Move Maps' back pointers from "transitions" to "constructor" field

src/arm64/full-codegen-arm64.cc

 // Copyright 2013 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/v8.h"
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 3466 matching lines @@
   __ B(eq, &function);
 
   __ Cmp(x11, LAST_SPEC_OBJECT_TYPE);
   STATIC_ASSERT(LAST_NONCALLABLE_SPEC_OBJECT_TYPE ==
                 LAST_SPEC_OBJECT_TYPE - 1);
   __ B(eq, &function);
   // Assume that there is no larger type.
   STATIC_ASSERT(LAST_NONCALLABLE_SPEC_OBJECT_TYPE == LAST_TYPE - 1);
 
   // Check if the constructor in the map is a JS function.
-  __ Ldr(x12, FieldMemOperand(x10, Map::kConstructorOffset));
-  __ JumpIfNotObjectType(x12, x13, x14, JS_FUNCTION_TYPE,
-                         &non_function_constructor);
+  Register instance_type = x14;
+  __ GetMapConstructor(x12, x10, x13, instance_type);
+  __ Cmp(instance_type, JS_FUNCTION_TYPE);
+  __ B(ne, &non_function_constructor);
 
   // x12 now contains the constructor function. Grab the
   // instance class name from there.
   __ Ldr(x13, FieldMemOperand(x12, JSFunction::kSharedFunctionInfoOffset));
   __ Ldr(x0,
          FieldMemOperand(x13, SharedFunctionInfo::kInstanceClassNameOffset));
   __ B(&done);
 
   // Functions have class 'Function'.
   __ Bind(&function);
@@ skipping 1980 matching lines @@
   return previous_;
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64