Remove more dead code now that legacy const is gone

src/full-codegen/x64/full-codegen-x64.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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 744 matching lines @@
         // No write barrier since the hole value is in old space.
         PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       }
       break;
 
     case VariableLocation::LOOKUP: {
       Comment cmnt(masm_, "[ VariableDeclaration");
       __ Push(variable->name());
       // Declaration nodes are always introduced in one of four modes.
       DCHECK(IsDeclaredVariableMode(mode));
-      // Push initial value, if any.
-      // Note: For variables we must not push an initial value (such as
-      // 'undefined') because we may have a (legal) redeclaration and we
-      // must not destroy the current value.
-      if (hole_init) {
-        __ PushRoot(Heap::kTheHoleValueRootIndex);
-      } else {
-        __ Push(Smi::FromInt(0));  // Indicates no initial value.
-      }
+      DCHECK(!hole_init);
+      __ Push(Smi::FromInt(0));  // Indicates no initial value.
       __ Push(Smi::FromInt(variable->DeclarationPropertyAttributes()));
       __ CallRuntime(Runtime::kDeclareLookupSlot);
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
   }
 }
 
 
 void FullCodeGenerator::VisitFunctionDeclaration(
@@ skipping 2920 matching lines @@
   DCHECK_EQ(
       isolate->builtins()->OnStackReplacement()->entry(),
       Assembler::target_address_at(call_target_address, unoptimized_code));
   return ON_STACK_REPLACEMENT;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64