Re: [ssaupdate] Local dominance info

[Andrew MacLeod <amacleod@redhat.com>]

On Wed, 2004-10-20 at 15:27, Zdenek Dvorak wrote:
> Hello,
> 
> > > this patch adds dominance information to statements, i.e. it makes it
> > > possible to decide whether a statement precedes other one inside a basic
> > > block without need to scan the whole block.
> > > 
> > > To enable this, statements inside basic block are numbered (the
> > > numbering contains holes, so that new statements may be inserted).  This
> > > seems to work good enough (no measurable impact on compile time).
> > 
> > You want to keep and maintain this information all the time?
> 
> yes.  Given that it costs nothing, it seems to be the best choice to me.
> 
> > This strikes me *much* more as a local thing that an individual pass
> > might be interested in, and so should number the stmt's itself for the
> > duration of its interest. 
> 
> Still you would need some mechanism to update things when statements are
> inserted, so this would make things only more complicated.

and what wrong with the local_dom_insert_after() and
local_dom_insert_before() which call the bsi routines? It looks pretty
trivial to do that,  then the info only exists and is maintained when
you want it.

I don't see any reason why it should be kept up to date all the time
when virtually no-one else cares about it. It seems like its a cheap to
calculate on the fly, and if its a big deal to you, then its not
difficult to keep up to date locally if you use local dominator aware
insert routines which call the BSI ones.

Andrew