[interpreter] Add a fast path for dynamic local load

src/interpreter/bytecode-generator.cc

 // 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.
 
 #include "src/interpreter/bytecode-generator.h"
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/code-stubs.h"
 #include "src/compilation-info.h"
@@ skipping 1949 matching lines @@
         depth = 0;
       } else {
         context_reg = execution_context()->reg();
       }
 
       builder()->LoadContextSlot(context_reg, variable->index(), depth);
       BuildHoleCheckForVariableLoad(variable);
       break;
     }
     case VariableLocation::LOOKUP: {
-      builder()->LoadLookupSlot(variable->name(), typeof_mode);
+      switch (variable->mode()) {
+        case DYNAMIC_LOCAL: {
+          Variable* local_variable = variable->local_if_not_shadowed();
+          int depth =
+              execution_context()->ContextChainDepth(local_variable->scope());
+          builder()->LoadLookupContextSlot(variable->name(), typeof_mode,
+                                           local_variable->index(), depth);
+          BuildHoleCheckForVariableLoad(variable);
+          break;
+        }
+        default:
+          builder()->LoadLookupSlot(variable->name(), typeof_mode);
+      }
       break;
     }
     case VariableLocation::MODULE: {
       ModuleDescriptor* descriptor = scope()->GetModuleScope()->module();
       if (variable->IsExport()) {
         auto it = descriptor->regular_exports().find(variable->raw_name());
         DCHECK(it != descriptor->regular_exports().end());
         Register export_name = register_allocator()->NewRegister();
         builder()
             ->LoadLiteral(it->second->export_name->string())
@@ skipping 1445 matching lines @@
   return execution_context()->scope()->language_mode();
 }
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return TypeFeedbackVector::GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8