Re: Question regarding ICE in instantiate_virtual_regs_1, at function.c:3880

["John David Anglin" <dave at hiauly1 dot hia dot nrc dot ca>]

> > I have come to the conclusion that there is a problem with
> > GO_IF_LEGITIMATE_ADDRESS on the vax (ie, it shouldn't accept a
> > DCmode MEM with the above indexing) since the maximum number
> > of bytes that can be moved in a single insn is 8.
> Yes, this is the complex type hackery - basically it does the DC modes behind
> scene w/o validation from backend splitting it later.
> What you need is to figure out from where the subreg is comming and replace
> gen_SUBREG by simplify_gen_subreg. That should be enought I guess.
> 
> In case simplify_gen_subreg for some purpose refuse to simplify memory in question,
> let me know.

The subreg is coming from simplify_gen_subreg:

  new = simplify_subreg (outermode, op, innermode, byte);
  if (new)
    return new;

  if (GET_CODE (op) == SUBREG || GET_MODE (op) == VOIDmode)
    return NULL_RTX;

  return gen_rtx_SUBREG (outermode, op, byte);
}

The call to simplify_subreg us not successful because mode_dependent_address_p

returns true for:

(plus:SI (mult:SI (reg:SI 21)
        (const_int 16 [0x10]))
    (mem/f:SI (reg/f:SI 16 virtual-incoming-args) [0 t+0 S4 A32]))

At the moment, GO_IF_MODE_DEPENDENT_ADDRESS only accepts a plus with
a register and a constant address.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)