typedef long long v2di __attribute__ ((__vector_size__ (16)));
v2di test;
test = (v2di) {0, 1};
the last line gets flagged as "Excess elements in scalar initializer". You can find those vector types in NEON and SSE headers.
http://clang.llvm.org/docs/LanguageExtensions.html#vectors-and-extended-vectors
https://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html