This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.
Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|
Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |
Other format: | [Raw text] |
While testing some other Thumb-1 changes, I got an abort while generating thumb_movhi_clobber for a secondary reload. The pattern calls gcc_unreachable when it finds a case it can't handle. There's a FIXME there that other cases might need to be handled, but looking closer, the entire pattern seems bogus; it requests two scratch regs (one DImode reg) and doesn't use them. The circumstances in which we arrive there also seemed suspect. We were reloading an insn of the form (set (mem:HI (some address)) (subreg:HI (reg:SI 7))) Reload did _not_ choose the reg->mem alternative of the movhi pattern, which is crazy. The reason it didn't is that reg 7 is the hard frame pointer, and simplify_subreg_regno didn't want to simplify the subreg here (-fomit-frame-pointer was on of course). So, find_reloads set force_reload for the register operand, which seems to have been enough to confuse its cost calculations. Fixed by the first part of this patch; I see no reason to treat the hard frame pointer register specially - it's typically just a general reg. If FRAME_POINTER_REGNUM == HARD_FRAME_POINTER_REGNUM, the test will have the same effect as before, which is probably still wrong, but for now it's a safe change to make. The other part removes the strange-looking part frmo the thumb_movhi_clobber register and restores it to just a call to gcc_unreachable. This is still ugly, but it's essentially the state it was in before http://gcc.gnu.org/ml/gcc-patches/2005-08/msg01210.html which presumably changed this because of the bug I'm fixing here. Regression tested, together with some other patches, on qemu-system-armv7-3/arch=armv7-a/thumb qemu-system-armv7-3/thumb qemu-system-armv7-3 which only showed up one unrelated problem for which I'm testing a fix. Ok (rtlanal and ARM parts)? Bernd
Attachment:
subreg-problem.diff
Description: Text document
Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|
Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |