1 /*
   2  * Copyright (c) 2009, 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 "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     _end(end),
  70     _begin(NULL),
  71     _multiple(false),
  72     _string_alloc(NULL),
  73     _stringopts(stringopts) {
  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;
 325   call->extract_projections(&projs, false);
 326   if (projs.fallthrough_catchproj != NULL) {
 327     C->gvn_replace_by(projs.fallthrough_catchproj, call->in(TypeFunc::Control));
 328   }
 329   if (projs.fallthrough_memproj != NULL) {
 330     C->gvn_replace_by(projs.fallthrough_memproj, call->in(TypeFunc::Memory));
 331   }
 332   if (projs.catchall_memproj != NULL) {
 333     C->gvn_replace_by(projs.catchall_memproj, C->top());
 334   }
 335   if (projs.fallthrough_ioproj != NULL) {
 336     C->gvn_replace_by(projs.fallthrough_ioproj, call->in(TypeFunc::I_O));
 337   }
 338   if (projs.catchall_ioproj != NULL) {
 339     C->gvn_replace_by(projs.catchall_ioproj, C->top());
 340   }
 341   if (projs.catchall_catchproj != NULL) {
 342     // EA can't cope with the partially collapsed graph this
 343     // creates so put it on the worklist to be collapsed later.
 344     for (SimpleDUIterator i(projs.catchall_catchproj); i.has_next(); i.next()) {
 345       Node *use = i.get();
 346       int opc = use->Opcode();
 347       if (opc == Op_CreateEx || opc == Op_Region) {
 348         _stringopts->record_dead_node(use);
 349       }
 350     }
 351     C->gvn_replace_by(projs.catchall_catchproj, C->top());
 352   }
 353   if (projs.resproj != NULL) {
 354     C->gvn_replace_by(projs.resproj, 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(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(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   char_adr_idx = C->get_alias_index(TypeAryPtr::CHARS);
 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(), err_msg_res("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                        err_msg_res("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             assert(iff->is_If(), "must be if");
 826             // Verify that the other arm is an uncommon trap
 827             Node* otherproj = iff->proj_out(1 - ctrl->as_Proj()->_con);
 828             CallStaticJavaNode* call = otherproj->unique_out()->isa_CallStaticJava();
 829             assert(strcmp(call->_name, "uncommon_trap") == 0, "must be uncommond trap");
 830             ctrl = iff->in(0);
 831           } else {
 832             break;
 833           }
 834         }
 835 
 836         assert(ctrl->is_Proj(), "must be a projection");
 837         assert(ctrl->in(0)->is_Initialize(), "should be initialize");
 838         for (SimpleDUIterator i(ctrl); i.has_next(); i.next()) {
 839           Node* use = i.get();
 840           assert(use == copy || use == iff || use == curr || use->is_CheckCastPP() || use->is_Load(),
 841                  err_msg_res("unexpected user: %s", use->Name()));
 842         }
 843 #endif // ASSERT
 844       }
 845     }
 846   }
 847 
 848 #ifndef PRODUCT
 849   if (PrintOptimizeStringConcat) {
 850     tty->print("fusion has correct memory flow for ");
 851     _begin->jvms()->dump_spec(tty); tty->cr();
 852     tty->cr();
 853   }
 854 #endif
 855   return true;
 856 }
 857 
 858 bool StringConcat::validate_control_flow() {
 859   // We found all the calls and arguments now lets see if it's
 860   // safe to transform the graph as we would expect.
 861 
 862   // Check to see if this resulted in too many uncommon traps previously
 863   if (Compile::current()->too_many_traps(_begin->jvms()->method(), _begin->jvms()->bci(),
 864                         Deoptimization::Reason_intrinsic)) {
 865     return false;
 866   }
 867 
 868   // Walk backwards over the control flow from toString to the
 869   // allocation and make sure all the control flow is ok.  This
 870   // means it's either going to be eliminated once the calls are
 871   // removed or it can safely be transformed into an uncommon
 872   // trap.
 873 
 874   int null_check_count = 0;
 875   Unique_Node_List ctrl_path;
 876 
 877   assert(_control.contains(_begin), "missing");
 878   assert(_control.contains(_end), "missing");
 879 
 880   // Collect the nodes that we know about and will eliminate into ctrl_path
 881   for (uint i = 0; i < _control.size(); i++) {
 882     // Push the call and it's control projection
 883     Node* n = _control.at(i);
 884     if (n->is_Allocate()) {
 885       AllocateNode* an = n->as_Allocate();
 886       InitializeNode* init = an->initialization();
 887       ctrl_path.push(init);
 888       ctrl_path.push(init->as_Multi()->proj_out(0));
 889     }
 890     if (n->is_Call()) {
 891       CallNode* cn = n->as_Call();
 892       ctrl_path.push(cn);
 893       ctrl_path.push(cn->proj_out(0));
 894       ctrl_path.push(cn->proj_out(0)->unique_out());
 895       if (cn->proj_out(0)->unique_out()->as_Catch()->proj_out(0) != NULL) {
 896         ctrl_path.push(cn->proj_out(0)->unique_out()->as_Catch()->proj_out(0));
 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         fail = true;
 918         break;
 919       }
 920 
 921       Node* cmp = b->in(1);
 922       Node* v1 = cmp->in(1);
 923       Node* v2 = cmp->in(2);
 924       Node* otherproj = iff->proj_out(1 - ptr->as_Proj()->_con);
 925 
 926       // Null check of the return of append which can simply be eliminated
 927       if (b->_test._test == BoolTest::ne &&
 928           v2->bottom_type() == TypePtr::NULL_PTR &&
 929           v1->is_Proj() && ctrl_path.member(v1->in(0))) {
 930         // NULL check of the return value of the append
 931         null_check_count++;
 932         if (otherproj->outcnt() == 1) {
 933           CallStaticJavaNode* call = otherproj->unique_out()->isa_CallStaticJava();
 934           if (call != NULL && call->_name != NULL && strcmp(call->_name, "uncommon_trap") == 0) {
 935             ctrl_path.push(call);
 936           }
 937         }
 938         _control.push(ptr);
 939         ptr = ptr->in(0)->in(0);
 940         continue;
 941       }
 942 
 943       // A test which leads to an uncommon trap which should be safe.
 944       // Later this trap will be converted into a trap that restarts
 945       // at the beginning.
 946       if (otherproj->outcnt() == 1) {
 947         CallStaticJavaNode* call = otherproj->unique_out()->isa_CallStaticJava();
 948         if (call != NULL && call->_name != NULL && strcmp(call->_name, "uncommon_trap") == 0) {
 949           // control flow leads to uct so should be ok
 950           _uncommon_traps.push(call);
 951           ctrl_path.push(call);
 952           ptr = ptr->in(0)->in(0);
 953           continue;
 954         }
 955       }
 956 
 957 #ifndef PRODUCT
 958       // Some unexpected control flow we don't know how to handle.
 959       if (PrintOptimizeStringConcat) {
 960         tty->print_cr("failing with unknown test");
 961         b->dump();
 962         cmp->dump();
 963         v1->dump();
 964         v2->dump();
 965         tty->cr();
 966       }
 967 #endif
 968       fail = true;
 969       break;
 970     } else if (ptr->is_Proj() && ptr->in(0)->is_Initialize()) {
 971       ptr = ptr->in(0)->in(0);
 972     } else if (ptr->is_Region()) {
 973       Node* copy = ptr->as_Region()->is_copy();
 974       if (copy != NULL) {
 975         ptr = copy;
 976         continue;
 977       }
 978       if (ptr->req() == 3 &&
 979           ptr->in(1) != NULL && ptr->in(1)->is_Proj() &&
 980           ptr->in(2) != NULL && ptr->in(2)->is_Proj() &&
 981           ptr->in(1)->in(0) == ptr->in(2)->in(0) &&
 982           ptr->in(1)->in(0) != NULL && ptr->in(1)->in(0)->is_If()) {
 983         // Simple diamond.
 984         // XXX should check for possibly merging stores.  simple data merges are ok.
 985         // The IGVN will make this simple diamond go away when it
 986         // transforms the Region. Make sure it sees it.
 987         Compile::current()->record_for_igvn(ptr);
 988         ptr = ptr->in(1)->in(0)->in(0);
 989         continue;
 990       }
 991 #ifndef PRODUCT
 992       if (PrintOptimizeStringConcat) {
 993         tty->print_cr("fusion would fail for region");
 994         _begin->dump();
 995         ptr->dump(2);
 996       }
 997 #endif
 998       fail = true;
 999       break;
1000     } else {
1001       // other unknown control
1002       if (!fail) {
1003 #ifndef PRODUCT
1004         if (PrintOptimizeStringConcat) {
1005           tty->print_cr("fusion would fail for");
1006           _begin->dump();
1007         }
1008 #endif
1009         fail = true;
1010       }
1011 #ifndef PRODUCT
1012       if (PrintOptimizeStringConcat) {
1013         ptr->dump();
1014       }
1015 #endif
1016       ptr = ptr->in(0);
1017     }
1018   }
1019 #ifndef PRODUCT
1020   if (PrintOptimizeStringConcat && fail) {
1021     tty->cr();
1022   }
1023 #endif
1024   if (fail) return !fail;
1025 
1026   // Validate that all these results produced are contained within
1027   // this cluster of objects.  First collect all the results produced
1028   // by calls in the region.
1029   _stringopts->_visited.Clear();
1030   Node_List worklist;
1031   Node* final_result = _end->proj_out(TypeFunc::Parms);
1032   for (uint i = 0; i < _control.size(); i++) {
1033     CallNode* cnode = _control.at(i)->isa_Call();
1034     if (cnode != NULL) {
1035       _stringopts->_visited.test_set(cnode->_idx);
1036     }
1037     Node* result = cnode != NULL ? cnode->proj_out(TypeFunc::Parms) : NULL;
1038     if (result != NULL && result != final_result) {
1039       worklist.push(result);
1040     }
1041   }
1042 
1043   Node* last_result = NULL;
1044   while (worklist.size() > 0) {
1045     Node* result = worklist.pop();
1046     if (_stringopts->_visited.test_set(result->_idx))
1047       continue;
1048     for (SimpleDUIterator i(result); i.has_next(); i.next()) {
1049       Node *use = i.get();
1050       if (ctrl_path.member(use)) {
1051         // already checked this
1052         continue;
1053       }
1054       int opc = use->Opcode();
1055       if (opc == Op_CmpP || opc == Op_Node) {
1056         ctrl_path.push(use);
1057         continue;
1058       }
1059       if (opc == Op_CastPP || opc == Op_CheckCastPP) {
1060         for (SimpleDUIterator j(use); j.has_next(); j.next()) {
1061           worklist.push(j.get());
1062         }
1063         worklist.push(use->in(1));
1064         ctrl_path.push(use);
1065         continue;
1066       }
1067 #ifndef PRODUCT
1068       if (PrintOptimizeStringConcat) {
1069         if (result != last_result) {
1070           last_result = result;
1071           tty->print_cr("extra uses for result:");
1072           last_result->dump();
1073         }
1074         use->dump();
1075       }
1076 #endif
1077       fail = true;
1078       break;
1079     }
1080   }
1081 
1082 #ifndef PRODUCT
1083   if (PrintOptimizeStringConcat && !fail) {
1084     ttyLocker ttyl;
1085     tty->cr();
1086     tty->print("fusion has correct control flow (%d %d) for ", null_check_count, _uncommon_traps.size());
1087     _begin->jvms()->dump_spec(tty); tty->cr();
1088     for (int i = 0; i < num_arguments(); i++) {
1089       argument(i)->dump();
1090     }
1091     _control.dump();
1092     tty->cr();
1093   }
1094 #endif
1095 
1096   return !fail;
1097 }
1098 
1099 Node* PhaseStringOpts::fetch_static_field(GraphKit& kit, ciField* field) {
1100   const TypeInstPtr* mirror_type = TypeInstPtr::make(field->holder()->java_mirror());
1101   Node* klass_node = __ makecon(mirror_type);
1102   BasicType bt = field->layout_type();
1103   ciType* field_klass = field->type();
1104 
1105   const Type *type;
1106   if( bt == T_OBJECT ) {
1107     if (!field->type()->is_loaded()) {
1108       type = TypeInstPtr::BOTTOM;
1109     } else if (field->is_constant()) {
1110       // This can happen if the constant oop is non-perm.
1111       ciObject* con = field->constant_value().as_object();
1112       // Do not "join" in the previous type; it doesn't add value,
1113       // and may yield a vacuous result if the field is of interface type.
1114       type = TypeOopPtr::make_from_constant(con, true)->isa_oopptr();
1115       assert(type != NULL, "field singleton type must be consistent");
1116       return __ makecon(type);
1117     } else {
1118       type = TypeOopPtr::make_from_klass(field_klass->as_klass());
1119     }
1120   } else {
1121     type = Type::get_const_basic_type(bt);
1122   }
1123 
1124   return kit.make_load(NULL, kit.basic_plus_adr(klass_node, field->offset_in_bytes()),
1125                        type, T_OBJECT,
1126                        C->get_alias_index(mirror_type->add_offset(field->offset_in_bytes())),
1127                        MemNode::unordered);
1128 }
1129 
1130 Node* PhaseStringOpts::int_stringSize(GraphKit& kit, Node* arg) {
1131   RegionNode *final_merge = new RegionNode(3);
1132   kit.gvn().set_type(final_merge, Type::CONTROL);
1133   Node* final_size = new PhiNode(final_merge, TypeInt::INT);
1134   kit.gvn().set_type(final_size, TypeInt::INT);
1135 
1136   IfNode* iff = kit.create_and_map_if(kit.control(),
1137                                       __ Bool(__ CmpI(arg, __ intcon(0x80000000)), BoolTest::ne),
1138                                       PROB_FAIR, COUNT_UNKNOWN);
1139   Node* is_min = __ IfFalse(iff);
1140   final_merge->init_req(1, is_min);
1141   final_size->init_req(1, __ intcon(11));
1142 
1143   kit.set_control(__ IfTrue(iff));
1144   if (kit.stopped()) {
1145     final_merge->init_req(2, C->top());
1146     final_size->init_req(2, C->top());
1147   } else {
1148 
1149     // int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
1150     RegionNode *r = new RegionNode(3);
1151     kit.gvn().set_type(r, Type::CONTROL);
1152     Node *phi = new PhiNode(r, TypeInt::INT);
1153     kit.gvn().set_type(phi, TypeInt::INT);
1154     Node *size = new PhiNode(r, TypeInt::INT);
1155     kit.gvn().set_type(size, TypeInt::INT);
1156     Node* chk = __ CmpI(arg, __ intcon(0));
1157     Node* p = __ Bool(chk, BoolTest::lt);
1158     IfNode* iff = kit.create_and_map_if(kit.control(), p, PROB_FAIR, COUNT_UNKNOWN);
1159     Node* lessthan = __ IfTrue(iff);
1160     Node* greaterequal = __ IfFalse(iff);
1161     r->init_req(1, lessthan);
1162     phi->init_req(1, __ SubI(__ intcon(0), arg));
1163     size->init_req(1, __ intcon(1));
1164     r->init_req(2, greaterequal);
1165     phi->init_req(2, arg);
1166     size->init_req(2, __ intcon(0));
1167     kit.set_control(r);
1168     C->record_for_igvn(r);
1169     C->record_for_igvn(phi);
1170     C->record_for_igvn(size);
1171 
1172     // for (int i=0; ; i++)
1173     //   if (x <= sizeTable[i])
1174     //     return i+1;
1175 
1176     // Add loop predicate first.
1177     kit.add_predicate();
1178 
1179     RegionNode *loop = new RegionNode(3);
1180     loop->init_req(1, kit.control());
1181     kit.gvn().set_type(loop, Type::CONTROL);
1182 
1183     Node *index = new PhiNode(loop, TypeInt::INT);
1184     index->init_req(1, __ intcon(0));
1185     kit.gvn().set_type(index, TypeInt::INT);
1186     kit.set_control(loop);
1187     Node* sizeTable = fetch_static_field(kit, size_table_field);
1188 
1189     Node* value = kit.load_array_element(NULL, sizeTable, index, TypeAryPtr::INTS);
1190     C->record_for_igvn(value);
1191     Node* limit = __ CmpI(phi, value);
1192     Node* limitb = __ Bool(limit, BoolTest::le);
1193     IfNode* iff2 = kit.create_and_map_if(kit.control(), limitb, PROB_MIN, COUNT_UNKNOWN);
1194     Node* lessEqual = __ IfTrue(iff2);
1195     Node* greater = __ IfFalse(iff2);
1196 
1197     loop->init_req(2, greater);
1198     index->init_req(2, __ AddI(index, __ intcon(1)));
1199 
1200     kit.set_control(lessEqual);
1201     C->record_for_igvn(loop);
1202     C->record_for_igvn(index);
1203 
1204     final_merge->init_req(2, kit.control());
1205     final_size->init_req(2, __ AddI(__ AddI(index, size), __ intcon(1)));
1206   }
1207 
1208   kit.set_control(final_merge);
1209   C->record_for_igvn(final_merge);
1210   C->record_for_igvn(final_size);
1211 
1212   return final_size;
1213 }
1214 
1215 void PhaseStringOpts::int_getChars(GraphKit& kit, Node* arg, Node* char_array, Node* start, Node* end) {
1216   RegionNode *final_merge = new RegionNode(4);
1217   kit.gvn().set_type(final_merge, Type::CONTROL);
1218   Node *final_mem = PhiNode::make(final_merge, kit.memory(char_adr_idx), Type::MEMORY, TypeAryPtr::CHARS);
1219   kit.gvn().set_type(final_mem, Type::MEMORY);
1220 
1221   // need to handle Integer.MIN_VALUE specially because negating doesn't make it positive
1222   {
1223     // i == MIN_VALUE
1224     IfNode* iff = kit.create_and_map_if(kit.control(),
1225                                         __ Bool(__ CmpI(arg, __ intcon(0x80000000)), BoolTest::ne),
1226                                         PROB_FAIR, COUNT_UNKNOWN);
1227 
1228     Node* old_mem = kit.memory(char_adr_idx);
1229 
1230     kit.set_control(__ IfFalse(iff));
1231     if (kit.stopped()) {
1232       // Statically not equal to MIN_VALUE so this path is dead
1233       final_merge->init_req(3, kit.control());
1234     } else {
1235       copy_string(kit, __ makecon(TypeInstPtr::make(C->env()->the_min_jint_string())),
1236                   char_array, start);
1237       final_merge->init_req(3, kit.control());
1238       final_mem->init_req(3, kit.memory(char_adr_idx));
1239     }
1240 
1241     kit.set_control(__ IfTrue(iff));
1242     kit.set_memory(old_mem, char_adr_idx);
1243   }
1244 
1245 
1246   // Simplified version of Integer.getChars
1247 
1248   // int q, r;
1249   // int charPos = index;
1250   Node* charPos = end;
1251 
1252   // char sign = 0;
1253 
1254   Node* i = arg;
1255   Node* sign = __ intcon(0);
1256 
1257   // if (i < 0) {
1258   //     sign = '-';
1259   //     i = -i;
1260   // }
1261   {
1262     IfNode* iff = kit.create_and_map_if(kit.control(),
1263                                         __ Bool(__ CmpI(arg, __ intcon(0)), BoolTest::lt),
1264                                         PROB_FAIR, COUNT_UNKNOWN);
1265 
1266     RegionNode *merge = new RegionNode(3);
1267     kit.gvn().set_type(merge, Type::CONTROL);
1268     i = new PhiNode(merge, TypeInt::INT);
1269     kit.gvn().set_type(i, TypeInt::INT);
1270     sign = new PhiNode(merge, TypeInt::INT);
1271     kit.gvn().set_type(sign, TypeInt::INT);
1272 
1273     merge->init_req(1, __ IfTrue(iff));
1274     i->init_req(1, __ SubI(__ intcon(0), arg));
1275     sign->init_req(1, __ intcon('-'));
1276     merge->init_req(2, __ IfFalse(iff));
1277     i->init_req(2, arg);
1278     sign->init_req(2, __ intcon(0));
1279 
1280     kit.set_control(merge);
1281 
1282     C->record_for_igvn(merge);
1283     C->record_for_igvn(i);
1284     C->record_for_igvn(sign);
1285   }
1286 
1287   // for (;;) {
1288   //     q = i / 10;
1289   //     r = i - ((q << 3) + (q << 1));  // r = i-(q*10) ...
1290   //     buf [--charPos] = digits [r];
1291   //     i = q;
1292   //     if (i == 0) break;
1293   // }
1294 
1295   {
1296     // Add loop predicate first.
1297     kit.add_predicate();
1298 
1299     RegionNode *head = new RegionNode(3);
1300     head->init_req(1, kit.control());
1301     kit.gvn().set_type(head, Type::CONTROL);
1302     Node *i_phi = new PhiNode(head, TypeInt::INT);
1303     i_phi->init_req(1, i);
1304     kit.gvn().set_type(i_phi, TypeInt::INT);
1305     charPos = PhiNode::make(head, charPos);
1306     kit.gvn().set_type(charPos, TypeInt::INT);
1307     Node *mem = PhiNode::make(head, kit.memory(char_adr_idx), Type::MEMORY, TypeAryPtr::CHARS);
1308     kit.gvn().set_type(mem, Type::MEMORY);
1309     kit.set_control(head);
1310     kit.set_memory(mem, char_adr_idx);
1311 
1312     Node* q = __ DivI(NULL, i_phi, __ intcon(10));
1313     Node* r = __ SubI(i_phi, __ AddI(__ LShiftI(q, __ intcon(3)),
1314                                      __ LShiftI(q, __ intcon(1))));
1315     Node* m1 = __ SubI(charPos, __ intcon(1));
1316     Node* ch = __ AddI(r, __ intcon('0'));
1317 
1318     Node* st = __ store_to_memory(kit.control(), kit.array_element_address(char_array, m1, T_CHAR),
1319                                   ch, T_CHAR, char_adr_idx, MemNode::unordered);
1320 
1321 
1322     IfNode* iff = kit.create_and_map_if(head, __ Bool(__ CmpI(q, __ intcon(0)), BoolTest::ne),
1323                                         PROB_FAIR, COUNT_UNKNOWN);
1324     Node* ne = __ IfTrue(iff);
1325     Node* eq = __ IfFalse(iff);
1326 
1327     head->init_req(2, ne);
1328     mem->init_req(2, st);
1329     i_phi->init_req(2, q);
1330     charPos->init_req(2, m1);
1331 
1332     charPos = m1;
1333 
1334     kit.set_control(eq);
1335     kit.set_memory(st, char_adr_idx);
1336 
1337     C->record_for_igvn(head);
1338     C->record_for_igvn(mem);
1339     C->record_for_igvn(i_phi);
1340     C->record_for_igvn(charPos);
1341   }
1342 
1343   {
1344     // if (sign != 0) {
1345     //     buf [--charPos] = sign;
1346     // }
1347     IfNode* iff = kit.create_and_map_if(kit.control(),
1348                                         __ Bool(__ CmpI(sign, __ intcon(0)), BoolTest::ne),
1349                                         PROB_FAIR, COUNT_UNKNOWN);
1350 
1351     final_merge->init_req(2, __ IfFalse(iff));
1352     final_mem->init_req(2, kit.memory(char_adr_idx));
1353 
1354     kit.set_control(__ IfTrue(iff));
1355     if (kit.stopped()) {
1356       final_merge->init_req(1, C->top());
1357       final_mem->init_req(1, C->top());
1358     } else {
1359       Node* m1 = __ SubI(charPos, __ intcon(1));
1360       Node* st = __ store_to_memory(kit.control(), kit.array_element_address(char_array, m1, T_CHAR),
1361                                     sign, T_CHAR, char_adr_idx, MemNode::unordered);
1362 
1363       final_merge->init_req(1, kit.control());
1364       final_mem->init_req(1, st);
1365     }
1366 
1367     kit.set_control(final_merge);
1368     kit.set_memory(final_mem, char_adr_idx);
1369 
1370     C->record_for_igvn(final_merge);
1371     C->record_for_igvn(final_mem);
1372   }
1373 }
1374 
1375 
1376 Node* PhaseStringOpts::copy_string(GraphKit& kit, Node* str, Node* char_array, Node* start) {
1377   Node* string = str;
1378   Node* offset = kit.load_String_offset(kit.control(), string);
1379   Node* count  = kit.load_String_length(kit.control(), string);
1380   Node* value  = kit.load_String_value (kit.control(), string);
1381 
1382   // copy the contents
1383   if (offset->is_Con() && count->is_Con() && value->is_Con() && count->get_int() < unroll_string_copy_length) {
1384     // For small constant strings just emit individual stores.
1385     // A length of 6 seems like a good space/speed tradeof.
1386     int c = count->get_int();
1387     int o = offset->get_int();
1388     const TypeOopPtr* t = kit.gvn().type(value)->isa_oopptr();
1389     ciTypeArray* value_array = t->const_oop()->as_type_array();
1390     for (int e = 0; e < c; e++) {
1391       __ store_to_memory(kit.control(), kit.array_element_address(char_array, start, T_CHAR),
1392                          __ intcon(value_array->char_at(o + e)), T_CHAR, char_adr_idx,
1393                          MemNode::unordered);
1394       start = __ AddI(start, __ intcon(1));
1395     }
1396   } else {
1397     Node* src_ptr = kit.array_element_address(value, offset, T_CHAR);
1398     Node* dst_ptr = kit.array_element_address(char_array, start, T_CHAR);
1399     Node* c = count;
1400     Node* extra = NULL;
1401 #ifdef _LP64
1402     c = __ ConvI2L(c);
1403     extra = C->top();
1404 #endif
1405     Node* call = kit.make_runtime_call(GraphKit::RC_LEAF|GraphKit::RC_NO_FP,
1406                                        OptoRuntime::fast_arraycopy_Type(),
1407                                        CAST_FROM_FN_PTR(address, StubRoutines::jshort_disjoint_arraycopy()),
1408                                        "jshort_disjoint_arraycopy", TypeAryPtr::CHARS,
1409                                        src_ptr, dst_ptr, c, extra);
1410     start = __ AddI(start, count);
1411   }
1412   return start;
1413 }
1414 
1415 
1416 void PhaseStringOpts::replace_string_concat(StringConcat* sc) {
1417   // Log a little info about the transformation
1418   sc->maybe_log_transform();
1419 
1420   // pull the JVMState of the allocation into a SafePointNode to serve as
1421   // as a shim for the insertion of the new code.
1422   JVMState* jvms     = sc->begin()->jvms()->clone_shallow(C);
1423   uint size = sc->begin()->req();
1424   SafePointNode* map = new SafePointNode(size, jvms);
1425 
1426   // copy the control and memory state from the final call into our
1427   // new starting state.  This allows any preceeding tests to feed
1428   // into the new section of code.
1429   for (uint i1 = 0; i1 < TypeFunc::Parms; i1++) {
1430     map->init_req(i1, sc->end()->in(i1));
1431   }
1432   // blow away old allocation arguments
1433   for (uint i1 = TypeFunc::Parms; i1 < jvms->debug_start(); i1++) {
1434     map->init_req(i1, C->top());
1435   }
1436   // Copy the rest of the inputs for the JVMState
1437   for (uint i1 = jvms->debug_start(); i1 < sc->begin()->req(); i1++) {
1438     map->init_req(i1, sc->begin()->in(i1));
1439   }
1440   // Make sure the memory state is a MergeMem for parsing.
1441   if (!map->in(TypeFunc::Memory)->is_MergeMem()) {
1442     map->set_req(TypeFunc::Memory, MergeMemNode::make(map->in(TypeFunc::Memory)));
1443   }
1444 
1445   jvms->set_map(map);
1446   map->ensure_stack(jvms, jvms->method()->max_stack());
1447 
1448 
1449   // disconnect all the old StringBuilder calls from the graph
1450   sc->eliminate_unneeded_control();
1451 
1452   // At this point all the old work has been completely removed from
1453   // the graph and the saved JVMState exists at the point where the
1454   // final toString call used to be.
1455   GraphKit kit(jvms);
1456 
1457   // There may be uncommon traps which are still using the
1458   // intermediate states and these need to be rewritten to point at
1459   // the JVMState at the beginning of the transformation.
1460   sc->convert_uncommon_traps(kit, jvms);
1461 
1462   // Now insert the logic to compute the size of the string followed
1463   // by all the logic to construct array and resulting string.
1464 
1465   Node* null_string = __ makecon(TypeInstPtr::make(C->env()->the_null_string()));
1466 
1467   // Create a region for the overflow checks to merge into.
1468   int args = MAX2(sc->num_arguments(), 1);
1469   RegionNode* overflow = new RegionNode(args);
1470   kit.gvn().set_type(overflow, Type::CONTROL);
1471 
1472   // Create a hook node to hold onto the individual sizes since they
1473   // are need for the copying phase.
1474   Node* string_sizes = new Node(args);
1475 
1476   Node* length = __ intcon(0);
1477   for (int argi = 0; argi < sc->num_arguments(); argi++) {
1478     Node* arg = sc->argument(argi);
1479     switch (sc->mode(argi)) {
1480       case StringConcat::IntMode: {
1481         Node* string_size = int_stringSize(kit, arg);
1482 
1483         // accumulate total
1484         length = __ AddI(length, string_size);
1485 
1486         // Cache this value for the use by int_toString
1487         string_sizes->init_req(argi, string_size);
1488         break;
1489       }
1490       case StringConcat::StringNullCheckMode: {
1491         const Type* type = kit.gvn().type(arg);
1492         assert(type != TypePtr::NULL_PTR, "missing check");
1493         if (!type->higher_equal(TypeInstPtr::NOTNULL)) {
1494           // Null check with uncommont trap since
1495           // StringBuilder(null) throws exception.
1496           // Use special uncommon trap instead of
1497           // calling normal do_null_check().
1498           Node* p = __ Bool(__ CmpP(arg, kit.null()), BoolTest::ne);
1499           IfNode* iff = kit.create_and_map_if(kit.control(), p, PROB_MIN, COUNT_UNKNOWN);
1500           overflow->add_req(__ IfFalse(iff));
1501           Node* notnull = __ IfTrue(iff);
1502           kit.set_control(notnull); // set control for the cast_not_null
1503           arg = kit.cast_not_null(arg, false);
1504           sc->set_argument(argi, arg);
1505         }
1506         assert(kit.gvn().type(arg)->higher_equal(TypeInstPtr::NOTNULL), "sanity");
1507         // Fallthrough to add string length.
1508       }
1509       case StringConcat::StringMode: {
1510         const Type* type = kit.gvn().type(arg);
1511         Node* count = NULL;
1512         if (type == TypePtr::NULL_PTR) {
1513           // replace the argument with the null checked version
1514           arg = null_string;
1515           sc->set_argument(argi, arg);
1516           count = kit.load_String_length(kit.control(), arg);
1517         } else if (!type->higher_equal(TypeInstPtr::NOTNULL)) {
1518           // s = s != null ? s : "null";
1519           // length = length + (s.count - s.offset);
1520           RegionNode *r = new RegionNode(3);
1521           kit.gvn().set_type(r, Type::CONTROL);
1522           Node *phi = new PhiNode(r, type);
1523           kit.gvn().set_type(phi, phi->bottom_type());
1524           Node* p = __ Bool(__ CmpP(arg, kit.null()), BoolTest::ne);
1525           IfNode* iff = kit.create_and_map_if(kit.control(), p, PROB_MIN, COUNT_UNKNOWN);
1526           Node* notnull = __ IfTrue(iff);
1527           Node* isnull =  __ IfFalse(iff);
1528           kit.set_control(notnull); // set control for the cast_not_null
1529           r->init_req(1, notnull);
1530           phi->init_req(1, kit.cast_not_null(arg, false));
1531           r->init_req(2, isnull);
1532           phi->init_req(2, null_string);
1533           kit.set_control(r);
1534           C->record_for_igvn(r);
1535           C->record_for_igvn(phi);
1536           // replace the argument with the null checked version
1537           arg = phi;
1538           sc->set_argument(argi, arg);
1539           count = kit.load_String_length(kit.control(), arg);
1540         } else {
1541           // A corresponding nullcheck will be connected during IGVN MemNode::Ideal_common_DU_postCCP
1542           // kit.control might be a different test, that can be hoisted above the actual nullcheck
1543           // in case, that the control input is not null, Ideal_common_DU_postCCP will not look for a nullcheck.
1544           count = kit.load_String_length(NULL, arg);
1545         }
1546         length = __ AddI(length, count);
1547         string_sizes->init_req(argi, NULL);
1548         break;
1549       }
1550       case StringConcat::CharMode: {
1551         // one character only
1552         length = __ AddI(length, __ intcon(1));
1553         break;
1554       }
1555       default:
1556         ShouldNotReachHere();
1557     }
1558     if (argi > 0) {
1559       // Check that the sum hasn't overflowed
1560       IfNode* iff = kit.create_and_map_if(kit.control(),
1561                                           __ Bool(__ CmpI(length, __ intcon(0)), BoolTest::lt),
1562                                           PROB_MIN, COUNT_UNKNOWN);
1563       kit.set_control(__ IfFalse(iff));
1564       overflow->set_req(argi, __ IfTrue(iff));
1565     }
1566   }
1567 
1568   {
1569     // Hook
1570     PreserveJVMState pjvms(&kit);
1571     kit.set_control(overflow);
1572     C->record_for_igvn(overflow);
1573     kit.uncommon_trap(Deoptimization::Reason_intrinsic,
1574                       Deoptimization::Action_make_not_entrant);
1575   }
1576 
1577   Node* result;
1578   if (!kit.stopped()) {
1579     Node* char_array = NULL;
1580     if (sc->num_arguments() == 1 &&
1581           (sc->mode(0) == StringConcat::StringMode ||
1582            sc->mode(0) == StringConcat::StringNullCheckMode)) {
1583       // Handle the case when there is only a single String argument.
1584       // In this case, we can just pull the value from the String itself.
1585       char_array = kit.load_String_value(kit.control(), sc->argument(0));
1586     } else {
1587       // length now contains the number of characters needed for the
1588       // char[] so create a new AllocateArray for the char[]
1589       {
1590         PreserveReexecuteState preexecs(&kit);
1591         // The original jvms is for an allocation of either a String or
1592         // StringBuffer so no stack adjustment is necessary for proper
1593         // reexecution.  If we deoptimize in the slow path the bytecode
1594         // will be reexecuted and the char[] allocation will be thrown away.
1595         kit.jvms()->set_should_reexecute(true);
1596         char_array = kit.new_array(__ makecon(TypeKlassPtr::make(ciTypeArrayKlass::make(T_CHAR))),
1597                                    length, 1);
1598       }
1599 
1600       // Mark the allocation so that zeroing is skipped since the code
1601       // below will overwrite the entire array
1602       AllocateArrayNode* char_alloc = AllocateArrayNode::Ideal_array_allocation(char_array, _gvn);
1603       char_alloc->maybe_set_complete(_gvn);
1604 
1605       // Now copy the string representations into the final char[]
1606       char_array = __ shenandoah_write_barrier(char_array);
1607       Node* start = __ intcon(0);
1608       for (int argi = 0; argi < sc->num_arguments(); argi++) {
1609         Node* arg = sc->argument(argi);
1610         switch (sc->mode(argi)) {
1611           case StringConcat::IntMode: {
1612             Node* end = __ AddI(start, string_sizes->in(argi));
1613             // getChars words backwards so pass the ending point as well as the start
1614             int_getChars(kit, arg, char_array, start, end);
1615             start = end;
1616             break;
1617           }
1618           case StringConcat::StringNullCheckMode:
1619           case StringConcat::StringMode: {
1620             start = copy_string(kit, arg, char_array, start);
1621             break;
1622           }
1623           case StringConcat::CharMode: {
1624             __ store_to_memory(kit.control(), kit.array_element_address(char_array, start, T_CHAR),
1625                                arg, T_CHAR, char_adr_idx, MemNode::unordered);
1626             start = __ AddI(start, __ intcon(1));
1627             break;
1628           }
1629           default:
1630             ShouldNotReachHere();
1631         }
1632       }
1633     }
1634 
1635     // If we're not reusing an existing String allocation then allocate one here.
1636     result = sc->string_alloc();
1637     if (result == NULL) {
1638       PreserveReexecuteState preexecs(&kit);
1639       // The original jvms is for an allocation of either a String or
1640       // StringBuffer so no stack adjustment is necessary for proper
1641       // reexecution.
1642       kit.jvms()->set_should_reexecute(true);
1643       result = kit.new_instance(__ makecon(TypeKlassPtr::make(C->env()->String_klass())));
1644     }
1645 
1646     // Intialize the string
1647     if (java_lang_String::has_offset_field()) {
1648       kit.store_String_offset(kit.control(), result, __ intcon(0));
1649       kit.store_String_length(kit.control(), result, length);
1650     }
1651     kit.store_String_value(kit.control(), result, char_array);
1652   } else {
1653     result = C->top();
1654   }
1655   // hook up the outgoing control and result
1656   kit.replace_call(sc->end(), result);
1657 
1658   // Unhook any hook nodes
1659   string_sizes->disconnect_inputs(NULL, C);
1660   sc->cleanup();
1661 }