Re: DFA for PPro, P2, P3

[law at redhat dot com]

In message <20020502173331.A5369@redhat.com>, Richard Henderson writes:
 > On Thu, May 02, 2002 at 04:55:46PM -0600, law@redhat.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
should be.  

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
tables.

jeff