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Re: [PATCH] Conditionally turn off cfg cleanup for PHI-OPT if nothing is done


> 
> On 3/3/06, Diego Novillo <dnovillo@redhat.com> wrote:
> > On 03/03/06 14:17, Devang Patel wrote:
> >
> > > If cleanup_cfg() is smart and if it  does not start walking blocks
> > > unless cfg was manipulated then there is no need to worry about
> > > unnecessary TODO_cleanup_cfg flags. They cost more or less as much as
> > > empty call at compile time.
> > >
> > OK, if you have a scheme by which cleanup_cfg can determine whether it
> > needs to run, without context information and without walking the CFG,
> > I'm all ears.
> 
> CFG is manipulated using hooks only. It is possible for these hooks to
> set cfg-is-dirty bit. Right now it doesn't do this. It may require
> more work then I'm imagining but that seems right approach. Unless you
> know some gotcha that I am completely missing :) And it sounds like, I
> am missing something here.

What happens when you propagate 0 into an if, CFG is not manupulated at
all in that case as far as I know.

-- Pinski


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