Hi: I'm from https://gcc.gnu.org/pipermail/gcc-patches/2022-November/606040.html. > } > > /* See if we can get a better vector mode before extracting. */ > diff --git a/gcc/optabs.cc b/gcc/optabs.cc > index > cff37ccb0dfc3dd79b97d0abfd872f340855dc96..f338df410265dfe55b6896160090a453cc6a28d9 > 100644 > --- a/gcc/optabs.cc > +++ b/gcc/optabs.cc > @@ -6267,6 +6267,7 @@ expand_vec_perm_const (machine_mode mode, rtx v0, rtx > v1, > v0_qi = gen_lowpart (qimode, v0); > v1_qi = gen_lowpart (qimode, v1); > if (targetm.vectorize.vec_perm_const != NULL > + && targetm.can_change_mode_class (mode, qimode, ALL_REGS) It looks like you want to guard gen_lowpart, shouldn't it be better to use validate_subreg or (tmp = gen_lowpart_if_possible (mode, target_qi)). IMHO, targetm.can_change_mode_class is mostly used for RA, but not to guard gen_lowpart. I did similar things in https://gcc.gnu.org/pipermail/gcc-patches/2021-September/579296.html (and ALL_REGS doesn't cover all cases for registers which are both available for qimode and mode, ALL_REGS fail doesn't mean it can't be subreg, it just means parts of ALL_REGS can't be subreg. but with a subset of ALL_REGS, there could be a reg class which return true for targetm.can_change_mode_class) > && targetm.vectorize.vec_perm_const (qimode, qimode, target_qi, > v0_qi, > v1_qi, qimode_indices)) > return gen_lowpart (mode, target_qi); > @@ -6311,7 +6312,8 @@ expand_vec_perm_const (machine_mode mode, rtx v0, rtx > v1, > } > > if (qimode != VOIDmode > - && selector_fits_mode_p (qimode, qimode_indices)) > + && selector_fits_mode_p (qimode, qimode_indices) > + && targetm.can_change_mode_class (mode, qimode, ALL_REGS)) > { > icode = direct_optab_handler (vec_perm_optab, qimode); > if (icode != CODE_FOR_nothing) > diff --git a/gcc/testsuite/gcc.target/aarch64/ext_1.c > b/gcc/testsuite/gcc.target/aarch64/ext_1.c > new file mode 100644 > index > 0000000000000000000000000000000000000000..18a10a14f1161584267a8472e571b3bc2ddf887a
-- BR, Hongtao
