Do not look for the slot in the ScopeInfo's global range when it's not necessary.

src/scopeinfo.h

 // Copyright 2011 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.
 
 #ifndef V8_SCOPEINFO_H_
 #define V8_SCOPEINFO_H_
 
 #include "src/allocation.h"
 #include "src/modules.h"
 #include "src/variables.h"
 
 namespace v8 {
 namespace internal {
 
 // Cache for mapping (data, property name) into context slot index.
 // The cache contains both positive and negative results.
 // Slot index equals -1 means the property is absent.
 // Cleared at startup and prior to mark sweep collection.
 class ContextSlotCache {
  public:
   // Lookup context slot index for (data, name).
   // If absent, kNotFound is returned.
   int Lookup(Object* data, String* name, VariableMode* mode,
-             VariableLocation* location, InitializationFlag* init_flag,
+             InitializationFlag* init_flag,
              MaybeAssignedFlag* maybe_assigned_flag);
 
   // Update an element in the cache.
   void Update(Handle<Object> data, Handle<String> name, VariableMode mode,
-              VariableLocation location, InitializationFlag init_flag,
+              InitializationFlag init_flag,
               MaybeAssignedFlag maybe_assigned_flag, int slot_index);
 
   // Clear the cache.
   void Clear();
 
   static const int kNotFound = -2;
 
  private:
   ContextSlotCache() {
     for (int i = 0; i < kLength; ++i) {
       keys_[i].data = NULL;
       keys_[i].name = NULL;
       values_[i] = kNotFound;
     }
   }
 
   inline static int Hash(Object* data, String* name);
 
 #ifdef DEBUG
   void ValidateEntry(Handle<Object> data, Handle<String> name,
-                     VariableMode mode, VariableLocation location,
-                     InitializationFlag init_flag,
+                     VariableMode mode, InitializationFlag init_flag,
                      MaybeAssignedFlag maybe_assigned_flag, int slot_index);
 #endif
 
   static const int kLength = 256;
   struct Key {
     Object* data;
     String* name;
   };
 
   struct Value {
-    enum VariableLocationFlag { kContext, kGlobal };
-
-    Value(VariableMode mode, VariableLocation location,
-          InitializationFlag init_flag, MaybeAssignedFlag maybe_assigned_flag,
-          int index) {
-      DCHECK(location == VariableLocation::CONTEXT ||
-             location == VariableLocation::GLOBAL);
-      VariableLocationFlag location_flag =
-          location == VariableLocation::CONTEXT ? kContext : kGlobal;
+    Value(VariableMode mode, InitializationFlag init_flag,
+          MaybeAssignedFlag maybe_assigned_flag, int index) {
       DCHECK(ModeField::is_valid(mode));
-      DCHECK(VariableLocationField::is_valid(location_flag));
       DCHECK(InitField::is_valid(init_flag));
       DCHECK(MaybeAssignedField::is_valid(maybe_assigned_flag));
       DCHECK(IndexField::is_valid(index));
       value_ = ModeField::encode(mode) | IndexField::encode(index) |
-               VariableLocationField::encode(location_flag) |
                InitField::encode(init_flag) |
                MaybeAssignedField::encode(maybe_assigned_flag);
       DCHECK(mode == this->mode());
-      DCHECK(location == this->location());
       DCHECK(init_flag == this->initialization_flag());
       DCHECK(maybe_assigned_flag == this->maybe_assigned_flag());
       DCHECK(index == this->index());
     }
 
     explicit inline Value(uint32_t value) : value_(value) {}
 
     uint32_t raw() { return value_; }
 
     VariableMode mode() { return ModeField::decode(value_); }
 
-    VariableLocation location() {
-      switch (VariableLocationField::decode(value_)) {
-        case kContext:
-          return VariableLocation::CONTEXT;
-        case kGlobal:
-          return VariableLocation::GLOBAL;
-      }
-      UNREACHABLE();
-      return VariableLocation::CONTEXT;
-    }
-
     InitializationFlag initialization_flag() {
       return InitField::decode(value_);
     }
 
     MaybeAssignedFlag maybe_assigned_flag() {
       return MaybeAssignedField::decode(value_);
     }
 
     int index() { return IndexField::decode(value_); }
 
     // Bit fields in value_ (type, shift, size). Must be public so the
     // constants can be embedded in generated code.
     class ModeField : public BitField<VariableMode, 0, 4> {};
     class InitField : public BitField<InitializationFlag, 4, 1> {};
     class MaybeAssignedField : public BitField<MaybeAssignedFlag, 5, 1> {};
-    class VariableLocationField : public BitField<VariableLocationFlag, 6, 1> {
-    };
-    class IndexField : public BitField<int, 7, 32 - 7> {};
+    class IndexField : public BitField<int, 6, 32 - 6> {};
 
    private:
     uint32_t value_;
   };
 
   Key keys_[kLength];
   uint32_t values_[kLength];
 
   friend class Isolate;
   DISALLOW_COPY_AND_ASSIGN(ContextSlotCache);
@@ skipping 57 matching lines @@
   }
   void set_index(int i, int index) {
     set(index_offset(i), Smi::FromInt(index));
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPEINFO_H_