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Fix regression timeouts via range condition simplification

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- Simplify trivial range bounds in derive_range: when lo=0, omit
  the lo<=x condition; when hi=max_char, omit the x<=hi condition.
  Full charset ranges return epsilon directly.

- Add char_le(0,x)=true and char_le(x,max)=true to eval_cond for
  always-valid bounds.

- Add range implication logic to simplify_ite_rec: when path has
  negated/positive char_le constraints, detect implied or contradicted
  char_le conditions (e.g., ¬(x<=127) implies 128<=x).

- Add is_subset(a, .+) check: non-nullable regexes are subsets of .+

- In update_state_graph, skip recursive exploration of nullable targets
  to avoid state explosion.

These fixes resolve timeouts on 5724 (all problems), 5721 P1, and 5693.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Nikolaj Bjorner 2026-06-04 12:16:56 -07:00
parent 88a177f6c5
commit d54d62a07a
3 changed files with 170 additions and 6 deletions
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10
src/smt/seq_regex.cpp
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@ -891,6 +891,16 @@ namespace smt {
m_state_graph.add_edge(r_id, dr_id, maybecycle);
}
m_state_graph.mark_done(r_id);
// Recursively explore unexplored targets for dead state detection
// Skip targets that are nullable to avoid state explosion
for (auto const& dr: derivatives) {
unsigned dr_id = get_state_id(dr);
if (m_state_graph.is_done(dr_id) || m_state_graph.is_live(dr_id))
continue;
if (re().get_info(dr).nullable == l_true)
continue;
update_state_graph(dr);
}
}
STRACE(seq_regex, m_state_graph.display(tout););