Implement write barrier on ARM.

runtime/vm/assembler_arm.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_ASSEMBLER_ARM_H_
 #define VM_ASSEMBLER_ARM_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_arm.h directly; use assembler.h instead.
 #endif
@@ skipping 536 matching lines @@
                       Register scratch, Condition cond = AL);
 
   void MarkExceptionHandler(Label* label);
 
   void Drop(intptr_t stack_elements);
 
   void LoadObject(Register rd, const Object& object);
   void PushObject(const Object& object);
   void CompareObject(Register rn, const Object& object);
 
+  void StoreIntoObject(Register object,  // Object we are storing into.
+                       const Address& dest,  // Where we are storing into.
+                       Register value,  // Value we are storing.
+                       bool can_value_be_smi = true);
+
+  void StoreIntoObjectNoBarrier(Register object,
+                                const Address& dest,
+                                Register value);
+  void StoreIntoObjectNoBarrier(Register object,
+                                const Address& dest,
+                                const Object& value);
+
   void LoadClassId(Register result, Register object);
   void LoadClassById(Register result, Register class_id);
   void LoadClass(Register result, Register object, Register scratch);
   void CompareClassId(Register object, intptr_t class_id, Register scratch);
 
   void LoadWordFromPoolOffset(Register rd, int32_t offset);
   void LoadFromOffset(LoadOperandType type,
                       Register reg,
                       Register base,
                       int32_t offset,
@@ skipping 198 matching lines @@
                  int32_t opcode,
                  DRegister dd,
                  SRegister sm);
 
   void EmitBranch(Condition cond, Label* label, bool link);
   static int32_t EncodeBranchOffset(int32_t offset, int32_t inst);
   static int DecodeBranchOffset(int32_t inst);
   int32_t EncodeTstOffset(int32_t offset, int32_t inst);
   int DecodeTstOffset(int32_t inst);
 
-  // Returns whether or not the given register is used for passing parameters.
-  static int RegisterCompare(const Register* reg1, const Register* reg2) {
-    return *reg1 - *reg2;
-  }
+  void StoreIntoObjectFilter(Register object, Register value, Label* no_update);
+
+  // Shorter filtering sequence that assumes that value is not a smi.
+  void StoreIntoObjectFilterNoSmi(Register object,
+                                  Register value,
+                                  Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_ARM_H_