Use generated Neon version of MemCopy() on ARM, if platform supports it.

src/platform-posix.cc

 // Copyright 2012 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 297 matching lines @@
     // If the length is zero, the assignment fails.
     if (str.length() > 0)
       str[str.length() - 1] = '\0';
     return -1;
   } else {
     return n;
   }
 }
 
 
-#if defined(V8_TARGET_ARCH_IA32)
+#if defined(V8_GENERATED_MEMCPY)
 static OS::MemCopyFunction memcopy_function = NULL;
-// Defined in codegen-ia32.cc.
+// Defined in codegen-<arch>.cc.
 OS::MemCopyFunction CreateMemCopyFunction();
 
 // Copy memory area to disjoint memory area.
 void OS::MemCopy(void* dest, const void* src, size_t size) {
   // Note: here we rely on dependent reads being ordered. This is true
   // on all architectures we currently support.
   (*memcopy_function)(dest, src, size);
 #ifdef DEBUG
   CHECK_EQ(0, memcmp(dest, src, size));
 #endif
 }
-#endif  // V8_TARGET_ARCH_IA32
+#endif  // V8_GENERATED_MEMCPY
 
 
 void POSIXPostSetUp() {
-#if defined(V8_TARGET_ARCH_IA32)
+#if defined(V8_GENERATED_MEMCPY)
   memcopy_function = CreateMemCopyFunction();
 #endif
   init_fast_sin_function();
   init_fast_cos_function();
   init_fast_tan_function();
   init_fast_log_function();
   // fast_exp is initialized lazily.
   init_fast_sqrt_function();
 }
 
@@ skipping 203 matching lines @@
   return ntohl(value);
 }
 
 
 Socket* OS::CreateSocket() {
   return new POSIXSocket();
 }
 
 
 } }  // namespace v8::internal