Before this change, if a global variable is required to be statically initialized (e.g. due to @_section attribute), we don't allow its type to be a struct, only a scalar type works. This change improves on that by teaching MandatoryPerformanceOptimizations pass to inline struct initializer calls into initializer of globals, as long as they are simple enough so that we can be sure that we don't trigger recursive/infinite inlining.
Generic specialization drops metatype arguments and therefore exposes opportunities to remove dead metatype instructions.
Instead of removing dead metatype instructions before specialization, try to remove them after specialization.