Helper macro to define registry class.
Declared in <llvm/Support/Registry.h>
#define LLVM_DEFINE_REGISTRY(REGISTRY_CLASS)
Technically, these macros don't instantiate Registry despite the name. They handle underlying storage that used by Registry indirectly, enforcing proper declarations/definitions by compilers or linkers. If you forget to place LLVM_DEFINE_REGISTRY, your linker will complain about a missing getRegistryLinkListInstance definiton.