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Add interval-based range simplification for ITE conditions

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Introduce exclusion intervals alongside the existing path-based condition
tracking in simplify_ite_rec. The intervals track which character values
are still possible at each point in the ITE tree, enabling simplification
of nested range conditions that the per-entry path approach cannot handle.

Key additions:
- intervals_t type and push_intervals() to maintain live character ranges
- eval_range_cond() checks AND-of-char_le conditions against intervals
- intersect_intervals/exclude_interval utilities from seq_rewriter pattern
- Negated AND handling: ¬(lo<=x ∧ x<=hi) excludes [lo,hi] from intervals

The interval check runs before the existing eval_path_cond logic, catching
cases like: if(0<=x<=10, t, if(1<=x<=8, t2, e2)) → if(0<=x<=10, t, e2)
where the inner range [1,8] is fully contained in the excluded outer range.

Fixes remaining regression timeouts on 5728 P2 and 5731 P4.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Nikolaj Bjorner 2026-06-04 16:59:59 -07:00
parent ebdbf83314
commit dc8179212e
2 changed files with 169 additions and 37 deletions
Download patch file Download diff file Expand all files Collapse all files

197
src/ast/rewriter/seq_derive.cpp
View file

@ -1091,14 +1091,146 @@ namespace seq {
}
}
std::pair<expr_ref, expr_ref> derive::simplify_ite_rec(path_t& path, expr* c, expr* t, expr* e) {
void derive::push_intervals(intervals_t& intervals, expr* c, bool sign) {
expr* lhs = nullptr, * rhs = nullptr;
unsigned val = 0;
if (m_util.is_char_le(c, lhs, rhs)) {
if (!sign) {
if (lhs == m_ele && m_util.is_const_char(rhs, val))
intersect_intervals(0, val, intervals);
else if (rhs == m_ele && m_util.is_const_char(lhs, val))
intersect_intervals(val, u().max_char(), intervals);
} else {
if (lhs == m_ele && m_util.is_const_char(rhs, val))
exclude_interval(0, val, intervals, u().max_char());
else if (rhs == m_ele && m_util.is_const_char(lhs, val))
exclude_interval(val, u().max_char(), intervals, u().max_char());
}
} else if (!sign && m.is_and(c)) {
for (expr* arg : *to_app(c))
push_intervals(intervals, arg, false);
} else if (sign && m.is_or(c)) {
for (expr* arg : *to_app(c))
push_intervals(intervals, arg, true);
} else if (sign && m.is_and(c)) {
// ¬(and(lo<=x, x<=hi)) → exclude [lo, hi]
unsigned lo = 0, hi = u().max_char();
bool got_lo = false, got_hi = false;
for (expr* arg : *to_app(c)) {
expr* a_lhs = nullptr, * a_rhs = nullptr;
unsigned a_val = 0;
if (m_util.is_char_le(arg, a_lhs, a_rhs)) {
if (a_lhs == m_ele && m_util.is_const_char(a_rhs, a_val))
{ hi = std::min(hi, a_val); got_hi = true; }
else if (a_rhs == m_ele && m_util.is_const_char(a_lhs, a_val))
{ lo = std::max(lo, a_val); got_lo = true; }
}
}
if (got_lo || got_hi)
exclude_interval(lo, hi, intervals, u().max_char());
}
}
void derive::intersect_intervals(unsigned lo, unsigned hi, intervals_t& ranges) {
unsigned j = 0;
for (unsigned i = 0; i < ranges.size(); ++i) {
auto [lo1, hi1] = ranges[i];
if (hi < lo1)
break;
if (hi1 >= lo)
ranges[j++] = std::make_pair(std::max(lo1, lo), std::min(hi1, hi));
}
ranges.shrink(j);
}
void derive::exclude_interval(unsigned lo, unsigned hi, intervals_t& ranges, unsigned max_char) {
if (lo == 0 && hi >= max_char) { ranges.reset(); return; }
if (lo == 0) { intersect_intervals(hi + 1, max_char, ranges); return; }
if (hi >= max_char) { intersect_intervals(0, lo - 1, ranges); return; }
intervals_t right(ranges);
intersect_intervals(0, lo - 1, ranges);
intersect_intervals(hi + 1, max_char, right);
ranges.append(right);
}
lbool derive::eval_range_cond(intervals_t const& intervals, expr* c) {
if (intervals.empty())
return l_false;
expr* lhs = nullptr, * rhs = nullptr;
unsigned val = 0;
// Handle AND of char_le as range [lo, hi]
if (m.is_and(c)) {
unsigned lo = 0, hi = u().max_char();
bool got_lo = false, got_hi = false;
bool all_char_le = true;
for (expr* arg : *to_app(c)) {
expr* a_lhs = nullptr, * a_rhs = nullptr;
unsigned a_val = 0;
if (m_util.is_char_le(arg, a_lhs, a_rhs)) {
if (a_lhs == m_ele && m_util.is_const_char(a_rhs, a_val))
{ hi = std::min(hi, a_val); got_hi = true; }
else if (a_rhs == m_ele && m_util.is_const_char(a_lhs, a_val))
{ lo = std::max(lo, a_val); got_lo = true; }
else all_char_le = false;
} else all_char_le = false;
}
if (all_char_le && (got_lo || got_hi)) {
if (lo > hi) return l_false;
bool any_overlap = false;
bool all_contained = true;
for (auto const& [r_lo, r_hi] : intervals) {
if (std::max(r_lo, lo) <= std::min(r_hi, hi))
any_overlap = true;
if (r_lo < lo || r_hi > hi)
all_contained = false;
}
if (!any_overlap) return l_false;
if (all_contained) return l_true;
}
return l_undef;
}
// Handle single char_le
if (!m_util.is_char_le(c, lhs, rhs))
return l_undef;
if (lhs == m_ele && m_util.is_const_char(rhs, val)) {
// c is (x <= val): true if all hi <= val, false if all lo > val
bool all_le = true, any_le = false;
for (auto const& [r_lo, r_hi] : intervals) {
if (r_lo <= val) any_le = true;
if (r_hi > val) all_le = false;
}
if (all_le) return l_true;
if (!any_le) return l_false;
} else if (rhs == m_ele && m_util.is_const_char(lhs, val)) {
// c is (val <= x): true if all lo >= val, false if all hi < val
bool all_ge = true, any_ge = false;
for (auto const& [r_lo, r_hi] : intervals) {
if (r_hi >= val) any_ge = true;
if (r_lo < val) all_ge = false;
}
if (all_ge) return l_true;
if (!any_ge) return l_false;
}
return l_undef;
}
std::pair<expr_ref, expr_ref> derive::simplify_ite_rec(path_t& path, intervals_t& intervals, expr* c, expr* t, expr* e) {
auto sz = path.size();
auto saved_intervals = intervals;
push_path(path, c, false);
expr_ref st = simplify_ite_rec(path, t);
push_intervals(intervals, c, false);
expr_ref st = simplify_ite_rec(path, intervals, t);
path.shrink(sz);
intervals = saved_intervals;
push_path(path, c, true);
expr_ref se = simplify_ite_rec(path, e);
push_intervals(intervals, c, true);
expr_ref se = simplify_ite_rec(path, intervals, e);
path.shrink(sz);
intervals = saved_intervals;
return { st, se };
}
@ -1112,19 +1244,26 @@ namespace seq {
if (cond_val == l_false) return simplify_ite(e);
path_t path;
auto [st, se] = simplify_ite_rec(path, c, t, e);
intervals_t intervals;
intervals.push_back(std::make_pair(0u, u().max_char()));
auto [st, se] = simplify_ite_rec(path, intervals, c, t, e);
return mk_ite(c, st, se);
}
expr_ref derive::simplify_ite_rec(path_t& path, expr* d) {
expr_ref derive::simplify_ite_rec(path_t& path, intervals_t& intervals, expr* d) {
expr* c, * t, * e;
if (!m.is_ite(d, c, t, e))
return expr_ref(d, m);
// Try to evaluate c directly
lbool cond_val = eval_cond(c);
if (cond_val == l_true) return simplify_ite_rec(path, t);
if (cond_val == l_false) return simplify_ite_rec(path, e);
if (cond_val == l_true) return simplify_ite_rec(path, intervals, t);
if (cond_val == l_false) return simplify_ite_rec(path, intervals, e);
// Use interval-based range reasoning (catches AND range vs disjoint intervals)
lbool range_val = eval_range_cond(intervals, c);
if (range_val == l_true) return simplify_ite_rec(path, intervals, t);
if (range_val == l_false) return simplify_ite_rec(path, intervals, e);
// When c is an AND (range condition), check each conjunct against the path.
// If any conjunct is contradicted by the path, c is false → take else.
@ -1140,21 +1279,21 @@ namespace seq {
if (arg_val == l_undef)
and_result = l_undef;
}
if (and_result == l_true) return simplify_ite_rec(path, t);
if (and_result == l_false) return simplify_ite_rec(path, e);
if (and_result == l_true) return simplify_ite_rec(path, intervals, t);
if (and_result == l_false) return simplify_ite_rec(path, intervals, e);
}
// When c is a single char_le, also check against the path
else {
lbool c_val = eval_path_cond(path, c);
if (c_val == l_true) return simplify_ite_rec(path, t);
if (c_val == l_false) return simplify_ite_rec(path, e);
if (c_val == l_true) return simplify_ite_rec(path, intervals, t);
if (c_val == l_false) return simplify_ite_rec(path, intervals, e);
}
// Check if c can be determined from the path (legacy checks for equality conditions)
for (auto const& [cond, sign] : path) {
// Direct match: c == cond
if (c == cond)
return sign ? simplify_ite_rec(path, e) : simplify_ite_rec(path, t);
return sign ? simplify_ite_rec(path, intervals, e) : simplify_ite_rec(path, intervals, t);
// c is (x = v), cond is (x = w) with sign=false (cond is true, so x=w)
// If v != w, then c is false → take else branch
@ -1163,7 +1302,7 @@ namespace seq {
if (m.is_value(lhs1)) std::swap(lhs1, rhs1);
if (m.is_value(lhs2)) std::swap(lhs2, rhs2);
if (lhs1 == lhs2 && m.are_distinct(rhs1, rhs2))
return simplify_ite_rec(path, e);
return simplify_ite_rec(path, intervals, e);
}
// Range constraint: cond is (lo <= x) or (x <= hi) with sign=false
@ -1175,56 +1314,44 @@ namespace seq {
expr* le_lhs = nullptr, * le_rhs = nullptr;
if (m_util.is_char_le(cond, le_lhs, le_rhs) && le_rhs == lhs2 &&
m_util.is_const_char(le_lhs, lo_val) && v_val < lo_val)
return simplify_ite_rec(path, e);
return simplify_ite_rec(path, intervals, e);
if (m_util.is_char_le(cond, le_lhs, le_rhs) && le_lhs == lhs2 &&
m_util.is_const_char(le_rhs, hi_val) && v_val > hi_val)
return simplify_ite_rec(path, e);
return simplify_ite_rec(path, intervals, e);
}
}
// Range implication between char_le conditions:
// If c is char_le(lo, x) [lo <= x] and path has ¬(x <= hi) [x > hi]:
// ¬(x <= hi) means x >= hi+1. If lo <= hi+1, then lo <= x is implied → c is true.
// If c is char_le(x, hi) [x <= hi] and path has ¬(lo <= x) [x < lo]:
// ¬(lo <= x) means x <= lo-1. If lo-1 <= hi, then x <= hi is implied → c is true.
expr* c_lhs = nullptr, * c_rhs = nullptr;
expr* p_lhs = nullptr, * p_rhs = nullptr;
if (m_util.is_char_le(c, c_lhs, c_rhs) && m_util.is_char_le(cond, p_lhs, p_rhs)) {
unsigned c_lo = 0, c_hi = 0, p_lo = 0, p_hi = 0;
if (sign) {
// cond is negated (¬cond is true)
// c is (lo <= x), cond is (x <= hi) with sign=true means ¬(x <= hi) i.e. x > hi i.e. x >= hi+1
if (m_util.is_const_char(c_lhs, c_lo) && c_rhs == m_ele &&
p_lhs == m_ele && m_util.is_const_char(p_rhs, p_hi) &&
c_lo <= p_hi + 1)
return simplify_ite_rec(path, t);
// c is (x <= hi), cond is (lo <= x) with sign=true means ¬(lo <= x) i.e. x < lo i.e. x <= lo-1
return simplify_ite_rec(path, intervals, t);
if (c_lhs == m_ele && m_util.is_const_char(c_rhs, c_hi) &&
m_util.is_const_char(p_lhs, p_lo) && p_rhs == m_ele &&
p_lo > 0 && p_lo - 1 <= c_hi)
return simplify_ite_rec(path, t);
return simplify_ite_rec(path, intervals, t);
} else {
// cond is true (not negated)
// c is (lo <= x), cond is (x <= hi) true: x <= hi. If lo > hi → c is false.
if (m_util.is_const_char(c_lhs, c_lo) && c_rhs == m_ele &&
p_lhs == m_ele && m_util.is_const_char(p_rhs, p_hi) &&
c_lo > p_hi)
return simplify_ite_rec(path, e);
// c is (x <= hi), cond is (lo <= x) true: lo <= x. If hi < lo → c is false.
return simplify_ite_rec(path, intervals, e);
if (c_lhs == m_ele && m_util.is_const_char(c_rhs, c_hi) &&
m_util.is_const_char(p_lhs, p_lo) && p_rhs == m_ele &&
c_hi < p_lo)
return simplify_ite_rec(path, e);
// c is (lo <= x), cond is (lo2 <= x) true: lo2 <= x. If lo <= lo2 → c is true.
return simplify_ite_rec(path, intervals, e);
if (m_util.is_const_char(c_lhs, c_lo) && c_rhs == m_ele &&
m_util.is_const_char(p_lhs, p_lo) && p_rhs == m_ele &&
c_lo <= p_lo)
return simplify_ite_rec(path, t);
// c is (x <= hi), cond is (x <= hi2) true: x <= hi2. If hi >= hi2 → c is true.
return simplify_ite_rec(path, intervals, t);
if (c_lhs == m_ele && m_util.is_const_char(c_rhs, c_hi) &&
p_lhs == m_ele && m_util.is_const_char(p_rhs, p_hi) &&
c_hi >= p_hi)
return simplify_ite_rec(path, t);
return simplify_ite_rec(path, intervals, t);
}
}
}
@ -1251,14 +1378,14 @@ namespace seq {
}
}
if (has_lo && has_hi && lo_bound <= v_val && v_val <= hi_bound) {
auto [st, se] = simplify_ite_rec(path, c, t, e);
auto [st, se] = simplify_ite_rec(path, intervals, c, t, e);
return mk_ite(c, st, se);
}
}
}
// Cannot simplify c: recurse into branches with extended paths
auto [st, se] = simplify_ite_rec(path, c, t, e);
auto [st, se] = simplify_ite_rec(path, intervals, c, t, e);
return mk_ite(c, st, se);
}