[Bug tree-optimization/18133] computed gotos are not folded back to regular gotos when it is found that they are not computed gotos at all

["law at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From law at redhat dot com  2005-01-24 21:08 -------
Subject: Re:  computed gotos are not folded
	back to regular gotos when it is found that they are not computed gotos at
	all

On Mon, 2005-01-24 at 20:56 +0000, kazu at cs dot umass dot edu wrote:
> ------- Additional Comments From kazu at cs dot umass dot edu  2005-01-24 20:56 -------
> Subject: Re:  computed gotos are not folded
>  back to regular gotos when it is found that they are not computed gotos at
>  all
> 
> Hi Jeff,
> 
> > Interesting approach.   I'm not sure if your approach is easier
> > than just expanding the threading code to handle threading indirect
> > jumps.
> > 
> > I don't initially *think* that extending the threading code would be 
> > all that difficult.  In fact, all I think we need to do is update
> > the selection code to detect this case -- I think the code to update
> > the CFG and SSA graphs will DTRT without any changes.
> 
> Some people do not want to see DOM getting bigger and bigger, so I
> just wanted to point out that there is an approach without making DOM
> any bigger, but then you're right.  I don't think extending the jump
> threader is all that difficult or dirty, either.  Either approach
> works for me.
Understood.  What I expect long term is DOM will degenerate into just
a context sensitive optimizer.  The bulk of its copy propagation and
expression elimination will ultimately be subsumed by other, better
optimization passes.

Extending DOM to handle this case would fit into that long term goal
since we'd be extending the part of DOM which is not likely to be
subsumed by better optimizers.

jeff




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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18133