PreParsing inner funcs: Do fewer variable name lookups.

src/ast/scopes.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/ast/scopes.h"
 
 #include <set>
 
 #include "src/accessors.h"
 #include "src/ast/ast.h"
@@ skipping 1019 matching lines @@
   DCHECK(GetDeclarationScope()->is_being_lazily_parsed());
 
   if (mode == VAR && !is_declaration_scope()) {
     return GetDeclarationScope()->DeclareVariableName(name, mode);
   }
   DCHECK(!is_catch_scope());
   DCHECK(!is_with_scope());
   DCHECK(!is_eval_scope());
   DCHECK(is_declaration_scope() ||
          (IsLexicalVariableMode(mode) && is_block_scope()));
+  DCHECK(scope_info_.is_null());
 
   // Declare the variable in the declaration scope.
-  if (LookupLocal(name) == nullptr) {
-    variables_.DeclareName(zone(), name);
-  }
+  variables_.DeclareName(zone(), name);
 }
 
 VariableProxy* Scope::NewUnresolved(AstNodeFactory* factory,
                                     const AstRawString* name,
                                     int start_position, VariableKind kind) {
   // Note that we must not share the unresolved variables with
   // the same name because they may be removed selectively via
   // RemoveUnresolved().
   DCHECK(!already_resolved_);
   DCHECK_EQ(factory->zone(), zone());
@@ skipping 1072 matching lines @@
   Variable* function =
       is_function_scope() ? AsDeclarationScope()->function_var() : nullptr;
   bool is_function_var_in_context =
       function != nullptr && function->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
          (is_function_var_in_context ? 1 : 0);
 }
 
 }  // namespace internal
 }  // namespace v8