[arm64] Change comparison to CBNZ in PropertyHandlerCompiler::CheckPrototypes.

src/ic/arm64/handler-compiler-arm64.cc

 // Copyright 2014 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_ARM64
 
 #include "src/ic/handler-compiler.h"
 
 #include "src/api-arguments.h"
 #include "src/field-type.h"
@@ skipping 460 matching lines @@
   // object_reg and holder_reg registers can alias.
   DCHECK(!AreAliased(object_reg, scratch1, scratch2));
   DCHECK(!AreAliased(holder_reg, scratch1, scratch2));
 
   Handle<Cell> validity_cell =
       Map::GetOrCreatePrototypeChainValidityCell(receiver_map, isolate());
   if (!validity_cell.is_null()) {
     DCHECK_EQ(Smi::FromInt(Map::kPrototypeChainValid), validity_cell->value());
     __ Mov(scratch1, Operand(validity_cell));
     __ Ldr(scratch1, FieldMemOperand(scratch1, Cell::kValueOffset));
-    __ Cmp(scratch1, Operand(Smi::FromInt(Map::kPrototypeChainValid)));
-    __ B(ne, miss);
+    // Compare scratch1 against Map::kPrototypeChainValid.
+    static_assert(Map::kPrototypeChainValid == 0,
+                  "Map::kPrototypeChainValid has unexpected value");
+    __ Cbnz(scratch1, miss);
   }
 
   // Keep track of the current object in register reg.
   Register reg = object_reg;
   int depth = 0;
 
   Handle<JSObject> current = Handle<JSObject>::null();
   if (receiver_map->IsJSGlobalObjectMap()) {
     current = isolate()->global_object();
   }
@@ skipping 189 matching lines @@
   // Return the generated code.
   return GetCode(kind(), name);
 }
 
 
 #undef __
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32