Remove more dead code now that legacy const is gone

src/full-codegen/mips64/full-codegen-mips64.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_MIPS64
 
 // Note on Mips implementation:
 //
 // The result_register() for mips is the 'v0' register, which is defined
 // by the ABI to contain function return values. However, the first
@@ skipping 781 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");
       __ li(a2, Operand(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) {
-        __ LoadRoot(a0, Heap::kTheHoleValueRootIndex);
-      } else {
-        DCHECK(Smi::FromInt(0) == 0);
-        __ mov(a0, zero_reg);  // Smi::FromInt(0) indicates no initial value.
-      }
+      DCHECK(!hole_init);
+      DCHECK(Smi::FromInt(0) == 0);
+      __ mov(a0, zero_reg);  // Smi::FromInt(0) indicates no initial value.
       __ Push(a2, a0);
       __ Push(Smi::FromInt(variable->DeclarationPropertyAttributes()));
       __ CallRuntime(Runtime::kDeclareLookupSlot);
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
   }
 }
 
 
@@ skipping 3013 matching lines @@
          reinterpret_cast<uint64_t>(
              isolate->builtins()->OnStackReplacement()->entry()));
   return ON_STACK_REPLACEMENT;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS64