[AArch64] Implement vector float->double widening and double->float narrowing.
gcc/
* config/aarch64/aarch64-simd-builtins.def (vec_unpacks_hi_): New.
(float_truncate_hi_): Likewise.
(float_extend_lo_): Likewise.
(float_truncate_lo_): Likewise.
* config/aarch64/aarch64-simd.md (vec_unpacks_lo_v4sf): New.
(aarch64_float_extend_lo_v2df): Likewise.
(vec_unpacks_hi_v4sf): Likewise.
(aarch64_float_truncate_lo_v2sf): Likewise.
(aarch64_float_truncate_hi_v4sf): Likewise.
(vec_pack_trunc_v2df): Likewise.
(vec_pack_trunc_df): Likewise.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@198400 138bc75d-0d04-0410-961f-82ee72b054a4