Do not go to slow mode and back to fast in initializer blocks.

src/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 814 matching lines @@
   Handle<FixedArray> elements = factory->NewFixedArray(args.length());
   for (int i = 0; i < args.length(); i++) {
     elements->set(i, *args[i]);
   }
   Handle<JSArray> array = factory->NewJSArrayWithElements(elements);
   Handle<Object> result = factory->NewSyntaxError(type, array);
   isolate()->Throw(*result, &location);
 }
 
 
-// Base class containing common code for the different finder classes used by
-// the parser.
-class ParserFinder {
- protected:
-  ParserFinder() {}
-  static Assignment* AsAssignment(Statement* stat) {
-    if (stat == NULL) return NULL;
-    ExpressionStatement* exp_stat = stat->AsExpressionStatement();
-    if (exp_stat == NULL) return NULL;
-    return exp_stat->expression()->AsAssignment();
-  }
-};
-
-
-// An InitializationBlockFinder finds and marks sequences of statements of the
-// form expr.a = ...; expr.b = ...; etc.
-class InitializationBlockFinder : public ParserFinder {
- public:
-  // We find and mark the initialization blocks in top level
-  // non-looping code only. This is because the optimization prevents
-  // reuse of the map transitions, so it should be used only for code
-  // that will only be run once.
-  InitializationBlockFinder(Scope* top_scope, Target* target)
-      : enabled_(top_scope->DeclarationScope()->is_global_scope() &&
-                 !IsLoopTarget(target)),
-        first_in_block_(NULL),
-        last_in_block_(NULL),
-        block_size_(0) {}
-
-  ~InitializationBlockFinder() {
-    if (!enabled_) return;
-    if (InBlock()) EndBlock();
-  }
-
-  void Update(Statement* stat) {
-    if (!enabled_) return;
-    Assignment* assignment = AsAssignment(stat);
-    if (InBlock()) {
-      if (BlockContinues(assignment)) {
-        UpdateBlock(assignment);
-      } else {
-        EndBlock();
-      }
-    }
-    if (!InBlock() && (assignment != NULL) &&
-        (assignment->op() == Token::ASSIGN)) {
-      StartBlock(assignment);
-    }
-  }
-
- private:
-  // The minimum number of contiguous assignment that will
-  // be treated as an initialization block. Benchmarks show that
-  // the overhead exceeds the savings below this limit.
-  static const int kMinInitializationBlock = 3;
-
-  static bool IsLoopTarget(Target* target) {
-    while (target != NULL) {
-      if (target->node()->AsIterationStatement() != NULL) return true;
-      target = target->previous();
-    }
-    return false;
-  }
-
-  // Returns true if the expressions appear to denote the same object.
-  // In the context of initialization blocks, we only consider expressions
-  // of the form 'expr.x' or expr["x"].
-  static bool SameObject(Expression* e1, Expression* e2) {
-    VariableProxy* v1 = e1->AsVariableProxy();
-    VariableProxy* v2 = e2->AsVariableProxy();
-    if (v1 != NULL && v2 != NULL) {
-      return v1->name()->Equals(*v2->name());
-    }
-    Property* p1 = e1->AsProperty();
-    Property* p2 = e2->AsProperty();
-    if ((p1 == NULL) || (p2 == NULL)) return false;
-    Literal* key1 = p1->key()->AsLiteral();
-    Literal* key2 = p2->key()->AsLiteral();
-    if ((key1 == NULL) || (key2 == NULL)) return false;
-    if (!key1->handle()->IsString() || !key2->handle()->IsString()) {
-      return false;
-    }
-    String* name1 = String::cast(*key1->handle());
-    String* name2 = String::cast(*key2->handle());
-    if (!name1->Equals(name2)) return false;
-    return SameObject(p1->obj(), p2->obj());
-  }
-
-  // Returns true if the expressions appear to denote different properties
-  // of the same object.
-  static bool PropertyOfSameObject(Expression* e1, Expression* e2) {
-    Property* p1 = e1->AsProperty();
-    Property* p2 = e2->AsProperty();
-    if ((p1 == NULL) || (p2 == NULL)) return false;
-    return SameObject(p1->obj(), p2->obj());
-  }
-
-  bool BlockContinues(Assignment* assignment) {
-    if ((assignment == NULL) || (first_in_block_ == NULL)) return false;
-    if (assignment->op() != Token::ASSIGN) return false;
-    return PropertyOfSameObject(first_in_block_->target(),
-                                assignment->target());
-  }
-
-  void StartBlock(Assignment* assignment) {
-    first_in_block_ = assignment;
-    last_in_block_ = assignment;
-    block_size_ = 1;
-  }
-
-  void UpdateBlock(Assignment* assignment) {
-    last_in_block_ = assignment;
-    ++block_size_;
-  }
-
-  void EndBlock() {
-    if (block_size_ >= kMinInitializationBlock) {
-      first_in_block_->mark_block_start();
-      last_in_block_->mark_block_end();
-    }
-    last_in_block_ = first_in_block_ = NULL;
-    block_size_ = 0;
-  }
-
-  bool InBlock() { return first_in_block_ != NULL; }
-
-  const bool enabled_;
-  Assignment* first_in_block_;
-  Assignment* last_in_block_;
-  int block_size_;
-
-  DISALLOW_COPY_AND_ASSIGN(InitializationBlockFinder);
-};
-
-
 // A ThisNamedPropertyAssignmentFinder finds and marks statements of the form
 // this.x = ...;, where x is a named property. It also determines whether a
 // function contains only assignments of this type.
-class ThisNamedPropertyAssignmentFinder : public ParserFinder {
+class ThisNamedPropertyAssignmentFinder {
  public:
   ThisNamedPropertyAssignmentFinder(Isolate* isolate, Zone* zone)
       : isolate_(isolate),
         only_simple_this_property_assignments_(true),
         names_(0, zone),
         assigned_arguments_(0, zone),
         assigned_constants_(0, zone),
         zone_(zone) {
   }
 
+  static Assignment* AsAssignment(Statement* stat) {
+    if (stat == NULL) return NULL;
+    ExpressionStatement* exp_stat = stat->AsExpressionStatement();
+    if (exp_stat == NULL) return NULL;
+    return exp_stat->expression()->AsAssignment();
+  }
+
   void Update(Scope* scope, Statement* stat) {
     // Bail out if function already has property assignment that are
     // not simple this property assignments.
     if (!only_simple_this_property_assignments_) {
       return;
     }
 
     // Check whether this statement is of the form this.x = ...;
     Assignment* assignment = AsAssignment(stat);
     if (IsThisPropertyAssignment(assignment)) {
@@ skipping 145 matching lines @@
   // SourceElements ::
   //   (ModuleElement)* <end_token>
 
   // Allocate a target stack to use for this set of source
   // elements. This way, all scripts and functions get their own
   // target stack thus avoiding illegal breaks and continues across
   // functions.
   TargetScope scope(&this->target_stack_);
 
   ASSERT(processor != NULL);
-  InitializationBlockFinder block_finder(top_scope_, target_stack_);
   ThisNamedPropertyAssignmentFinder this_property_assignment_finder(isolate(),
                                                                     zone());
   bool directive_prologue = true;     // Parsing directive prologue.
 
   while (peek() != end_token) {
     if (directive_prologue && peek() != Token::STRING) {
       directive_prologue = false;
     }
 
     Scanner::Location token_loc = scanner().peek_location();
@@ skipping 34 matching lines @@
                                       ? EXTENDED_MODE : STRICT_MODE);
           // "use strict" is the only directive for now.
           directive_prologue = false;
         }
       } else {
         // End of the directive prologue.
         directive_prologue = false;
       }
     }
 
-    block_finder.Update(stat);
     // Find and mark all assignments to named properties in this (this.x =)
     if (top_scope_->is_function_scope()) {
       this_property_assignment_finder.Update(top_scope_, stat);
     }
     processor->Add(stat, zone());
   }
 
   // Propagate the collected information on this property assignments.
   if (top_scope_->is_function_scope()) {
     bool only_simple_this_property_assignments =
@@ skipping 132 matching lines @@
 
   Expect(Token::LBRACE, CHECK_OK);
   scope->set_start_position(scanner().location().beg_pos);
   scope->SetLanguageMode(EXTENDED_MODE);
 
   {
     BlockState block_state(this, scope);
     TargetCollector collector(zone());
     Target target(&this->target_stack_, &collector);
     Target target_body(&this->target_stack_, body);
-    InitializationBlockFinder block_finder(top_scope_, target_stack_);
 
     while (peek() != Token::RBRACE) {
       Statement* stat = ParseModuleElement(NULL, CHECK_OK);
       if (stat && !stat->IsEmpty()) {
         body->AddStatement(stat, zone());
-        block_finder.Update(stat);
       }
     }
   }
 
   Expect(Token::RBRACE, CHECK_OK);
   scope->set_end_position(scanner().location().end_pos);
   body->set_scope(scope);
 
   // Check that all exports are bound.
   Interface* interface = scope->interface();
@@ skipping 655 matching lines @@
   // Block ::
   //   '{' Statement* '}'
 
   // Note that a Block does not introduce a new execution scope!
   // (ECMA-262, 3rd, 12.2)
   //
   // Construct block expecting 16 statements.
   Block* result = factory()->NewBlock(labels, 16, false);
   Target target(&this->target_stack_, result);
   Expect(Token::LBRACE, CHECK_OK);
-  InitializationBlockFinder block_finder(top_scope_, target_stack_);
   while (peek() != Token::RBRACE) {
     Statement* stat = ParseStatement(NULL, CHECK_OK);
     if (stat && !stat->IsEmpty()) {
       result->AddStatement(stat, zone());
-      block_finder.Update(stat);
     }
   }
   Expect(Token::RBRACE, CHECK_OK);
   return result;
 }
 
 
 Block* Parser::ParseScopedBlock(ZoneStringList* labels, bool* ok) {
   // The harmony mode uses block elements instead of statements.
   //
   // Block ::
   //   '{' BlockElement* '}'
 
   // Construct block expecting 16 statements.
   Block* body = factory()->NewBlock(labels, 16, false);
   Scope* block_scope = NewScope(top_scope_, BLOCK_SCOPE);
 
   // Parse the statements and collect escaping labels.
   Expect(Token::LBRACE, CHECK_OK);
   block_scope->set_start_position(scanner().location().beg_pos);
   { BlockState block_state(this, block_scope);
     TargetCollector collector(zone());
     Target target(&this->target_stack_, &collector);
     Target target_body(&this->target_stack_, body);
-    InitializationBlockFinder block_finder(top_scope_, target_stack_);
 
     while (peek() != Token::RBRACE) {
       Statement* stat = ParseBlockElement(NULL, CHECK_OK);
       if (stat && !stat->IsEmpty()) {
         body->AddStatement(stat, zone());
-        block_finder.Update(stat);
       }
     }
   }
   Expect(Token::RBRACE, CHECK_OK);
   block_scope->set_end_position(scanner().location().end_pos);
   block_scope = block_scope->FinalizeBlockScope();
   body->set_scope(block_scope);
   return body;
 }
 
@@ skipping 4018 matching lines @@
       ASSERT(info->isolate()->has_pending_exception());
     } else {
       result = parser.ParseProgram();
     }
   }
   info->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal