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Re: DFA for PPro, P2, P3
- From: law at redhat dot com
- To: Richard Henderson <rth at redhat dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Thu, 02 May 2002 20:32:02 -0600
- Subject: Re: DFA for PPro, P2, P3
- Reply-to: law at redhat dot com
In message <20020502173331.A5369@redhat.com>, Richard Henderson writes:
> On Thu, May 02, 2002 at 04:55:46PM -0600, email@example.com wrote:
> > 3. There is a performance problem in building some of the tables in
> > genautomata/genattrtab that is preventing me from modeling
> > fdiv/fsqrt like the old description. Vlad is working on fixing
> > the performance issue with an algorithmic change in how the
> > particular table is built.
> Incidentally, I ran into this same problem on Alpha.
> Originally I put all the units (for a given cpu) in the same automata.
> This was of the unacceptable go-out-for-dinner-come-back-and-kill-it
> sort of build time.
> Then I followed advice seen elsewhere about putting all of the
> long-latency units in a separate automata. This helped, bringing
> the build time down to ~3 minutes.
> Today I put each pair of long-latency units in multiple separate
> automata. For instance, given
Yup. I know about factoring the DFA; regardless, the algorithm to
compute the minimum issue delay is, err, expensive, more so than it
I've primarily seen factoring the DFA help in the time to create the
automaton; the problem Vlad is working on is in forming the automata