[interpreter] Add a fast path for dynamic local load

src/interpreter/bytecode-array-builder.h

 // Copyright 2015 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_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_
 #define V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_
 
 #include "src/ast/ast.h"
 #include "src/interpreter/bytecode-array-writer.h"
 #include "src/interpreter/bytecode-register-allocator.h"
@@ skipping 113 matching lines @@
                                            int feedback_slot,
                                            LanguageMode language_mode);
   BytecodeArrayBuilder& StoreKeyedProperty(Register object, Register key,
                                            int feedback_slot,
                                            LanguageMode language_mode);
 
   // Lookup the variable with |name|.
   BytecodeArrayBuilder& LoadLookupSlot(const Handle<String> name,
                                        TypeofMode typeof_mode);
 
+  // Lookup the variable with |name|, which is known to be at |slot_index| at
+  // |depth| in the context chain if not shadowed by a context extension
+  // somewhere in that context chain.
+  BytecodeArrayBuilder& LoadLookupContextSlot(const Handle<String> name,
+                                              TypeofMode typeof_mode,
+                                              int slot_index, int depth);
+
   // Store value in the accumulator into the variable with |name|.
   BytecodeArrayBuilder& StoreLookupSlot(const Handle<String> name,
                                         LanguageMode language_mode);
 
   // Create a new closure for a SharedFunctionInfo which will be inserted at
   // constant pool index |entry|.
   BytecodeArrayBuilder& CreateClosure(size_t entry, int flags);
 
   // Create a new local context for a |scope_info| and a closure which should be
   // in the accumulator.
@@ skipping 261 matching lines @@
   static int const kNoFeedbackSlot = 0;
 
   DISALLOW_COPY_AND_ASSIGN(BytecodeArrayBuilder);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_