https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112611
--- Comment #4 from Xi Ruoyao <xry111 at gcc dot gnu.org> --- (In reply to Jiahao Xu from comment #3) > We now consider it as undefined behavior rather than a bug for [x]vshuf > instructions. In vec_perm pattern, we use vector logical AND instructions to > perform modulo operations in order to correctly use the [x]vshuf > instructions. Therefore, we have decided to rewrite the two tests and ensure > that the index values in the selector do not exceed 64. I guess it would be better to also document this issue somewhere (extend.texi ?) and recommends to just use __builtin_shuffle instead of the intrinsic (unless the programmer knows the AND operation is not needed but the compiler does not).
