Representing dllexport/dllimport as distinct linkage types prevents using these attributes on templates and inline functions.
Instead of introducing further mixed linkage types to include linkonce and weak ODR, the old import/export linkage types are replaced with new function attributes (DLLExport, DLLImport) and an extension to global variables:
@Exp = global i32 1, align 4, dllexport @Imp = external global i32, dllimport
Linkage for dllexported globals and functions is now equal to their linkage without dllexport. Imported globals and functions must be either declarations, or definitions with AvailableExternallyLinkage. An alias is exported if the aliasee is exported.