jvms();
 215       while (p != NULL) {
 216         log->elem("jvms bci='%d' method='%d'", p->bci(), log->identify(p->method()));
 217         p = p->caller();
 218       }
 219       log->tail("replace_string_concat");
 220     }
 221   }
 222 
 223   void convert_uncommon_traps(GraphKit& kit, const JVMState* jvms) {
 224     for (uint u = 0; u < _uncommon_traps.size(); u++) {
 225       Node* uct = _uncommon_traps.at(u);
 226 
 227       // Build a new call using the jvms state of the allocate
 228       address call_addr = SharedRuntime::uncommon_trap_blob()->entry_point();
 229       const TypeFunc* call_type = OptoRuntime::uncommon_trap_Type();
 230       const TypePtr* no_memory_effects = NULL;
 231       Compile* C = _stringopts->C;
 232       CallStaticJavaNode* call = new CallStaticJavaNode(call_type, call_addr, "uncommon_trap",
 233                                                         jvms->bci(), no_memory_effects);
 234       for (int e = 0; e < TypeFunc::Parms; e++) {
 235         call->init_req(e, uct->in(e));
 236       }
 237       // Set the trap request to record intrinsic failure if this trap
 238       // is taken too many times.  Ideally we would handle then traps by
 239       // doing the original bookkeeping in the MDO so that if it caused
 240       // the code to be thrown out we could still recompile and use the
 241       // optimization.  Failing the uncommon traps doesn't really mean
 242       // that the optimization is a bad idea but there's no other way to
 243       // do the MDO updates currently.
 244       int trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_intrinsic,
 245                                                            Deoptimization::Action_make_not_entrant);
 246       call->init_req(TypeFunc::Parms, __ intcon(trap_request));
 247       kit.add_safepoint_edges(call);
 248 
 249       _stringopts->gvn()->transform(call);
 250       C->gvn_replace_by(uct, call);
 251       uct->disconnect_inputs(NULL, C);
 252     }
 253   }
 254 
 255   void cleanup() {
 256     // disconnect the hook node
 257     _arguments->disconnect_inputs(NULL, _stringopts->C);
 258   }
 259 };
 260 
 261 
 262 void StringConcat::eliminate_unneeded_control() {
 263   for (uint i = 0; i < _control.size(); i++) {
 264     Node* n = _control.at(i);
 265     if (n->is_Allocate()) {
 266       eliminate_initialize(n->as_Allocate()->initialization());
 267     }
 268     if (n->is_Call()) {
 269       if (n != _end) {
 270         eliminate_call(n->as_Call());
 271       }
 272     } else if (n->is_IfTrue()) {
 273       Compile* C = _stringopts->C;
 274       C->gvn_replace_by(n, n->in(0)->in(0));
 275       // get rid of the other projection
 276       C->gvn_replace_by(n->in(0)->as_If()->proj_out(false), C->top());
 277     }
 278   }
 279 }
 280 
 281 
 282 StringConcat* StringConcat::merge(StringConcat* other, Node* arg) {
 283   StringConcat* result = new StringConcat(_stringopts, _end);
 284   for (uint x = 0; x < _control.size(); x++) {
 285     Node* n = _control.at(x);
 286     if (n->is_Call()) {
 287       result->_control.push(n);
 288     }
 289   }
 290   for (uint x = 0; x < other->_control.size(); x++) {
 291     Node* n = other->_control.at(x);
 292     if (n->is_Call()) {
 293       result->_control.push(n);
 294     }
 295   }
 296   assert(result->_control.contains(other->_end), "what?");
 297   assert(result->_control.contains(_begin), "what?");
 298   for (int x = 0; x < num_arguments(); x++) {
 299     Node* argx = argument_uncast(x);
 300     if (argx == arg) {
 301       // replace the toString result with the all the arguments that
 302       // made up the other StringConcat
 303       for (int y = 0; y < other->num_arguments(); y++) {
 304         result->append(other->argument(y), other->mode(y));
 305       }
 306     } else {
 307       result->append(argx, mode(x));
 308     }
 309   }
 310   result->set_allocation(other->_begin);
 311   for (uint i = 0; i < _constructors.size(); i++) {
 312     result->add_constructor(_constructors.at(i));
 313   }
 314   for (uint i = 0; i < other->_constructors.size(); i++) {
 315     result->add_constructor(other->_constructors.at(i));
 316   }
 317   result->_multiple = true;
 318   return result;
 319 }
 320 
 321 
 322 void StringConcat::eliminate_call(CallNode* call) {
 323   Compile* C = _stringopts->C;
 324   CallProjections* projs = call->extract_projections(false);
 325   if (projs->fallthrough_catchproj != NULL) {
 326     C->gvn_replace_by(projs->fallthrough_catchproj, call->in(TypeFunc::Control));
 327   }
 328   if (projs->fallthrough_memproj != NULL) {
 329     C->gvn_replace_by(projs->fallthrough_memproj, call->in(TypeFunc::Memory));
 330   }
 331   if (projs->catchall_memproj != NULL) {
 332     C->gvn_replace_by(projs->catchall_memproj, C->top());
 333   }
 334   if (projs->fallthrough_ioproj != NULL) {
 335     C->gvn_replace_by(projs->fallthrough_ioproj, call->in(TypeFunc::I_O));
 336   }
 337   if (projs->catchall_ioproj != NULL) {
 338     C->gvn_replace_by(projs->catchall_ioproj, C->top());
 339   }
 340   if (projs->catchall_catchproj != NULL) {
 341     // EA can't cope with the partially collapsed graph this
 342     // creates so put it on the worklist to be collapsed later.
 343     for (SimpleDUIterator i(projs->catchall_catchproj); i.has_next(); i.next()) {
 344       Node *use = i.get();
 345       int opc = use->Opcode();
 346       if (opc == Op_CreateEx || opc == Op_Region) {
 347         _stringopts->record_dead_node(use);
 348       }
 349     }
 350     C->gvn_replace_by(projs->catchall_catchproj, C->top());
 351   }
 352   if (projs->resproj[0] != NULL) {
 353     assert(projs->nb_resproj == 1, "unexpected number of results");
 354     C->gvn_replace_by(projs->resproj[0], C->top());
 355   }
 356   C->gvn_replace_by(call, C->top());
 357 }
 358 
 359 void StringConcat::eliminate_initialize(InitializeNode* init) {
 360   Compile* C = _stringopts->C;
 361 
 362   // Eliminate Initialize node.
 363   assert(init->outcnt() <= 2, "only a control and memory projection expected");
 364   assert(init->req() <= InitializeNode::RawStores, "no pending inits");
 365   Node *ctrl_proj = init->proj_out_or_null(TypeFunc::Control);
 366   if (ctrl_proj != NULL) {
 367     C->gvn_replace_by(ctrl_proj, init->in(TypeFunc::Control));
 368   }
 369   Node *mem_proj = init->proj_out_or_null(TypeFunc::Memory);
 370   if (mem_proj != NULL) {
 371     Node *mem = init->in(TypeFunc::Memory);
 372     C->gvn_replace_by(mem_proj, mem);
 373   }
 374   C->gvn_replace_by(init, C->top());
 375   init->disconnect_inputs(NULL, C);
 376 }
 377 
 378 Node_List PhaseStringOpts::collect_toString_calls() {
 379   Node_List string_calls;
 380   Node_List worklist;
 381 
 382   _visited.Clear();
 383 
 384   // Prime the worklist
 385   for (uint i = 1; i < C->root()->len(); i++) {
 386     Node* n = C->root()->in(i);
 387     if (n != NULL && !_visited.test_set(n->_idx)) {
 388       worklist.push(n);
 389     }
 390   }
 391 
 392   while (worklist.size() > 0) {
 393     Node* ctrl = worklist.pop();
 394     if (StringConcat::is_SB_toString(ctrl)) {
 395       CallStaticJavaNode* csj = ctrl->as_CallStaticJava();
 396       string_calls.push(csj);
 397     }
 398     if (ctrl->in(0) != NULL && !_visited.test_set(ctrl->in(0)->_idx)) {
 399       worklist.push(ctrl->in(0));
 400     }
 401     if (ctrl->is_Region()) {
 402       for (uint i = 1; i < ctrl->len(); i++) {
 403         if (ctrl->in(i) != NULL && !_visited.test_set(ctrl->in(i)->_idx)) {
 404           worklist.push(ctrl->in(i));
 405         }
 406       }
 407     }
 408   }
 409   return string_calls;
 410 }
 411 
 412 
 413 StringConcat* PhaseStringOpts::build_candidate(CallStaticJavaNode* call) {
 414   ciMethod* m = call->method();
 415   ciSymbol* string_sig;
 416   ciSymbol* int_sig;
 417   ciSymbol* char_sig;
 418   if (m->holder() == C->env()->StringBuilder_klass()) {
 419     string_sig = ciSymbol::String_StringBuilder_signature();
 420     int_sig = ciSymbol::int_StringBuilder_signature();
 421     char_sig = ciSymbol::char_StringBuilder_signature();
 422   } else if (m->holder() == C->env()->StringBuffer_klass()) {
 423     string_sig = ciSymbol::String_StringBuffer_signature();
 424     int_sig = ciSymbol::int_StringBuffer_signature();
 425     char_sig = ciSymbol::char_StringBuffer_signature();
 426   } else {
 427     return NULL;
 428   }
 429 #ifndef PRODUCT
 430   if (PrintOptimizeStringConcat) {
 431     tty->print("considering toString call in ");
 432     call->jvms()->dump_spec(tty); tty->cr();
 433   }
 434 #endif
 435 
 436   StringConcat* sc = new StringConcat(this, call);
 437 
 438   AllocateNode* alloc = NULL;
 439   InitializeNode* init = NULL;
 440 
 441   // possible opportunity for StringBuilder fusion
 442   CallStaticJavaNode* cnode = call;
 443   while (cnode) {
 444     Node* recv = cnode->in(TypeFunc::Parms)->uncast();
 445     if (recv->is_Proj()) {
 446       recv = recv->in(0);
 447     }
 448     cnode = recv->isa_CallStaticJava();
 449     if (cnode == NULL) {
 450       alloc = recv->isa_Allocate();
 451       if (alloc == NULL) {
 452         break;
 453       }
 454       // Find the constructor call
 455       Node* result = alloc->result_cast();
 456       if (result == NULL || !result->is_CheckCastPP() || alloc->in(TypeFunc::Memory)->is_top()) {
 457         // strange looking allocation
 458 #ifndef PRODUCT
 459         if (PrintOptimizeStringConcat) {
 460           tty->print("giving up because allocation looks strange ");
 461           alloc->jvms()->dump_spec(tty); tty->cr();
 462         }
 463 #endif
 464         break;
 465       }
 466       Node* constructor = NULL;
 467       for (SimpleDUIterator i(result); i.has_next(); i.next()) {
 468         CallStaticJavaNode *use = i.get()->isa_CallStaticJava();
 469         if (use != NULL &&
 470             use->method() != NULL &&
 471             !use->method()->is_static() &&
 472             use->method()->name() == ciSymbol::object_initializer_name() &&
 473             use->method()->holder() == m->holder()) {
 474           // Matched the constructor.
 475           ciSymbol* sig = use->method()->signature()->as_symbol();
 476           if (sig == ciSymbol::void_method_signature() ||
 477               sig == ciSymbol::int_void_signature() ||
 478               sig == ciSymbol::string_void_signature()) {
 479             if (sig == ciSymbol::string_void_signature()) {
 480               // StringBuilder(String) so pick this up as the first argument
 481               assert(use->in(TypeFunc::Parms + 1) != NULL, "what?");
 482               const Type* type = _gvn->type(use->in(TypeFunc::Parms + 1));
 483               if (type == TypePtr::NULL_PTR) {
 484                 // StringBuilder(null) throws exception.
 485 #ifndef PRODUCT
 486                 if (PrintOptimizeStringConcat) {
 487                   tty->print("giving up because StringBuilder(null) throws exception");
 488                   alloc->jvms()->dump_spec(tty); tty->cr();
 489                 }
 490 #endif
 491                 return NULL;
 492               }
 493               // StringBuilder(str) argument needs null check.
 494               sc->push_string_null_check(use->in(TypeFunc::Parms + 1));
 495             }
 496             // The int variant takes an initial size for the backing
 497             // array so just treat it like the void version.
 498             constructor = use;
 499           } else {
 500 #ifndef PRODUCT
 501             if (PrintOptimizeStringConcat) {
 502               tty->print("unexpected constructor signature: %s", sig->as_utf8());
 503             }
 504 #endif
 505           }
 506           break;
 507         }
 508       }
 509       if (constructor == NULL) {
 510         // couldn't find constructor
 511 #ifndef PRODUCT
 512         if (PrintOptimizeStringConcat) {
 513           tty->print("giving up because couldn't find constructor ");
 514           alloc->jvms()->dump_spec(tty); tty->cr();
 515         }
 516 #endif
 517         break;
 518       }
 519 
 520       // Walked all the way back and found the constructor call so see
 521       // if this call converted into a direct string concatenation.
 522       sc->add_control(call);
 523       sc->add_control(constructor);
 524       sc->add_control(alloc);
 525       sc->set_allocation(alloc);
 526       sc->add_constructor(constructor);
 527       if (sc->validate_control_flow() && sc->validate_mem_flow()) {
 528         return sc;
 529       } else {
 530         return NULL;
 531       }
 532     } else if (cnode->method() == NULL) {
 533       break;
 534     } else if (!cnode->method()->is_static() &&
 535                cnode->method()->holder() == m->holder() &&
 536                cnode->method()->name() == ciSymbol::append_name() &&
 537                (cnode->method()->signature()->as_symbol() == string_sig ||
 538                 cnode->method()->signature()->as_symbol() == char_sig ||
 539                 cnode->method()->signature()->as_symbol() == int_sig)) {
 540       sc->add_control(cnode);
 541       Node* arg = cnode->in(TypeFunc::Parms + 1);
 542       if (cnode->method()->signature()->as_symbol() == int_sig) {
 543         sc->push_int(arg);
 544       } else if (cnode->method()->signature()->as_symbol() == char_sig) {
 545         sc->push_char(arg);
 546       } else {
 547         if (arg->is_Proj() && arg->in(0)->is_CallStaticJava()) {
 548           CallStaticJavaNode* csj = arg->in(0)->as_CallStaticJava();
 549           if (csj->method() != NULL &&
 550               csj->method()->intrinsic_id() == vmIntrinsics::_Integer_toString &&
 551               arg->outcnt() == 1) {
 552             // _control is the list of StringBuilder calls nodes which
 553             // will be replaced by new String code after this optimization.
 554             // Integer::toString() call is not part of StringBuilder calls
 555             // chain. It could be eliminated only if its result is used
 556             // only by this SB calls chain.
 557             // Another limitation: it should be used only once because
 558             // it is unknown that it is used only by this SB calls chain
 559             // until all related SB calls nodes are collected.
 560             assert(arg->unique_out() == cnode, "sanity");
 561             sc->add_control(csj);
 562             sc->push_int(csj->in(TypeFunc::Parms));
 563             continue;
 564           }
 565         }
 566         sc->push_string(arg);
 567       }
 568       continue;
 569     } else {
 570       // some unhandled signature
 571 #ifndef PRODUCT
 572       if (PrintOptimizeStringConcat) {
 573         tty->print("giving up because encountered unexpected signature ");
 574         cnode->tf()->dump(); tty->cr();
 575         cnode->in(TypeFunc::Parms + 1)->dump();
 576       }
 577 #endif
 578       break;
 579     }
 580   }
 581   return NULL;
 582 }
 583 
 584 
 585 PhaseStringOpts::PhaseStringOpts(PhaseGVN* gvn, Unique_Node_List*):
 586   Phase(StringOpts),
 587   _gvn(gvn),
 588   _visited(Thread::current()->resource_area()) {
 589 
 590   assert(OptimizeStringConcat, "shouldn't be here");
 591 
 592   size_table_field = C->env()->Integer_klass()->get_field_by_name(ciSymbol::make("sizeTable"),
 593                                                                   ciSymbol::make("[I"), true);
 594   if (size_table_field == NULL) {
 595     // Something wrong so give up.
 596     assert(false, "why can't we find Integer.sizeTable?");
 597     return;
 598   }
 599 
 600   // Collect the types needed to talk about the various slices of memory
 601   byte_adr_idx = C->get_alias_index(TypeAryPtr::BYTES);
 602 
 603   // For each locally allocated StringBuffer see if the usages can be
 604   // collapsed into a single String construction.
 605 
 606   // Run through the list of allocation looking for SB.toString to see
 607   // if it's possible to fuse the usage of the SB into a single String
 608   // construction.
 609   GrowableArray<StringConcat*> concats;
 610   Node_List toStrings = collect_toString_calls();
 611   while (toStrings.size() > 0) {
 612     StringConcat* sc = build_candidate(toStrings.pop()->as_CallStaticJava());
 613     if (sc != NULL) {
 614       concats.push(sc);
 615     }
 616   }
 617 
 618   // try to coalesce separate concats
 619  restart:
 620   for (int c = 0; c < concats.length(); c++) {
 621     StringConcat* sc = concats.at(c);
 622     for (int i = 0; i < sc->num_arguments(); i++) {
 623       Node* arg = sc->argument_uncast(i);
 624       if (arg->is_Proj() && StringConcat::is_SB_toString(arg->in(0))) {
 625         CallStaticJavaNode* csj = arg->in(0)->as_CallStaticJava();
 626         for (int o = 0; o < concats.length(); o++) {
 627           if (c == o) continue;
 628           StringConcat* other = concats.at(o);
 629           if (other->end() == csj) {
 630 #ifndef PRODUCT
 631             if (PrintOptimizeStringConcat) {
 632               tty->print_cr("considering stacked concats");
 633             }
 634 #endif
 635 
 636             StringConcat* merged = sc->merge(other, arg);
 637             if (merged->validate_control_flow() && merged->validate_mem_flow()) {
 638 #ifndef PRODUCT
 639               if (PrintOptimizeStringConcat) {
 640                 tty->print_cr("stacking would succeed");
 641               }
 642 #endif
 643               if (c < o) {
 644                 concats.remove_at(o);
 645                 concats.at_put(c, merged);
 646               } else {
 647                 concats.remove_at(c);
 648                 concats.at_put(o, merged);
 649               }
 650               goto restart;
 651             } else {
 652 #ifndef PRODUCT
 653               if (PrintOptimizeStringConcat) {
 654                 tty->print_cr("stacking would fail");
 655               }
 656 #endif
 657             }
 658           }
 659         }
 660       }
 661     }
 662   }
 663 
 664 
 665   for (int c = 0; c < concats.length(); c++) {
 666     StringConcat* sc = concats.at(c);
 667     replace_string_concat(sc);
 668   }
 669 
 670   remove_dead_nodes();
 671 }
 672 
 673 void PhaseStringOpts::record_dead_node(Node* dead) {
 674   dead_worklist.push(dead);
 675 }
 676 
 677 void PhaseStringOpts::remove_dead_nodes() {
 678   // Delete any dead nodes to make things clean enough that escape
 679   // analysis doesn't get unhappy.
 680   while (dead_worklist.size() > 0) {
 681     Node* use = dead_worklist.pop();
 682     int opc = use->Opcode();
 683     switch (opc) {
 684       case Op_Region: {
 685         uint i = 1;
 686         for (i = 1; i < use->req(); i++) {
 687           if (use->in(i) != C->top()) {
 688             break;
 689           }
 690         }
 691         if (i >= use->req()) {
 692           for (SimpleDUIterator i(use); i.has_next(); i.next()) {
 693             Node* m = i.get();
 694             if (m->is_Phi()) {
 695               dead_worklist.push(m);
 696             }
 697           }
 698           C->gvn_replace_by(use, C->top());
 699         }
 700         break;
 701       }
 702       case Op_AddP:
 703       case Op_CreateEx: {
 704         // Recurisvely clean up references to CreateEx so EA doesn't
 705         // get unhappy about the partially collapsed graph.
 706         for (SimpleDUIterator i(use); i.has_next(); i.next()) {
 707           Node* m = i.get();
 708           if (m->is_AddP()) {
 709             dead_worklist.push(m);
 710           }
 711         }
 712         C->gvn_replace_by(use, C->top());
 713         break;
 714       }
 715       case Op_Phi:
 716         if (use->in(0) == C->top()) {
 717           C->gvn_replace_by(use, C->top());
 718         }
 719         break;
 720     }
 721   }
 722 }
 723 
 724 
 725 bool StringConcat::validate_mem_flow() {
 726   Compile* C = _stringopts->C;
 727 
 728   for (uint i = 0; i < _control.size(); i++) {
 729 #ifndef PRODUCT
 730     Node_List path;
 731 #endif
 732     Node* curr = _control.at(i);
 733     if (curr->is_Call() && curr != _begin) { // For all calls except the first allocation
 734       // Now here's the main invariant in our case:
 735       // For memory between the constructor, and appends, and toString we should only see bottom memory,
 736       // produced by the previous call we know about.
 737       if (!_constructors.contains(curr)) {
 738         NOT_PRODUCT(path.push(curr);)
 739         Node* mem = curr->in(TypeFunc::Memory);
 740         assert(mem != NULL, "calls should have memory edge");
 741         assert(!mem->is_Phi(), "should be handled by control flow validation");
 742         NOT_PRODUCT(path.push(mem);)
 743         while (mem->is_MergeMem()) {
 744           for (uint i = 1; i < mem->req(); i++) {
 745             if (i != Compile::AliasIdxBot && mem->in(i) != C->top()) {
 746 #ifndef PRODUCT
 747               if (PrintOptimizeStringConcat) {
 748                 tty->print("fusion has incorrect memory flow (side effects) for ");
 749                 _begin->jvms()->dump_spec(tty); tty->cr();
 750                 path.dump();
 751               }
 752 #endif
 753               return false;
 754             }
 755           }
 756           // skip through a potential MergeMem chain, linked through Bot
 757           mem = mem->in(Compile::AliasIdxBot);
 758           NOT_PRODUCT(path.push(mem);)
 759         }
 760         // now let it fall through, and see if we have a projection
 761         if (mem->is_Proj()) {
 762           // Should point to a previous known call
 763           Node *prev = mem->in(0);
 764           NOT_PRODUCT(path.push(prev);)
 765           if (!prev->is_Call() || !_control.contains(prev)) {
 766 #ifndef PRODUCT
 767             if (PrintOptimizeStringConcat) {
 768               tty->print("fusion has incorrect memory flow (unknown call) for ");
 769               _begin->jvms()->dump_spec(tty); tty->cr();
 770               path.dump();
 771             }
 772 #endif
 773             return false;
 774           }
 775         } else {
 776           assert(mem->is_Store() || mem->is_LoadStore(), "unexpected node type: %s", mem->Name());
 777 #ifndef PRODUCT
 778           if (PrintOptimizeStringConcat) {
 779             tty->print("fusion has incorrect memory flow (unexpected source) for ");
 780             _begin->jvms()->dump_spec(tty); tty->cr();
 781             path.dump();
 782           }
 783 #endif
 784           return false;
 785         }
 786       } else {
 787         // For memory that feeds into constructors it's more complicated.
 788         // However the advantage is that any side effect that happens between the Allocate/Initialize and
 789         // the constructor will have to be control-dependent on Initialize.
 790         // So we actually don't have to do anything, since it's going to be caught by the control flow
 791         // analysis.
 792 #ifdef ASSERT
 793         // Do a quick verification of the control pattern between the constructor and the initialize node
 794         assert(curr->is_Call(), "constructor should be a call");
 795         // Go up the control starting from the constructor call
 796         Node* ctrl = curr->in(0);
 797         IfNode* iff = NULL;
 798         RegionNode* copy = NULL;
 799 
 800         while (true) {
 801           // skip known check patterns
 802           if (ctrl->is_Region()) {
 803             if (ctrl->as_Region()->is_copy()) {
 804               copy = ctrl->as_Region();
 805               ctrl = copy->is_copy();
 806             } else { // a cast
 807               assert(ctrl->req() == 3 &&
 808                      ctrl->in(1) != NULL && ctrl->in(1)->is_Proj() &&
 809                      ctrl->in(2) != NULL && ctrl->in(2)->is_Proj() &&
 810                      ctrl->in(1)->in(0) == ctrl->in(2)->in(0) &&
 811                      ctrl->in(1)->in(0) != NULL && ctrl->in(1)->in(0)->is_If(),
 812                      "must be a simple diamond");
 813               Node* true_proj = ctrl->in(1)->is_IfTrue() ? ctrl->in(1) : ctrl->in(2);
 814               for (SimpleDUIterator i(true_proj); i.has_next(); i.next()) {
 815                 Node* use = i.get();
 816                 assert(use == ctrl || use->is_ConstraintCast(),
 817                        "unexpected user: %s", use->Name());
 818               }
 819 
 820               iff = ctrl->in(1)->in(0)->as_If();
 821               ctrl = iff->in(0);
 822             }
 823           } else if (ctrl->is_IfTrue()) { // null checks, class checks
 824             iff = ctrl->in(0)->as_If();
 825             // Verify that the other arm is an uncommon trap
 826             Node* otherproj = iff->proj_out(1 - ctrl->as_Proj()->_con);
 827             CallStaticJavaNode* call = otherproj->unique_out()->isa_CallStaticJava();
 828             assert(strcmp(call->_name, "uncommon_trap") == 0, "must be uncommon trap");
 829             ctrl = iff->in(0);
 830           } else {
 831             break;
 832           }
 833         }
 834 
 835         assert(ctrl->is_Proj(), "must be a projection");
 836         assert(ctrl->in(0)->is_Initialize(), "should be initialize");
 837         for (SimpleDUIterator i(ctrl); i.has_next(); i.next()) {
 838           Node* use = i.get();
 839           assert(use == copy || use == iff || use == curr || use->is_CheckCastPP() || use->is_Load(),
 840                  "unexpected user: %s", use->Name());
 841         }
 842 #endif // ASSERT
 843       }
 844     }
 845   }
 846 
 847 #ifndef PRODUCT
 848   if (PrintOptimizeStringConcat) {
 849     tty->print("fusion has correct memory flow for ");
 850     _begin->jvms()->dump_spec(tty); tty->cr();
 851     tty->cr();
 852   }
 853 #endif
 854   return true;
 855 }
 856 
 857 bool StringConcat::validate_control_flow() {
 858   // We found all the calls and arguments now lets see if it's
 859   // safe to transform the graph as we would expect.
 860 
 861   // Check to see if this resulted in too many uncommon traps previously
 862   if (Compile::current()->too_many_traps(_begin->jvms()->method(), _begin->jvms()->bci(),
 863                         Deoptimization::Reason_intrinsic)) {
 864     return false;
 865   }
 866 
 867   // Walk backwards over the control flow from toString to the
 868   // allocation and make sure all the control flow is ok.  This
 869   // means it's either going to be eliminated once the calls are
 870   // removed or it can safely be transformed into an uncommon
 871   // trap.
 872 
 873   int null_check_count = 0;
 874   Unique_Node_List ctrl_path;
 875 
 876   assert(_control.contains(_begin), "missing");
 877   assert(_control.contains(_end), "missing");
 878 
 879   // Collect the nodes that we know about and will eliminate into ctrl_path
 880   for (uint i = 0; i < _control.size(); i++) {
 881     // Push the call and it's control projection
 882     Node* n = _control.at(i);
 883     if (n->is_Allocate()) {
 884       AllocateNode* an = n->as_Allocate();
 885       InitializeNode* init = an->initialization();
 886       ctrl_path.push(init);
 887       ctrl_path.push(init->as_Multi()->proj_out(0));
 888     }
 889     if (n->is_Call()) {
 890       CallNode* cn = n->as_Call();
 891       ctrl_path.push(cn);
 892       ctrl_path.push(cn->proj_out(0));
 893       ctrl_path.push(cn->proj_out(0)->unique_out());
 894       Node* catchproj = cn->proj_out(0)->unique_out()->as_Catch()->proj_out_or_null(0);
 895       if (catchproj != NULL) {
 896         ctrl_path.push(catchproj);
 897       }
 898     } else {
 899       ShouldNotReachHere();
 900     }
 901   }
 902 
 903   // Skip backwards through the control checking for unexpected control flow
 904   Node* ptr = _end;
 905   bool fail = false;
 906   while (ptr != _begin) {
 907     if (ptr->is_Call() && ctrl_path.member(ptr)) {
 908       ptr = ptr->in(0);
 909     } else if (ptr->is_CatchProj() && ctrl_path.member(ptr)) {
 910       ptr = ptr->in(0)->in(0)->in(0);
 911       assert(ctrl_path.member(ptr), "should be a known piece of control");
 912     } else if (ptr->is_IfTrue()) {
 913       IfNode* iff = ptr->in(0)->as_If();
 914       BoolNode* b = iff->in(1)->isa_Bool();
 915 
 916       if (b == NULL) {
 917 #ifndef PRODUCT
 918         if (PrintOptimizeStringConcat) {
 919           tty->print_cr("unexpected input to IfNode");
 920           iff->in(1)->dump();
 921           tty->cr();
 922         }
 923 #endif
 924         fail = true;
 925         break;
 926       }
 927 
 928       Node* cmp = b->in(1);
 929       Node* v1 = cmp->in(1);
 930       Node* v2 = cmp->in(2);
 931       Node* otherproj = iff->proj_out(1 - ptr->as_Proj()->_con);
 932 
 933       // Null check of the return of append which can simply be eliminated
 934       if (b->_test._test == BoolTest::ne &&
 935           v2->bottom_type() == TypePtr::NULL_PTR &&
 936           v1->is_Proj() && ctrl_path.member(v1->in(0))) {
 937         // NULL check of the return value of the append
 938         null_check_count++;
 939         if (otherproj->outcnt() == 1) {
 940           CallStaticJavaNode* call = otherproj->unique_out()->isa_CallStaticJava();
 941           if (call != NULL && call->_name != NULL && strcmp(call->_name, "uncommon_trap") == 0) {
 942             ctrl_path.push(call);
 943           }
 944         }
 945         _control.push(ptr);
 946         ptr = ptr->in(0)->in(0);
 947         continue;
 948       }
 949 
 950       // A test which leads to an uncommon trap which should be safe.
 951       // Later this trap will be converted into a trap that restarts
 952       // at the beginning.
 953       if (otherproj->outcnt() == 1) {
 954         CallStaticJavaNode* call = otherproj->unique_out()->isa_CallStaticJava();
 955         if (call != NULL && call->_name != NULL && strcmp(call->_name, "uncommon_trap") == 0) {
 956           // control flow leads to uct so should be ok
 957           _uncommon_traps.push(call);
 958           ctrl_path.push(call);
 959           ptr = ptr->in(0)->in(0);
 960           continue;
 961         }
 962       }
 963 
 964 #ifndef PRODUCT
 965       // Some unexpected control flow we don't know how to handle.
 966       if (PrintOptimizeStringConcat) {
 967         tty->print_cr("failing with unknown test");
 968         b->dump();
 969         cmp->dump();
 970         v1->dump();
 971         v2->dump();
 972         tty->cr();
 973       }
 974 #endif
 975       fail = true;
 976       break;
 977     } else if (ptr->is_Proj() && ptr->in(0)->is_Initialize()) {
 978       ptr = ptr->in(0)->in(0);
 979     } else if (ptr->is_Region()) {
 980       Node* copy = ptr->as_Region()->is_copy();
 981       if (copy != NULL) {
 982         ptr = copy;
 983         continue;
 984       }
 985       if (ptr->req() == 3 &&
 986           ptr->in(1) != NULL && ptr->in(1)->is_Proj() &&
 987           ptr->in(2) != NULL && ptr->in(2)->is_Proj() &&
 988           ptr->in(1)->in(0) == ptr->in(2)->in(0) &&
 989           ptr->in(1)->in(0) != NULL && ptr->in(1)->in(0)->is_If()) {
 990         // Simple diamond.
 991         // XXX should check for possibly merging stores.  simple data merges are ok.
 992         // The IGVN will make this simple diamond go away when it
 993         // transforms the Region. Make sure it sees it.
 994         Compile::current()->record_for_igvn(ptr);
 995         ptr = ptr->in(1)->in(0)->in(0);
 996         continue;
 997       }
 998 #ifndef PRODUCT
 999       if (PrintOptimizeStringConcat) {
1000         tty->print_cr("fusion would fail for region");
1001         _begin->dump();
1002         ptr->dump(2);
1003       }
1004 #endif
1005       fail = true;
1006       break;
1007     } else {
1008       // other unknown control
1009       if (!fail) {
1010 #ifndef PRODUCT
1011         if (PrintOptimizeStringConcat) {
1012           tty->print_cr("fusion would fail for");
1013           _begin->dump();
1014         }
1015 #endif
1016         fail = true;
1017       }
1018 #ifndef PRODUCT
1019       if (PrintOptimizeStringConcat) {
1020         ptr->dump();
1021       }
1022 #endif
1023       ptr = ptr->in(0);
1024     }
1025   }
1026 #ifndef PRODUCT
1027   if (PrintOptimizeStringConcat && fail) {
1028     tty->cr();
1029   }
1030 #endif
1031   if (fail) return !fail;
1032 
1033   // Validate that all these results produced are contained within
1034   // this cluster of objects.  First collect all the results produced
1035   // by calls in the region.
1036   _stringopts->_visited.Clear();
1037   Node_List worklist;
1038   Node* final_result = _end->proj_out_or_null(TypeFunc::Parms);
1039   for (uint i = 0; i < _control.size(); i++) {
1040     CallNode* cnode = _control.at(i)->isa_Call();
1041     if (cnode != NULL) {
1042       _stringopts->_visited.test_set(cnode->_idx);
1043     }
1044     Node* result = cnode != NULL ? cnode->proj_out_or_null(TypeFunc::Parms) : NULL;
1045     if (result != NULL && result != final_result) {
1046       worklist.push(result);
1047     }
1048   }
1049 
1050   Node* last_result = NULL;
1051   while (worklist.size() > 0) {
1052     Node* result = worklist.pop();
1053     if (_stringopts->_visited.test_set(result->_idx))
1054       continue;
1055     for (SimpleDUIterator i(result); i.has_next(); i.next()) {
1056       Node *use = i.get();
1057       if (ctrl_path.member(use)) {
1058         // already checked this
1059         continue;
1060       }
1061       int opc = use->Opcode();
1062       if (opc == Op_CmpP || opc == Op_Node) {
1063         ctrl_path.push(use);
1064         continue;
1065       }
1066       if (opc == Op_CastPP || opc == Op_CheckCastPP) {
1067         for (SimpleDUIterator j(use); j.has_next(); j.next()) {
1068           worklist.push(j.get());
1069         }
1070         worklist.push(use->in(1));
1071         ctrl_path.push(use);
1072         continue;
1073       }
1074 #ifndef PRODUCT
1075       if (PrintOptimizeStringConcat) {
1076         if (result != last_result) {
1077           last_result = result;
1078           tty->print_cr("extra uses for result:");
1079           last_result->dump();
1080         }
1081         use->dump();
1082       }
1083 #endif
1084       fail = true;
1085       break;
1086     }
1087   }
1088 
1089 #ifndef PRODUCT
1090   if (PrintOptimizeStringConcat && !fail) {
1091     ttyLocker ttyl;
1092     tty->cr();
1093     tty->print("fusion has correct control flow (%d %d) for ", null_check_count, _uncommon_traps.size());
1094     _begin->jvms()->dump_spec(tty); tty->cr();
1095     for (int i = 0; i < num_arguments(); i++) {
1096       argument(i)->dump();
1097     }
1098     _control.dump();
1099     tty->cr();
1100   }
1101 #endif
1102 
1103   return !fail;
1104 }
1105 
1106 Node* PhaseStringOpts::fetch_static_field(GraphKit& kit, ciField* field) {
1107   const TypeInstPtr* mirror_type = TypeInstPtr::make(field->holder()->java_mirror());
1108   Node* klass_node = __ makecon(mirror_type);
1109   BasicType bt = field->layout_type();
1110   ciType* field_klass = field->type();
1111 
1112   const Type *type;
1113   if( bt == T_OBJECT ) {
1114     if (!field->type()->is_loaded()) {
1115       type = TypeInstPtr::BOTTOM;
1116     } else if (field->is_static_constant()) {
1117       // This can happen if the constant oop is non-perm.
1118       ciObject* con = field->constant_value().as_object();
1119       // Do not "join" in the previous type; it doesn't add value,
1120       // and may yield a vacuous result if the field is of interface type.
1121       type = TypeOopPtr::make_from_constant(con, true)->isa_oopptr();
1122       assert(type != NULL, "field singleton type must be consistent");
1123       return __ makecon(type);
1124     } else {
1125       type = TypeOopPtr::make_from_klass(field_klass->as_klass());
1126     }
1127   } else {
1128     type = Type::get_const_basic_type(bt);
1129   }
1130 
1131   return kit.make_load(NULL, kit.basic_plus_adr(klass_node, field->offset_in_bytes()),
1132                        type, T_OBJECT,
1133                        C->get_alias_index(mirror_type->add_offset(field->offset_in_bytes())),
1134                        MemNode::unordered);
1135 }
1136 
1137 Node* PhaseStringOpts::int_stringSize(GraphKit& kit, Node* arg) {
1138   if (arg->is_Con()) {
1139     // Constant integer. Compute constant length using Integer.sizeTable
1140     int arg_val = arg->get_int();
1141     int count = 1;
1142     if (arg_val < 0) {
1143       arg_val = -arg_val;
1144       count++;
1145     }
1146 
1147     ciArray* size_table = (ciArray*)size_table_field->constant_value().as_object();
1148     for (int i = 0; i < size_table->length(); i++) {
1149       if (arg_val <= size_table->element_value(i).as_int()) {
1150         count += i;
1151         break;
1152       }
1153     }
1154     return __ intcon(count);
1155   }
1156 
1157   RegionNode *final_merge = new RegionNode(3);
1158   kit.gvn().set_type(final_merge, Type::CONTROL);
1159   Node* final_size = new PhiNode(final_merge, TypeInt::INT);
1160   kit.gvn().set_type(final_size, TypeInt::INT);
1161 
1162   IfNode* iff = kit.create_and_map_if(kit.control(),
1163                                       __ Bool(__ CmpI(arg, __ intcon(0x80000000)), BoolTest::ne),
1164                                       PROB_FAIR, COUNT_UNKNOWN);
1165   Node* is_min = __ IfFalse(iff);
1166   final_merge->init_req(1, is_min);
1167   final_size->init_req(1, __ intcon(11));
1168 
1169   kit.set_control(__ IfTrue(iff));
1170   if (kit.stopped()) {
1171     final_merge->init_req(2, C->top());
1172     final_size->init_req(2, C->top());
1173   } else {
1174 
1175     // int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
1176     RegionNode *r = new RegionNode(3);
1177     kit.gvn().set_type(r, Type::CONTROL);
1178     Node *phi = new PhiNode(r, TypeInt::INT);
1179     kit.gvn().set_type(phi, TypeInt::INT);
1180     Node *size = new PhiNode(r, TypeInt::INT);
1181     kit.gvn().set_type(size, TypeInt::INT);
1182     Node* chk = __ CmpI(arg, __ intcon(0));
1183     Node* p = __ Bool(chk, BoolTest::lt);
1184     IfNode* iff = kit.create_and_map_if(kit.control(), p, PROB_FAIR, COUNT_UNKNOWN);
1185     Node* lessthan = __ IfTrue(iff);
1186     Node* greaterequal = __ IfFalse(iff);
1187     r->init_req(1, lessthan);
1188     phi->init_req(1, __ SubI(__ intcon(0), arg));
1189     size->init_req(1, __ intcon(1));
1190     r->init_req(2, greaterequal);
1191     phi->init_req(2, arg);
1192     size->init_req(2, __ intcon(0));
1193     kit.set_control(r);
1194     C->record_for_igvn(r);
1195     C->record_for_igvn(phi);
1196     C->record_for_igvn(size);
1197 
1198     // for (int i=0; ; i++)
1199     //   if (x <= sizeTable[i])
1200     //     return i+1;
1201 
1202     // Add loop predicate first.
1203     kit.add_predicate();
1204 
1205     RegionNode *loop = new RegionNode(3);
1206     loop->init_req(1, kit.control());
1207     kit.gvn().set_type(loop, Type::CONTROL);
1208 
1209     Node *index = new PhiNode(loop, TypeInt::INT);
1210     index->init_req(1, __ intcon(0));
1211     kit.gvn().set_type(index, TypeInt::INT);
1212     kit.set_control(loop);
1213     Node* sizeTable = fetch_static_field(kit, size_table_field);
1214 
1215     sizeTable = kit.access_resolve(sizeTable, ACCESS_READ);
1216     Node* value = kit.load_array_element(NULL, sizeTable, index, TypeAryPtr::INTS);
1217     C->record_for_igvn(value);
1218     Node* limit = __ CmpI(phi, value);
1219     Node* limitb = __ Bool(limit, BoolTest::le);
1220     IfNode* iff2 = kit.create_and_map_if(kit.control(), limitb, PROB_MIN, COUNT_UNKNOWN);
1221     Node* lessEqual = __ IfTrue(iff2);
1222     Node* greater = __ IfFalse(iff2);
1223 
1224     loop->init_req(2, greater);
1225     index->init_req(2, __ AddI(index, __ intcon(1)));
1226 
1227     kit.set_control(lessEqual);
1228     C->record_for_igvn(loop);
1229     C->record_for_igvn(index);
1230 
1231     final_merge->init_req(2, kit.control());
1232     final_size->init_req(2, __ AddI(__ AddI(index, size), __ intcon(1)));
1233   }
1234 
1235   kit.set_control(final_merge);
1236   C->record_for_igvn(final_merge);
1237   C->record_for_igvn(final_size);
1238 
1239   return final_size;
1240 }
1241 
1242 // Simplified version of Integer.getChars
1243 void PhaseStringOpts::getChars(GraphKit& kit, Node* arg, Node* dst_array, BasicType bt, Node* end, Node* final_merge, Node* final_mem, int merge_index) {
1244   // if (i < 0) {
1245   //     sign = '-';
1246   //     i = -i;
1247   // }
1248   IfNode* iff = kit.create_and_map_if(kit.control(), __ Bool(__ CmpI(arg, __ intcon(0)), BoolTest::lt),
1249                                       PROB_FAIR, COUNT_UNKNOWN);
1250 
1251   RegionNode* merge = new RegionNode(3);
1252   kit.gvn().set_type(merge, Type::CONTROL);
1253   Node* i = new PhiNode(merge, TypeInt::INT);
1254   kit.gvn().set_type(i, TypeInt::INT);
1255   Node* sign = new PhiNode(merge, TypeInt::INT);
1256   kit.gvn().set_type(sign, TypeInt::INT);
1257 
1258   merge->init_req(1, __ IfTrue(iff));
1259   i->init_req(1, __ SubI(__ intcon(0), arg));
1260   sign->init_req(1, __ intcon('-'));
1261   merge->init_req(2, __ IfFalse(iff));
1262   i->init_req(2, arg);
1263   sign->init_req(2, __ intcon(0));
1264 
1265   kit.set_control(merge);
1266 
1267   C->record_for_igvn(merge);
1268   C->record_for_igvn(i);
1269   C->record_for_igvn(sign);
1270 
1271   // for (;;) {
1272   //     q = i / 10;
1273   //     r = i - ((q << 3) + (q << 1));  // r = i-(q*10) ...
1274   //     buf [--charPos] = digits [r];
1275   //     i = q;
1276   //     if (i == 0) break;
1277   // }
1278 
1279   // Add loop predicate first.
1280   kit.add_predicate();
1281 
1282   RegionNode* head = new RegionNode(3);
1283   head->init_req(1, kit.control());
1284 
1285   kit.gvn().set_type(head, Type::CONTROL);
1286   Node* i_phi = new PhiNode(head, TypeInt::INT);
1287   i_phi->init_req(1, i);
1288   kit.gvn().set_type(i_phi, TypeInt::INT);
1289   Node* charPos = new PhiNode(head, TypeInt::INT);
1290   charPos->init_req(1, end);
1291   kit.gvn().set_type(charPos, TypeInt::INT);
1292   Node* mem = PhiNode::make(head, kit.memory(byte_adr_idx), Type::MEMORY, TypeAryPtr::BYTES);
1293   kit.gvn().set_type(mem, Type::MEMORY);
1294 
1295   kit.set_control(head);
1296   kit.set_memory(mem, byte_adr_idx);
1297 
1298   Node* q = __ DivI(kit.null(), i_phi, __ intcon(10));
1299   Node* r = __ SubI(i_phi, __ AddI(__ LShiftI(q, __ intcon(3)),
1300                                    __ LShiftI(q, __ intcon(1))));
1301   Node* index = __ SubI(charPos, __ intcon((bt == T_BYTE) ? 1 : 2));
1302   Node* ch = __ AddI(r, __ intcon('0'));
1303   Node* st = __ store_to_memory(kit.control(), kit.array_element_address(dst_array, index, T_BYTE),
1304                                 ch, bt, byte_adr_idx, MemNode::unordered, (bt != T_BYTE) /* mismatched */);
1305 
1306   iff = kit.create_and_map_if(head, __ Bool(__ CmpI(q, __ intcon(0)), BoolTest::ne),
1307                               PROB_FAIR, COUNT_UNKNOWN);
1308   Node* ne = __ IfTrue(iff);
1309   Node* eq = __ IfFalse(iff);
1310 
1311   head->init_req(2, ne);
1312   mem->init_req(2, st);
1313 
1314   i_phi->init_req(2, q);
1315   charPos->init_req(2, index);
1316   charPos = index;
1317 
1318   kit.set_control(eq);
1319   kit.set_memory(st, byte_adr_idx);
1320 
1321   C->record_for_igvn(head);
1322   C->record_for_igvn(mem);
1323   C->record_for_igvn(i_phi);
1324   C->record_for_igvn(charPos);
1325 
1326   // if (sign != 0) {
1327   //     buf [--charPos] = sign;
1328   // }
1329   iff = kit.create_and_map_if(kit.control(), __ Bool(__ CmpI(sign, __ intcon(0)), BoolTest::ne),
1330                               PROB_FAIR, COUNT_UNKNOWN);
1331 
1332   final_merge->init_req(merge_index + 2, __ IfFalse(iff));
1333   final_mem->init_req(merge_index + 2, kit.memory(byte_adr_idx));
1334 
1335   kit.set_control(__ IfTrue(iff));
1336   if (kit.stopped()) {
1337     final_merge->init_req(merge_index + 1, C->top());
1338     final_mem->init_req(merge_index + 1, C->top());
1339   } else {
1340     Node* index = __ SubI(charPos, __ intcon((bt == T_BYTE) ? 1 : 2));
1341     st = __ store_to_memory(kit.control(), kit.array_element_address(dst_array, index, T_BYTE),
1342                             sign, bt, byte_adr_idx, MemNode::unordered, (bt != T_BYTE) /* mismatched */);
1343 
1344     final_merge->init_req(merge_index + 1, kit.control());
1345     final_mem->init_req(merge_index + 1, st);
1346   }
1347 }
1348 
1349 // Copy the characters representing arg into dst_array starting at start
1350 Node* PhaseStringOpts::int_getChars(GraphKit& kit, Node* arg, Node* dst_array, Node* dst_coder, Node* start, Node* size) {
1351   bool dcon = dst_coder->is_Con();
1352   bool dbyte = dcon ? (dst_coder->get_int() == java_lang_String::CODER_LATIN1) : false;
1353   Node* end = __ AddI(start, __ LShiftI(size, dst_coder));
1354 
1355   // The final_merge node has 4 entries in case the encoding is known:
1356   // (0) Control, (1) result w/ sign, (2) result w/o sign, (3) result for Integer.min_value
1357   // or 6 entries in case the encoding is not known:
1358   // (0) Control, (1) Latin1 w/ sign, (2) Latin1 w/o sign, (3) min_value, (4) UTF16 w/ sign, (5) UTF16 w/o sign
1359   RegionNode* final_merge = new RegionNode(dcon ? 4 : 6);
1360   kit.gvn().set_type(final_merge, Type::CONTROL);
1361 
1362   Node* final_mem = PhiNode::make(final_merge, kit.memory(byte_adr_idx), Type::MEMORY, TypeAryPtr::BYTES);
1363   kit.gvn().set_type(final_mem, Type::MEMORY);
1364 
1365   // need to handle arg == Integer.MIN_VALUE specially because negating doesn't make it positive
1366   IfNode* iff = kit.create_and_map_if(kit.control(), __ Bool(__ CmpI(arg, __ intcon(0x80000000)), BoolTest::ne),
1367                                       PROB_FAIR, COUNT_UNKNOWN);
1368 
1369   Node* old_mem = kit.memory(byte_adr_idx);
1370 
1371   kit.set_control(__ IfFalse(iff));
1372   if (kit.stopped()) {
1373     // Statically not equal to MIN_VALUE so this path is dead
1374     final_merge->init_req(3, kit.control());
1375   } else {
1376     copy_string(kit, __ makecon(TypeInstPtr::make(C->env()->the_min_jint_string())),
1377                 dst_array, dst_coder, start);
1378     final_merge->init_req(3, kit.control());
1379     final_mem->init_req(3, kit.memory(byte_adr_idx));
1380   }
1381 
1382   kit.set_control(__ IfTrue(iff));
1383   kit.set_memory(old_mem, byte_adr_idx);
1384 
1385   if (!dcon) {
1386     // Check encoding of destination
1387     iff = kit.create_and_map_if(kit.control(), __ Bool(__ CmpI(dst_coder, __ intcon(0)), BoolTest::eq),
1388                                 PROB_FAIR, COUNT_UNKNOWN);
1389     old_mem = kit.memory(byte_adr_idx);
1390   }
1391   if (!dcon || dbyte) {
1392     // Destination is Latin1,
1393     if (!dcon) {
1394       kit.set_control(__ IfTrue(iff));
1395     }
1396     getChars(kit, arg, dst_array, T_BYTE, end, final_merge, final_mem);
1397   }
1398   if (!dcon || !dbyte) {
1399     // Destination is UTF16
1400     int merge_index = 0;
1401     if (!dcon) {
1402       kit.set_control(__ IfFalse(iff));
1403       kit.set_memory(old_mem, byte_adr_idx);
1404       merge_index = 3; // Account for Latin1 case
1405     }
1406     getChars(kit, arg, dst_array, T_CHAR, end, final_merge, final_mem, merge_index);
1407   }
1408 
1409   // Final merge point for Latin1 and UTF16 case
1410   kit.set_control(final_merge);
1411   kit.set_memory(final_mem, byte_adr_idx);
1412 
1413   C->record_for_igvn(final_merge);
1414   C->record_for_igvn(final_mem);
1415   return end;
1416 }
1417 
1418 // Copy 'count' bytes/chars from src_array to dst_array starting at index start
1419 void PhaseStringOpts::arraycopy(GraphKit& kit, IdealKit& ideal, Node* src_array, Node* dst_array, BasicType elembt, Node* start, Node* count) {
1420   assert(elembt == T_BYTE || elembt == T_CHAR, "Invalid type for arraycopy");
1421 
1422   if (elembt == T_CHAR) {
1423     // Get number of chars
1424     count = __ RShiftI(count, __ intcon(1));
1425   }
1426 
1427   Node* extra = NULL;
1428 #ifdef _LP64
1429   count = __ ConvI2L(count);
1430   extra = C->top();
1431 #endif
1432 
1433   Node* src_ptr = __ array_element_address(src_array, __ intcon(0), T_BYTE);
1434   Node* dst_ptr = __ array_element_address(dst_array, start, T_BYTE);
1435   // Check if destination address is aligned to HeapWordSize
1436   const TypeInt* tdst = __ gvn().type(start)->is_int();
1437   bool aligned = tdst->is_con() && ((tdst->get_con() * type2aelembytes(T_BYTE)) % HeapWordSize == 0);
1438   // Figure out which arraycopy runtime method to call (disjoint, uninitialized).
1439   const char* copyfunc_name = "arraycopy";
1440   address     copyfunc_addr = StubRoutines::select_arraycopy_function(elembt, aligned, true, copyfunc_name, true);
1441   ideal.make_leaf_call_no_fp(OptoRuntime::fast_arraycopy_Type(), copyfunc_addr, copyfunc_name,
1442                              TypeAryPtr::BYTES, src_ptr, dst_ptr, count, extra);
1443 }
1444 
1445 #undef __
1446 #define __ ideal.
1447 
1448 // Copy contents of a Latin1 encoded string from src_array to dst_array
1449 void PhaseStringOpts::copy_latin1_string(GraphKit& kit, IdealKit& ideal, Node* src_array, IdealVariable& count,
1450                                          Node* dst_array, Node* dst_coder, Node* start) {
1451   bool dcon = dst_coder->is_Con();
1452   bool dbyte = dcon ? (dst_coder->get_int() == java_lang_String::CODER_LATIN1) : false;
1453 
1454   if (!dcon) {
1455     __ if_then(dst_coder, BoolTest::eq, __ ConI(java_lang_String::CODER_LATIN1));
1456   }
1457   if (!dcon || dbyte) {
1458     // Destination is Latin1. Simply emit a byte arraycopy.
1459     arraycopy(kit, ideal, src_array, dst_array, T_BYTE, start, __ value(count));
1460   }
1461   if (!dcon) {
1462     __ else_();
1463   }
1464   if (!dcon || !dbyte) {
1465     // Destination is UTF16. Inflate src_array into dst_array.
1466     kit.sync_kit(ideal);
1467     if (Matcher::match_rule_supported(Op_StrInflatedCopy)) {
1468       // Use fast intrinsic
1469       Node* src = kit.array_element_address(src_array, kit.intcon(0), T_BYTE);
1470       Node* dst = kit.array_element_address(dst_array, start, T_BYTE);
1471       kit.inflate_string(src, dst, TypeAryPtr::BYTES, __ value(count));
1472     } else {
1473       // No intrinsic available, use slow method
1474       kit.inflate_string_slow(src_array, dst_array, start, __ value(count));
1475     }
1476     ideal.sync_kit(&kit);
1477     // Multiply count by two since we now need two bytes per char
1478     __ set(count, __ LShiftI(__ value(count), __ ConI(1)));
1479   }
1480   if (!dcon) {
1481     __ end_if();
1482   }
1483 }
1484 
1485 // Read two bytes from index and index+1 and convert them to a char
1486 static jchar readChar(ciTypeArray* array, int index) {
1487   int shift_high, shift_low;
1488 #ifdef VM_LITTLE_ENDIAN
1489     shift_high = 0;
1490     shift_low = 8;
1491 #else
1492     shift_high = 8;
1493     shift_low = 0;
1494 #endif
1495 
1496   jchar b1 = ((jchar) array->byte_at(index)) & 0xff;
1497   jchar b2 = ((jchar) array->byte_at(index+1)) & 0xff;
1498   return (b1 << shift_high) | (b2 << shift_low);
1499 }
1500 
1501 // Copy contents of constant src_array to dst_array by emitting individual stores
1502 void PhaseStringOpts::copy_constant_string(GraphKit& kit, IdealKit& ideal, ciTypeArray* src_array, IdealVariable& count,
1503                                            bool src_is_byte, Node* dst_array, Node* dst_coder, Node* start) {
1504   bool dcon = dst_coder->is_Con();
1505   bool dbyte = dcon ? (dst_coder->get_int() == java_lang_String::CODER_LATIN1) : false;
1506   int length = src_array->length();
1507 
1508   if (!dcon) {
1509     __ if_then(dst_coder, BoolTest::eq, __ ConI(java_lang_String::CODER_LATIN1));
1510   }
1511   if (!dcon || dbyte) {
1512     // Destination is Latin1. Copy each byte of src_array into dst_array.
1513     Node* index = start;
1514     for (int i = 0; i < length; i++) {
1515       Node* adr = kit.array_element_address(dst_array, index, T_BYTE);
1516       Node* val = __ ConI(src_array->byte_at(i));
1517       __ store(__ ctrl(), adr, val, T_BYTE, byte_adr_idx, MemNode::unordered);
1518       index = __ AddI(index, __ ConI(1));
1519     }
1520   }
1521   if (!dcon) {
1522     __ else_();
1523   }
1524   if (!dcon || !dbyte) {
1525     // Destination is UTF16. Copy each char of src_array into dst_array.
1526     Node* index = start;
1527     for (int i = 0; i < length; i++) {
1528       Node* adr = kit.array_element_address(dst_array, index, T_BYTE);
1529       jchar val;
1530       if (src_is_byte) {
1531         val = src_array->byte_at(i) & 0xff;
1532       } else {
1533         val = readChar(src_array, i++);
1534       }
1535       __ store(__ ctrl(), adr, __ ConI(val), T_CHAR, byte_adr_idx, MemNode::unordered, true /* mismatched */);
1536       index = __ AddI(index, __ ConI(2));
1537     }
1538     if (src_is_byte) {
1539       // Multiply count by two since we now need two bytes per char
1540       __ set(count, __ ConI(2 * length));
1541     }
1542   }
1543   if (!dcon) {
1544     __ end_if();
1545   }
1546 }
1547 
1548 // Compress copy contents of the byte/char String str into dst_array starting at index start.
1549 Node* PhaseStringOpts::copy_string(GraphKit& kit, Node* str, Node* dst_array, Node* dst_coder, Node* start) {
1550   Node* src_array = kit.load_String_value(str, true);
1551   src_array = kit.access_resolve(src_array, ACCESS_READ);
1552 
1553   IdealKit ideal(&kit, true, true);
1554   IdealVariable count(ideal); __ declarations_done();
1555 
1556   if (str->is_Con()) {
1557     // Constant source string
1558     ciTypeArray* src_array_type = get_constant_value(kit, str);
1559 
1560     // Check encoding of constant string
1561     bool src_is_byte = (get_constant_coder(kit, str) == java_lang_String::CODER_LATIN1);
1562 
1563     // For small constant strings just emit individual stores.
1564     // A length of 6 seems like a good space/speed tradeof.
1565     __ set(count, __ ConI(src_array_type->length()));
1566     int src_len = src_array_type->length() / (src_is_byte ? 1 : 2);
1567     if (src_len < unroll_string_copy_length) {
1568       // Small constant string
1569       copy_constant_string(kit, ideal, src_array_type, count, src_is_byte, dst_array, dst_coder, start);
1570     } else if (src_is_byte) {
1571       // Source is Latin1
1572       copy_latin1_string(kit, ideal, src_array, count, dst_array, dst_coder, start);
1573     } else {
1574       // Source is UTF16 (destination too). Simply emit a char arraycopy.
1575       arraycopy(kit, ideal, src_array, dst_array, T_CHAR, start, __ value(count));
1576     }
1577   } else {
1578     Node* size = kit.load_array_length(src_array);
1579     __ set(count, size);
1580     // Non-constant source string
1581     if (CompactStrings) {
1582       // Emit runtime check for coder
1583       Node* coder = kit.load_String_coder(str, true);
1584       __ if_then(coder, BoolTest::eq, __ ConI(java_lang_String::CODER_LATIN1)); {
1585         // Source is Latin1
1586         copy_latin1_string(kit, ideal, src_array, count, dst_array, dst_coder, start);
1587       } __ else_();
1588     }
1589     // Source is UTF16 (destination too). Simply emit a char arraycopy.
1590     arraycopy(kit, ideal, src_array, dst_array, T_CHAR, start, __ value(count));
1591 
1592     if (CompactStrings) {
1593       __ end_if();
1594     }
1595   }
1596 
1597   // Finally sync IdealKit and GraphKit.
1598   kit.sync_kit(ideal);
1599   return __ AddI(start, __ value(count));
1600 }
1601 
1602 // Compress copy the char into dst_array at index start.
1603 Node* PhaseStringOpts::copy_char(GraphKit& kit, Node* val, Node* dst_array, Node* dst_coder, Node* start) {
1604   bool dcon = (dst_coder != NULL) && dst_coder->is_Con();
1605   bool dbyte = dcon ? (dst_coder->get_int() == java_lang_String::CODER_LATIN1) : false;
1606 
1607   IdealKit ideal(&kit, true, true);
1608   IdealVariable end(ideal); __ declarations_done();
1609   Node* adr = kit.array_element_address(dst_array, start, T_BYTE);
1610   if (!dcon){
1611     __ if_then(dst_coder, BoolTest::eq, __ ConI(java_lang_String::CODER_LATIN1));
1612   }
1613   if (!dcon || dbyte) {
1614     // Destination is Latin1. Store a byte.
1615     __ store(__ ctrl(), adr, val, T_BYTE, byte_adr_idx, MemNode::unordered);
1616     __ set(end, __ AddI(start, __ ConI(1)));
1617   }
1618   if (!dcon) {
1619     __ else_();
1620   }
1621   if (!dcon || !dbyte) {
1622     // Destination is UTF16. Store a char.
1623     __ store(__ ctrl(), adr, val, T_CHAR, byte_adr_idx, MemNode::unordered, true /* mismatched */);
1624     __ set(end, __ AddI(start, __ ConI(2)));
1625   }
1626   if (!dcon) {
1627     __ end_if();
1628   }
1629   // Finally sync IdealKit and GraphKit.
1630   kit.sync_kit(ideal);
1631   return __ value(end);
1632 }
1633 
1634 #undef __
1635 #define __ kit.
1636 
1637 // Allocate a byte array of specified length.
1638 Node* PhaseStringOpts::allocate_byte_array(GraphKit& kit, IdealKit* ideal, Node* length) {
1639   if (ideal != NULL) {
1640     // Sync IdealKit and graphKit.
1641     kit.sync_kit(*ideal);
1642   }
1643   Node* byte_array = NULL;
1644   {
1645     PreserveReexecuteState preexecs(&kit);
1646     // The original jvms is for an allocation of either a String or
1647     // StringBuffer so no stack adjustment is necessary for proper
1648     // reexecution.  If we deoptimize in the slow path the bytecode
1649     // will be reexecuted and the char[] allocation will be thrown away.
1650     kit.jvms()->set_should_reexecute(true);
1651     byte_array = kit.new_array(__ makecon(TypeKlassPtr::make(ciTypeArrayKlass::make(T_BYTE))),
1652                                length, 1);
1653   }
1654 
1655   // Mark the allocation so that zeroing is skipped since the code
1656   // below will overwrite the entire array
1657   AllocateArrayNode* byte_alloc = AllocateArrayNode::Ideal_array_allocation(byte_array, _gvn);
1658   byte_alloc->maybe_set_complete(_gvn);
1659 
1660   if (ideal != NULL) {
1661     // Sync IdealKit and graphKit.
1662     ideal->sync_kit(&kit);
1663   }
1664   return byte_array;
1665 }
1666 
1667 jbyte PhaseStringOpts::get_constant_coder(GraphKit& kit, Node* str) {
1668   assert(str->is_Con(), "String must be constant");
1669   const TypeOopPtr* str_type = kit.gvn().type(str)->isa_oopptr();
1670   ciInstance* str_instance = str_type->const_oop()->as_instance();
1671   jbyte coder = str_instance->field_value_by_offset(java_lang_String::coder_offset_in_bytes()).as_byte();
1672   assert(CompactStrings || (coder == java_lang_String::CODER_UTF16), "Strings must be UTF16 encoded");
1673   return coder;
1674 }
1675 
1676 int PhaseStringOpts::get_constant_length(GraphKit& kit, Node* str) {
1677   assert(str->is_Con(), "String must be constant");
1678   return get_constant_value(kit, str)->length();
1679 }
1680 
1681 ciTypeArray* PhaseStringOpts::get_constant_value(GraphKit& kit, Node* str) {
1682   assert(str->is_Con(), "String must be constant");
1683   const TypeOopPtr* str_type = kit.gvn().type(str)->isa_oopptr();
1684   ciInstance* str_instance = str_type->const_oop()->as_instance();
1685   ciObject* src_array = str_instance->field_value_by_offset(java_lang_String::value_offset_in_bytes()).as_object();
1686   return src_array->as_type_array();
1687 }
1688 
1689 void PhaseStringOpts::replace_string_concat(StringConcat* sc) {
1690   // Log a little info about the transformation
1691   sc->maybe_log_transform();
1692 
1693   // pull the JVMState of the allocation into a SafePointNode to serve as
1694   // as a shim for the insertion of the new code.
1695   JVMState* jvms     = sc->begin()->jvms()->clone_shallow(C);
1696   uint size = sc->begin()->req();
1697   SafePointNode* map = new SafePointNode(size, jvms);
1698 
1699   // copy the control and memory state from the final call into our
1700   // new starting state.  This allows any preceeding tests to feed
1701   // into the new section of code.
1702   for (uint i1 = 0; i1 < TypeFunc::Parms; i1++) {
1703     map->init_req(i1, sc->end()->in(i1));
1704   }
1705   // blow away old allocation arguments
1706   for (uint i1 = TypeFunc::Parms; i1 < jvms->debug_start(); i1++) {
1707     map->init_req(i1, C->top());
1708   }
1709   // Copy the rest of the inputs for the JVMState
1710   for (uint i1 = jvms->debug_start(); i1 < sc->begin()->req(); i1++) {
1711     map->init_req(i1, sc->begin()->in(i1));
1712   }
1713   // Make sure the memory state is a MergeMem for parsing.
1714   if (!map->in(TypeFunc::Memory)->is_MergeMem()) {
1715     map->set_req(TypeFunc::Memory, MergeMemNode::make(map->in(TypeFunc::Memory)));
1716   }
1717 
1718   jvms->set_map(map);
1719   map->ensure_stack(jvms, jvms->method()->max_stack());
1720 
1721   // disconnect all the old StringBuilder calls from the graph
1722   sc->eliminate_unneeded_control();
1723 
1724   // At this point all the old work has been completely removed from
1725   // the graph and the saved JVMState exists at the point where the
1726   // final toString call used to be.
1727   GraphKit kit(jvms);
1728 
1729   // There may be uncommon traps which are still using the
1730   // intermediate states and these need to be rewritten to point at
1731   // the JVMState at the beginning of the transformation.
1732   sc->convert_uncommon_traps(kit, jvms);
1733 
1734   // Now insert the logic to compute the size of the string followed
1735   // by all the logic to construct array and resulting string.
1736 
1737   Node* null_string = __ makecon(TypeInstPtr::make(C->env()->the_null_string()));
1738 
1739   // Create a region for the overflow checks to merge into.
1740   int args = MAX2(sc->num_arguments(), 1);
1741   RegionNode* overflow = new RegionNode(args);
1742   kit.gvn().set_type(overflow, Type::CONTROL);
1743 
1744   // Create a hook node to hold onto the individual sizes since they
1745   // are need for the copying phase.
1746   Node* string_sizes = new Node(args);
1747 
1748   Node* coder = __ intcon(0);
1749   Node* length = __ intcon(0);
1750   // If at least one argument is UTF16 encoded, we can fix the encoding.
1751   bool coder_fixed = false;
1752 
1753   if (!CompactStrings) {
1754     // Fix encoding of result string to UTF16
1755     coder_fixed = true;
1756     coder = __ intcon(java_lang_String::CODER_UTF16);
1757   }
1758 
1759   for (int argi = 0; argi < sc->num_arguments(); argi++) {
1760     Node* arg = sc->argument(argi);
1761     switch (sc->mode(argi)) {
1762       case StringConcat::IntMode: {
1763         Node* string_size = int_stringSize(kit, arg);
1764 
1765         // accumulate total
1766         length = __ AddI(length, string_size);
1767 
1768         // Cache this value for the use by int_toString
1769         string_sizes->init_req(argi, string_size);
1770         break;
1771       }
1772       case StringConcat::StringNullCheckMode: {
1773         const Type* type = kit.gvn().type(arg);
1774         assert(type != TypePtr::NULL_PTR, "missing check");
1775         if (!type->higher_equal(TypeInstPtr::NOTNULL)) {
1776           // Null check with uncommon trap since
1777           // StringBuilder(null) throws exception.
1778           // Use special uncommon trap instead of
1779           // calling normal do_null_check().
1780           Node* p = __ Bool(__ CmpP(arg, kit.null()), BoolTest::ne);
1781           IfNode* iff = kit.create_and_map_if(kit.control(), p, PROB_MIN, COUNT_UNKNOWN);
1782           overflow->add_req(__ IfFalse(iff));
1783           Node* notnull = __ IfTrue(iff);
1784           kit.set_control(notnull); // set control for the cast_not_null
1785           arg = kit.cast_not_null(arg, false);
1786           sc->set_argument(argi, arg);
1787         }
1788         assert(kit.gvn().type(arg)->higher_equal(TypeInstPtr::NOTNULL), "sanity");
1789         // Fallthrough to add string length.
1790       }
1791       case StringConcat::StringMode: {
1792         const Type* type = kit.gvn().type(arg);
1793         Node* count = NULL;
1794         Node* arg_coder = NULL;
1795         if (type == TypePtr::NULL_PTR) {
1796           // replace the argument with the null checked version
1797           arg = null_string;
1798           sc->set_argument(argi, arg);
1799           count = kit.load_String_length(arg, true);
1800           arg_coder = kit.load_String_coder(arg, true);
1801         } else if (!type->higher_equal(TypeInstPtr::NOTNULL)) {
1802           // s = s != null ? s : "null";
1803           // length = length + (s.count - s.offset);
1804           RegionNode *r = new RegionNode(3);
1805           kit.gvn().set_type(r, Type::CONTROL);
1806           Node *phi = new PhiNode(r, type);
1807           kit.gvn().set_type(phi, phi->bottom_type());
1808           Node* p = __ Bool(__ CmpP(arg, kit.null()), BoolTest::ne);
1809           IfNode* iff = kit.create_and_map_if(kit.control(), p, PROB_MIN, COUNT_UNKNOWN);
1810           Node* notnull = __ IfTrue(iff);
1811           Node* isnull =  __ IfFalse(iff);
1812           kit.set_control(notnull); // set control for the cast_not_null
1813           r->init_req(1, notnull);
1814           phi->init_req(1, kit.cast_not_null(arg, false));
1815           r->init_req(2, isnull);
1816           phi->init_req(2, null_string);
1817           kit.set_control(r);
1818           C->record_for_igvn(r);
1819           C->record_for_igvn(phi);
1820           // replace the argument with the null checked version
1821           arg = phi;
1822           sc->set_argument(argi, arg);
1823           count = kit.load_String_length(arg, true);
1824           arg_coder = kit.load_String_coder(arg, true);
1825         } else {
1826           // A corresponding nullcheck will be connected during IGVN MemNode::Ideal_common_DU_postCCP
1827           // kit.control might be a different test, that can be hoisted above the actual nullcheck
1828           // in case, that the control input is not null, Ideal_common_DU_postCCP will not look for a nullcheck.
1829           count = kit.load_String_length(arg, false);
1830           arg_coder = kit.load_String_coder(arg, false);
1831         }
1832         if (arg->is_Con()) {
1833           // Constant string. Get constant coder and length.
1834           jbyte const_coder = get_constant_coder(kit, arg);
1835           int const_length = get_constant_length(kit, arg);
1836           if (const_coder == java_lang_String::CODER_LATIN1) {
1837             // Can be latin1 encoded
1838             arg_coder = __ intcon(const_coder);
1839             count = __ intcon(const_length);
1840           } else {
1841             // Found UTF16 encoded string. Fix result array encoding to UTF16.
1842             coder_fixed = true;
1843             coder = __ intcon(const_coder);
1844             count = __ intcon(const_length / 2);
1845           }
1846         }
1847 
1848         if (!coder_fixed) {
1849           coder = __ OrI(coder, arg_coder);
1850         }
1851         length = __ AddI(length, count);
1852         string_sizes->init_req(argi, NULL);
1853         break;
1854       }
1855       case StringConcat::CharMode: {
1856         // one character only
1857         const TypeInt* t = kit.gvn().type(arg)->is_int();
1858         if (!coder_fixed && t->is_con()) {
1859           // Constant char
1860           if (t->get_con() <= 255) {
1861             // Can be latin1 encoded
1862             coder = __ OrI(coder, __ intcon(java_lang_String::CODER_LATIN1));
1863           } else {
1864             // Must be UTF16 encoded. Fix result array encoding to UTF16.
1865             coder_fixed = true;
1866             coder = __ intcon(java_lang_String::CODER_UTF16);
1867           }
1868         } else if (!coder_fixed) {
1869           // Not constant
1870 #undef __
1871 #define __ ideal.
1872           IdealKit ideal(&kit, true, true);
1873           IdealVariable char_coder(ideal); __ declarations_done();
1874           // Check if character can be latin1 encoded
1875           __ if_then(arg, BoolTest::le, __ ConI(0xFF));
1876             __ set(char_coder, __ ConI(java_lang_String::CODER_LATIN1));
1877           __ else_();
1878             __ set(char_coder, __ ConI(java_lang_String::CODER_UTF16));
1879           __ end_if();
1880           kit.sync_kit(ideal);
1881           coder = __ OrI(coder, __ value(char_coder));
1882 #undef __
1883 #define __ kit.
1884         }
1885         length = __ AddI(length, __ intcon(1));
1886         break;
1887       }
1888       default:
1889         ShouldNotReachHere();
1890     }
1891     if (argi > 0) {
1892       // Check that the sum hasn't overflowed
1893       IfNode* iff = kit.create_and_map_if(kit.control(),
1894                                           __ Bool(__ CmpI(length, __ intcon(0)), BoolTest::lt),
1895                                           PROB_MIN, COUNT_UNKNOWN);
1896       kit.set_control(__ IfFalse(iff));
1897       overflow->set_req(argi, __ IfTrue(iff));
1898     }
1899   }
1900 
1901   {
1902     // Hook
1903     PreserveJVMState pjvms(&kit);
1904     kit.set_control(overflow);
1905     C->record_for_igvn(overflow);
1906     kit.uncommon_trap(Deoptimization::Reason_intrinsic,
1907                       Deoptimization::Action_make_not_entrant);
1908   }
1909 
1910   Node* result;
1911   if (!kit.stopped()) {
1912     assert(CompactStrings || (coder->is_Con() && coder->get_int() == java_lang_String::CODER_UTF16),
1913            "Result string must be UTF16 encoded if CompactStrings is disabled");
1914 
1915     Node* dst_array = NULL;
1916     if (sc->num_arguments() == 1 &&
1917         (sc->mode(0) == StringConcat::StringMode ||
1918          sc->mode(0) == StringConcat::StringNullCheckMode)) {
1919       // Handle the case when there is only a single String argument.
1920       // In this case, we can just pull the value from the String itself.
1921       dst_array = kit.load_String_value(sc->argument(0), true);
1922     } else {
1923       // Allocate destination byte array according to coder
1924       dst_array = allocate_byte_array(kit, NULL, __ LShiftI(length, coder));
1925 
1926       // Now copy the string representations into the final byte[]
1927       Node* start = __ intcon(0);
1928       for (int argi = 0; argi < sc->num_arguments(); argi++) {
1929         Node* arg = sc->argument(argi);
1930         switch (sc->mode(argi)) {
1931           case StringConcat::IntMode: {
1932             start = int_getChars(kit, arg, dst_array, coder, start, string_sizes->in(argi));
1933             break;
1934           }
1935           case StringConcat::StringNullCheckMode:
1936           case StringConcat::StringMode: {
1937             start = copy_string(kit, arg, dst_array, coder, start);
1938             break;
1939           }
1940           case StringConcat::CharMode: {
1941             start = copy_char(kit, arg, dst_array, coder, start);
1942           break;
1943           }
1944           default:
1945             ShouldNotReachHere();
1946         }
1947       }
1948     }
1949 
1950     // If we're not reusing an existing String allocation then allocate one here.
1951     result = sc->string_alloc();
1952     if (result == NULL) {
1953       PreserveReexecuteState preexecs(&kit);
1954       // The original jvms is for an allocation of either a String or
1955       // StringBuffer so no stack adjustment is necessary for proper
1956       // reexecution.
1957       kit.jvms()->set_should_reexecute(true);
1958       result = kit.new_instance(__ makecon(TypeKlassPtr::make(C->env()->String_klass())));
1959     }
1960 
1961     // Initialize the string
1962     kit.store_String_value(result, dst_array);
1963     kit.store_String_coder(result, coder);
1964 
1965     // The value field is final. Emit a barrier here to ensure that the effect
1966     // of the initialization is committed to memory before any code publishes
1967     // a reference to the newly constructed object (see Parse::do_exits()).
1968     assert(AllocateNode::Ideal_allocation(result, _gvn) != NULL, "should be newly allocated");
1969     kit.insert_mem_bar(Op_MemBarRelease, result);
1970   } else {
1971     result = C->top();
1972   }
1973   // hook up the outgoing control and result
1974   kit.replace_call(sc->end(), result);
1975 
1976   // Unhook any hook nodes
1977   string_sizes->disconnect_inputs(NULL, C);
1978   sc->cleanup();
1979 }