C++11 added the alignas attribute, with behavior similar to that of gcc's __attribute__((aligned(x))) or Visual Studio's __declspec(align(x)).

We can phase out the use of the macro in favor of the standard attribute.  In the meantime, we can replace the toolchain specific definitions of ATTRIBUTE_ALIGNED with a portable definition, perhaps to use alignas itself. We might deprecate the use of the macro, but changing its implementation quickly and cleanly applies the feature where the macro is being used.

This will require adding the alignas attribute to the list of language features approved for use in HotSpot code.