Re: Impact assessment of dse.c:emit_inc_dec_insn_before (Was: Re: Use of FLAGS_REGNUM clashes with generates insn)

[Joern Rennecke]

Quoting DJ Delorie <d...@redhat.com>:

m32c.c:m32c_legitimate_address_p allows any rubbish inside a
PRE_MODIFY, as long as the address register is the stack pointer.
OTOH, it does not define any HAVE_*_MODIFY_* macro.

m32c has push/pop and no other pre/post modify

I was talking about what addresses are allowed by
the TARGET_LEGITIMATE_ADDRESS_P, not what the hardware implements or
what the register allocator is guided to produce; some optimizers can
get quite 'creative' in mashing rtl together.

Considering the following stanza from m32c_legitimate_address_p,
I don't see how it would reject
(pre_modify:HI
  (reg:CC SP_REGNO)
  (cond_exec:V2HI (pc:SC)
                  (if_then_else:PSI (scratch:BLK) (reg 4004) (return:QI))))


  /* allowing PLUS yields mem:HI(plus:SI(mem:SI(plus:SI in m32c_split_move */
  if (GET_CODE (x) == PRE_DEC
      || GET_CODE (x) == POST_INC || GET_CODE (x) == PRE_MODIFY)
    {
      return (GET_CODE (XEXP (x, 0)) == REG
              && REGNO (XEXP (x, 0)) == SP_REGNO);
    }