Fix CPU features detection and stack alignment assert on iOS

runtime/vm/os_macos.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include "vm/os.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 123 matching lines @@
   return malloc(size);
 }
 
 
 void OS::AlignedFree(void* ptr) {
   free(ptr);
 }
 
 
 intptr_t OS::ActivationFrameAlignment() {
+#if TARGET_OS_IOS
+#if TARGET_ARCH_ARM
+  return 8;

[rmacnak, 2015/10/27 20:44:22]

// Even if we generate code that maintains a strong alignment, we cannot assert
the stronger stack alignment because C++ code will not maintain it.

[Chinmay, 2015/10/27 20:49:47]

ack

+#elif TARGET_ARCH_ARM64
+  return 16;
+#endif
+#else  // TARGET_OS_IOS
   // OS X activation frames must be 16 byte-aligned; see "Mac OS X ABI
   // Function Call Guide".
   return 16;
+#endif  // TARGET_OS_IOS
 }
 
 
 intptr_t OS::PreferredCodeAlignment() {
   ASSERT(32 <= OS::kMaxPreferredCodeAlignment);
   return 32;
 }
 
 
 bool OS::AllowStackFrameIteratorFromAnotherThread() {
@@ skipping 181 matching lines @@
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)