src/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 "v8.h"
   7
   8 #include "liveedit.h"
   9
  10 #include "code-stubs.h"
  11 #include "compilation-cache.h"
  12 #include "compiler.h"
  13 #include "debug.h"
  14 #include "deoptimizer.h"
  15 #include "global-handles.h"
  16 #include "messages.h"
  17 #include "parser.h"
  18 #include "scopeinfo.h"
  19 #include "scopes.h"
  20 #include "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     ASSERT((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 = -1 << 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,
 611                                                int param_num,
 612                                                int literal_count,
 613                                                int slot_count,
 614                                                int parent_index) {
 615   HandleScope scope(isolate());
 616   this->SetField(kFunctionNameOffset_, name);
 617   this->SetSmiValueField(kStartPositionOffset_, start_position);
 618   this->SetSmiValueField(kEndPositionOffset_, end_position);
 619   this->SetSmiValueField(kParamNumOffset_, param_num);
 620   this->SetSmiValueField(kLiteralNumOffset_, literal_count);
 621   this->SetSmiValueField(kSlotNumOffset_, slot_count);
 622   this->SetSmiValueField(kParentIndexOffset_, parent_index);
 623 }
 624
 625
 626 void FunctionInfoWrapper::SetFunctionCode(Handle<Code> function_code,
 627                                           Handle<HeapObject> code_scope_info) {
 628   Handle<JSValue> code_wrapper = WrapInJSValue(function_code);
 629   this->SetField(kCodeOffset_, code_wrapper);
 630
 631   Handle<JSValue> scope_wrapper = WrapInJSValue(code_scope_info);
 632   this->SetField(kCodeScopeInfoOffset_, scope_wrapper);
 633 }
 634
 635
 636 void FunctionInfoWrapper::SetSharedFunctionInfo(
 637     Handle<SharedFunctionInfo> info) {
 638   Handle<JSValue> info_holder = WrapInJSValue(info);
 639   this->SetField(kSharedFunctionInfoOffset_, info_holder);
 640 }
 641
 642
 643 Handle<Code> FunctionInfoWrapper::GetFunctionCode() {
 644   Handle<Object> element = this->GetField(kCodeOffset_);
 645   Handle<JSValue> value_wrapper = Handle<JSValue>::cast(element);
 646   Handle<Object> raw_result = UnwrapJSValue(value_wrapper);
 647   CHECK(raw_result->IsCode());
 648   return Handle<Code>::cast(raw_result);
 649 }
 650
 651
 652 Handle<FixedArray> FunctionInfoWrapper::GetFeedbackVector() {
 653   Handle<Object> element = this->GetField(kSharedFunctionInfoOffset_);
 654   Handle<FixedArray> result;
 655   if (element->IsJSValue()) {
 656     Handle<JSValue> value_wrapper = Handle<JSValue>::cast(element);
 657     Handle<Object> raw_result = UnwrapJSValue(value_wrapper);
 658     Handle<SharedFunctionInfo> shared =
 659         Handle<SharedFunctionInfo>::cast(raw_result);
 660     result = Handle<FixedArray>(shared->feedback_vector(), isolate());
 661     CHECK_EQ(result->length(), GetSlotCount());
 662   } else {
 663     // Scripts may never have a SharedFunctionInfo created, so
 664     // create a type feedback vector here.
 665     int slot_count = GetSlotCount();
 666     result = isolate()->factory()->NewTypeFeedbackVector(slot_count);
 667   }
 668   return result;
 669 }
 670
 671
 672 Handle<Object> FunctionInfoWrapper::GetCodeScopeInfo() {
 673   Handle<Object> element = this->GetField(kCodeScopeInfoOffset_);
 674   return UnwrapJSValue(Handle<JSValue>::cast(element));
 675 }
 676
 677
 678 void SharedInfoWrapper::SetProperties(Handle<String> name,
 679                                       int start_position,
 680                                       int end_position,
 681                                       Handle<SharedFunctionInfo> info) {
 682   HandleScope scope(isolate());
 683   this->SetField(kFunctionNameOffset_, name);
 684   Handle<JSValue> info_holder = WrapInJSValue(info);
 685   this->SetField(kSharedInfoOffset_, info_holder);
 686   this->SetSmiValueField(kStartPositionOffset_, start_position);
 687   this->SetSmiValueField(kEndPositionOffset_, end_position);
 688 }
 689
 690
 691 Handle<SharedFunctionInfo> SharedInfoWrapper::GetInfo() {
 692   Handle<Object> element = this->GetField(kSharedInfoOffset_);
 693   Handle<JSValue> value_wrapper = Handle<JSValue>::cast(element);
 694   return UnwrapSharedFunctionInfoFromJSValue(value_wrapper);
 695 }
 696
 697
 698 class FunctionInfoListener {
 699  public:
 700   explicit FunctionInfoListener(Isolate* isolate) {
 701     current_parent_index_ = -1;
 702     len_ = 0;
 703     result_ = isolate->factory()->NewJSArray(10);
 704   }
 705
 706   void FunctionStarted(FunctionLiteral* fun) {
 707     HandleScope scope(isolate());
 708     FunctionInfoWrapper info = FunctionInfoWrapper::Create(isolate());
 709     info.SetInitialProperties(fun->name(), fun->start_position(),
 710                               fun->end_position(), fun->parameter_count(),
 711                               fun->materialized_literal_count(),
 712                               fun->slot_count(),
 713                               current_parent_index_);
 714     current_parent_index_ = len_;
 715     SetElementSloppy(result_, len_, info.GetJSArray());
 716     len_++;
 717   }
 718
 719   void FunctionDone() {
 720     HandleScope scope(isolate());
 721     FunctionInfoWrapper info =
 722         FunctionInfoWrapper::cast(
 723             *Object::GetElement(
 724                 isolate(), result_, current_parent_index_).ToHandleChecked());
 725     current_parent_index_ = info.GetParentIndex();
 726   }
 727
 728   // Saves only function code, because for a script function we
 729   // may never create a SharedFunctionInfo object.
 730   void FunctionCode(Handle<Code> function_code) {
 731     FunctionInfoWrapper info =
 732         FunctionInfoWrapper::cast(
 733             *Object::GetElement(
 734                 isolate(), result_, current_parent_index_).ToHandleChecked());
 735     info.SetFunctionCode(function_code,
 736                          Handle<HeapObject>(isolate()->heap()->null_value()));
 737   }
 738
 739   // Saves full information about a function: its code, its scope info
 740   // and a SharedFunctionInfo object.
 741   void FunctionInfo(Handle<SharedFunctionInfo> shared, Scope* scope,
 742                     Zone* zone) {
 743     if (!shared->IsSharedFunctionInfo()) {
 744       return;
 745     }
 746     FunctionInfoWrapper info =
 747         FunctionInfoWrapper::cast(
 748             *Object::GetElement(
 749                 isolate(), result_, current_parent_index_).ToHandleChecked());
 750     info.SetFunctionCode(Handle<Code>(shared->code()),
 751                          Handle<HeapObject>(shared->scope_info()));
 752     info.SetSharedFunctionInfo(shared);
 753
 754     Handle<Object> scope_info_list = SerializeFunctionScope(scope, zone);
 755     info.SetFunctionScopeInfo(scope_info_list);
 756   }
 757
 758   Handle<JSArray> GetResult() { return result_; }
 759
 760  private:
 761   Isolate* isolate() const { return result_->GetIsolate(); }
 762
 763   Handle<Object> SerializeFunctionScope(Scope* scope, Zone* zone) {
 764     Handle<JSArray> scope_info_list = isolate()->factory()->NewJSArray(10);
 765     int scope_info_length = 0;
 766
 767     // Saves some description of scope. It stores name and indexes of
 768     // variables in the whole scope chain. Null-named slots delimit
 769     // scopes of this chain.
 770     Scope* current_scope = scope;
 771     while (current_scope != NULL) {
 772       HandleScope handle_scope(isolate());
 773       ZoneList<Variable*> stack_list(current_scope->StackLocalCount(), zone);
 774       ZoneList<Variable*> context_list(
 775           current_scope->ContextLocalCount(), zone);
 776       current_scope->CollectStackAndContextLocals(&stack_list, &context_list);
 777       context_list.Sort(&Variable::CompareIndex);
 778
 779       for (int i = 0; i < context_list.length(); i++) {
 780         SetElementSloppy(scope_info_list,
 781                          scope_info_length,
 782                          context_list[i]->name());
 783         scope_info_length++;
 784         SetElementSloppy(
 785             scope_info_list,
 786             scope_info_length,
 787             Handle<Smi>(Smi::FromInt(context_list[i]->index()), isolate()));
 788         scope_info_length++;
 789       }
 790       SetElementSloppy(scope_info_list,
 791                        scope_info_length,
 792                        Handle<Object>(isolate()->heap()->null_value(),
 793                                       isolate()));
 794       scope_info_length++;
 795
 796       current_scope = current_scope->outer_scope();
 797     }
 798
 799     return scope_info_list;
 800   }
 801
 802   Handle<JSArray> result_;
 803   int len_;
 804   int current_parent_index_;
 805 };
 806
 807
 808 MaybeHandle<JSArray> LiveEdit::GatherCompileInfo(Handle<Script> script,
 809                                                  Handle<String> source) {
 810   Isolate* isolate = script->GetIsolate();
 811
 812   FunctionInfoListener listener(isolate);
 813   Handle<Object> original_source =
 814       Handle<Object>(script->source(), isolate);
 815   script->set_source(*source);
 816   isolate->set_active_function_info_listener(&listener);
 817
 818   {
 819     // Creating verbose TryCatch from public API is currently the only way to
 820     // force code save location. We do not use this the object directly.
 821     v8::TryCatch try_catch;
 822     try_catch.SetVerbose(true);
 823
 824     // A logical 'try' section.
 825     Compiler::CompileForLiveEdit(script);
 826   }
 827
 828   // A logical 'catch' section.
 829   Handle<JSObject> rethrow_exception;
 830   if (isolate->has_pending_exception()) {
 831     Handle<Object> exception(isolate->pending_exception(), isolate);
 832     MessageLocation message_location = isolate->GetMessageLocation();
 833
 834     isolate->clear_pending_message();
 835     isolate->clear_pending_exception();
 836
 837     // If possible, copy positions from message object to exception object.
 838     if (exception->IsJSObject() && !message_location.script().is_null()) {
 839       rethrow_exception = Handle<JSObject>::cast(exception);
 840
 841       Factory* factory = isolate->factory();
 842       Handle<String> start_pos_key = factory->InternalizeOneByteString(
 843           STATIC_ASCII_VECTOR("startPosition"));
 844       Handle<String> end_pos_key = factory->InternalizeOneByteString(
 845           STATIC_ASCII_VECTOR("endPosition"));
 846       Handle<String> script_obj_key = factory->InternalizeOneByteString(
 847           STATIC_ASCII_VECTOR("scriptObject"));
 848       Handle<Smi> start_pos(
 849           Smi::FromInt(message_location.start_pos()), isolate);
 850       Handle<Smi> end_pos(Smi::FromInt(message_location.end_pos()), isolate);
 851       Handle<JSObject> script_obj =
 852           Script::GetWrapper(message_location.script());
 853       JSReceiver::SetProperty(
 854           rethrow_exception, start_pos_key, start_pos, NONE, SLOPPY).Assert();
 855       JSReceiver::SetProperty(
 856           rethrow_exception, end_pos_key, end_pos, NONE, SLOPPY).Assert();
 857       JSReceiver::SetProperty(
 858           rethrow_exception, script_obj_key, script_obj, NONE, SLOPPY).Assert();
 859     }
 860   }
 861
 862   // A logical 'finally' section.
 863   isolate->set_active_function_info_listener(NULL);
 864   script->set_source(*original_source);
 865
 866   if (rethrow_exception.is_null()) {
 867     return listener.GetResult();
 868   } else {
 869     return isolate->Throw<JSArray>(rethrow_exception);
 870   }
 871 }
 872
 873
 874 void LiveEdit::WrapSharedFunctionInfos(Handle<JSArray> array) {
 875   Isolate* isolate = array->GetIsolate();
 876   HandleScope scope(isolate);
 877   int len = GetArrayLength(array);
 878   for (int i = 0; i < len; i++) {
 879     Handle<SharedFunctionInfo> info(
 880         SharedFunctionInfo::cast(
 881             *Object::GetElement(isolate, array, i).ToHandleChecked()));
 882     SharedInfoWrapper info_wrapper = SharedInfoWrapper::Create(isolate);
 883     Handle<String> name_handle(String::cast(info->name()));
 884     info_wrapper.SetProperties(name_handle, info->start_position(),
 885                                info->end_position(), info);
 886     SetElementSloppy(array, i, info_wrapper.GetJSArray());
 887   }
 888 }
 889
 890
 891 // Visitor that finds all references to a particular code object,
 892 // including "CODE_TARGET" references in other code objects and replaces
 893 // them on the fly.
 894 class ReplacingVisitor : public ObjectVisitor {
 895  public:
 896   explicit ReplacingVisitor(Code* original, Code* substitution)
 897     : original_(original), substitution_(substitution) {
 898   }
 899
 900   virtual void VisitPointers(Object** start, Object** end) {
 901     for (Object** p = start; p < end; p++) {
 902       if (*p == original_) {
 903         *p = substitution_;
 904       }
 905     }
 906   }
 907
 908   virtual void VisitCodeEntry(Address entry) {
 909     if (Code::GetObjectFromEntryAddress(entry) == original_) {
 910       Address substitution_entry = substitution_->instruction_start();
 911       Memory::Address_at(entry) = substitution_entry;
 912     }
 913   }
 914
 915   virtual void VisitCodeTarget(RelocInfo* rinfo) {
 916     if (RelocInfo::IsCodeTarget(rinfo->rmode()) &&
 917         Code::GetCodeFromTargetAddress(rinfo->target_address()) == original_) {
 918       Address substitution_entry = substitution_->instruction_start();
 919       rinfo->set_target_address(substitution_entry);
 920     }
 921   }
 922
 923   virtual void VisitDebugTarget(RelocInfo* rinfo) {
 924     VisitCodeTarget(rinfo);
 925   }
 926
 927  private:
 928   Code* original_;
 929   Code* substitution_;
 930 };
 931
 932
 933 // Finds all references to original and replaces them with substitution.
 934 static void ReplaceCodeObject(Handle<Code> original,
 935                               Handle<Code> substitution) {
 936   // Perform a full GC in order to ensure that we are not in the middle of an
 937   // incremental marking phase when we are replacing the code object.
 938   // Since we are not in an incremental marking phase we can write pointers
 939   // to code objects (that are never in new space) without worrying about
 940   // write barriers.
 941   Heap* heap = original->GetHeap();
 942   heap->CollectAllGarbage(Heap::kMakeHeapIterableMask,
 943                           "liveedit.cc ReplaceCodeObject");
 944
 945   ASSERT(!heap->InNewSpace(*substitution));
 946
 947   DisallowHeapAllocation no_allocation;
 948
 949   ReplacingVisitor visitor(*original, *substitution);
 950
 951   // Iterate over all roots. Stack frames may have pointer into original code,
 952   // so temporary replace the pointers with offset numbers
 953   // in prologue/epilogue.
 954   heap->IterateRoots(&visitor, VISIT_ALL);
 955
 956   // Now iterate over all pointers of all objects, including code_target
 957   // implicit pointers.
 958   HeapIterator iterator(heap);
 959   for (HeapObject* obj = iterator.next(); obj != NULL; obj = iterator.next()) {
 960     obj->Iterate(&visitor);
 961   }
 962 }
 963
 964
 965 // Patch function literals.
 966 // Name 'literals' is a misnomer. Rather it's a cache for complex object
 967 // boilerplates and for a native context. We must clean cached values.
 968 // Additionally we may need to allocate a new array if number of literals
 969 // changed.
 970 class LiteralFixer {
 971  public:
 972   static void PatchLiterals(FunctionInfoWrapper* compile_info_wrapper,
 973                             Handle<SharedFunctionInfo> shared_info,
 974                             Isolate* isolate) {
 975     int new_literal_count = compile_info_wrapper->GetLiteralCount();
 976     if (new_literal_count > 0) {
 977       new_literal_count += JSFunction::kLiteralsPrefixSize;
 978     }
 979     int old_literal_count = shared_info->num_literals();
 980
 981     if (old_literal_count == new_literal_count) {
 982       // If literal count didn't change, simply go over all functions
 983       // and clear literal arrays.
 984       ClearValuesVisitor visitor;
 985       IterateJSFunctions(*shared_info, &visitor);
 986     } else {
 987       // When literal count changes, we have to create new array instances.
 988       // Since we cannot create instances when iterating heap, we should first
 989       // collect all functions and fix their literal arrays.
 990       Handle<FixedArray> function_instances =
 991           CollectJSFunctions(shared_info, isolate);
 992       for (int i = 0; i < function_instances->length(); i++) {
 993         Handle<JSFunction> fun(JSFunction::cast(function_instances->get(i)));
 994         Handle<FixedArray> old_literals(fun->literals());
 995         Handle<FixedArray> new_literals =
 996             isolate->factory()->NewFixedArray(new_literal_count);
 997         if (new_literal_count > 0) {
 998           Handle<Context> native_context;
 999           if (old_literals->length() >
1000               JSFunction::kLiteralNativeContextIndex) {
1001             native_context = Handle<Context>(
1002                 JSFunction::NativeContextFromLiterals(fun->literals()));
1003           } else {
1004             native_context = Handle<Context>(fun->context()->native_context());
1005           }
1006           new_literals->set(JSFunction::kLiteralNativeContextIndex,
1007               *native_context);
1008         }
1009         fun->set_literals(*new_literals);
1010       }
1011
1012       shared_info->set_num_literals(new_literal_count);
1013     }
1014   }
1015
1016  private:
1017   // Iterates all function instances in the HEAP that refers to the
1018   // provided shared_info.
1019   template<typename Visitor>
1020   static void IterateJSFunctions(SharedFunctionInfo* shared_info,
1021                                  Visitor* visitor) {
1022     DisallowHeapAllocation no_allocation;
1023
1024     HeapIterator iterator(shared_info->GetHeap());
1025     for (HeapObject* obj = iterator.next(); obj != NULL;
1026         obj = iterator.next()) {
1027       if (obj->IsJSFunction()) {
1028         JSFunction* function = JSFunction::cast(obj);
1029         if (function->shared() == shared_info) {
1030           visitor->visit(function);
1031         }
1032       }
1033     }
1034   }
1035
1036   // Finds all instances of JSFunction that refers to the provided shared_info
1037   // and returns array with them.
1038   static Handle<FixedArray> CollectJSFunctions(
1039       Handle<SharedFunctionInfo> shared_info, Isolate* isolate) {
1040     CountVisitor count_visitor;
1041     count_visitor.count = 0;
1042     IterateJSFunctions(*shared_info, &count_visitor);
1043     int size = count_visitor.count;
1044
1045     Handle<FixedArray> result = isolate->factory()->NewFixedArray(size);
1046     if (size > 0) {
1047       CollectVisitor collect_visitor(result);
1048       IterateJSFunctions(*shared_info, &collect_visitor);
1049     }
1050     return result;
1051   }
1052
1053   class ClearValuesVisitor {
1054    public:
1055     void visit(JSFunction* fun) {
1056       FixedArray* literals = fun->literals();
1057       int len = literals->length();
1058       for (int j = JSFunction::kLiteralsPrefixSize; j < len; j++) {
1059         literals->set_undefined(j);
1060       }
1061     }
1062   };
1063
1064   class CountVisitor {
1065    public:
1066     void visit(JSFunction* fun) {
1067       count++;
1068     }
1069     int count;
1070   };
1071
1072   class CollectVisitor {
1073    public:
1074     explicit CollectVisitor(Handle<FixedArray> output)
1075         : m_output(output), m_pos(0) {}
1076
1077     void visit(JSFunction* fun) {
1078       m_output->set(m_pos, fun);
1079       m_pos++;
1080     }
1081    private:
1082     Handle<FixedArray> m_output;
1083     int m_pos;
1084   };
1085 };
1086
1087
1088 // Check whether the code is natural function code (not a lazy-compile stub
1089 // code).
1090 static bool IsJSFunctionCode(Code* code) {
1091   return code->kind() == Code::FUNCTION;
1092 }
1093
1094
1095 // Returns true if an instance of candidate were inlined into function's code.
1096 static bool IsInlined(JSFunction* function, SharedFunctionInfo* candidate) {
1097   DisallowHeapAllocation no_gc;
1098
1099   if (function->code()->kind() != Code::OPTIMIZED_FUNCTION) return false;
1100
1101   DeoptimizationInputData* data =
1102       DeoptimizationInputData::cast(function->code()->deoptimization_data());
1103
1104   if (data == function->GetIsolate()->heap()->empty_fixed_array()) {
1105     return false;
1106   }
1107
1108   FixedArray* literals = data->LiteralArray();
1109
1110   int inlined_count = data->InlinedFunctionCount()->value();
1111   for (int i = 0; i < inlined_count; ++i) {
1112     JSFunction* inlined = JSFunction::cast(literals->get(i));
1113     if (inlined->shared() == candidate) return true;
1114   }
1115
1116   return false;
1117 }
1118
1119
1120 // Marks code that shares the same shared function info or has inlined
1121 // code that shares the same function info.
1122 class DependentFunctionMarker: public OptimizedFunctionVisitor {
1123  public:
1124   SharedFunctionInfo* shared_info_;
1125   bool found_;
1126
1127   explicit DependentFunctionMarker(SharedFunctionInfo* shared_info)
1128     : shared_info_(shared_info), found_(false) { }
1129
1130   virtual void EnterContext(Context* context) { }  // Don't care.
1131   virtual void LeaveContext(Context* context)  { }  // Don't care.
1132   virtual void VisitFunction(JSFunction* function) {
1133     // It should be guaranteed by the iterator that everything is optimized.
1134     ASSERT(function->code()->kind() == Code::OPTIMIZED_FUNCTION);
1135     if (shared_info_ == function->shared() ||
1136         IsInlined(function, shared_info_)) {
1137       // Mark the code for deoptimization.
1138       function->code()->set_marked_for_deoptimization(true);
1139       found_ = true;
1140     }
1141   }
1142 };
1143
1144
1145 static void DeoptimizeDependentFunctions(SharedFunctionInfo* function_info) {
1146   DisallowHeapAllocation no_allocation;
1147   DependentFunctionMarker marker(function_info);
1148   // TODO(titzer): need to traverse all optimized code to find OSR code here.
1149   Deoptimizer::VisitAllOptimizedFunctions(function_info->GetIsolate(), &marker);
1150
1151   if (marker.found_) {
1152     // Only go through with the deoptimization if something was found.
1153     Deoptimizer::DeoptimizeMarkedCode(function_info->GetIsolate());
1154   }
1155 }
1156
1157
1158 void LiveEdit::ReplaceFunctionCode(
1159     Handle<JSArray> new_compile_info_array,
1160     Handle<JSArray> shared_info_array) {
1161   Isolate* isolate = new_compile_info_array->GetIsolate();
1162
1163   FunctionInfoWrapper compile_info_wrapper(new_compile_info_array);
1164   SharedInfoWrapper shared_info_wrapper(shared_info_array);
1165
1166   Handle<SharedFunctionInfo> shared_info = shared_info_wrapper.GetInfo();
1167
1168   isolate->heap()->EnsureHeapIsIterable();
1169
1170   if (IsJSFunctionCode(shared_info->code())) {
1171     Handle<Code> code = compile_info_wrapper.GetFunctionCode();
1172     ReplaceCodeObject(Handle<Code>(shared_info->code()), code);
1173     Handle<Object> code_scope_info = compile_info_wrapper.GetCodeScopeInfo();
1174     if (code_scope_info->IsFixedArray()) {
1175       shared_info->set_scope_info(ScopeInfo::cast(*code_scope_info));
1176     }
1177     shared_info->DisableOptimization(kLiveEdit);
1178     // Update the type feedback vector
1179     Handle<FixedArray> feedback_vector =
1180         compile_info_wrapper.GetFeedbackVector();
1181     shared_info->set_feedback_vector(*feedback_vector);
1182   }
1183
1184   if (shared_info->debug_info()->IsDebugInfo()) {
1185     Handle<DebugInfo> debug_info(DebugInfo::cast(shared_info->debug_info()));
1186     Handle<Code> new_original_code =
1187         isolate->factory()->CopyCode(compile_info_wrapper.GetFunctionCode());
1188     debug_info->set_original_code(*new_original_code);
1189   }
1190
1191   int start_position = compile_info_wrapper.GetStartPosition();
1192   int end_position = compile_info_wrapper.GetEndPosition();
1193   shared_info->set_start_position(start_position);
1194   shared_info->set_end_position(end_position);
1195
1196   LiteralFixer::PatchLiterals(&compile_info_wrapper, shared_info, isolate);
1197
1198   shared_info->set_construct_stub(
1199       isolate->builtins()->builtin(Builtins::kJSConstructStubGeneric));
1200
1201   DeoptimizeDependentFunctions(*shared_info);
1202   isolate->compilation_cache()->Remove(shared_info);
1203 }
1204
1205
1206 void LiveEdit::FunctionSourceUpdated(Handle<JSArray> shared_info_array) {
1207   SharedInfoWrapper shared_info_wrapper(shared_info_array);
1208   Handle<SharedFunctionInfo> shared_info = shared_info_wrapper.GetInfo();
1209
1210   DeoptimizeDependentFunctions(*shared_info);
1211   shared_info_array->GetIsolate()->compilation_cache()->Remove(shared_info);
1212 }
1213
1214
1215 void LiveEdit::SetFunctionScript(Handle<JSValue> function_wrapper,
1216                                  Handle<Object> script_handle) {
1217   Handle<SharedFunctionInfo> shared_info =
1218       UnwrapSharedFunctionInfoFromJSValue(function_wrapper);
1219   CHECK(script_handle->IsScript() || script_handle->IsUndefined());
1220   shared_info->set_script(*script_handle);
1221
1222   function_wrapper->GetIsolate()->compilation_cache()->Remove(shared_info);
1223 }
1224
1225
1226 // For a script text change (defined as position_change_array), translates
1227 // position in unchanged text to position in changed text.
1228 // Text change is a set of non-overlapping regions in text, that have changed
1229 // their contents and length. It is specified as array of groups of 3 numbers:
1230 // (change_begin, change_end, change_end_new_position).
1231 // Each group describes a change in text; groups are sorted by change_begin.
1232 // Only position in text beyond any changes may be successfully translated.
1233 // If a positions is inside some region that changed, result is currently
1234 // undefined.
1235 static int TranslatePosition(int original_position,
1236                              Handle<JSArray> position_change_array) {
1237   int position_diff = 0;
1238   int array_len = GetArrayLength(position_change_array);
1239   Isolate* isolate = position_change_array->GetIsolate();
1240   // TODO(635): binary search may be used here
1241   for (int i = 0; i < array_len; i += 3) {
1242     HandleScope scope(isolate);
1243     Handle<Object> element = Object::GetElement(
1244         isolate, position_change_array, i).ToHandleChecked();
1245     CHECK(element->IsSmi());
1246     int chunk_start = Handle<Smi>::cast(element)->value();
1247     if (original_position < chunk_start) {
1248       break;
1249     }
1250     element = Object::GetElement(
1251         isolate, position_change_array, i + 1).ToHandleChecked();
1252     CHECK(element->IsSmi());
1253     int chunk_end = Handle<Smi>::cast(element)->value();
1254     // Position mustn't be inside a chunk.
1255     ASSERT(original_position >= chunk_end);
1256     element = Object::GetElement(
1257         isolate, position_change_array, i + 2).ToHandleChecked();
1258     CHECK(element->IsSmi());
1259     int chunk_changed_end = Handle<Smi>::cast(element)->value();
1260     position_diff = chunk_changed_end - chunk_end;
1261   }
1262
1263   return original_position + position_diff;
1264 }
1265
1266
1267 // Auto-growing buffer for writing relocation info code section. This buffer
1268 // is a simplified version of buffer from Assembler. Unlike Assembler, this
1269 // class is platform-independent and it works without dealing with instructions.
1270 // As specified by RelocInfo format, the buffer is filled in reversed order:
1271 // from upper to lower addresses.
1272 // It uses NewArray/DeleteArray for memory management.
1273 class RelocInfoBuffer {
1274  public:
1275   RelocInfoBuffer(int buffer_initial_capicity, byte* pc) {
1276     buffer_size_ = buffer_initial_capicity + kBufferGap;
1277     buffer_ = NewArray<byte>(buffer_size_);
1278
1279     reloc_info_writer_.Reposition(buffer_ + buffer_size_, pc);
1280   }
1281   ~RelocInfoBuffer() {
1282     DeleteArray(buffer_);
1283   }
1284
1285   // As specified by RelocInfo format, the buffer is filled in reversed order:
1286   // from upper to lower addresses.
1287   void Write(const RelocInfo* rinfo) {
1288     if (buffer_ + kBufferGap >= reloc_info_writer_.pos()) {
1289       Grow();
1290     }
1291     reloc_info_writer_.Write(rinfo);
1292   }
1293
1294   Vector<byte> GetResult() {
1295     // Return the bytes from pos up to end of buffer.
1296     int result_size =
1297         static_cast<int>((buffer_ + buffer_size_) - reloc_info_writer_.pos());
1298     return Vector<byte>(reloc_info_writer_.pos(), result_size);
1299   }
1300
1301  private:
1302   void Grow() {
1303     // Compute new buffer size.
1304     int new_buffer_size;
1305     if (buffer_size_ < 2 * KB) {
1306       new_buffer_size = 4 * KB;
1307     } else {
1308       new_buffer_size = 2 * buffer_size_;
1309     }
1310     // Some internal data structures overflow for very large buffers,
1311     // they must ensure that kMaximalBufferSize is not too large.
1312     if (new_buffer_size > kMaximalBufferSize) {
1313       V8::FatalProcessOutOfMemory("RelocInfoBuffer::GrowBuffer");
1314     }
1315
1316     // Set up new buffer.
1317     byte* new_buffer = NewArray<byte>(new_buffer_size);
1318
1319     // Copy the data.
1320     int curently_used_size =
1321         static_cast<int>(buffer_ + buffer_size_ - reloc_info_writer_.pos());
1322     OS::MemMove(new_buffer + new_buffer_size - curently_used_size,
1323                 reloc_info_writer_.pos(), curently_used_size);
1324
1325     reloc_info_writer_.Reposition(
1326         new_buffer + new_buffer_size - curently_used_size,
1327         reloc_info_writer_.last_pc());
1328
1329     DeleteArray(buffer_);
1330     buffer_ = new_buffer;
1331     buffer_size_ = new_buffer_size;
1332   }
1333
1334   RelocInfoWriter reloc_info_writer_;
1335   byte* buffer_;
1336   int buffer_size_;
1337
1338   static const int kBufferGap = RelocInfoWriter::kMaxSize;
1339   static const int kMaximalBufferSize = 512*MB;
1340 };
1341
1342
1343 // Patch positions in code (changes relocation info section) and possibly
1344 // returns new instance of code.
1345 static Handle<Code> PatchPositionsInCode(
1346     Handle<Code> code,
1347     Handle<JSArray> position_change_array) {
1348   Isolate* isolate = code->GetIsolate();
1349
1350   RelocInfoBuffer buffer_writer(code->relocation_size(),
1351                                 code->instruction_start());
1352
1353   {
1354     for (RelocIterator it(*code); !it.done(); it.next()) {
1355       RelocInfo* rinfo = it.rinfo();
1356       if (RelocInfo::IsPosition(rinfo->rmode())) {
1357         int position = static_cast<int>(rinfo->data());
1358         int new_position = TranslatePosition(position,
1359                                              position_change_array);
1360         if (position != new_position) {
1361           RelocInfo info_copy(rinfo->pc(), rinfo->rmode(), new_position, NULL);
1362           buffer_writer.Write(&info_copy);
1363           continue;
1364         }
1365       }
1366       if (RelocInfo::IsRealRelocMode(rinfo->rmode())) {
1367         buffer_writer.Write(it.rinfo());
1368       }
1369     }
1370   }
1371
1372   Vector<byte> buffer = buffer_writer.GetResult();
1373
1374   if (buffer.length() == code->relocation_size()) {
1375     // Simply patch relocation area of code.
1376     OS::MemCopy(code->relocation_start(), buffer.start(), buffer.length());
1377     return code;
1378   } else {
1379     // Relocation info section now has different size. We cannot simply
1380     // rewrite it inside code object. Instead we have to create a new
1381     // code object.
1382     Handle<Code> result(isolate->factory()->CopyCode(code, buffer));
1383     return result;
1384   }
1385 }
1386
1387
1388 void LiveEdit::PatchFunctionPositions(Handle<JSArray> shared_info_array,
1389                                       Handle<JSArray> position_change_array) {
1390   SharedInfoWrapper shared_info_wrapper(shared_info_array);
1391   Handle<SharedFunctionInfo> info = shared_info_wrapper.GetInfo();
1392
1393   int old_function_start = info->start_position();
1394   int new_function_start = TranslatePosition(old_function_start,
1395                                              position_change_array);
1396   int new_function_end = TranslatePosition(info->end_position(),
1397                                            position_change_array);
1398   int new_function_token_pos =
1399       TranslatePosition(info->function_token_position(), position_change_array);
1400
1401   info->set_start_position(new_function_start);
1402   info->set_end_position(new_function_end);
1403   info->set_function_token_position(new_function_token_pos);
1404
1405   info->GetIsolate()->heap()->EnsureHeapIsIterable();
1406
1407   if (IsJSFunctionCode(info->code())) {
1408     // Patch relocation info section of the code.
1409     Handle<Code> patched_code = PatchPositionsInCode(Handle<Code>(info->code()),
1410                                                      position_change_array);
1411     if (*patched_code != info->code()) {
1412       // Replace all references to the code across the heap. In particular,
1413       // some stubs may refer to this code and this code may be being executed
1414       // on stack (it is safe to substitute the code object on stack, because
1415       // we only change the structure of rinfo and leave instructions
1416       // untouched).
1417       ReplaceCodeObject(Handle<Code>(info->code()), patched_code);
1418     }
1419   }
1420 }
1421
1422
1423 static Handle<Script> CreateScriptCopy(Handle<Script> original) {
1424   Isolate* isolate = original->GetIsolate();
1425
1426   Handle<String> original_source(String::cast(original->source()));
1427   Handle<Script> copy = isolate->factory()->NewScript(original_source);
1428
1429   copy->set_name(original->name());
1430   copy->set_line_offset(original->line_offset());
1431   copy->set_column_offset(original->column_offset());
1432   copy->set_type(original->type());
1433   copy->set_context_data(original->context_data());
1434   copy->set_eval_from_shared(original->eval_from_shared());
1435   copy->set_eval_from_instructions_offset(
1436       original->eval_from_instructions_offset());
1437
1438   // Copy all the flags, but clear compilation state.
1439   copy->set_flags(original->flags());
1440   copy->set_compilation_state(Script::COMPILATION_STATE_INITIAL);
1441
1442   return copy;
1443 }
1444
1445
1446 Handle<Object> LiveEdit::ChangeScriptSource(Handle<Script> original_script,
1447                                             Handle<String> new_source,
1448                                             Handle<Object> old_script_name) {
1449   Isolate* isolate = original_script->GetIsolate();
1450   Handle<Object> old_script_object;
1451   if (old_script_name->IsString()) {
1452     Handle<Script> old_script = CreateScriptCopy(original_script);
1453     old_script->set_name(String::cast(*old_script_name));
1454     old_script_object = old_script;
1455     isolate->debugger()->OnAfterCompile(
1456         old_script, Debugger::SEND_WHEN_DEBUGGING);
1457   } else {
1458     old_script_object = isolate->factory()->null_value();
1459   }
1460
1461   original_script->set_source(*new_source);
1462
1463   // Drop line ends so that they will be recalculated.
1464   original_script->set_line_ends(isolate->heap()->undefined_value());
1465
1466   return old_script_object;
1467 }
1468
1469
1470
1471 void LiveEdit::ReplaceRefToNestedFunction(
1472     Handle<JSValue> parent_function_wrapper,
1473     Handle<JSValue> orig_function_wrapper,
1474     Handle<JSValue> subst_function_wrapper) {
1475
1476   Handle<SharedFunctionInfo> parent_shared =
1477       UnwrapSharedFunctionInfoFromJSValue(parent_function_wrapper);
1478   Handle<SharedFunctionInfo> orig_shared =
1479       UnwrapSharedFunctionInfoFromJSValue(orig_function_wrapper);
1480   Handle<SharedFunctionInfo> subst_shared =
1481       UnwrapSharedFunctionInfoFromJSValue(subst_function_wrapper);
1482
1483   for (RelocIterator it(parent_shared->code()); !it.done(); it.next()) {
1484     if (it.rinfo()->rmode() == RelocInfo::EMBEDDED_OBJECT) {
1485       if (it.rinfo()->target_object() == *orig_shared) {
1486         it.rinfo()->set_target_object(*subst_shared);
1487       }
1488     }
1489   }
1490 }
1491
1492
1493 // Check an activation against list of functions. If there is a function
1494 // that matches, its status in result array is changed to status argument value.
1495 static bool CheckActivation(Handle<JSArray> shared_info_array,
1496                             Handle<JSArray> result,
1497                             StackFrame* frame,
1498                             LiveEdit::FunctionPatchabilityStatus status) {
1499   if (!frame->is_java_script()) return false;
1500
1501   Handle<JSFunction> function(JavaScriptFrame::cast(frame)->function());
1502
1503   Isolate* isolate = shared_info_array->GetIsolate();
1504   int len = GetArrayLength(shared_info_array);
1505   for (int i = 0; i < len; i++) {
1506     HandleScope scope(isolate);
1507     Handle<Object> element =
1508         Object::GetElement(isolate, shared_info_array, i).ToHandleChecked();
1509     Handle<JSValue> jsvalue = Handle<JSValue>::cast(element);
1510     Handle<SharedFunctionInfo> shared =
1511         UnwrapSharedFunctionInfoFromJSValue(jsvalue);
1512
1513     if (function->shared() == *shared || IsInlined(*function, *shared)) {
1514       SetElementSloppy(result, i, Handle<Smi>(Smi::FromInt(status), isolate));
1515       return true;
1516     }
1517   }
1518   return false;
1519 }
1520
1521
1522 // Iterates over handler chain and removes all elements that are inside
1523 // frames being dropped.
1524 static bool FixTryCatchHandler(StackFrame* top_frame,
1525                                StackFrame* bottom_frame) {
1526   Address* pointer_address =
1527       &Memory::Address_at(top_frame->isolate()->get_address_from_id(
1528           Isolate::kHandlerAddress));
1529
1530   while (*pointer_address < top_frame->sp()) {
1531     pointer_address = &Memory::Address_at(*pointer_address);
1532   }
1533   Address* above_frame_address = pointer_address;
1534   while (*pointer_address < bottom_frame->fp()) {
1535     pointer_address = &Memory::Address_at(*pointer_address);
1536   }
1537   bool change = *above_frame_address != *pointer_address;
1538   *above_frame_address = *pointer_address;
1539   return change;
1540 }
1541
1542
1543 // Removes specified range of frames from stack. There may be 1 or more
1544 // frames in range. Anyway the bottom frame is restarted rather than dropped,
1545 // and therefore has to be a JavaScript frame.
1546 // Returns error message or NULL.
1547 static const char* DropFrames(Vector<StackFrame*> frames,
1548                               int top_frame_index,
1549                               int bottom_js_frame_index,
1550                               Debug::FrameDropMode* mode,
1551                               Object*** restarter_frame_function_pointer) {
1552   if (!Debug::kFrameDropperSupported) {
1553     return "Stack manipulations are not supported in this architecture.";
1554   }
1555
1556   StackFrame* pre_top_frame = frames[top_frame_index - 1];
1557   StackFrame* top_frame = frames[top_frame_index];
1558   StackFrame* bottom_js_frame = frames[bottom_js_frame_index];
1559
1560   ASSERT(bottom_js_frame->is_java_script());
1561
1562   // Check the nature of the top frame.
1563   Isolate* isolate = bottom_js_frame->isolate();
1564   Code* pre_top_frame_code = pre_top_frame->LookupCode();
1565   bool frame_has_padding;
1566   if (pre_top_frame_code->is_inline_cache_stub() &&
1567       pre_top_frame_code->is_debug_stub()) {
1568     // OK, we can drop inline cache calls.
1569     *mode = Debug::FRAME_DROPPED_IN_IC_CALL;
1570     frame_has_padding = Debug::FramePaddingLayout::kIsSupported;
1571   } else if (pre_top_frame_code ==
1572              isolate->builtins()->builtin(Builtins::kSlot_DebugBreak)) {
1573     // OK, we can drop debug break slot.
1574     *mode = Debug::FRAME_DROPPED_IN_DEBUG_SLOT_CALL;
1575     frame_has_padding = Debug::FramePaddingLayout::kIsSupported;
1576   } else if (pre_top_frame_code ==
1577       isolate->builtins()->builtin(
1578           Builtins::kFrameDropper_LiveEdit)) {
1579     // OK, we can drop our own code.
1580     pre_top_frame = frames[top_frame_index - 2];
1581     top_frame = frames[top_frame_index - 1];
1582     *mode = Debug::CURRENTLY_SET_MODE;
1583     frame_has_padding = false;
1584   } else if (pre_top_frame_code ==
1585       isolate->builtins()->builtin(Builtins::kReturn_DebugBreak)) {
1586     *mode = Debug::FRAME_DROPPED_IN_RETURN_CALL;
1587     frame_has_padding = Debug::FramePaddingLayout::kIsSupported;
1588   } else if (pre_top_frame_code->kind() == Code::STUB &&
1589       pre_top_frame_code->major_key() == CodeStub::CEntry) {
1590     // Entry from our unit tests on 'debugger' statement.
1591     // It's fine, we support this case.
1592     *mode = Debug::FRAME_DROPPED_IN_DIRECT_CALL;
1593     // We don't have a padding from 'debugger' statement call.
1594     // Here the stub is CEntry, it's not debug-only and can't be padded.
1595     // If anyone would complain, a proxy padded stub could be added.
1596     frame_has_padding = false;
1597   } else if (pre_top_frame->type() == StackFrame::ARGUMENTS_ADAPTOR) {
1598     // This must be adaptor that remain from the frame dropping that
1599     // is still on stack. A frame dropper frame must be above it.
1600     ASSERT(frames[top_frame_index - 2]->LookupCode() ==
1601         isolate->builtins()->builtin(Builtins::kFrameDropper_LiveEdit));
1602     pre_top_frame = frames[top_frame_index - 3];
1603     top_frame = frames[top_frame_index - 2];
1604     *mode = Debug::CURRENTLY_SET_MODE;
1605     frame_has_padding = false;
1606   } else {
1607     return "Unknown structure of stack above changing function";
1608   }
1609
1610   Address unused_stack_top = top_frame->sp();
1611   Address unused_stack_bottom = bottom_js_frame->fp()
1612       - Debug::kFrameDropperFrameSize * kPointerSize  // Size of the new frame.
1613       + kPointerSize;  // Bigger address end is exclusive.
1614
1615   Address* top_frame_pc_address = top_frame->pc_address();
1616
1617   // top_frame may be damaged below this point. Do not used it.
1618   ASSERT(!(top_frame = NULL));
1619
1620   if (unused_stack_top > unused_stack_bottom) {
1621     if (frame_has_padding) {
1622       int shortage_bytes =
1623           static_cast<int>(unused_stack_top - unused_stack_bottom);
1624
1625       Address padding_start = pre_top_frame->fp() -
1626           Debug::FramePaddingLayout::kFrameBaseSize * kPointerSize;
1627
1628       Address padding_pointer = padding_start;
1629       Smi* padding_object =
1630           Smi::FromInt(Debug::FramePaddingLayout::kPaddingValue);
1631       while (Memory::Object_at(padding_pointer) == padding_object) {
1632         padding_pointer -= kPointerSize;
1633       }
1634       int padding_counter =
1635           Smi::cast(Memory::Object_at(padding_pointer))->value();
1636       if (padding_counter * kPointerSize < shortage_bytes) {
1637         return "Not enough space for frame dropper frame "
1638             "(even with padding frame)";
1639       }
1640       Memory::Object_at(padding_pointer) =
1641           Smi::FromInt(padding_counter - shortage_bytes / kPointerSize);
1642
1643       StackFrame* pre_pre_frame = frames[top_frame_index - 2];
1644
1645       OS::MemMove(padding_start + kPointerSize - shortage_bytes,
1646                   padding_start + kPointerSize,
1647                   Debug::FramePaddingLayout::kFrameBaseSize * kPointerSize);
1648
1649       pre_top_frame->UpdateFp(pre_top_frame->fp() - shortage_bytes);
1650       pre_pre_frame->SetCallerFp(pre_top_frame->fp());
1651       unused_stack_top -= shortage_bytes;
1652
1653       STATIC_ASSERT(sizeof(Address) == kPointerSize);
1654       top_frame_pc_address -= shortage_bytes / kPointerSize;
1655     } else {
1656       return "Not enough space for frame dropper frame";
1657     }
1658   }
1659
1660   // Committing now. After this point we should return only NULL value.
1661
1662   FixTryCatchHandler(pre_top_frame, bottom_js_frame);
1663   // Make sure FixTryCatchHandler is idempotent.
1664   ASSERT(!FixTryCatchHandler(pre_top_frame, bottom_js_frame));
1665
1666   Handle<Code> code = isolate->builtins()->FrameDropper_LiveEdit();
1667   *top_frame_pc_address = code->entry();
1668   pre_top_frame->SetCallerFp(bottom_js_frame->fp());
1669
1670   *restarter_frame_function_pointer =
1671       Debug::SetUpFrameDropperFrame(bottom_js_frame, code);
1672
1673   ASSERT((**restarter_frame_function_pointer)->IsJSFunction());
1674
1675   for (Address a = unused_stack_top;
1676       a < unused_stack_bottom;
1677       a += kPointerSize) {
1678     Memory::Object_at(a) = Smi::FromInt(0);
1679   }
1680
1681   return NULL;
1682 }
1683
1684
1685 static bool IsDropableFrame(StackFrame* frame) {
1686   return !frame->is_exit();
1687 }
1688
1689
1690 // Describes a set of call frames that execute any of listed functions.
1691 // Finding no such frames does not mean error.
1692 class MultipleFunctionTarget {
1693  public:
1694   MultipleFunctionTarget(Handle<JSArray> shared_info_array,
1695       Handle<JSArray> result)
1696       : m_shared_info_array(shared_info_array),
1697         m_result(result) {}
1698   bool MatchActivation(StackFrame* frame,
1699       LiveEdit::FunctionPatchabilityStatus status) {
1700     return CheckActivation(m_shared_info_array, m_result, frame, status);
1701   }
1702   const char* GetNotFoundMessage() {
1703     return NULL;
1704   }
1705  private:
1706   Handle<JSArray> m_shared_info_array;
1707   Handle<JSArray> m_result;
1708 };
1709
1710
1711 // Drops all call frame matched by target and all frames above them.
1712 template<typename TARGET>
1713 static const char* DropActivationsInActiveThreadImpl(
1714     Isolate* isolate, TARGET& target, bool do_drop) {
1715   Debug* debug = isolate->debug();
1716   Zone zone(isolate);
1717   Vector<StackFrame*> frames = CreateStackMap(isolate, &zone);
1718
1719
1720   int top_frame_index = -1;
1721   int frame_index = 0;
1722   for (; frame_index < frames.length(); frame_index++) {
1723     StackFrame* frame = frames[frame_index];
1724     if (frame->id() == debug->break_frame_id()) {
1725       top_frame_index = frame_index;
1726       break;
1727     }
1728     if (target.MatchActivation(
1729             frame, LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE)) {
1730       // We are still above break_frame. It is not a target frame,
1731       // it is a problem.
1732       return "Debugger mark-up on stack is not found";
1733     }
1734   }
1735
1736   if (top_frame_index == -1) {
1737     // We haven't found break frame, but no function is blocking us anyway.
1738     return target.GetNotFoundMessage();
1739   }
1740
1741   bool target_frame_found = false;
1742   int bottom_js_frame_index = top_frame_index;
1743   bool c_code_found = false;
1744
1745   for (; frame_index < frames.length(); frame_index++) {
1746     StackFrame* frame = frames[frame_index];
1747     if (!IsDropableFrame(frame)) {
1748       c_code_found = true;
1749       break;
1750     }
1751     if (target.MatchActivation(
1752             frame, LiveEdit::FUNCTION_BLOCKED_ON_ACTIVE_STACK)) {
1753       target_frame_found = true;
1754       bottom_js_frame_index = frame_index;
1755     }
1756   }
1757
1758   if (c_code_found) {
1759     // There is a C frames on stack. Check that there are no target frames
1760     // below them.
1761     for (; frame_index < frames.length(); frame_index++) {
1762       StackFrame* frame = frames[frame_index];
1763       if (frame->is_java_script()) {
1764         if (target.MatchActivation(
1765                 frame, LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE)) {
1766           // Cannot drop frame under C frames.
1767           return NULL;
1768         }
1769       }
1770     }
1771   }
1772
1773   if (!do_drop) {
1774     // We are in check-only mode.
1775     return NULL;
1776   }
1777
1778   if (!target_frame_found) {
1779     // Nothing to drop.
1780     return target.GetNotFoundMessage();
1781   }
1782
1783   Debug::FrameDropMode drop_mode = Debug::FRAMES_UNTOUCHED;
1784   Object** restarter_frame_function_pointer = NULL;
1785   const char* error_message = DropFrames(frames, top_frame_index,
1786                                          bottom_js_frame_index, &drop_mode,
1787                                          &restarter_frame_function_pointer);
1788
1789   if (error_message != NULL) {
1790     return error_message;
1791   }
1792
1793   // Adjust break_frame after some frames has been dropped.
1794   StackFrame::Id new_id = StackFrame::NO_ID;
1795   for (int i = bottom_js_frame_index + 1; i < frames.length(); i++) {
1796     if (frames[i]->type() == StackFrame::JAVA_SCRIPT) {
1797       new_id = frames[i]->id();
1798       break;
1799     }
1800   }
1801   debug->FramesHaveBeenDropped(new_id, drop_mode,
1802                                restarter_frame_function_pointer);
1803   return NULL;
1804 }
1805
1806
1807 // Fills result array with statuses of functions. Modifies the stack
1808 // removing all listed function if possible and if do_drop is true.
1809 static const char* DropActivationsInActiveThread(
1810     Handle<JSArray> shared_info_array, Handle<JSArray> result, bool do_drop) {
1811   MultipleFunctionTarget target(shared_info_array, result);
1812
1813   const char* message = DropActivationsInActiveThreadImpl(
1814       shared_info_array->GetIsolate(), target, do_drop);
1815   if (message) {
1816     return message;
1817   }
1818
1819   Isolate* isolate = shared_info_array->GetIsolate();
1820   int array_len = GetArrayLength(shared_info_array);
1821
1822   // Replace "blocked on active" with "replaced on active" status.
1823   for (int i = 0; i < array_len; i++) {
1824     Handle<Object> obj =
1825         Object::GetElement(isolate, result, i).ToHandleChecked();
1826     if (*obj == Smi::FromInt(LiveEdit::FUNCTION_BLOCKED_ON_ACTIVE_STACK)) {
1827       Handle<Object> replaced(
1828           Smi::FromInt(LiveEdit::FUNCTION_REPLACED_ON_ACTIVE_STACK), isolate);
1829       SetElementSloppy(result, i, replaced);
1830     }
1831   }
1832   return NULL;
1833 }
1834
1835
1836 class InactiveThreadActivationsChecker : public ThreadVisitor {
1837  public:
1838   InactiveThreadActivationsChecker(Handle<JSArray> shared_info_array,
1839                                    Handle<JSArray> result)
1840       : shared_info_array_(shared_info_array), result_(result),
1841         has_blocked_functions_(false) {
1842   }
1843   void VisitThread(Isolate* isolate, ThreadLocalTop* top) {
1844     for (StackFrameIterator it(isolate, top); !it.done(); it.Advance()) {
1845       has_blocked_functions_ |= CheckActivation(
1846           shared_info_array_, result_, it.frame(),
1847           LiveEdit::FUNCTION_BLOCKED_ON_OTHER_STACK);
1848     }
1849   }
1850   bool HasBlockedFunctions() {
1851     return has_blocked_functions_;
1852   }
1853
1854  private:
1855   Handle<JSArray> shared_info_array_;
1856   Handle<JSArray> result_;
1857   bool has_blocked_functions_;
1858 };
1859
1860
1861 Handle<JSArray> LiveEdit::CheckAndDropActivations(
1862     Handle<JSArray> shared_info_array, bool do_drop) {
1863   Isolate* isolate = shared_info_array->GetIsolate();
1864   int len = GetArrayLength(shared_info_array);
1865
1866   Handle<JSArray> result = isolate->factory()->NewJSArray(len);
1867
1868   // Fill the default values.
1869   for (int i = 0; i < len; i++) {
1870     SetElementSloppy(
1871         result,
1872         i,
1873         Handle<Smi>(Smi::FromInt(FUNCTION_AVAILABLE_FOR_PATCH), isolate));
1874   }
1875
1876
1877   // First check inactive threads. Fail if some functions are blocked there.
1878   InactiveThreadActivationsChecker inactive_threads_checker(shared_info_array,
1879                                                             result);
1880   isolate->thread_manager()->IterateArchivedThreads(
1881       &inactive_threads_checker);
1882   if (inactive_threads_checker.HasBlockedFunctions()) {
1883     return result;
1884   }
1885
1886   // Try to drop activations from the current stack.
1887   const char* error_message =
1888       DropActivationsInActiveThread(shared_info_array, result, do_drop);
1889   if (error_message != NULL) {
1890     // Add error message as an array extra element.
1891     Handle<String> str =
1892         isolate->factory()->NewStringFromAsciiChecked(error_message);
1893     SetElementSloppy(result, len, str);
1894   }
1895   return result;
1896 }
1897
1898
1899 // Describes a single callframe a target. Not finding this frame
1900 // means an error.
1901 class SingleFrameTarget {
1902  public:
1903   explicit SingleFrameTarget(JavaScriptFrame* frame)
1904       : m_frame(frame),
1905         m_saved_status(LiveEdit::FUNCTION_AVAILABLE_FOR_PATCH) {}
1906
1907   bool MatchActivation(StackFrame* frame,
1908       LiveEdit::FunctionPatchabilityStatus status) {
1909     if (frame->fp() == m_frame->fp()) {
1910       m_saved_status = status;
1911       return true;
1912     }
1913     return false;
1914   }
1915   const char* GetNotFoundMessage() {
1916     return "Failed to found requested frame";
1917   }
1918   LiveEdit::FunctionPatchabilityStatus saved_status() {
1919     return m_saved_status;
1920   }
1921  private:
1922   JavaScriptFrame* m_frame;
1923   LiveEdit::FunctionPatchabilityStatus m_saved_status;
1924 };
1925
1926
1927 // Finds a drops required frame and all frames above.
1928 // Returns error message or NULL.
1929 const char* LiveEdit::RestartFrame(JavaScriptFrame* frame) {
1930   SingleFrameTarget target(frame);
1931
1932   const char* result = DropActivationsInActiveThreadImpl(
1933       frame->isolate(), target, true);
1934   if (result != NULL) {
1935     return result;
1936   }
1937   if (target.saved_status() == LiveEdit::FUNCTION_BLOCKED_UNDER_NATIVE_CODE) {
1938     return "Function is blocked under native code";
1939   }
1940   return NULL;
1941 }
1942
1943
1944 LiveEditFunctionTracker::LiveEditFunctionTracker(Isolate* isolate,
1945                                                  FunctionLiteral* fun)
1946     : isolate_(isolate) {
1947   if (isolate_->active_function_info_listener() != NULL) {
1948     isolate_->active_function_info_listener()->FunctionStarted(fun);
1949   }
1950 }
1951
1952
1953 LiveEditFunctionTracker::~LiveEditFunctionTracker() {
1954   if (isolate_->active_function_info_listener() != NULL) {
1955     isolate_->active_function_info_listener()->FunctionDone();
1956   }
1957 }
1958
1959
1960 void LiveEditFunctionTracker::RecordFunctionInfo(
1961     Handle<SharedFunctionInfo> info, FunctionLiteral* lit,
1962     Zone* zone) {
1963   if (isolate_->active_function_info_listener() != NULL) {
1964     isolate_->active_function_info_listener()->FunctionInfo(info, lit->scope(),
1965                                                             zone);
1966   }
1967 }
1968
1969
1970 void LiveEditFunctionTracker::RecordRootFunctionInfo(Handle<Code> code) {
1971   isolate_->active_function_info_listener()->FunctionCode(code);
1972 }
1973
1974
1975 bool LiveEditFunctionTracker::IsActive(Isolate* isolate) {
1976   return isolate->active_function_info_listener() != NULL;
1977 }
1978
1979 } }  // namespace v8::internal