From a17d4e68eb483145ed27a29e6a74cfb7cf47a7d4 Mon Sep 17 00:00:00 2001
From: Nikolaj Bjorner <nbjorner@microsoft.com>
Date: Wed, 4 Dec 2024 15:32:08 -0800
Subject: [PATCH] bugfix to elim_uncnstr to ensure nodes are created. Prepare
 smt_internalizer to replay unit literals

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
---
 src/ast/expr_substitution.cpp              |  5 +++--
 src/ast/simplifiers/elim_unconstrained.cpp | 10 +++++++---
 src/smt/smt_context.cpp                    |  4 ++--
 src/smt/smt_internalizer.cpp               | 14 +++++++++-----
 4 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/src/ast/expr_substitution.cpp b/src/ast/expr_substitution.cpp
index 957b884fb..57cecc0b2 100644
--- a/src/ast/expr_substitution.cpp
+++ b/src/ast/expr_substitution.cpp
@@ -19,6 +19,7 @@ Notes:
 #include "util/ref_util.h"
 #include "ast/expr_substitution.h"
 #include "ast/ast_pp.h"
+#include "ast/ast_ll_pp.h"
 
 typedef obj_map<expr, proof*> expr2proof;
 typedef obj_map<expr, expr_dependency*> expr2expr_dependency;
@@ -58,8 +59,8 @@ expr_substitution::~expr_substitution() {
 }
 
 std::ostream& expr_substitution::display(std::ostream& out) {
-    for (auto & kv : m_subst) {
-        out << mk_pp(kv.m_key, m()) << " |-> " << mk_pp(kv.m_value, m()) << "\n";
+    for (auto & [k, v] : m_subst) {
+        out << mk_bounded_pp(k, m()) << " |-> " << mk_bounded_pp(v, m()) << "\n";
     }
     return out;
 }
diff --git a/src/ast/simplifiers/elim_unconstrained.cpp b/src/ast/simplifiers/elim_unconstrained.cpp
index 9ddee634a..4ed9f2f28 100644
--- a/src/ast/simplifiers/elim_unconstrained.cpp
+++ b/src/ast/simplifiers/elim_unconstrained.cpp
@@ -131,7 +131,9 @@ elim_unconstrained::~elim_unconstrained() {
 }
 
 bool elim_unconstrained::is_var_lt(int v1, int v2) const {   
-    return get_node(v1).num_parents() < get_node(v2).num_parents();
+    auto p1 = get_node(v1).num_parents();
+    auto p2 = get_node(v2).num_parents();
+    return  p1 < p2;
 }
 
 void elim_unconstrained::eliminate() {
@@ -287,8 +289,11 @@ void elim_unconstrained::init_nodes() {
 
     for (expr* e : subterms_postorder::all(terms)) {
         SASSERT(get_node(e).is_root());
-        if (is_uninterp_const(e))
+        
+        if (is_uninterp_const(e)) {
+            get_node(e); // ensure the node exists
             m_heap.insert(e->get_id());
+        }
     }
 
     // mark top level terms
@@ -390,7 +395,6 @@ void elim_unconstrained::update_model_trail(generic_model_converter& mc, vector<
             trail.hide(entry.m_f);
             break;
         case generic_model_converter::instruction::ADD:
-            // trail.push(entry.m_f, entry.m_def, nullptr, old_fmls);
             break;
         }
     }
diff --git a/src/smt/smt_context.cpp b/src/smt/smt_context.cpp
index b165e54a6..4c1ba3da7 100644
--- a/src/smt/smt_context.cpp
+++ b/src/smt/smt_context.cpp
@@ -2381,7 +2381,7 @@ namespace smt {
         unsigned i  = units_to_reassert_lim;
         unsigned sz = m_units_to_reassert.size();
         for (; i < sz; i++) {
-            auto& [unit, sign, is_relevant] = m_units_to_reassert[i];
+            auto [unit, sign, is_relevant] = m_units_to_reassert[i];
             bool gate_ctx = true;
             internalize(unit, gate_ctx);
             bool_var v    = get_bool_var(unit);
@@ -2389,7 +2389,7 @@ namespace smt {
             assign(l, b_justification::mk_axiom());
             if (is_relevant)
                 mark_as_relevant(l);
-            TRACE("reassert_units", tout << "reasserting #" << unit->get_id() << " " << sign << " @ " << m_scope_lvl << "\n";);
+            TRACE("reassert_units", tout << "reasserting #" << unit->get_id() << " " << sign << " @ " << m_scope_lvl << "\n";);            
         }
         if (at_base_level()) 
             m_units_to_reassert.reset();        
diff --git a/src/smt/smt_internalizer.cpp b/src/smt/smt_internalizer.cpp
index 9181c9025..f19144b62 100644
--- a/src/smt/smt_internalizer.cpp
+++ b/src/smt/smt_internalizer.cpp
@@ -1396,8 +1396,7 @@ namespace smt {
             DEBUG_CODE(for (literal lit : simp_lits) SASSERT(get_assignment(lit) == l_true););
             if (!simp_lits.empty()) {
                 j = mk_justification(unit_resolution_justification(*this, j, simp_lits.size(), simp_lits.data()));
-            }
-              
+            }            
             break;
         }
         case CLS_TH_LEMMA:
@@ -1423,6 +1422,7 @@ namespace smt {
         unsigned activity = 1;
         bool  lemma = is_lemma(k);
         m_stats.m_num_mk_lits += num_lits;
+
         switch (num_lits) {
         case 0:
             if (j && !j->in_region())
@@ -1431,12 +1431,16 @@ namespace smt {
             set_conflict(j == nullptr ? b_justification::mk_axiom() : b_justification(j));
             SASSERT(inconsistent());
             return nullptr;
-        case 1:
+        case 1: {
+            literal unit = lits[0];
+            expr* atom = m_bool_var2expr[unit.var()];
             if (j && !j->in_region())
                 m_justifications.push_back(j);
-            assign(lits[0], j);
-            inc_ref(lits[0]);
+            assign(unit, j);
+            inc_ref(unit);
+            // m_units_to_reassert.push_back({ expr_ref(atom, m), unit.sign(), is_relevant(unit) });
             return nullptr;
+        }
         case 2:
             if (use_binary_clause_opt(lits[0], lits[1], lemma)) {
                 literal l1 = lits[0];