[patch] TSP based bb reordering

[James Morrison]

Zdenek Dvorak <rakdver@atrey.karlin.mff.cuni.cz> writes:

> Hello,
> 
> > > + /* The parameters of the cost function for the tsp based reordering.  These
> > > +    can be redefined by targets as needed.  The values here correspond simply
> > > +    to minimising the total number of jumps executed, and a slight preference
> > > +    for the taken branch to be the less frequent one, which is usually a good
> > > +    thing to do.  Making the value of HIT_TAKEN_COST and MISS_TAKEN_COST
> > > +    different makes sense only on targets with static branch prediction.  */
> > > + 
> > > + /* Cost of an unconditional jump.  */
> > > + #define JUMP_COST 100
> > > + 
> > 
> > 
> >  Should JUMP_COST be wrapped in an ifndef?
> 
> no -- JUMP_COST is just a constant relative to that the other costs are
> defined; I will add a comment.

 Ok.

> > > + /* Solves a tsp instance of size N.  WEIGHTS is a matrix of weights of
> > > +    edges.  Result is retunrned in TOUR; the initial tour is also obtained
> > > +    from there.  */
> >             ^^^^^
> > 
> >  Does this indicate that TOUR holds both the optimal tour and the initial tour?
> 
> Yes -- that the initial tour is passed to the function in TOUR and
> replaced by the 'optimal' tour.

 Ok, I had misunderstood the use of obtained.  Perhaps, "optimize_tsp uses
TOUR as the initial tour."

> > > + static void
> > > + optimize_tsp (int n, int *tour, struct vertex *weights, int iterate)
> > > + {
...
> > > + #ifndef ENABLE_CHECKING
> > > +   if (dump_file)
> > > +     {
> > > + #endif
> > > +       value = tsp_value (n, tour);
> > > + #ifndef ENABLE_CHECKING
> > > +     }
> > > + #endif
> > 
> >  This looks strange, if checking is enabled but dump_file is 0 then
> > value, or new_value later on, will never be set.
> 
> No -- if checking is enabled, the checks for dump_file are disabled,
> so value and new_value are computed.  We normally do not need the values
> for anything; we just compute it when either checking is enabled (for
> verification purposes), or when we need to show them in dumps.
> 
> Zdenek

 Ahh, right, #ifndef, not #ifdef -- my bad.

Jim