scopes.cc.svn-base

Google浏览器V8内核代码

  // which we don't know anything at this point. Thus we must be conservative
  // and assume they may invoke eval themselves. Eventually we could capture
  // this information in the ScopeInfo and then use it here (by traversing
  // the call chain stack, at compile time).
  PropagateScopeInfo(is_eval_scope());

  // 2) Resolve variables.
  Scope* global_scope = NULL;
  if (is_global_scope()) global_scope = this;
  ResolveVariablesRecursively(global_scope);

  // 3) Allocate variables.
  AllocateVariablesRecursively();
}


bool Scope::SupportsEval() const {
  return scope_calls_eval_ || inner_scope_calls_eval_;
}


bool Scope::AllowsLazyCompilation() const {
  return !force_eager_compilation_ && HasTrivialOuterContext();
}


bool Scope::HasTrivialContext() const {
  // A function scope has a trivial context if it always is the global
  // context. We iteratively scan out the context chain to see if
  // there is anything that makes this scope non-trivial; otherwise we
  // return true.
  for (const Scope* scope = this; scope != NULL; scope = scope->outer_scope_) {
    if (scope->is_eval_scope()) return false;
    if (scope->scope_inside_with_) return false;
    if (scope->num_heap_slots_ > 0) return false;
  }
  return true;
}


bool Scope::HasTrivialOuterContext() const {
  Scope* outer = outer_scope_;
  if (outer == NULL) return true;
  // Note that the outer context may be trivial in general, but the current
  // scope may be inside a 'with' statement in which case the outer context
  // for this scope is not trivial.
  return !scope_inside_with_ && outer->HasTrivialContext();
}


int Scope::ContextChainLength(Scope* scope) {
  int n = 0;
  for (Scope* s = this; s != scope; s = s->outer_scope_) {
    ASSERT(s != NULL);  // scope must be in the scope chain
    if (s->num_heap_slots() > 0) n++;
  }
  return n;
}


#ifdef DEBUG
static const char* Header(Scope::Type type) {
  switch (type) {
    case Scope::EVAL_SCOPE: return "eval";
    case Scope::FUNCTION_SCOPE: return "function";
    case Scope::GLOBAL_SCOPE: return "global";
  }
  UNREACHABLE();
  return NULL;
}


static void Indent(int n, const char* str) {
  PrintF("%*s%s", n, "", str);
}


static void PrintName(Handle<String> name) {
  SmartPointer<char> s = name->ToCString(DISALLOW_NULLS);
  PrintF("%s", *s);
}


static void PrintVar(PrettyPrinter* printer, int indent, Variable* var) {
  if (var->var_uses()->is_used() || var->rewrite() != NULL) {
    Indent(indent, Variable::Mode2String(var->mode()));
    PrintF(" ");
    PrintName(var->name());
    PrintF(";  // ");
    if (var->rewrite() != NULL) PrintF("%s, ", printer->Print(var->rewrite()));
    if (var->is_accessed_from_inner_scope()) PrintF("inner scope access, ");
    PrintF("var ");
    var->var_uses()->Print();
    PrintF(", obj ");
    var->obj_uses()->Print();
    PrintF("\n");
  }
}


void Scope::Print(int n) {
  int n0 = (n > 0 ? n : 0);
  int n1 = n0 + 2;  // indentation

  // Print header.
  Indent(n0, Header(type_));
  if (scope_name_->length() > 0) {
    PrintF(" ");
    PrintName(scope_name_);
  }

  // Print parameters, if any.
  if (is_function_scope()) {
    PrintF(" (");
    for (int i = 0; i < params_.length(); i++) {
      if (i > 0) PrintF(", ");
      PrintName(params_[i]->name());
    }
    PrintF(")");
  }

  PrintF(" {\n");

  // Function name, if any (named function literals, only).
  if (function_ != NULL) {
    Indent(n1, "// (local) function name: ");
    PrintName(function_->name());
    PrintF("\n");
  }

  // Scope info.
  if (HasTrivialOuterContext()) {
    Indent(n1, "// scope has trivial outer context\n");
  }
  if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n");
  if (scope_contains_with_) Indent(n1, "// scope contains 'with'\n");
  if (scope_calls_eval_) Indent(n1, "// scope calls 'eval'\n");
  if (outer_scope_calls_eval_) Indent(n1, "// outer scope calls 'eval'\n");
  if (inner_scope_calls_eval_) Indent(n1, "// inner scope calls 'eval'\n");
  if (num_stack_slots_ > 0) { Indent(n1, "// ");
  PrintF("%d stack slots\n", num_stack_slots_); }
  if (num_heap_slots_ > 0) { Indent(n1, "// ");
  PrintF("%d heap slots\n", num_heap_slots_); }

  // Print locals.
  PrettyPrinter printer;
  Indent(n1, "// function var\n");
  if (function_ != NULL) {
    PrintVar(&printer, n1, function_);
  }

  Indent(n1, "// temporary vars\n");
  for (int i = 0; i < temps_.length(); i++) {
    PrintVar(&printer, n1, temps_[i]);
  }

  Indent(n1, "// local vars\n");
  for (LocalsMap::Entry* p = locals_.Start(); p != NULL; p = locals_.Next(p)) {
    Variable* var = reinterpret_cast<Variable*>(p->value);
    PrintVar(&printer, n1, var);
  }

  Indent(n1, "// nonlocal vars\n");
  for (int i = 0; i < nonlocals_.length(); i++)
    PrintVar(&printer, n1, nonlocals_[i]);

  // Print inner scopes (disable by providing negative n).
  if (n >= 0) {
    for (int i = 0; i < inner_scopes_.length(); i++) {
      PrintF("\n");
      inner_scopes_[i]->Print(n1);
    }
  }

  Indent(n0, "}\n");
}
#endif  // DEBUG


Variable* Scope::NonLocal(Handle<String> name) {
  // Space optimization: reuse existing non-local with the same name.
  for (int i = 0; i < nonlocals_.length(); i++) {
    Variable* var = nonlocals_[i];
    if (var->name().is_identical_to(name)) {
      ASSERT(var->mode() == Variable::DYNAMIC);
      return var;
    }
  }

  // Otherwise create a new new-local and add it to the list.
  Variable* var = new Variable(
    NULL /* we don't know the scope */,
    name, Variable::DYNAMIC, true, false);
  nonlocals_.Add(var);

  // Allocate it by giving it a dynamic lookup.
  var->rewrite_ = new Slot(var, Slot::LOOKUP, -1);

  return var;
}


// Lookup a variable starting with this scope. The result is either
// the statically resolved (local!) variable belonging to an outer scope,
// or NULL. It may be NULL because a) we couldn't find a variable, or b)
// because the variable is just a guess (and may be shadowed by another
// variable that is introduced dynamically via an 'eval' call or a 'with'
// statement).
Variable* Scope::LookupRecursive(Handle<String> name, bool inner_lookup) {
  // If we find a variable, but the current scope calls 'eval', the found
  // variable may not be the correct one (the 'eval' may introduce a
  // property with the same name). In that case, remember that the variable
  // found is just a guess.
  bool guess = scope_calls_eval_;

  // Try to find the variable in this scope.
  Variable* var = Lookup(name);

  if (var != NULL) {
    // We found a variable. If this is not an inner lookup, we are done.
    // (Even if there is an 'eval' in this scope which introduces the
    // same variable again, the resulting variable remains the same.
    // Note that enclosing 'with' statements are handled at the call site.)
    if (!inner_lookup)
      return var;

  } else {
    // We did not find a variable locally. Check against the function variable,
    // if any. We can do this for all scopes, since the function variable is
    // only present - if at all - for function scopes.
    //
    // This lookup corresponds to a lookup in the "intermediate" scope sitting
    // between this scope and the outer scope. (ECMA-262, 3rd., requires that
    // the name of named function literal is kept in an intermediate scope
    // inbetween this scope and the next outer scope.)
    if (function_ != NULL && function_->name().is_identical_to(name)) {
      var = function_;

    } else if (outer_scope_ != NULL) {
      var = outer_scope_->LookupRecursive(name, true /* inner lookup */);
      // We may have found a variable in an outer scope. However, if
      // the current scope is inside a 'with', the actual variable may
      // be a property introduced via the 'with' statement. Then, the
      // variable we may have found is just a guess.
      if (scope_inside_with_)
        guess = true;
    }

    // If we did not find a variable, we are done.
    if (var == NULL)
      return NULL;
  }

  ASSERT(var != NULL);

  // If this is a lookup from an inner scope, mark the variable.
  if (inner_lookup)
    var->is_accessed_from_inner_scope_ = true;

  // If the variable we have found is just a guess, invalidate the result.
  if (guess)
    var = NULL;

  return var;
}


void Scope::ResolveVariable(Scope* global_scope, VariableProxy* proxy) {
  ASSERT(global_scope == NULL || global_scope->is_global_scope());

  // If the proxy is already resolved there's nothing to do
  // (functions and consts may be resolved by the parser).
  if (proxy->var() != NULL) return;

  // Otherwise, try to resolve the variable.
  Variable* var = LookupRecursive(proxy->name(), false);

  if (proxy->inside_with()) {
    // If we are inside a local 'with' statement, all bets are off
    // and we cannot resolve the proxy to a local variable even if
    // we found an outer matching variable.
    // Note that we must do a lookup anyway, because if we find one,
    // we must mark that variable as potentially accessed from this
    // inner scope (the property may not be in the 'with' object).
    var = NonLocal(proxy->name());

  } else {
    // We are not inside a local 'with' statement.

    if (var == NULL) {
      // We did not find the variable. We have a global variable
      // if we are in the global scope (we know already that we
      // are outside a 'with' statement) or if there is no way
      // that the variable might be introduced dynamically (through
      // a local or outer eval() call, or an outer 'with' statement),
      // or we don't know about the outer scope (because we are
      // in an eval scope).
      if (!is_global_scope() &&
          (is_eval_scope() || outer_scope_calls_eval_ ||