> Jan Hubicka <[email protected]> writes:
>
> >>
> >> I can accept the issue as a matter of documentation, but I don't
> >> understand the rest. Remember that all the patterns are executed in
> >> parallel. I don't see how adding a USE in parallel could affect
> >> anything about how the operand is used.
> >
> >> >> >> (define_insn "*rep_movqi"
> >> >> >> [(set (match_operand:P 2 "register_operand" "=c") (const_int 0))
> >> >> >> (set (match_operand:P 0 "register_operand" "=D")
> >> >> >> (plus:P (match_operand:P 3 "register_operand" "0")
> >> >> >> (match_operand:P 5 "register_operand" "2")))
> >> >> >> (set (match_operand:P 1 "register_operand" "=S")
> >> >> >> (plus:P (match_operand:P 4 "register_operand" "1")
> >> >> >> (match_dup 5)))
> >> >> >> (set (mem:BLK (match_dup 3))
> >> >> >> (mem:BLK (match_dup 4)))
> >> >> >> (use (match_dup 5))]
> >
> > Without the extra use the patterns says that the only use of operand 5 (CX)
> > is
> > to add it to DX and SX.
> >
> > So seeing something like
> >
> > memcpy(DX,SX,10)
> > DX+=10
> > SX+=10
> >
> > is IMO foldable to
> >
> > memcpy(DX,SX,20)
> >
> > Not that current forwprop/combine would do that. But in theory I think it
> > is valid
> > transform.
>
> No, it's not. All the SETs are done in parallel--the define_insn has an
> implicit PARALLEL wrapped around the insns. You're trying to pull some
> of the outputs into the inputs, but that is not permitted by the rules
> of RTL.
In expanded form it is
(set (reg5) (const 10))
(parallel [(set (reg2) (const 0))
(set (reg0) (plus (reg3) (reg5)))
(set (reg1) (plus (reg4) (reg5)))
(set (mem (reg3)) (mem (reg4)))])
(set (reg0) (plus (reg0) (const 10)))
(set (reg1) (plus (reg1) (const 10)))
instructions separated by empty lines.
transformed into:
(set (reg5) (const 20))
(parallel [(set (reg2) (const 0))
(set (reg0) (plus (reg3) (reg5)))
(set (reg1) (plus (reg4) (reg5)))
(set (mem (reg3)) (mem (reg4)))])
I do not see puling inputs to outputs here.
>
> Ian
