deps/v8/src/liveedit.cc

   1 // Copyright 2012 the V8 project authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5
   6 #include "src/v8.h"
   7
   8 #include "src/liveedit.h"
   9
  10 #include "src/code-stubs.h"
  11 #include "src/compilation-cache.h"
  12 #include "src/compiler.h"
  13 #include "src/debug.h"
  14 #include "src/deoptimizer.h"
  15 #include "src/global-handles.h"
  16 #include "src/messages.h"
  17 #include "src/parser.h"
  18 #include "src/scopeinfo.h"
  19 #include "src/scopes.h"
  20 #include "src/v8memory.h"
  21
  22 namespace v8 {
  23 namespace internal {
  24
  25 void SetElementSloppy(Handle<JSObject> object,
  26                       uint32_t index,
  27                       Handle<Object> value) {
  28   // Ignore return value from SetElement. It can only be a failure if there
  29   // are element setters causing exceptions and the debugger context has none
  30   // of these.
  31   JSObject::SetElement(object, index, value, NONE, SLOPPY).Assert();
  32 }
  33
  34
  35 // A simple implementation of dynamic programming algorithm. It solves
  36 // the problem of finding the difference of 2 arrays. It uses a table of results
  37 // of subproblems. Each cell contains a number together with 2-bit flag
  38 // that helps building the chunk list.
  39 class Differencer {
  40  public:
  41   explicit Differencer(Comparator::Input* input)
  42       : input_(input), len1_(input->GetLength1()), len2_(input->GetLength2()) {
  43     buffer_ = NewArray<int>(len1_ * len2_);
  44   }
  45   ~Differencer() {
  46     DeleteArray(buffer_);
  47   }
  48
  49   void Initialize() {
  50     int array_size = len1_ * len2_;
  51     for (int i = 0; i < array_size; i++) {
  52       buffer_[i] = kEmptyCellValue;
  53     }
  54   }
  55
  56   // Makes sure that result for the full problem is calculated and stored
  57   // in the table together with flags showing a path through subproblems.
  58   void FillTable() {
  59     CompareUpToTail(0, 0);
  60   }
  61
  62   void SaveResult(Comparator::Output* chunk_writer) {
  63     ResultWriter writer(chunk_writer);
  64
  65     int pos1 = 0;
  66     int pos2 = 0;
  67     while (true) {
  68       if (pos1 < len1_) {
  69         if (pos2 < len2_) {
  70           Direction dir = get_direction(pos1, pos2);
  71           switch (dir) {
  72             case EQ:
  73               writer.eq();
  74               pos1++;
  75               pos2++;
  76               break;
  77             case SKIP1:
  78               writer.skip1(1);
  79               pos1++;
  80               break;
  81             case SKIP2:
  82             case SKIP_ANY:
  83               writer.skip2(1);
  84               pos2++;
  85               break;
  86             default:
  87               UNREACHABLE();
  88           }
  89         } else {
  90           writer.skip1(len1_ - pos1);
  91           break;
  92         }
  93       } else {
  94         if (len2_ != pos2) {
  95           writer.skip2(len2_ - pos2);
  96         }
  97         break;
  98       }
  99     }
 100     writer.close();
 101   }
 102
 103  private:
 104   Comparator::Input* input_;
 105   int* buffer_;
 106   int len1_;
 107   int len2_;
 108
 109   enum Direction {
 110     EQ = 0,
 111     SKIP1,
 112     SKIP2,
 113     SKIP_ANY,
 114
 115     MAX_DIRECTION_FLAG_VALUE = SKIP_ANY
 116   };
 117
 118   // Computes result for a subtask and optionally caches it in the buffer table.
 119   // All results values are shifted to make space for flags in the lower bits.
 120   int CompareUpToTail(int pos1, int pos2) {
 121     if (pos1 < len1_) {
 122       if (pos2 < len2_) {
 123         int cached_res = get_value4(pos1, pos2);
 124         if (cached_res == kEmptyCellValue) {
 125           Direction dir;
 126           int res;
 127           if (input_->Equals(pos1, pos2)) {
 128             res = CompareUpToTail(pos1 + 1, pos2 + 1);
 129             dir = EQ;
 130           } else {
 131             int res1 = CompareUpToTail(pos1 + 1, pos2) +
 132                 (1 << kDirectionSizeBits);
 133             int res2 = CompareUpToTail(pos1, pos2 + 1) +
 134                 (1 << kDirectionSizeBits);
 135             if (res1 == res2) {
 136               res = res1;
 137               dir = SKIP_ANY;
 138             } else if (res1 < res2) {
 139               res = res1;
 140               dir = SKIP1;
 141             } else {
 142               res = res2;
 143               dir = SKIP2;
 144             }
 145           }
 146           set_value4_and_dir(pos1, pos2, res, dir);
 147           cached_res = res;
 148         }
 149         return cached_res;
 150       } else {
 151         return (len1_ - pos1) << kDirectionSizeBits;
 152       }
 153     } else {
 154       return (len2_ - pos2) << kDirectionSizeBits;
 155     }
 156   }
 157
 158   inline int& get_cell(int i1, int i2) {
 159     return buffer_[i1 + i2 * len1_];
 160   }
 161
 162   // Each cell keeps a value plus direction. Value is multiplied by 4.
 163   void set_value4_and_dir(int i1, int i2, int value4, Direction dir) {
 164     DCHECK((value4 & kDirectionMask) == 0);
 165     get_cell(i1, i2) = value4 | dir;
 166   }
 167
 168   int get_value4(int i1, int i2) {
 169     return get_cell(i1, i2) & (kMaxUInt32 ^ kDirectionMask);
 170   }
 171   Direction get_direction(int i1, int i2) {
 172     return static_cast<Direction>(get_cell(i1, i2) & kDirectionMask);
 173   }
 174
 175   static const int kDirectionSizeBits = 2;
 176   static const int kDirectionMask = (1 << kDirectionSizeBits) - 1;
 177   static const int kEmptyCellValue = ~0u << kDirectionSizeBits;
 178
 179   // This method only holds static assert statement (unfortunately you cannot
 180   // place one in class scope).
 181   void StaticAssertHolder() {
 182     STATIC_ASSERT(MAX_DIRECTION_FLAG_VALUE < (1 << kDirectionSizeBits));
 183   }
 184
 185   class ResultWriter {
 186    public:
 187     explicit ResultWriter(Comparator::Output* chunk_writer)
 188         : chunk_writer_(chunk_writer), pos1_(0), pos2_(0),
 189           pos1_begin_(-1), pos2_begin_(-1), has_open_chunk_(false) {
 190     }
 191     void eq() {
 192       FlushChunk();
 193       pos1_++;
 194       pos2_++;
 195     }
 196     void skip1(int len1) {
 197       StartChunk();
 198       pos1_ += len1;
 199     }
 200     void skip2(int len2) {
 201       StartChunk();
 202       pos2_ += len2;
 203     }
 204     void close() {
 205       FlushChunk();
 206     }
 207
 208    private:
 209     Comparator::Output* chunk_writer_;
 210     int pos1_;
 211     int pos2_;
 212     int pos1_begin_;
 213     int pos2_begin_;
 214     bool has_open_chunk_;
 215
 216     void StartChunk() {
 217       if (!has_open_chunk_) {
 218         pos1_begin_ = pos1_;
 219         pos2_begin_ = pos2_;
 220         has_open_chunk_ = true;
 221       }
 222     }
 223
 224     void FlushChunk() {
 225       if (has_open_chunk_) {
 226         chunk_writer_->AddChunk(pos1_begin_, pos2_begin_,
 227                                 pos1_ - pos1_begin_, pos2_ - pos2_begin_);
 228         has_open_chunk_ = false;
 229       }
 230     }
 231   };
 232 };
 233
 234
 235 void Comparator::CalculateDifference(Comparator::Input* input,
 236                                      Comparator::Output* result_writer) {
 237   Differencer differencer(input);
 238   differencer.Initialize();
 239   differencer.FillTable();
 240   differencer.SaveResult(result_writer);
 241 }
 242
 243
 244 static bool CompareSubstrings(Handle<String> s1, int pos1,
 245                               Handle<String> s2, int pos2, int len) {
 246   for (int i = 0; i < len; i++) {
 247     if (s1->Get(i + pos1) != s2->Get(i + pos2)) {
 248       return false;
 249     }
 250   }
 251   return true;
 252 }
 253
 254
 255 // Additional to Input interface. Lets switch Input range to subrange.
 256 // More elegant way would be to wrap one Input as another Input object
 257 // and translate positions there, but that would cost us additional virtual
 258 // call per comparison.
 259 class SubrangableInput : public Comparator::Input {
 260  public:
 261   virtual void SetSubrange1(int offset, int len) = 0;
 262   virtual void SetSubrange2(int offset, int len) = 0;
 263 };
 264
 265
 266 class SubrangableOutput : public Comparator::Output {
 267  public:
 268   virtual void SetSubrange1(int offset, int len) = 0;
 269   virtual void SetSubrange2(int offset, int len) = 0;
 270 };
 271
 272
 273 static int min(int a, int b) {
 274   return a < b ? a : b;
 275 }
 276
 277
 278 // Finds common prefix and suffix in input. This parts shouldn't take space in
 279 // linear programming table. Enable subranging in input and output.
 280 static void NarrowDownInput(SubrangableInput* input,
 281     SubrangableOutput* output) {
 282   const int len1 = input->GetLength1();
 283   const int len2 = input->GetLength2();
 284
 285   int common_prefix_len;
 286   int common_suffix_len;
 287
 288   {
 289     common_prefix_len = 0;
 290     int prefix_limit = min(len1, len2);
 291     while (common_prefix_len < prefix_limit &&
 292         input->Equals(common_prefix_len, common_prefix_len)) {
 293       common_prefix_len++;
 294     }
 295
 296     common_suffix_len = 0;
 297     int suffix_limit = min(len1 - common_prefix_len, len2 - common_prefix_len);
 298
 299     while (common_suffix_len < suffix_limit &&
 300         input->Equals(len1 - common_suffix_len - 1,
 301         len2 - common_suffix_len - 1)) {
 302       common_suffix_len++;
 303     }
 304   }
 305
 306   if (common_prefix_len > 0 || common_suffix_len > 0) {
 307     int new_len1 = len1 - common_suffix_len - common_prefix_len;
 308     int new_len2 = len2 - common_suffix_len - common_prefix_len;
 309
 310     input->SetSubrange1(common_prefix_len, new_len1);
 311     input->SetSubrange2(common_prefix_len, new_len2);
 312
 313     output->SetSubrange1(common_prefix_len, new_len1);
 314     output->SetSubrange2(common_prefix_len, new_len2);
 315   }
 316 }
 317
 318
 319 // A helper class that writes chunk numbers into JSArray.
 320 // Each chunk is stored as 3 array elements: (pos1_begin, pos1_end, pos2_end).
 321 class CompareOutputArrayWriter {
 322  public:
 323   explicit CompareOutputArrayWriter(Isolate* isolate)
 324       : array_(isolate->factory()->NewJSArray(10)), current_size_(0) {}
 325
 326   Handle<JSArray> GetResult() {
 327     return array_;
 328   }
 329
 330   void WriteChunk(int char_pos1, int char_pos2, int char_len1, int char_len2) {
 331     Isolate* isolate = array_->GetIsolate();
 332     SetElementSloppy(array_,
 333                      current_size_,
 334                      Handle<Object>(Smi::FromInt(char_pos1), isolate));
 335     SetElementSloppy(array_,
 336                      current_size_ + 1,
 337                      Handle<Object>(Smi::FromInt(char_pos1 + char_len1),
 338                                     isolate));
 339     SetElementSloppy(array_,
 340                      current_size_ + 2,
 341                      Handle<Object>(Smi::FromInt(char_pos2 + char_len2),
 342                                     isolate));
 343     current_size_ += 3;
 344   }
 345
 346  private:
 347   Handle<JSArray> array_;
 348   int current_size_;
 349 };
 350
 351
 352 // Represents 2 strings as 2 arrays of tokens.
 353 // TODO(LiveEdit): Currently it's actually an array of charactres.
 354 //     Make array of tokens instead.
 355 class TokensCompareInput : public Comparator::Input {
 356  public:
 357   TokensCompareInput(Handle<String> s1, int offset1, int len1,
 358                        Handle<String> s2, int offset2, int len2)
 359       : s1_(s1), offset1_(offset1), len1_(len1),
 360         s2_(s2), offset2_(offset2), len2_(len2) {
 361   }
 362   virtual int GetLength1() {
 363     return len1_;
 364   }
 365   virtual int GetLength2() {
 366     return len2_;
 367   }
 368   bool Equals(int index1, int index2) {
 369     return s1_->Get(offset1_ + index1) == s2_->Get(offset2_ + index2);
 370   }
 371
 372  private:
 373   Handle<String> s1_;
 374   int offset1_;
 375   int len1_;
 376   Handle<String> s2_;
 377   int offset2_;
 378   int len2_;
 379 };
 380
 381
 382 // Stores compare result in JSArray. Converts substring positions
 383 // to absolute positions.
 384 class TokensCompareOutput : public Comparator::Output {
 385  public:
 386   TokensCompareOutput(CompareOutputArrayWriter* array_writer,
 387                       int offset1, int offset2)
 388         : array_writer_(array_writer), offset1_(offset1), offset2_(offset2) {
 389   }
 390
 391   void AddChunk(int pos1, int pos2, int len1, int len2) {
 392     array_writer_->WriteChunk(pos1 + offset1_, pos2 + offset2_, len1, len2);
 393   }
 394
 395  private:
 396   CompareOutputArrayWriter* array_writer_;
 397   int offset1_;
 398   int offset2_;
 399 };
 400
 401
 402 // Wraps raw n-elements line_ends array as a list of n+1 lines. The last line
 403 // never has terminating new line character.
 404 class LineEndsWrapper {
 405  public:
 406   explicit LineEndsWrapper(Handle<String> string)
 407       : ends_array_(String::CalculateLineEnds(string, false)),
 408         string_len_(string->length()) {
 409   }
 410   int length() {
 411     return ends_array_->length() + 1;
 412   }
 413   // Returns start for any line including start of the imaginary line after
 414   // the last line.
 415   int GetLineStart(int index) {
 416     if (index == 0) {
 417       return 0;
 418     } else {
 419       return GetLineEnd(index - 1);
 420     }
 421   }
 422   int GetLineEnd(int index) {
 423     if (index == ends_array_->length()) {
 424       // End of the last line is always an end of the whole string.
 425       // If the string ends with a new line character, the last line is an
 426       // empty string after this character.
 427       return string_len_;
 428     } else {
 429       return GetPosAfterNewLine(index);
 430     }
 431   }
 432
 433  private:
 434   Handle<FixedArray> ends_array_;
 435   int string_len_;
 436
 437   int GetPosAfterNewLine(int index) {
 438     return Smi::cast(ends_array_->get(index))->value() + 1;
 439   }
 440 };
 441
 442
 443 // Represents 2 strings as 2 arrays of lines.
 444 class LineArrayCompareInput : public SubrangableInput {
 445  public:
 446   LineArrayCompareInput(Handle<String> s1, Handle<String> s2,
 447                         LineEndsWrapper line_ends1, LineEndsWrapper line_ends2)
 448       : s1_(s1), s2_(s2), line_ends1_(line_ends1),
 449         line_ends2_(line_ends2),
 450         subrange_offset1_(0), subrange_offset2_(0),
 451         subrange_len1_(line_ends1_.length()),
 452         subrange_len2_(line_ends2_.length()) {
 453   }
 454   int GetLength1() {
 455     return subrange_len1_;
 456   }
 457   int GetLength2() {
 458     return subrange_len2_;
 459   }
 460   bool Equals(int index1, int index2) {
 461     index1 += subrange_offset1_;
 462     index2 += subrange_offset2_;
 463
 464     int line_start1 = line_ends1_.GetLineStart(index1);
 465     int line_start2 = line_ends2_.GetLineStart(index2);
 466     int line_end1 = line_ends1_.GetLineEnd(index1);
 467     int line_end2 = line_ends2_.GetLineEnd(index2);
 468     int len1 = line_end1 - line_start1;
 469     int len2 = line_end2 - line_start2;
 470     if (len1 != len2) {
 471       return false;
 472     }
 473     return CompareSubstrings(s1_, line_start1, s2_, line_start2,
 474                              len1);
 475   }
 476   void SetSubrange1(int offset, int len) {
 477     subrange_offset1_ = offset;
 478     subrange_len1_ = len;
 479   }
 480   void SetSubrange2(int offset, int len) {
 481     subrange_offset2_ = offset;
 482     subrange_len2_ = len;
 483   }
 484
 485  private:
 486   Handle<String> s1_;
 487   Handle<String> s2_;
 488   LineEndsWrapper line_ends1_;
 489   LineEndsWrapper line_ends2_;
 490   int subrange_offset1_;
 491   int subrange_offset2_;
 492   int subrange_len1_;
 493   int subrange_len2_;
 494 };
 495
 496
 497 // Stores compare result in JSArray. For each chunk tries to conduct
 498 // a fine-grained nested diff token-wise.
 499 class TokenizingLineArrayCompareOutput : public SubrangableOutput {
 500  public:
 501   TokenizingLineArrayCompareOutput(LineEndsWrapper line_ends1,
 502                                    LineEndsWrapper line_ends2,
 503                                    Handle<String> s1, Handle<String> s2)
 504       : array_writer_(s1->GetIsolate()),
 505         line_ends1_(line_ends1), line_ends2_(line_ends2), s1_(s1), s2_(s2),
 506         subrange_offset1_(0), subrange_offset2_(0) {
 507   }
 508
 509   void AddChunk(int line_pos1, int line_pos2, int line_len1, int line_len2) {
 510     line_pos1 += subrange_offset1_;
 511     line_pos2 += subrange_offset2_;
 512
 513     int char_pos1 = line_ends1_.GetLineStart(line_pos1);
 514     int char_pos2 = line_ends2_.GetLineStart(line_pos2);
 515     int char_len1 = line_ends1_.GetLineStart(line_pos1 + line_len1) - char_pos1;
 516     int char_len2 = line_ends2_.GetLineStart(line_pos2 + line_len2) - char_pos2;
 517
 518     if (char_len1 < CHUNK_LEN_LIMIT && char_len2 < CHUNK_LEN_LIMIT) {
 519       // Chunk is small enough to conduct a nested token-level diff.
 520       HandleScope subTaskScope(s1_->GetIsolate());
 521
 522       TokensCompareInput tokens_input(s1_, char_pos1, char_len1,
 523                                       s2_, char_pos2, char_len2);
 524       TokensCompareOutput tokens_output(&array_writer_, char_pos1,
 525                                           char_pos2);
 526
 527       Comparator::CalculateDifference(&tokens_input, &tokens_output);
 528     } else {
 529       array_writer_.WriteChunk(char_pos1, char_pos2, char_len1, char_len2);
 530     }
 531   }
 532   void SetSubrange1(int offset, int len) {
 533     subrange_offset1_ = offset;
 534   }
 535   void SetSubrange2(int offset, int len) {
 536     subrange_offset2_ = offset;
 537   }
 538
 539   Handle<JSArray> GetResult() {
 540     return array_writer_.GetResult();
 541   }
 542
 543  private:
 544   static const int CHUNK_LEN_LIMIT = 800;
 545
 546   CompareOutputArrayWriter array_writer_;
 547   LineEndsWrapper line_ends1_;
 548   LineEndsWrapper line_ends2_;
 549   Handle<String> s1_;
 550   Handle<String> s2_;
 551   int subrange_offset1_;
 552   int subrange_offset2_;
 553 };
 554
 555
 556 Handle<JSArray> LiveEdit::CompareStrings(Handle<String> s1,
 557                                          Handle<String> s2) {
 558   s1 = String::Flatten(s1);
 559   s2 = String::Flatten(s2);
 560
 561   LineEndsWrapper line_ends1(s1);
 562   LineEndsWrapper line_ends2(s2);
 563
 564   LineArrayCompareInput input(s1, s2, line_ends1, line_ends2);
 565   TokenizingLineArrayCompareOutput output(line_ends1, line_ends2, s1, s2);
 566
 567   NarrowDownInput(&input, &output);
 568
 569   Comparator::CalculateDifference(&input, &output);
 570
 571   return output.GetResult();
 572 }
 573
 574
 575 // Unwraps JSValue object, returning its field "value"
 576 static Handle<Object> UnwrapJSValue(Handle<JSValue> jsValue) {
 577   return Handle<Object>(jsValue->value(), jsValue->GetIsolate());
 578 }
 579
 580
 581 // Wraps any object into a OpaqueReference, that will hide the object
 582 // from JavaScript.
 583 static Handle<JSValue> WrapInJSValue(Handle<HeapObject> object) {
 584   Isolate* isolate = object->GetIsolate();
 585   Handle<JSFunction> constructor = isolate->opaque_reference_function();
 586   Handle<JSValue> result =
 587       Handle<JSValue>::cast(isolate->factory()->NewJSObject(constructor));
 588   result->set_value(*object);
 589   return result;
 590 }
 591
 592
 593 static Handle<SharedFunctionInfo> UnwrapSharedFunctionInfoFromJSValue(
 594     Handle<JSValue> jsValue) {
 595   Object* shared = jsValue->value();
 596   CHECK(shared->IsSharedFunctionInfo());
 597   return Handle<SharedFunctionInfo>(SharedFunctionInfo::cast(shared));
 598 }
 599
 600
 601 static int GetArrayLength(Handle<JSArray> array) {
 602   Object* length = array->length();
 603   CHECK(length->IsSmi());
 604   return Smi::cast(length)->value();
 605 }
 606
 607
 608 void FunctionInfoWrapper::SetInitialProperties(Handle<String> name,
 609                                                int start_position,
 610                                                int end_position, int param_num,
 611                                                int literal_count,
 612                                                int parent_index) {
 613   HandleScope scope(isolate());
 614   this->SetField(kFunctionNameOffset_, name);
 615   this->SetSmiValueField(kStartPositionOffset_, start_position);
 616   this->SetSmiValueField(kEndPositionOffset_, end_position);
 617   this->SetSmiValueField(kParamNumOffset_, param_num);
 618   this->SetSmiValueField(kLiteralNumOffset_, literal_count);
 619   this->SetSmiValueField(kParentIndexOffset_, parent_index);
 620 }
 621
 622
 623 void FunctionInfoWrapper::SetFunctionCode(Handle<Code> function_code,
 624                                           Handle<HeapObject> code_scope_info) {
 625   Handle<JSValue> code_wrapper = WrapInJSValue(function_code);
 626   this->SetField(kCodeOffset_, code_wrapper);
 627
 628   Handle<JSValue> scope_wrapper = WrapInJSValue(code_scope_info);
 629   this->SetField(kCodeScopeInfoOffset_, scope_wrapper);
 630 }
 631
 632
 633 void FunctionInfoWrapper::SetSharedFunctionInfo(
 634     Handle<SharedFunctionInfo> info) {
 635   Handle<JSValue> info_holder = WrapInJSValue(info);
 636   this->SetField(kSharedFunctionInfoOffset_, info_holder);
 637 }
 638
 639
 640 Handle<Code> FunctionInfoWrapper::GetFunctionCode() {
 641   Handle<Object> element = this->GetField(kCodeOffset_);
 642   Handle<JSValue> value_wrapper = Handle<JSValue>::cast(element);
 643   Handle<Object> raw_result = UnwrapJSValue(value_wrapper);
 644   CHECK(raw_result->IsCode());
 645   return Handle<Code>::cast(raw_result);
 646 }
 647
 648
 649 MaybeHandle<TypeFeedbackVector> FunctionInfoWrapper::GetFeedbackVector() {
 650   Handle<Object> element = this->GetField(kSharedFunctionInfoOffset_);
 651   if (element->IsJSValue()) {
 652     Handle<JSValue> value_wrapper = Handle<JSValue>::cast(element);
 653     Handle<Object> raw_result = UnwrapJSValue(value_wrapper);
 654     Handle<SharedFunctionInfo> shared =
 655         Handle<SharedFunctionInfo>::cast(raw_result);
 656     return Handle<TypeFeedbackVector>(shared->feedback_vector(), isolate());
 657   } else {
 658     // Scripts may never have a SharedFunctionInfo created.
 659     return MaybeHandle<TypeFeedbackVector>();
 660   }
 661 }
 662
 663
 664 Handle<Object> FunctionInfoWrapper::GetCodeScopeInfo() {
 665   Handle<Object> element = this->GetField(kCodeScopeInfoOffset_);
 666   return UnwrapJSValue(Handle<JSValue>::cast(element));
 667 }
 668
 669
 670 void SharedInfoWrapper::SetProperties(Handle<String> name,
 671                                       int start_position,
 672                                       int end_position,
 673                                       Handle<SharedFunctionInfo> info) {
 674   HandleScope scope(isolate());
 675   this->SetField(kFunctionNameOffset_, name);
 676   Handle<JSValue> info_holder = WrapInJSValue(info);
 677   this->SetField(kSharedInfoOffset_, info_holder);
 678   this->SetSmiValueField(kStartPositionOffset_, start_position);
 679   this->SetSmiValueField(kEndPositionOffset_, end_position);
 680 }
 681
 682
 683 Handle<SharedFunctionInfo> SharedInfoWrapper::GetInfo() {
 684   Handle<Object> element = this->GetField(kSharedInfoOffset_);
 685   Handle<JSValue> value_wrapper = Handle<JSValue>::cast(element);
 686   return UnwrapSharedFunctionInfoFromJSValue(value_wrapper);
 687 }
 688
 689
 690 class FunctionInfoListener {
 691  public:
 692   explicit FunctionInfoListener(Isolate* isolate) {
 693     current_parent_index_ = -1;
 694     len_ = 0;
 695     result_ = isolate->factory()->NewJSArray(10);
 696   }
 697
 698   void FunctionStarted(FunctionLiteral* fun) {
 699     HandleScope scope(isolate());
 700     FunctionInfoWrapper info = FunctionInfoWrapper::Create(isolate());
 701     info.SetInitialProperties(fun->name(), fun->start_position(),
 702                               fun->end_position(), fun->parameter_count(),
 703                               fun->materialized_literal_count(),
 704                               current_parent_index_);
 705     current_parent_index_ = len_;
 706     SetElementSloppy(result_, len_, info.GetJSArray());
 707     len_++;
 708   }
 709
 710   void FunctionDone() {
 711     HandleScope scope(isolate());
 712     FunctionInfoWrapper info =
 713         FunctionInfoWrapper::cast(
 714             *Object::GetElement(
 715                 isolate(), result_, current_parent_index_).ToHandleChecked());
 716     current_parent_index_ = info.GetParentIndex();
 717   }
 718
 719   // Saves only function code, because for a script function we
 720   // may never create a SharedFunctionInfo object.
 721   void FunctionCode(Handle<Code> function_code) {
 722     FunctionInfoWrapper info =
 723         FunctionInfoWrapper::cast(
 724             *Object::GetElement(
 725                 isolate(), result_, current_parent_index_).ToHandleChecked());
 726     info.SetFunctionCode(function_code,
 727                          Handle<HeapObject>(isolate()->heap()->null_value()));
 728   }
 729
 730   // Saves full information about a function: its code, its scope info
 731   // and a SharedFunctionInfo object.
 732   void FunctionInfo(Handle<SharedFunctionInfo> shared, Scope* scope,
 733                     Zone* zone) {
 734     if (!shared->IsSharedFunctionInfo()) {
 735       return;
 736     }
 737     FunctionInfoWrapper info =
 738         FunctionInfoWrapper::cast(
 739             *Object::GetElement(
 740                 isolate(), result_, current_parent_index_).ToHandleChecked());
 741     info.SetFunctionCode(Handle<Code>(shared->code()),
 742                          Handle<HeapObject>(shared->scope_info()));
 743     info.SetSharedFunctionInfo(shared);
 744
 745     Handle<Object> scope_info_list = SerializeFunctionScope(scope, zone);
 746     info.SetFunctionScopeInfo(scope_info_list);
 747   }
 748
 749   Handle<JSArray> GetResult() { return result_; }
 750
 751  private:
 752   Isolate* isolate() const { return result_->GetIsolate(); }
 753
 754   Handle<Object> SerializeFunctionScope(Scope* scope, Zone* zone) {
 755     Handle<JSArray> scope_info_list = isolate()->factory()->NewJSArray(10);
 756     int scope_info_length = 0;
 757
 758     // Saves some description of scope. It stores name and indexes of
 759     // variables in the whole scope chain. Null-named slots delimit
 760     // scopes of this chain.
 761     Scope* current_scope = scope;
 762     while (current_scope != NULL) {
 763       HandleScope handle_scope(isolate());
 764       ZoneList<Variable*> stack_list(current_scope->StackLocalCount(), zone);
 765       ZoneList<Variable*> context_list(
 766           current_scope->ContextLocalCount(), zone);
 767       current_scope->CollectStackAndContextLocals(&stack_list, &context_list);
 768       context_list.Sort(&Variable::CompareIndex);
 769
 770       for (int i = 0; i < context_list.length(); i++) {
 771         SetElementSloppy(scope_info_list,
 772                          scope_info_length,
 773                          context_list[i]->name());
 774         scope_info_length++;
 775         SetElementSloppy(
 776             scope_info_list,
 777             scope_info_length,
 778             Handle<Smi>(Smi::FromInt(context_list[i]->index()), isolate()));
 779         scope_info_length++;
 780       }
 781       SetElementSloppy(scope_info_list,
 782                        scope_info_length,
 783                        Handle<Object>(isolate()->heap()->null_value(),
 784                                       isolate()));
 785       scope_info_length++;
 786
 787       current_scope = current_scope->outer_scope();
 788     }
 789
 790     return scope_info_list;
 791   }
 792
 793   Handle<JSArray> result_;
 794   int len_;
 795   int current_parent_index_;
 796 };
 797
 798
 799 void LiveEdit::InitializeThreadLocal(Debug* debug) {
 800   debug->thread_local_.frame_drop_mode_ = LiveEdit::FRAMES_UNTOUCHED;
 801 }
 802
 803
 804 bool LiveEdit::SetAfterBreakTarget(Debug* debug) {
 805   Code* code = NULL;
 806   Isolate* isolate = debug->isolate_;
 807   switch (debug->thread_local_.frame_drop_mode_) {
 808     case FRAMES_UNTOUCHED:
 809       return false;
 810     case FRAME_DROPPED_IN_IC_CALL:
 811       // We must have been calling IC stub. Do not go there anymore.
 812       code = isolate->builtins()->builtin(Builtins::kPlainReturn_LiveEdit);
 813       break;
 814     case FRAME_DROPPED_IN_DEBUG_SLOT_CALL:
 815       // Debug break slot stub does not return normally, instead it manually
 816       // cleans the stack and jumps. We should patch the jump address.
 817       code = isolate->builtins()->builtin(Builtins::kFrameDropper_LiveEdit);
 818       break;
 819     case FRAME_DROPPED_IN_DIRECT_CALL:
 820       // Nothing to do, after_break_target is not used here.
 821       return true;
 822     case FRAME_DROPPED_IN_RETURN_CALL:
 823       code = isolate->builtins()->builtin(Builtins::kFrameDropper_LiveEdit);
 824       break;
 825     case CURRENTLY_SET_MODE:
 826       UNREACHABLE();
 827       break;
 828   }
 829   debug->after_break_target_ = code->entry();
 830   return true;
 831 }
 832
 833
 834 MaybeHandle<JSArray> LiveEdit::GatherCompileInfo(Handle<Script> script,
 835                                                  Handle<String> source) {
 836   Isolate* isolate = script->GetIsolate();
 837
 838   FunctionInfoListener listener(isolate);
 839   Handle<Object> original_source =
 840       Handle<Object>(script->source(), isolate);
 841   script->set_source(*source);
 842   isolate->set_active_function_info_listener(&listener);
 843
 844   {
 845     // Creating verbose TryCatch from public API is currently the only way to
 846     // force code save location. We do not use this the object directly.
 847     v8::TryCatch try_catch;
 848     try_catch.SetVerbose(true);
 849
 850     // A logical 'try' section.
 851     Compiler::CompileForLiveEdit(script);
 852   }
 853
 854   // A logical 'catch' section.
 855   Handle<JSObject> rethrow_exception;
 856   if (isolate->has_pending_exception()) {
 857     Handle<Object> exception(isolate->pending_exception(), isolate);
 858     MessageLocation message_location = isolate->GetMessageLocation();
 859
 860     isolate->clear_pending_message();
 861     isolate->clear_pending_exception();
 862
 863     // If possible, copy positions from message object to exception object.
 864     if (exception->IsJSObject() && !message_location.script().is_null()) {
 865       rethrow_exception = Handle<JSObject>::cast(exception);
 866
 867       Factory* factory = isolate->factory();
 868       Handle<String> start_pos_key = factory->InternalizeOneByteString(
 869           STATIC_CHAR_VECTOR("startPosition"));
 870       Handle<String> end_pos_key =
 871           factory->InternalizeOneByteString(STATIC_CHAR_VECTOR("endPosition"));
 872       Handle<String> script_obj_key =
 873           factory->InternalizeOneByteString(STATIC_CHAR_VECTOR("scriptObject"));
 874       Handle<Smi> start_pos(
 875           Smi::FromInt(message_location.start_pos()), isolate);
 876       Handle<Smi> end_pos(Smi::FromInt(message_location.end_pos()), isolate);
 877       Handle<JSObject> script_obj =
 878           Script::GetWrapper(message_location.script());
 879       Object::SetProperty(rethrow_exception, start_pos_key, start_pos, SLOPPY)
 880           .Assert();
 881       Object::SetProperty(rethrow_exception, end_pos_key, end_pos, SLOPPY)
 882           .Assert();
 883       Object::SetProperty(rethrow_exception, script_obj_key, script_obj, SLOPPY)
 884           .Assert();
 885     }
 886   }
 887
 888   // A logical 'finally' section.
 889   isolate->set_active_function_info_listener(NULL);
 890   script->set_source(*original_source);
 891
 892   if (rethrow_exception.is_null()) {
 893     return listener.GetResult();
 894   } else {
 895     return isolate->Throw<JSArray>(rethrow_exception);
 896   }
 897 }
 898
 899
 900 void LiveEdit::WrapSharedFunctionInfos(Handle<JSArray> array) {
 901   Isolate* isolate = array->GetIsolate();
 902   HandleScope scope(isolate);
 903   int len = GetArrayLength(array);
 904   for (int i = 0; i < len; i++) {
 905     Handle<SharedFunctionInfo> info(
 906         SharedFunctionInfo::cast(
 907             *Object::GetElement(isolate, array, i).ToHandleChecked()));
 908     SharedInfoWrapper info_wrapper = SharedInfoWrapper::Create(isolate);
 909     Handle<String> name_handle(String::cast(info->name()));
 910     info_wrapper.SetProperties(name_handle, info->start_position(),
 911                                info->end_position(), info);
 912     SetElementSloppy(array, i, info_wrapper.GetJSArray());
 913   }
 914 }
 915
 916
 917 // Visitor that finds all references to a particular code object,
 918 // including "CODE_TARGET" references in other code objects and replaces
 919 // them on the fly.
 920 class ReplacingVisitor : public ObjectVisitor {
 921  public:
 922   explicit ReplacingVisitor(Code* original, Code* substitution)
 923     : original_(original), substitution_(substitution) {
 924   }
 925
 926   virtual void VisitPointers(Object** start, Object** end) {
 927     for (Object** p = start; p < end; p++) {
 928       if (*p == original_) {
 929         *p = substitution_;
 930       }
 931     }
 932   }
 933
 934   virtual void VisitCodeEntry(Address entry) {
 935     if (Code::GetObjectFromEntryAddress(entry) == original_) {
 936       Address substitution_entry = substitution_->instruction_start();
 937       Memory::Address_at(entry) = substitution_entry;
 938     }
 939   }
 940
 941   virtual void VisitCodeTarget(RelocInfo* rinfo) {
 942     if (RelocInfo::IsCodeTarget(rinfo->rmode()) &&
 943         Code::GetCodeFromTargetAddress(rinfo->target_address()) == original_) {
 944       Address substitution_entry = substitution_->instruction_start();
 945       rinfo->set_target_address(substitution_entry);
 946     }
 947   }
 948
 949   virtual void VisitDebugTarget(RelocInfo* rinfo) {
 950     VisitCodeTarget(rinfo);
 951   }
 952
 953  private:
 954   Code* original_;
 955   Code* substitution_;
 956 };
 957
 958
 959 // Finds all references to original and replaces them with substitution.
 960 static void ReplaceCodeObject(Handle<Code> original,
 961                               Handle<Code> substitution) {
 962   // Perform a full GC in order to ensure that we are not in the middle of an
 963   // incremental marking phase when we are replacing the code object.
 964   // Since we are not in an incremental marking phase we can write pointers
 965   // to code objects (that are never in new space) without worrying about
 966   // write barriers.
 967   Heap* heap = original->GetHeap();
 968   HeapIterator iterator(heap);
 969
 970   DCHECK(!heap->InNewSpace(*substitution));
 971
 972   ReplacingVisitor visitor(*original, *substitution);
 973
 974   // Iterate over all roots. Stack frames may have pointer into original code,
 975   // so temporary replace the pointers with offset numbers
 976   // in prologue/epilogue.
 977   heap->IterateRoots(&visitor, VISIT_ALL);
 978
 979   // Now iterate over all pointers of all objects, including code_target
 980   // implicit pointers.
 981   for (HeapObject* obj = iterator.next(); obj != NULL; obj = iterator.next()) {
 982     obj->Iterate(&visitor);
 983   }
 984 }
 985
 986
 987 // Patch function literals.
 988 // Name 'literals' is a misnomer. Rather it's a cache for complex object
 989 // boilerplates and for a native context. We must clean cached values.
 990 // Additionally we may need to allocate a new array if number of literals
 991 // changed.
 992 class LiteralFixer {
 993  public:
 994   static void PatchLiterals(FunctionInfoWrapper* compile_info_wrapper,
 995                             Handle<SharedFunctionInfo> shared_info,
 996                             Isolate* isolate) {
 997     int new_literal_count = compile_info_wrapper->GetLiteralCount();
 998     if (new_literal_count > 0) {
 999       new_literal_count += JSFunction::kLiteralsPrefixSize;
1000     }
1001     int old_literal_count = shared_info->num_literals();
1002
1003     if (old_literal_count == new_literal_count) {
1004       // If literal count didn't change, simply go over all functions
1005       // and clear literal arrays.
1006       ClearValuesVisitor visitor;
1007       IterateJSFunctions(shared_info, &visitor);
1008     } else {
1009       // When literal count changes, we have to create new array instances.
1010       // Since we cannot create instances when iterating heap, we should first
1011       // collect all functions and fix their literal arrays.
1012       Handle<FixedArray> function_instances =
1013           CollectJSFunctions(shared_info, isolate);
1014       for (int i = 0; i < function_instances->length(); i++) {
1015         Handle<JSFunction> fun(JSFunction::cast(function_instances->get(i)));
1016         Handle<FixedArray> old_literals(fun->literals());
1017         Handle<FixedArray> new_literals =
1018             isolate->factory()->NewFixedArray(new_literal_count);
1019         if (new_literal_count > 0) {
1020           Handle<Context> native_context;
1021           if (old_literals->length() >
1022               JSFunction::kLiteralNativeContextIndex) {
1023             native_context = Handle<Context>(
1024                 JSFunction::NativeContextFromLiterals(fun->literals()));
1025           } else {
1026             native_context = Handle<Context>(fun->context()->native_context());
1027           }
1028           new_literals->set(JSFunction::kLiteralNativeContextIndex,
1029               *native_context);
1030         }
1031         fun->set_literals(*new_literals);
1032       }
1033
1034       shared_info->set_num_literals(new_literal_count);
1035     }
1036   }
1037
1038  private:
1039   // Iterates all function instances in the HEAP that refers to the
1040   // provided shared_info.
1041   template<typename Visitor>
1042   static void IterateJSFunctions(Handle<SharedFunctionInfo> shared_info,
1043                                  Visitor* visitor) {
1044     HeapIterator iterator(shared_info->GetHeap());
1045     for (HeapObject* obj = iterator.next(); obj != NULL;
1046         obj = iterator.next()) {
1047       if (obj->IsJSFunction()) {
1048         JSFunction* function = JSFunction::cast(obj);
1049         if (function->shared() == *shared_info) {
1050           visitor->visit(function);
1051         }
1052       }
1053     }
1054   }
1055
1056   // Finds all instances of JSFunction that refers to the provided shared_info
1057   // and returns array with them.
1058   static Handle<FixedArray> CollectJSFunctions(
1059       Handle<SharedFunctionInfo> shared_info, Isolate* isolate) {
1060     CountVisitor count_visitor;
1061     count_visitor.count = 0;
1062     IterateJSFunctions(shared_info, &count_visitor);
1063     int size = count_visitor.count;
1064
1065     Handle<FixedArray> result = isolate->factory()->NewFixedArray(size);
1066     if (size > 0) {
1067       CollectVisitor collect_visitor(result);
1068       IterateJSFunctions(shared_info, &collect_visitor);
1069     }
1070     return result;
1071   }
1072
1073   class ClearValuesVisitor {
1074    public:
1075     void visit(JSFunction* fun) {
1076       FixedArray* literals = fun->literals();
1077       int len = literals->length();
1078       for (int j = JSFunction::kLiteralsPrefixSize; j < len; j++) {
1079         literals->set_undefined(j);
1080       }
1081     }
1082   };
1083
1084   class CountVisitor {
1085    public:
1086     void visit(JSFunction* fun) {
1087       count++;
1088     }
1089     int count;
1090   };
1091
1092   class CollectVisitor {
1093    public:
1094     explicit CollectVisitor(Handle<FixedArray> output)
1095         : m_output(output), m_pos(0) {}
1096
1097     void visit(JSFunction* fun) {
1098       m_output->set(m_pos, fun);
1099       m_pos++;
1100     }
1101    private:
1102     Handle<FixedArray> m_output;
1103     int m_pos;
1104   };
1105 };
1106
1107
1108 // Check whether the code is natural function code (not a lazy-compile stub
1109 // code).
1110 static bool IsJSFunctionCode(Code* code) {
1111   return code->kind() == Code::FUNCTION;
1112 }
1113
1114
1115 // Returns true if an instance of candidate were inlined into function's code.
1116 static bool IsInlined(JSFunction* function, SharedFunctionInfo* candidate) {
1117   DisallowHeapAllocation no_gc;
1118
1119   if (function->code()->kind() != Code::OPTIMIZED_FUNCTION) return false;
1120
1121   DeoptimizationInputData* data =
1122       DeoptimizationInputData::cast(function->code()->deoptimization_data());
1123
1124   if (data == function->GetIsolate()->heap()->empty_fixed_array()) {
1125     return false;
1126   }
1127
1128   FixedArray* literals = data->LiteralArray();
1129
1130   int inlined_count = data->InlinedFunctionCount()->value();
1131   for (int i = 0; i < inlined_count; ++i) {
1132     JSFunction* inlined = JSFunction::cast(literals->get(i));
1133     if (inlined->shared() == candidate) return true;
1134   }
1135
1136   return false;
1137 }
1138
1139
1140 // Marks code that shares the same shared function info or has inlined
1141 // code that shares the same function info.
1142 class DependentFunctionMarker: public OptimizedFunctionVisitor {
1143  public:
1144   SharedFunctionInfo* shared_info_;
1145   bool found_;
1146
1147   explicit DependentFunctionMarker(SharedFunctionInfo* shared_info)
1148     : shared_info_(shared_info), found_(false) { }
1149
1150   virtual void EnterContext(Context* context) { }  // Don't care.
1151   virtual void LeaveContext(Context* context)  { }  // Don't care.
1152   virtual void VisitFunction(JSFunction* function) {
1153     // It should be guaranteed by the iterator that everything is optimized.
1154     DCHECK(function->code()->kind() == Code::OPTIMIZED_FUNCTION);
1155     if (shared_info_ == function->shared() ||
1156         IsInlined(function, shared_info_)) {
1157       // Mark the code for deoptimization.
1158       function->code()->set_marked_for_deoptimization(true);
1159       found_ = true;
1160     }
1161   }
1162 };
1163
1164
1165 static void DeoptimizeDependentFunctions(SharedFunctionInfo* function_info) {
1166   DisallowHeapAllocation no_allocation;
1167   DependentFunctionMarker marker(function_info);
1168   // TODO(titzer): need to traverse all optimized code to find OSR code here.
1169   Deoptimizer::VisitAllOptimizedFunctions(function_info->GetIsolate(), &marker);
1170
1171   if (marker.found_) {
1172     // Only go through with the deoptimization if something was found.
1173     Deoptimizer::DeoptimizeMarkedCode(function_info->GetIsolate());
1174   }
1175 }
1176
1177
1178 void LiveEdit::ReplaceFunctionCode(
1179     Handle<JSArray> new_compile_info_array,
1180     Handle<JSArray> shared_info_array) {
1181   Isolate* isolate = new_compile_info_array->GetIsolate();
1182
1183   FunctionInfoWrapper compile_info_wrapper(new_compile_info_array);
1184   SharedInfoWrapper shared_info_wrapper(shared_info_array);
1185
1186   Handle<SharedFunctionInfo> shared_info = shared_info_wrapper.GetInfo();
1187
1188   if (IsJSFunctionCode(shared_info->code())) {
1189     Handle<Code> code = compile_info_wrapper.GetFunctionCode();
1190     ReplaceCodeObject(Handle<Code>(shared_info->code()), code);
1191     Handle<Object> code_scope_info = compile_info_wrapper.GetCodeScopeInfo();
1192     if (code_scope_info->IsFixedArray()) {
1193       shared_info->set_scope_info(ScopeInfo::cast(*code_scope_info));
1194     }
1195     shared_info->DisableOptimization(kLiveEdit);
1196     // Update the type feedback vector, if needed.
1197     MaybeHandle<TypeFeedbackVector> feedback_vector =
1198         compile_info_wrapper.GetFeedbackVector();
1199     if (!feedback_vector.is_null()) {
1200       shared_info->set_feedback_vector(*feedback_vector.ToHandleChecked());
1201     }
1202   }
1203
1204   if (shared_info->debug_info()->IsDebugInfo()) {
1205     Handle<DebugInfo> debug_info(DebugInfo::cast(shared_info->debug_info()));
1206     Handle<Code> new_original_code =
1207         isolate->factory()->CopyCode(compile_info_wrapper.GetFunctionCode());
1208     debug_info->set_original_code(*new_original_code);
1209   }
1210
1211   int start_position = compile_info_wrapper.GetStartPosition();
1212   int end_position = compile_info_wrapper.GetEndPosition();
1213   shared_info->set_start_position(start_position);
1214   shared_info->set_end_position(end_position);
1215
1216   LiteralFixer::PatchLiterals(&compile_info_wrapper, shared_info, isolate);
1217
1218   shared_info->set_construct_stub(
1219       isolate->builtins()->builtin(Builtins::kJSConstructStubGeneric));
1220
1221   DeoptimizeDependentFunctions(*shared_info);
1222   isolate->compilation_cache()->Remove(shared_info);
1223 }
1224
1225
1226 void LiveEdit::FunctionSourceUpdated(Handle<JSArray> shared_info_array) {
1227   SharedInfoWrapper shared_info_wrapper(shared_info_array);
1228   Handle<SharedFunctionInfo> shared_info = shared_info_wrapper.GetInfo();
1229
1230   DeoptimizeDependentFunctions(*shared_info);
1231   shared_info_array->GetIsolate()->compilation_cache()->Remove(shared_info);
1232 }
1233
1234
1235 void LiveEdit::SetFunctionScript(Handle<JSValue> function_wrapper,
1236                                  Handle<Object> script_handle) {
1237   Handle<SharedFunctionInfo> shared_info =
1238       UnwrapSharedFunctionInfoFromJSValue(function_wrapper);
1239   CHECK(script_handle->IsScript() || script_handle->IsUndefined());
1240   shared_info->set_script(*script_handle);
1241   shared_info->DisableOptimization(kLiveEdit);
1242
1243   function_wrapper->GetIsolate()->compilation_cache()->Remove(shared_info);
1244 }
1245
1246
1247 // For a script text change (defined as position_change_array), translates
1248 // position in unchanged text to position in changed text.
1249 // Text change is a set of non-overlapping regions in text, that have changed
1250 // their contents and length. It is specified as array of groups of 3 numbers:
1251 // (change_begin, change_end, change_end_new_position).
1252 // Each group describes a change in text; groups are sorted by change_begin.
1253 // Only position in text beyond any changes may be successfully translated.
1254 // If a positions is inside some region that changed, result is currently
1255 // undefined.
1256 static int TranslatePosition(int original_position,
1257                              Handle<JSArray> position_change_array) {
1258   int position_diff = 0;
1259   int array_len = GetArrayLength(position_change_array);
1260   Isolate* isolate = position_change_array->GetIsolate();
1261   // TODO(635): binary search may be used here
1262   for (int i = 0; i < array_len; i += 3) {
1263     HandleScope scope(isolate);
1264     Handle<Object> element = Object::GetElement(
1265         isolate, position_change_array, i).ToHandleChecked();
1266     CHECK(element->IsSmi());
1267     int chunk_start = Handle<Smi>::cast(element)->value();
1268     if (original_position < chunk_start) {
1269       break;
1270     }
1271     element = Object::GetElement(
1272         isolate, position_change_array, i + 1).ToHandleChecked();
1273     CHECK(element->IsSmi());
1274     int chunk_end = Handle<Smi>::cast(element)->value();
1275     // Position mustn't be inside a chunk.
1276     DCHECK(original_position >= chunk_end);
1277     element = Object::GetElement(
1278         isolate, position_change_array, i + 2).ToHandleChecked();
1279     CHECK(element->IsSmi());
1280     int chunk_changed_end = Handle<Smi>::cast(element)->value();
1281     position_diff = chunk_changed_end - chunk_end;
1282   }
1283
1284   return original_position + position_diff;
1285 }
1286
1287
1288 // Auto-growing buffer for writing relocation info code section. This buffer
1289 // is a simplified version of buffer from Assembler. Unlike Assembler, this
1290 // class is platform-independent and it works without dealing with instructions.
1291 // As specified by RelocInfo format, the buffer is filled in reversed order:
1292 // from upper to lower addresses.
1293 // It uses NewArray/DeleteArray for memory management.
1294 class RelocInfoBuffer {
1295  public:
1296   RelocInfoBuffer(int buffer_initial_capicity, byte* pc) {
1297     buffer_size_ = buffer_initial_capicity + kBufferGap;
1298     buffer_ = NewArray<byte>(buffer_size_);
1299
1300     reloc_info_writer_.Reposition(buffer_ + buffer_size_, pc);
1301   }
1302   ~RelocInfoBuffer() {
1303     DeleteArray(buffer_);
1304   }
1305
1306   // As specified by RelocInfo format, the buffer is filled in reversed order:
1307   // from upper to lower addresses.
1308   void Write(const RelocInfo* rinfo) {
1309     if (buffer_ + kBufferGap >= reloc_info_writer_.pos()) {
1310       Grow();
1311     }
1312     reloc_info_writer_.Write(rinfo);
1313   }
1314
1315   Vector<byte> GetResult() {
1316     // Return the bytes from pos up to end of buffer.
1317     int result_size =
1318         static_cast<int>((buffer_ + buffer_size_) - reloc_info_writer_.pos());
1319     return Vector<byte>(reloc_info_writer_.pos(), result_size);
1320   }
1321
1322  private:
1323   void Grow() {
1324     // Compute new buffer size.
1325     int new_buffer_size;
1326     if (buffer_size_ < 2 * KB) {
1327       new_buffer_size = 4 * KB;
1328     } else {
1329       new_buffer_size = 2 * buffer_size_;
1330     }
1331     // Some internal data structures overflow for very large buffers,
1332     // they must ensure that kMaximalBufferSize is not too large.
1333     if (new_buffer_size > kMaximalBufferSize) {
1334       V8::FatalProcessOutOfMemory("RelocInfoBuffer::GrowBuffer");
1335     }
1336
1337     // Set up new buffer.
1338     byte* new_buffer = NewArray<byte>(new_buffer_size);
1339
1340     // Copy the data.
1341     int curently_used_size =
1342         static_cast<int>(buffer_ + buffer_size_ - reloc_info_writer_.pos());
1343     MemMove(new_buffer + new_buffer_size - curently_used_size,
1344             reloc_info_writer_.pos(), curently_used_size);
1345
1346     reloc_info_writer_.Reposition(
1347         new_buffer + new_buffer_size - curently_used_size,
1348         reloc_info_writer_.last_pc());
1349
1350     DeleteArray(buffer_);
1351     buffer_ = new_buffer;
1352     buffer_size_ = new_buffer_size;
1353   }
1354
1355   RelocInfoWriter reloc_info_writer_;
1356   byte* buffer_;
1357   int buffer_size_;
1358
1359   static const int kBufferGap = RelocInfoWriter::kMaxSize;
1360   static const int kMaximalBufferSize = 512*MB;
1361 };
1362
1363
1364 // Patch positions in code (changes relocation info section) and possibly
1365 // returns new instance of code.
1366 static Handle<Code> PatchPositionsInCode(
1367     Handle<Code> code,
1368     Handle<JSArray> position_change_array) {
1369   Isolate* isolate = code->GetIsolate();
1370
1371   RelocInfoBuffer buffer_writer(code->relocation_size(),
1372                                 code->instruction_start());
1373
1374   {
1375     for (RelocIterator it(*code); !it.done(); it.next()) {
1376       RelocInfo* rinfo = it.rinfo();
1377       if (RelocInfo::IsPosition(rinfo->rmode())) {
1378         int position = static_cast<int>(rinfo->data());
1379         int new_position = TranslatePosition(position,
1380                                              position_change_array);
1381         if (position != new_position) {
1382           RelocInfo info_copy(rinfo->pc(), rinfo->rmode(), new_position, NULL);
1383           buffer_writer.Write(&info_copy);
1384           continue;
1385         }
1386       }
1387       if (RelocInfo::IsRealRelocMode(rinfo->rmode())) {
1388         buffer_writer.Write(it.rinfo());
1389       }
1390     }
1391   }
1392
1393   Vector<byte> buffer = buffer_writer.GetResult();
1394
1395   if (buffer.length() == code->relocation_size()) {
1396     // Simply patch relocation area of code.
1397     MemCopy(code->relocation_start(), buffer.start(), buffer.length());
1398     return code;
1399   } else {
1400     // Relocation info section now has different size. We cannot simply
1401     // rewrite it inside code object. Instead we have to create a new
1402     // code object.
1403     Handle<Code> result(isolate->factory()->CopyCode(code, buffer));
1404     return result;
1405   }
1406 }
1407
1408
1409 void LiveEdit::PatchFunctionPositions(Handle<JSArray> shared_info_array,
1410                                       Handle<JSArray> position_change_array) {
1411   SharedInfoWrapper shared_info_wrapper(shared_info_array);
1412   Handle<SharedFunctionInfo> info = shared_info_wrapper.GetInfo();
1413
1414   int old_function_start = info->start_position();
1415   int new_function_start = TranslatePosition(old_function_start,
1416                                              position_change_array);
1417   int new_function_end = TranslatePosition(info->end_position(),
1418                                            position_change_array);
1419   int new_function_token_pos =
1420       TranslatePosition(info->function_token_position(), position_change_array);
1421
1422   info->set_start_position(new_function_start);
1423   info->set_end_position(new_function_end);
1424   info->set_function_token_position(new_function_token_pos);
1425
1426   if (IsJSFunctionCode(info->code())) {
1427     // Patch relocation info section of the code.
1428     Handle<Code> patched_code = PatchPositionsInCode(Handle<Code>(info->code()),
1429                                                      position_change_array);
1430     if (*patched_code != info->code()) {
1431       // Replace all references to the code across the heap. In particular,
1432       // some stubs may refer to this code and this code may be being executed
1433       // on stack (it is safe to substitute the code object on stack, because
1434       // we only change the structure of rinfo and leave instructions
1435       // untouched).
1436       ReplaceCodeObject(Handle<Code>(info->code()), patched_code);
1437     }
1438   }
1439 }
1440
1441
1442 static Handle<Script> CreateScriptCopy(Handle<Script> original) {
1443   Isolate* isolate = original->GetIsolate();
1444
1445   Handle<String> original_source(String::cast(original->source()));
1446   Handle<Script> copy = isolate->factory()->NewScript(original_source);
1447
1448   copy->set_name(original->name());
1449   copy->set_line_offset(original->line_offset());
1450   copy->set_column_offset(original->column_offset());
1451   copy->set_type(original->type());
1452   copy->set_context_data(original->context_data());
1453   copy->set_eval_from_shared(original->eval_from_shared());
1454   copy->set_eval_from_instructions_offset(
1455       original->eval_from_instructions_offset());
1456
1457   // Copy all the flags, but clear compilation state.
1458   copy->set_flags(original->flags());
1459   copy->set_compilation_state(Script::COMPILATION_STATE_INITIAL);
1460
1461   return copy;
1462 }
1463
1464
1465 Handle<Object> LiveEdit::ChangeScriptSource(Handle<Script> original_script,
1466                                             Handle<String> new_source,
1467                                             Handle<Object> old_script_name) {
1468   Isolate* isolate = original_script->GetIsolate();
1469   Handle<Object> old_script_object;
1470   if (old_script_name->IsString()) {
1471     Handle<Script> old_script = CreateScriptCopy(original_script);
1472     old_script->set_name(String::cast(*old_script_name));
1473     old_script_object = old_script;
1474     isolate->debug()->OnAfterCompile(old_script);
1475   } else {
1476     old_script_object = isolate->factory()->null_value();
1477   }
1478
1479   original_script->set_source(*new_source);
1480
1481   // Drop line ends so that they will be recalculated.
1482   original_script->set_line_ends(isolate->heap()->undefined_value());
1483
1484   return old_script_object;
1485 }
1486
1487
1488
1489 void LiveEdit::ReplaceRefToNestedFunction(
1490     Handle<JSValue> parent_function_wrapper,
1491     Handle<JSValue> orig_function_wrapper,
1492     Handle<JSValue> subst_function_wrapper) {
1493
1494   Handle<SharedFunctionInfo> parent_shared =
1495       UnwrapSharedFunctionInfoFromJSValue(parent_function_wrapper);
1496   Handle<SharedFunctionInfo> orig_shared =
1497       UnwrapSharedFunctionInfoFromJSValue(orig_function_wrapper);
1498   Handle<SharedFunctionInfo> subst_shared =
1499       UnwrapSharedFunctionInfoFromJSValue(subst_function_wrapper);
1500
1501   for (RelocIterator it(parent_shared->code()); !it.done(); it.next()) {
1502     if (it.rinfo()->rmode() == RelocInfo::EMBEDDED_OBJECT) {
1503       if (it.rinfo()->target_object() == *orig_shared) {
1504         it.rinfo()->set_target_object(*subst_shared);
1505       }
1506     }
1507   }
1508 }
1509
1510
1511 // Check an activation against list of functions. If there is a function
1512 // that matches, its status in result array is changed to status argument value.
1513 static bool CheckActivation(Handle<JSArray> shared_info_array,
1514                             Handle<JSArray> result,
1515                             StackFrame* frame,
1516                             LiveEdit::FunctionPatchabilityStatus status) {
1517   if (!frame->is_java_script()) return false;
1518
1519   Handle<JSFunction> function(JavaScriptFrame::cast(frame)->function());
1520
1521   Isolate* isolate = shared_info_array->GetIsolate();
1522   int len = GetArrayLength(shared_info_array);
1523   for (int i = 0; i < len; i++) {
1524     HandleScope scope(isolate);
1525     Handle<Object> element =
1526         Object::GetElement(isolate, shared_info_array, i).ToHandleChecked();
1527     Handle<JSValue> jsvalue = Handle<JSValue>::cast(element);
1528     Handle<SharedFunctionInfo> shared =
1529         UnwrapSharedFunctionInfoFromJSValue(jsvalue);
1530
1531     if (function->shared() == *shared || IsInlined(*function, *shared)) {
1532       SetElementSloppy(result, i, Handle<Smi>(Smi::FromInt(status), isolate));
1533       return true;
1534     }
1535   }
1536   return false;
1537 }
1538
1539
1540 // Iterates over handler chain and removes all elements that are inside
1541 // frames being dropped.
1542 static bool FixTryCatchHandler(StackFrame* top_frame,
1543                                StackFrame* bottom_frame) {
1544   Address* pointer_address =
1545       &Memory::Address_at(top_frame->isolate()->get_address_from_id(
1546           Isolate::kHandlerAddress));
1547
1548   while (*pointer_address < top_frame->sp()) {
1549     pointer_address = &Memory::Address_at(*pointer_address);
1550   }
1551   Address* above_frame_address = pointer_address;
1552   while (*pointer_address < bottom_frame->fp()) {
1553     pointer_address = &Memory::Address_at(*pointer_address);
1554   }
1555   bool change = *above_frame_address != *pointer_address;
1556   *above_frame_address = *pointer_address;
1557   return change;
1558 }
1559
1560
1561 // Initializes an artificial stack frame. The data it contains is used for:
1562 //  a. successful work of frame dropper code which eventually gets control,
1563 //  b. being compatible with regular stack structure for various stack
1564 //     iterators.
1565 // Returns address of stack allocated pointer to restarted function,
1566 // the value that is called 'restarter_frame_function_pointer'. The value
1567 // at this address (possibly updated by GC) may be used later when preparing
1568 // 'step in' operation.
1569 // Frame structure (conforms InternalFrame structure):
1570 //   -- code
1571 //   -- SMI maker
1572 //   -- function (slot is called "context")
1573 //   -- frame base
1574 static Object** SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
1575                                        Handle<Code> code) {
1576   DCHECK(bottom_js_frame->is_java_script());
1577
1578   Address fp = bottom_js_frame->fp();
1579
1580   // Move function pointer into "context" slot.
1581   Memory::Object_at(fp + StandardFrameConstants::kContextOffset) =
1582       Memory::Object_at(fp + JavaScriptFrameConstants::kFunctionOffset);
1583
1584   Memory::Object_at(fp + InternalFrameConstants::kCodeOffset) = *code;
1585   Memory::Object_at(fp + StandardFrameConstants::kMarkerOffset) =
1586       Smi::FromInt(StackFrame::INTERNAL);
1587
1588   return reinterpret_cast<Object**>(&Memory::Object_at(
1589       fp + StandardFrameConstants::kContextOffset));
1590 }
1591
1592
1593 // Removes specified range of frames from stack. There may be 1 or more
1594 // frames in range. Anyway the bottom frame is restarted rather than dropped,
1595 // and therefore has to be a JavaScript frame.
1596 // Returns error message or NULL.
1597 static const char* DropFrames(Vector<StackFrame*> frames,
1598                               int top_frame_index,
1599                               int bottom_js_frame_index,
1600                               LiveEdit::FrameDropMode* mode,
1601                               Object*** restarter_frame_function_pointer) {
1602   if (!LiveEdit::kFrameDropperSupported) {
1603     return "Stack manipulations are not supported in this architecture.";
1604   }
1605
1606   StackFrame* pre_top_frame = frames[top_frame_index - 1];
1607   StackFrame* top_frame = frames[top_frame_index];
1608   StackFrame* bottom_js_frame = frames[bottom_js_frame_index];
1609
1610   DCHECK(bottom_js_frame->is_java_script());
1611
1612   // Check the nature of the top frame.
1613   Isolate* isolate = bottom_js_frame->isolate();
1614   Code* pre_top_frame_code = pre_top_frame->LookupCode();
1615   bool frame_has_padding = true;
1616   if (pre_top_frame_code->is_inline_cache_stub() &&
1617       pre_top_frame_code->is_debug_stub()) {
1618     // OK, we can drop inline cache calls.
1619     *mode = LiveEdit::FRAME_DROPPED_IN_IC_CALL;
1620   } else if (pre_top_frame_code ==
1621              isolate->builtins()->builtin(Builtins::kSlot_DebugBreak)) {
1622     // OK, we can drop debug break slot.
1623     *mode = LiveEdit::FRAME_DROPPED_IN_DEBUG_SLOT_CALL;
1624   } else if (pre_top_frame_code ==
1625              isolate->builtins()->builtin(Builtins::kFrameDropper_LiveEdit)) {
1626     // OK, we can drop our own code.
1627     pre_top_frame = frames[top_frame_index - 2];
1628     top_frame = frames[top_frame_index - 1];
1629     *mode = LiveEdit::CURRENTLY_SET_MODE;
1630     frame_has_padding = false;
1631   } else if (pre_top_frame_code ==
1632              isolate->builtins()->builtin(Builtins::kReturn_DebugBreak)) {
1633     *mode = LiveEdit::FRAME_DROPPED_IN_RETURN_CALL;
1634   } else if (pre_top_frame_code->kind() == Code::STUB &&
1635              CodeStub::GetMajorKey(pre_top_frame_code) == CodeStub::CEntry) {
1636     // Entry from our unit tests on 'debugger' statement.
1637     // It's fine, we support this case.
1638     *mode = LiveEdit::FRAME_DROPPED_IN_DIRECT_CALL;
1639     // We don't have a padding from 'debugger' statement call.
1640     // Here the stub is CEntry, it's not debug-only and can't be padded.
1641     // If anyone would complain, a proxy padded stub could be added.
1642     frame_has_padding = false;
1643   } else if (pre_top_frame->type() == StackFrame::ARGUMENTS_ADAPTOR) {
1644     // This must be adaptor that remain from the frame dropping that
1645     // is still on stack. A frame dropper frame must be above it.
1646     DCHECK(frames[top_frame_index - 2]->LookupCode() ==
1647            isolate->builtins()->builtin(Builtins::kFrameDropper_LiveEdit));
1648     pre_top_frame = frames[top_frame_index - 3];
1649     top_frame = frames[top_frame_index - 2];
1650     *mode = LiveEdit::CURRENTLY_SET_MODE;
1651     frame_has_padding = false;
1652   } else {
1653     return "Unknown structure of stack above changing function";
1654   }
1655
1656   Address unused_stack_top = top_frame->sp();
1657   int new_frame_size = LiveEdit::kFrameDropperFrameSize * kPointerSize;
1658   Address unused_stack_bottom = bottom_js_frame->fp()
1659       - new_frame_size + kPointerSize;  // Bigger address end is exclusive.
1660
1661   Address* top_frame_pc_address = top_frame->pc_address();
1662
1663   // top_frame may be damaged below this point. Do not used it.
1664   DCHECK(!(top_frame = NULL));
1665
1666   if (unused_stack_top > unused_stack_bottom) {
1667     if (frame_has_padding) {
1668       int shortage_bytes =
1669           static_cast<int>(unused_stack_top - unused_stack_bottom);
1670
1671       Address padding_start = pre_top_frame->fp() -
1672           LiveEdit::kFrameDropperFrameSize * kPointerSize;
1673
1674       Address padding_pointer = padding_start;
1675       Smi* padding_object = Smi::FromInt(LiveEdit::kFramePaddingValue);
1676       while (Memory::Object_at(padding_pointer) == padding_object) {
1677         padding_pointer -= kPointerSize;
1678       }
1679       int padding_counter =
1680           Smi::cast(Memory::Object_at(padding_pointer))->value();
1681       if (padding_counter * kPointerSize < shortage_bytes) {
1682         return "Not enough space for frame dropper frame "
1683             "(even with padding frame)";
1684       }
1685       Memory::Object_at(padding_pointer) =
1686           Smi::FromInt(padding_counter - shortage_bytes / kPointerSize);
1687
1688       StackFrame* pre_pre_frame = frames[top_frame_index - 2];
1689
1690       MemMove(padding_start + kPointerSize - shortage_bytes,
1691               padding_start + kPointerSize,
1692               LiveEdit::kFrameDropperFrameSize * kPointerSize);
1693
1694       pre_top_frame->UpdateFp(pre_top_frame->fp() - shortage_bytes);
1695       pre_pre_frame->SetCallerFp(pre_top_frame->fp());
1696       unused_stack_top -= shortage_bytes;
1697
1698       STATIC_ASSERT(sizeof(Address) == kPointerSize);
1699       top_frame_pc_address -= shortage_bytes / kPointerSize;
1700     } else {
1701       return "Not enough space for frame dropper frame";
1702     }
1703   }
1704
1705   // Committing now. After this point we should return only NULL value.
1706
1707   FixTryCatchHandler(pre_top_frame, bottom_js_frame);
1708   // Make sure FixTryCatchHandler is idempotent.
1709   DCHECK(!FixTryCatchHandler(pre_top_frame, bottom_js_frame));
1710
1711   Handle<Code> code = isolate->builtins()->FrameDropper_LiveEdit();
1712   *top_frame_pc_address = code->entry();
1713   pre_top_frame->SetCallerFp(bottom_js_frame->fp());
1714
1715   *restarter_frame_function_pointer =
1716       SetUpFrameDropperFrame(bottom_js_frame, code);
1717
1718   DCHECK((**restarter_frame_function_pointer)->IsJSFunction());
1719
1720   for (Address a = unused_stack_top;
1721       a < unused_stack_bottom;
1722       a += kPointerSize) {
1723     Memory::Object_at(a) = Smi::FromInt(0);
1724   }
1725
1726   return NULL;
1727 }
1728
1729
1730 // Describes a set of call frames that execute any of listed functions.
1731 // Finding no such frames does not mean error.
1732 class MultipleFunctionTarget {
1733  public:
1734   MultipleFunctionTarget(Handle<JSArray> shared_info_array,
1735       Handle<JSArray> result)
1736       : m_shared_info_array(shared_info_array),
1737         m_result(result) {}
1738   bool MatchActivation(StackFrame* frame,
1739       LiveEdit::FunctionPatchabilityStatus status) {
1740     return CheckActivation(m_shared_info_array, m_result, frame, status);
1741   }
1742   const char* GetNotFoundMessage() const {
1743     return NULL;
1744   }
1745  private:
1746   Handle<JSArray> m_shared_info_array;
1747   Handle<JSArray> m_result;
1748 };
1749
1750
1751 // Drops all call frame matched by target and all frames above them.
1752 template <typename TARGET>
1753 static const char* DropActivationsInActiveThreadImpl(Isolate* isolate,
1754                                                      TARGET& target,  // NOLINT
1755                                                      bool do_drop) {
1756   Debug* debug = isolate->debug();
1757   Zone zone;
1758   Vector<StackFrame*> frames = CreateStackMap(isolate, &zone);
1759
1760
1761   int top_frame_index = -1;
1762   int frame_index = 0;
1763   for (; frame_index < frames.length(); frame_index++) {
1764     StackFrame* frame = frames[frame_index];
1765     if (frame->id() == debug->break_frame_id()) {
1766       top_frame_index = frame_index;
1767       break;
1768     }
1769     if (target.MatchActivation(
1770             frame, LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE)) {
1771       // We are still above break_frame. It is not a target frame,
1772       // it is a problem.
1773       return "Debugger mark-up on stack is not found";
1774     }
1775   }
1776
1777   if (top_frame_index == -1) {
1778     // We haven't found break frame, but no function is blocking us anyway.
1779     return target.GetNotFoundMessage();
1780   }
1781
1782   bool target_frame_found = false;
1783   int bottom_js_frame_index = top_frame_index;
1784   bool non_droppable_frame_found = false;
1785   LiveEdit::FunctionPatchabilityStatus non_droppable_reason;
1786
1787   for (; frame_index < frames.length(); frame_index++) {
1788     StackFrame* frame = frames[frame_index];
1789     if (frame->is_exit()) {
1790       non_droppable_frame_found = true;
1791       non_droppable_reason = LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE;
1792       break;
1793     }
1794     if (frame->is_java_script() &&
1795         JavaScriptFrame::cast(frame)->function()->shared()->is_generator()) {
1796       non_droppable_frame_found = true;
1797       non_droppable_reason = LiveEdit::FUNCTION_BLOCKED_UNDER_GENERATOR;
1798       break;
1799     }
1800     if (target.MatchActivation(
1801             frame, LiveEdit::FUNCTION_BLOCKED_ON_ACTIVE_STACK)) {
1802       target_frame_found = true;
1803       bottom_js_frame_index = frame_index;
1804     }
1805   }
1806
1807   if (non_droppable_frame_found) {
1808     // There is a C or generator frame on stack.  We can't drop C frames, and we
1809     // can't restart generators.  Check that there are no target frames below
1810     // them.
1811     for (; frame_index < frames.length(); frame_index++) {
1812       StackFrame* frame = frames[frame_index];
1813       if (frame->is_java_script()) {
1814         if (target.MatchActivation(frame, non_droppable_reason)) {
1815           // Fail.
1816           return NULL;
1817         }
1818       }
1819     }
1820   }
1821
1822   if (!do_drop) {
1823     // We are in check-only mode.
1824     return NULL;
1825   }
1826
1827   if (!target_frame_found) {
1828     // Nothing to drop.
1829     return target.GetNotFoundMessage();
1830   }
1831
1832   LiveEdit::FrameDropMode drop_mode = LiveEdit::FRAMES_UNTOUCHED;
1833   Object** restarter_frame_function_pointer = NULL;
1834   const char* error_message = DropFrames(frames, top_frame_index,
1835                                          bottom_js_frame_index, &drop_mode,
1836                                          &restarter_frame_function_pointer);
1837
1838   if (error_message != NULL) {
1839     return error_message;
1840   }
1841
1842   // Adjust break_frame after some frames has been dropped.
1843   StackFrame::Id new_id = StackFrame::NO_ID;
1844   for (int i = bottom_js_frame_index + 1; i < frames.length(); i++) {
1845     if (frames[i]->type() == StackFrame::JAVA_SCRIPT) {
1846       new_id = frames[i]->id();
1847       break;
1848     }
1849   }
1850   debug->FramesHaveBeenDropped(
1851       new_id, drop_mode, restarter_frame_function_pointer);
1852   return NULL;
1853 }
1854
1855
1856 // Fills result array with statuses of functions. Modifies the stack
1857 // removing all listed function if possible and if do_drop is true.
1858 static const char* DropActivationsInActiveThread(
1859     Handle<JSArray> shared_info_array, Handle<JSArray> result, bool do_drop) {
1860   MultipleFunctionTarget target(shared_info_array, result);
1861   Isolate* isolate = shared_info_array->GetIsolate();
1862
1863   const char* message =
1864       DropActivationsInActiveThreadImpl(isolate, target, do_drop);
1865   if (message) {
1866     return message;
1867   }
1868
1869   int array_len = GetArrayLength(shared_info_array);
1870
1871   // Replace "blocked on active" with "replaced on active" status.
1872   for (int i = 0; i < array_len; i++) {
1873     Handle<Object> obj =
1874         Object::GetElement(isolate, result, i).ToHandleChecked();
1875     if (*obj == Smi::FromInt(LiveEdit::FUNCTION_BLOCKED_ON_ACTIVE_STACK)) {
1876       Handle<Object> replaced(
1877           Smi::FromInt(LiveEdit::FUNCTION_REPLACED_ON_ACTIVE_STACK), isolate);
1878       SetElementSloppy(result, i, replaced);
1879     }
1880   }
1881   return NULL;
1882 }
1883
1884
1885 bool LiveEdit::FindActiveGenerators(Handle<FixedArray> shared_info_array,
1886                                     Handle<FixedArray> result,
1887                                     int len) {
1888   Isolate* isolate = shared_info_array->GetIsolate();
1889   bool found_suspended_activations = false;
1890
1891   DCHECK_LE(len, result->length());
1892
1893   FunctionPatchabilityStatus active = FUNCTION_BLOCKED_ACTIVE_GENERATOR;
1894
1895   Heap* heap = isolate->heap();
1896   HeapIterator iterator(heap);
1897   HeapObject* obj = NULL;
1898   while ((obj = iterator.next()) != NULL) {
1899     if (!obj->IsJSGeneratorObject()) continue;
1900
1901     JSGeneratorObject* gen = JSGeneratorObject::cast(obj);
1902     if (gen->is_closed()) continue;
1903
1904     HandleScope scope(isolate);
1905
1906     for (int i = 0; i < len; i++) {
1907       Handle<JSValue> jsvalue =
1908           Handle<JSValue>::cast(FixedArray::get(shared_info_array, i));
1909       Handle<SharedFunctionInfo> shared =
1910           UnwrapSharedFunctionInfoFromJSValue(jsvalue);
1911
1912       if (gen->function()->shared() == *shared) {
1913         result->set(i, Smi::FromInt(active));
1914         found_suspended_activations = true;
1915       }
1916     }
1917   }
1918
1919   return found_suspended_activations;
1920 }
1921
1922
1923 class InactiveThreadActivationsChecker : public ThreadVisitor {
1924  public:
1925   InactiveThreadActivationsChecker(Handle<JSArray> shared_info_array,
1926                                    Handle<JSArray> result)
1927       : shared_info_array_(shared_info_array), result_(result),
1928         has_blocked_functions_(false) {
1929   }
1930   void VisitThread(Isolate* isolate, ThreadLocalTop* top) {
1931     for (StackFrameIterator it(isolate, top); !it.done(); it.Advance()) {
1932       has_blocked_functions_ |= CheckActivation(
1933           shared_info_array_, result_, it.frame(),
1934           LiveEdit::FUNCTION_BLOCKED_ON_OTHER_STACK);
1935     }
1936   }
1937   bool HasBlockedFunctions() {
1938     return has_blocked_functions_;
1939   }
1940
1941  private:
1942   Handle<JSArray> shared_info_array_;
1943   Handle<JSArray> result_;
1944   bool has_blocked_functions_;
1945 };
1946
1947
1948 Handle<JSArray> LiveEdit::CheckAndDropActivations(
1949     Handle<JSArray> shared_info_array, bool do_drop) {
1950   Isolate* isolate = shared_info_array->GetIsolate();
1951   int len = GetArrayLength(shared_info_array);
1952
1953   DCHECK(shared_info_array->HasFastElements());
1954   Handle<FixedArray> shared_info_array_elements(
1955       FixedArray::cast(shared_info_array->elements()));
1956
1957   Handle<JSArray> result = isolate->factory()->NewJSArray(len);
1958   Handle<FixedArray> result_elements =
1959       JSObject::EnsureWritableFastElements(result);
1960
1961   // Fill the default values.
1962   for (int i = 0; i < len; i++) {
1963     FunctionPatchabilityStatus status = FUNCTION_AVAILABLE_FOR_PATCH;
1964     result_elements->set(i, Smi::FromInt(status));
1965   }
1966
1967   // Scan the heap for active generators -- those that are either currently
1968   // running (as we wouldn't want to restart them, because we don't know where
1969   // to restart them from) or suspended.  Fail if any one corresponds to the set
1970   // of functions being edited.
1971   if (FindActiveGenerators(shared_info_array_elements, result_elements, len)) {
1972     return result;
1973   }
1974
1975   // Check inactive threads. Fail if some functions are blocked there.
1976   InactiveThreadActivationsChecker inactive_threads_checker(shared_info_array,
1977                                                             result);
1978   isolate->thread_manager()->IterateArchivedThreads(
1979       &inactive_threads_checker);
1980   if (inactive_threads_checker.HasBlockedFunctions()) {
1981     return result;
1982   }
1983
1984   // Try to drop activations from the current stack.
1985   const char* error_message =
1986       DropActivationsInActiveThread(shared_info_array, result, do_drop);
1987   if (error_message != NULL) {
1988     // Add error message as an array extra element.
1989     Handle<String> str =
1990         isolate->factory()->NewStringFromAsciiChecked(error_message);
1991     SetElementSloppy(result, len, str);
1992   }
1993   return result;
1994 }
1995
1996
1997 // Describes a single callframe a target. Not finding this frame
1998 // means an error.
1999 class SingleFrameTarget {
2000  public:
2001   explicit SingleFrameTarget(JavaScriptFrame* frame)
2002       : m_frame(frame),
2003         m_saved_status(LiveEdit::FUNCTION_AVAILABLE_FOR_PATCH) {}
2004
2005   bool MatchActivation(StackFrame* frame,
2006       LiveEdit::FunctionPatchabilityStatus status) {
2007     if (frame->fp() == m_frame->fp()) {
2008       m_saved_status = status;
2009       return true;
2010     }
2011     return false;
2012   }
2013   const char* GetNotFoundMessage() const {
2014     return "Failed to found requested frame";
2015   }
2016   LiveEdit::FunctionPatchabilityStatus saved_status() {
2017     return m_saved_status;
2018   }
2019  private:
2020   JavaScriptFrame* m_frame;
2021   LiveEdit::FunctionPatchabilityStatus m_saved_status;
2022 };
2023
2024
2025 // Finds a drops required frame and all frames above.
2026 // Returns error message or NULL.
2027 const char* LiveEdit::RestartFrame(JavaScriptFrame* frame) {
2028   SingleFrameTarget target(frame);
2029
2030   const char* result =
2031       DropActivationsInActiveThreadImpl(frame->isolate(), target, true);
2032   if (result != NULL) {
2033     return result;
2034   }
2035   if (target.saved_status() == LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE) {
2036     return "Function is blocked under native code";
2037   }
2038   if (target.saved_status() == LiveEdit::FUNCTION_BLOCKED_UNDER_GENERATOR) {
2039     return "Function is blocked under a generator activation";
2040   }
2041   return NULL;
2042 }
2043
2044
2045 LiveEditFunctionTracker::LiveEditFunctionTracker(Isolate* isolate,
2046                                                  FunctionLiteral* fun)
2047     : isolate_(isolate) {
2048   if (isolate_->active_function_info_listener() != NULL) {
2049     isolate_->active_function_info_listener()->FunctionStarted(fun);
2050   }
2051 }
2052
2053
2054 LiveEditFunctionTracker::~LiveEditFunctionTracker() {
2055   if (isolate_->active_function_info_listener() != NULL) {
2056     isolate_->active_function_info_listener()->FunctionDone();
2057   }
2058 }
2059
2060
2061 void LiveEditFunctionTracker::RecordFunctionInfo(
2062     Handle<SharedFunctionInfo> info, FunctionLiteral* lit,
2063     Zone* zone) {
2064   if (isolate_->active_function_info_listener() != NULL) {
2065     isolate_->active_function_info_listener()->FunctionInfo(info, lit->scope(),
2066                                                             zone);
2067   }
2068 }
2069
2070
2071 void LiveEditFunctionTracker::RecordRootFunctionInfo(Handle<Code> code) {
2072   isolate_->active_function_info_listener()->FunctionCode(code);
2073 }
2074
2075
2076 bool LiveEditFunctionTracker::IsActive(Isolate* isolate) {
2077   return isolate->active_function_info_listener() != NULL;
2078 }
2079
2080 } }  // namespace v8::internal