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add simplification rule to concatentations of regex to avoid stack overflow in derivatives of very long expressions

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2026-04-20 18:19:16 +02:00
parent 41412293fe
commit e172aa370d
2 changed files with 7 additions and 0 deletions
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5
src/ast/rewriter/seq_rewriter.cpp
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@ -4539,6 +4539,11 @@ br_status seq_rewriter::mk_re_concat(expr* a, expr* b, expr_ref& result) {
result = re().mk_plus(b);
return BR_DONE;
}
expr *x = nullptr, *y = nullptr;
if (re().is_concat(a, x, y) && re().is_full_seq(y) && re().is_full_seq(b)) {
result = a;
return BR_DONE;
}
expr_ref a_str(m());
expr_ref b_str(m());
if (lift_str_from_to_re(a, a_str) && lift_str_from_to_re(b, b_str)) {