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Re: query automaton
- From: Alex Turjan <aturjan at yahoo dot com>
- To: Vladimir Makarov <vmakarov at redhat dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Fri, 27 Feb 2009 07:50:05 -0800 (PST)
- Subject: Re: query automaton
- Reply-to: aturjan at yahoo dot com
Dear Vladimir,
> Not really. There is no requirement for "the units
> part of the alternatives of a reservation must belong to the
> same automaton". Querying should also work in this
> case because function cpu_unit_reservation_p checks all
> automata for an unit reservation.
Indeed it checks all automata but Im afraid that according to my pipeline description this check is not enough to guarantee a correct scheduling decision, e.g.,
suppose the following insn reservation:
(define_reservation "move" "( (unit1_aut1, unit1_aut2) | (*)
(unit2_aut1, unit2_aut2) )
,where unitN_autM refers to unit N from automata M. In this case there are 2 automata.
Now supose a scheduling state S made of the individual states of the two automatons S=<S_aut1,S_aut2>. According to what I see happening in insn-automata.c (and target.dfa), from S_aut1 there is a transition for unit1_aut1 and from S_aut2 there is a transition for unit2_aut2.
It seems that the automata do not communicate with each other. As a consequence,
A scheduling decision which results in the resource reservation
(unit1_aut1, unit2_aut2) would not be rejected, while it should.
In my opinion, the current implementation sees the reservation defined in (*)
As equivalent to the following one
(define_reservation "move" "( (unit1_aut1| unit2_aut1) ,
(unit1_aut2| unit2_aut2) )
Which does not seem true to me.
Is there a way for automatons to communicate so that the alternative
(unit1_aut1, unit2_aut2) would be rejected?
regards,
Alex