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

src/arm/full-codegen-arm.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.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 3759 matching lines @@
   __ b(eq, &function);
 
   __ cmp(r1, Operand(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(r0, FieldMemOperand(r0, Map::kConstructorOffset));
-  __ CompareObjectType(r0, r1, r1, JS_FUNCTION_TYPE);
+  Register instance_type = r2;
+  __ GetMapConstructor(r0, r0, r1, instance_type);
+  __ cmp(instance_type, Operand(JS_FUNCTION_TYPE));
   __ b(ne, &non_function_constructor);
 
   // r0 now contains the constructor function. Grab the
   // instance class name from there.
   __ ldr(r0, FieldMemOperand(r0, JSFunction::kSharedFunctionInfoOffset));
   __ ldr(r0, FieldMemOperand(r0, SharedFunctionInfo::kInstanceClassNameOffset));
   __ b(&done);
 
   // Functions have class 'Function'.
   __ bind(&function);
@@ skipping 1709 matching lines @@
 
   DCHECK(interrupt_address ==
          isolate->builtins()->OsrAfterStackCheck()->entry());
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM