[Atomics] code stubs for atomic operations

src/arm/simulator-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 <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #if V8_TARGET_ARCH_ARM
 
@@ skipping 3886 matching lines @@
           }
         }
       } else {
         UNIMPLEMENTED();
       }
       break;
     case 0xA:
     case 0xB:
       if ((instr->Bits(22, 20) == 5) && (instr->Bits(15, 12) == 0xf)) {
         // pld: ignore instruction.
+      } else if (instr->SpecialValue() == 0xA && instr->Bits(22, 20) == 7) {
+        // dsb, dmb, isb: ignore instruction for now.
+        // TODO(binji): implement
       } else {
         UNIMPLEMENTED();
       }
       break;
     case 0x1D:
       if (instr->Opc1Value() == 0x7 && instr->Opc3Value() == 0x1 &&
           instr->Bits(11, 9) == 0x5 && instr->Bits(19, 18) == 0x2) {
         if (instr->SzValue() == 0x1) {
           int vm = instr->VFPMRegValue(kDoublePrecision);
           int vd = instr->VFPDRegValue(kDoublePrecision);
@@ skipping 298 matching lines @@
   set_register(sp, current_sp + sizeof(uintptr_t));
   return address;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // USE_SIMULATOR
 
 #endif  // V8_TARGET_ARCH_ARM