Re: PATCH: remove bb_ann_d's num_preds field

[Andrew MacLeod <amacleod at redhat dot com>]

On Wed, 2004-09-29 at 13:28, Jeffrey A Law wrote:
> On Wed, 2004-09-29 at 07:54, Ben Elliston wrote:

> Probably the next thing to figure out is how to map between
> incoming edges and phi node elements.
> 
> One possibility would be to record the index of each edge in its
> pred/succ vectors.  So given an edge E, we can get the PHI arguments
> associated with that edge from PHI_ARG_DEF (phi, E->pred_index).  At
> first glance I tend to lean this direction, though I don't
> particularly like the idea of enlarging the edge structure and
> keeping the indices up-to-date.
> 
> Another would be to keep edges in the array in some well defined
> order and use a binary search instead of a linear search.
> 
> Hopefully others have already thought through this problem enough to
> provide better and more concrete suggestions.

For the immediate_uses stuff, I need to attach more use info to the PHI
arguments. In doing so, we could also put each phi argument into a
linked list hung off the edge. Given an edge, you could find all phi
arguments associated with it. Given a phi argument, you could either
traverse the list to the edge node, or alternatively keep a pointer to
the edge.  More memory of course.

The list off the edge has some very nice properties for  removing edges
or PHI nodes, but I havent gone down this path to actually implement it
yet. It might not be so pleasant for other endevours.

Andrew