https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116466
--- Comment #6 from Jeffrey A. Law <law at gcc dot gnu.org> --- Created attachment 59003 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59003&action=edit Hack from the RAU team Attached is the hack from the RAU team. It was initially used to help identify cases where we were emitting extension requests that were known to be redundant -- instead of the emit_insn;DONE sequence it would abort indicating it found a obviously redundant extension. That's how we knew about the case in the addv/subv expanders. I think it shows the key issue here in that you can't just remove the expansion, you have to convert it into a suitable subreg expression which will remain in the IL until register allocation and reloading. It may still be useful to integrate -- my testers run with it enabled, but it hasn't been worth my time to officially submit it to the project.
