reorg bug + patch

[Jeffrey A Law]

  In message < 200001061056.CAA01708@netcom.com >you write:
  > The problem occurs on targets with a delayed branch instruction
  > and an addressing mode with side effects (e.g. postinc, etc), such
  > as the Hitachi SH.
There's a few targets this can potentially effect.  Luckily the code in
question isn't triggered all that often (which probably explains why you've
been the only folks to have problems with it).


  > Here is a dump of the rtx just prior to the delayed branch filling pass:
[ ... ]

  > (insn 4919 4541 4916 (parallel[
  >             (set (reg:SF 24 fr0)
  >                 (mem/s:SF (post_inc:SI (reg:SI 2 r2))))	<- look here
  >             (use (reg/v:PSI 48 fpscr))
  >             (clobber (scratch:SI))
  >         ] ) 157 {movsf_ie} (nil)
  >     (nil))
Per our earlier discussion reload needs to attach a REG_INC note to this
insn and should be doing so in the current development sources.  Right?

  > The culprit appears to be this chunk of code in reorg.c:
  > 
  >       /* If this insn is a register-register copy and the next insn has
  >          a use of our destination, change it to use our source.  That way,
  >          it will become a candidate for our delay slot the next time
  >          through this loop.  This case occurs commonly in loops that
  >          scan a list.
Yup.

  > Anyway, here is my first patch to fix the first problem:
  > 
  > Jan  6 02:14:33 PST 2000  Toshiyasu Morita (toshi.morita@sega.com)
  > 
  >         * reorg.c (fill_slots_from_thread): Actually check modified_in_p()
  >         before replacing rtx.
The comment isn't actually useful.  reorg runs long after regmove, so the
code in reorg should not effect address inheritance in any way shape or form.

  > *************** fill_slots_from_thread (insn, condition,
  > *** 3729,3734 ****
  > --- 3732,3738 ----
  >   	      && ! reg_set_p (SET_DEST (pat), next)
  >   	      && ! reg_set_p (SET_SRC (pat), next)
  >   	      && reg_referenced_p (SET_DEST (pat), PATTERN (next))
  > + 	      && ! modified_in_p (SET_DEST (pat), next))
  >   	    validate_replace_rtx (SET_DEST (pat), SET_SRC (pat), next);
I'm not sure how you made this diff since the reg_referenced_p line should
have had another close paren in the original sources.  Anyway, I added the
call to modified_in_p to this code in the development sources by hand.

Thanks,
jeff