[PowerPC] [Clang] Add vector int128 pack/unpack builtins

unsigned long long builtin_unpack_vector_int128 (vector int128_t, int);
vector int128_t builtin_pack_vector_int128 (unsigned long long, unsigned long long);

Builtins should behave the same way as in GCC.

Patch By: wuzish (Zixuan Wu)
Differential Revision: https://reviews.llvm.org/D52074


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@342614 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed