Right. So the question I have is how/why did DOM leave anything in the map.
And if DOM is fixed to not leave stuff lying around, can we then assert that
nothing is ever left in those maps between passes? There's certainly no good
reason I'm aware of why DOM would leave things in this state.
It happens not only with DOM but with all passes doing edge redirection.
This is because the map is populated by GIMPLE cfg hooks just in case
it might be used. But there is no such thing as a "start CFG manip"
and "end CFG manip" to cleanup such dead state.
IMHO the redirect-edge-var-map stuff is just the very most possible
unclean implementation possible. :( (see how remove_edge "clears"
stale info from the map to avoid even more "interesting" stale
data)
Ideally we could assert the map is empty whenever we leave a pass,
but as said it triggers all over the place. Even cfg-cleanup causes
such stale data.
I agree that the patch is only a half-way "solution", but a full
solution would require sth more explicit, like we do with
initialize_original_copy_tables/free_original_copy_tables. Thus
require passes to explicitely request the edge data to be preserved
with a initialize_edge_var_map/free_edge_var_map call pair.
Not appropriate at this stage IMHO (well, unless it turns out to be
a very localized patch).