> IIRC, fill_eager and its related friends are all speculative in some way > and aren't those precisely the ones that are causing us problems. Also > note we have backends working around this stuff in fairly blunt ways:
I'd say that the PA back-end went a bit too far here, especially if it marks some insns of the epilogue as frame-related. dwarf2cfi.c has special code to handle delay slots (SEQUENCEs) so it's not an all-or-nothing game. > Given architectural difficulties of delay slots on modern processors, > would it be that painful to just not allow filling slots with frame > insns and let dbr try to find something else or drop in a nop? I > wouldn't be all that surprised if there wasn't a measurable performance > difference on something like a modern Sparc. Yes, modern SPARCs have (short) branches without delay slots. But the other big contender is MIPS here and the story might be different for it. -- Eric Botcazou
