https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88602
--- Comment #1 from Jan Hubicka <hubicka at gcc dot gnu.org> --- It turns out that ext_vector_type attribute is not only about declaring vector variable but also affects semantics. Brief documentation is in https://clang.llvm.org/docs/LanguageExtensions.html#vectors-and-extended-vectors and see also discussion in http://hubicka.blogspot.com/2018/12/even-more-fun-with-building-and.html I can confirm that Skia code is somewhat more compact/ergonomic with the extension though i still do not fully understand the design.
