Remember to update the write barrier when storing into...

src/arm/macro-assembler-arm.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 259 matching lines @@
   // object: address of remembered set word
   // offset: bit offset of store position
   and_(offset, offset, Operand(kBitsPerInt - 1));
 
   ldr(scratch, MemOperand(object));
   mov(ip, Operand(1));
   orr(scratch, scratch, Operand(ip, LSL, offset));
   str(scratch, MemOperand(object));
 
   bind(&done);
+
+  // Clobber all input registers when running with the debug-code flag
+  // turned on to provoke errors.
+  if (FLAG_debug_code) {
+    mov(object, Operand(bit_cast<int32_t>(kZapValue)));
+    mov(offset, Operand(bit_cast<int32_t>(kZapValue)));
+    mov(scratch, Operand(bit_cast<int32_t>(kZapValue)));
+  }
 }
 
 
 void MacroAssembler::EnterFrame(StackFrame::Type type) {
   // r0-r3: preserved
   stm(db_w, sp, cp.bit() | fp.bit() | lr.bit());
   mov(ip, Operand(Smi::FromInt(type)));
   push(ip);
   mov(ip, Operand(CodeObject()));
   push(ip);
@@ skipping 1009 matching lines @@
 }
 
 
 void CodePatcher::Emit(Address addr) {
   masm()->emit(reinterpret_cast<Instr>(addr));
 }
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 
 } }  // namespace v8::internal