https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124804
--- Comment #26 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Unfortunately, right now there are no hooks that could choose to change simplify_subreg_regno behavior just for the subregs of OOmode/XOmode VSX registers and not other multireg regs, all the target can do is define REG_WORDS_BIG_ENDIAN perhaps differently from WORDS_BIG_ENDIAN so that the reg subregs could follow the memory order. Anyway, will defer this PR to somebody knowledgeable about PowerPC.
