Pass specific annotation data for trees

[Andrew MacLeod]

On Fri, 2004-05-21 at 14:12, Daniel Berlin wrote:
> Currently, we use the tree annotations for some pass specific data 
> (in_ccp_worklist in stmt_ann_t, partition/root_index in var_ann_t, 
> etc).

> 
> There are a variety of solutions, such as union of pass specific 
> structures (like so):
> 
> struct stmt_ann_d
> {
> 	<common statement stuff>
> 	union
> 	{
> 		struct pass_ccp *ccp_data;
> 		struct pass_whatever *whatever_data;
> 	}
> }

If doing this, you have to be careful that a pass isn't called from
within another pass. out-of-ssa can be called from within DOM, for
instance, so dom and out-of-ssa can't have their pass info in a union.

This is the same situation we have with tree_nodes and all the
bits/flags found therein.

Andrew