https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90275
--- Comment #21 from Jeffrey A. Law <law at redhat dot com> --- So we may be able to address this by setting "do_not_record" if we have multiple sets in an insn, one of which is a reg->reg copy to a destination that is mentioned in a REG_UNUSED note. We'd only need to set it when processing the set with the destination referenced in the REG_UNUSED note. If the sets were in different insns, then the reg->reg copy with an unused destination would be removed as dead. If the source of the set were anything but a register, then we wouldn't be getting into the insert_regs routine with the validation check we're tripping. I suspect there's still a problem if we have multiple sets, one of which is a nop set. We may want to proactively address this case too, even if we don't have a C testcase which triggers it.
