Don't duplicate OS::ActivationFrameAlignment() for every POSIX platform.

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 83 matching lines @@
 // limit.
 
 intptr_t OS::MaxVirtualMemory() {
   struct rlimit limit;
   int result = getrlimit(RLIMIT_DATA, &limit);
   if (result != 0) return 0;
   return limit.rlim_cur;
 }
 
 
+int OS::ActivationFrameAlignment() {
+#if V8_TARGET_ARCH_ARM
+  // On EABI ARM targets this is required for fp correctness in the
+  // runtime system.
+  return 8;
+#elif V8_TARGET_ARCH_MIPS
+  return 8;
+#else
+  // Otherwise we just assume 16 byte alignment, i.e.:
+  // - With gcc 4.4 the tree vectorization optimizer can generate code
+  //   that requires 16 byte alignment such as movdqa on x86.
+  // - Mac OS X and Solaris (64-bit) activation frames must be 16 byte-aligned;
+  //   see "Mac OS X ABI Function Call Guide"
+  return 16;
+#endif
+}
+
+
 intptr_t OS::CommitPageSize() {
   static intptr_t page_size = getpagesize();
   return page_size;
 }
 
 
 void OS::Free(void* address, const size_t size) {
   // TODO(1240712): munmap has a return value which is ignored here.
   int result = munmap(address, size);
   USE(result);
@@ skipping 858 matching lines @@
   return ntohl(value);
 }
 
 
 Socket* OS::CreateSocket() {
   return new POSIXSocket();
 }
 
 
 } }  // namespace v8::internal