Don't assume we want the iOS ABI if running simarm on Mac and the EABI otherwise.

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 186 matching lines @@
 #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;
+#if defined(TARGET_ARCH_IA32) ||                                               \
+    defined(TARGET_ARCH_X64) ||                                                \
+    defined(TARGET_ARCH_ARM64) ||                                              \
+    defined(TARGET_ARCH_DBC)
+  const int kMinimumAlignment = 32;
+#elif defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_MIPS)
+  const int kMinimumAlignment = 16;
+#else
+#error Unsupported architecture.
+#endif
+  intptr_t alignment = kMinimumAlignment;
+  // TODO(5411554): Allow overriding default code alignment for
+  // testing purposes.
+  // Flags::DebugIsInt("codealign", &alignment);
+  ASSERT(Utils::IsPowerOfTwo(alignment));
+  ASSERT(alignment >= kMinimumAlignment);
+  ASSERT(alignment <= OS::kMaxPreferredCodeAlignment);
+  return alignment;
 }
 
 
 bool OS::AllowStackFrameIteratorFromAnotherThread() {
   return false;
 }
 
 
 int OS::NumberOfAvailableProcessors() {
   return sysconf(_SC_NPROCESSORS_ONLN);
@@ skipping 191 matching lines @@
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)