1 /*++
2 Copyright (c) 2007 Microsoft Corporation
3
4 Module Name:
5
6 var_subst.cpp
7
8 Abstract:
9
10 Variable substitution.
11
12 Author:
13
14 Leonardo (leonardo) 2008-01-10
15
16 Notes:
17
18 --*/
19 #include "ast/rewriter/var_subst.h"
20 #include "ast/rewriter/expr_safe_replace.h"
21 #include "ast/ast_ll_pp.h"
22 #include "ast/ast_pp.h"
23 #include "ast/ast_smt2_pp.h"
24 #include "ast/well_sorted.h"
25 #include "ast/for_each_expr.h"
26
operator ()(expr * n,unsigned num_args,expr * const * args)27 expr_ref var_subst::operator()(expr * n, unsigned num_args, expr * const * args) {
28 ast_manager& m = m_reducer.m();
29 expr_ref result(m);
30 if (is_ground(n) || num_args == 0) {
31 result = n;
32 //application does not have free variables or nested quantifiers.
33 //There is no need to print the bindings here?
34 SCTRACE("bindings", is_trace_enabled("coming_from_quant"),
35 tout << "(ground)\n";
36 for (unsigned i = 0; i < num_args; i++) {
37 if (args[i]) {
38 tout << i << ": " << mk_ismt2_pp(args[i], result.m()) << ";\n";
39 }
40 }
41 tout.flush(););
42
43 return result;
44 }
45 if (has_quantifiers(n)) {
46 expr_safe_replace rep(m);
47 for (unsigned k = 0; k < num_args; ++k) {
48 expr* arg = args[k];
49 if (arg)
50 rep.insert(m.mk_var(m_std_order ? num_args - k - 1 : k, arg->get_sort()), arg);
51 }
52 rep(n, result);
53 return result;
54 }
55 SASSERT(is_well_sorted(result.m(), n));
56 m_reducer.reset();
57 if (m_std_order)
58 m_reducer.set_inv_bindings(num_args, args);
59 else
60 m_reducer.set_bindings(num_args, args);
61 m_reducer(n, result);
62 SASSERT(is_well_sorted(m, result));
63 TRACE("var_subst_bug",
64 tout << "m_std_order: " << m_std_order << "\n" << mk_ismt2_pp(n, m) << "\nusing\n";
65 for (unsigned i = 0; i < num_args; i++) tout << mk_ismt2_pp(args[i], m) << "\n";
66 tout << "\n------>\n";
67 tout << result << "\n";);
68 return result;
69 }
70
unused_vars_eliminator(ast_manager & m,params_ref const & params)71 unused_vars_eliminator::unused_vars_eliminator(ast_manager & m, params_ref const & params) :
72 m(m), m_subst(m), m_params(params)
73 {
74 m_ignore_patterns_on_ground_qbody = m_params.get_bool("ignore_patterns_on_ground_qbody", true);
75 }
76
operator ()(quantifier * q)77 expr_ref unused_vars_eliminator::operator()(quantifier* q) {
78 expr_ref result(m);
79 SASSERT(is_well_sorted(m, q));
80 TRACE("elim_unused_vars", tout << expr_ref(q, m) << "\n";);
81 if (is_lambda(q)) {
82 result = q;
83 return result;
84 }
85 if (m_ignore_patterns_on_ground_qbody && is_ground(q->get_expr())) {
86 // Ignore patterns if the body is a ground formula.
87 result = q->get_expr();
88 return result;
89 }
90 if (!q->may_have_unused_vars()) {
91 result = q;
92 return result;
93 }
94 unsigned num_decls = q->get_num_decls();
95 m_used.reset();
96 m_used.set_num_decls(num_decls);
97 m_used.process(q->get_expr());
98 unsigned num_patterns = q->get_num_patterns();
99 for (unsigned i = 0; i < num_patterns; i++)
100 m_used.process(q->get_pattern(i));
101 unsigned num_no_patterns = q->get_num_no_patterns();
102 for (unsigned i = 0; i < num_no_patterns; i++)
103 m_used.process(q->get_no_pattern(i));
104
105
106 if (m_used.uses_all_vars(num_decls)) {
107 q->set_no_unused_vars();
108 result = q;
109 return result;
110 }
111
112 ptr_buffer<sort> used_decl_sorts;
113 buffer<symbol> used_decl_names;
114 for (unsigned i = 0; i < num_decls; ++i) {
115 if (m_used.contains(num_decls - i - 1)) {
116 used_decl_sorts.push_back(q->get_decl_sort(i));
117 used_decl_names.push_back(q->get_decl_name(i));
118 }
119 }
120
121 unsigned num_removed = 0;
122 expr_ref_buffer var_mapping(m);
123 int next_idx = 0;
124 unsigned sz = m_used.get_max_found_var_idx_plus_1();
125
126 for (unsigned i = 0; i < num_decls; ++i) {
127 sort * s = m_used.contains(i);
128 if (s) {
129 var_mapping.push_back(m.mk_var(next_idx, s));
130 next_idx++;
131 }
132 else {
133 num_removed++;
134 var_mapping.push_back(nullptr);
135 }
136 }
137 // (VAR 0) is in the first position of var_mapping.
138
139 for (unsigned i = num_decls; i < sz; i++) {
140 sort * s = m_used.contains(i);
141 if (s)
142 var_mapping.push_back(m.mk_var(i - num_removed, s));
143 else
144 var_mapping.push_back(nullptr);
145 }
146
147 // Remark:
148 // (VAR 0) should be in the last position of var_mapping.
149 // ...
150 // (VAR (var_mapping.size() - 1)) should be in the first position.
151 std::reverse(var_mapping.data(), var_mapping.data() + var_mapping.size());
152
153 expr_ref new_expr(m);
154
155 new_expr = m_subst(q->get_expr(), var_mapping.size(), var_mapping.data());
156
157 if (num_removed == num_decls) {
158 result = new_expr;
159 return result;
160 }
161
162 expr_ref_buffer new_patterns(m);
163 expr_ref_buffer new_no_patterns(m);
164
165 for (unsigned i = 0; i < num_patterns; i++) {
166 new_patterns.push_back(m_subst(q->get_pattern(i), var_mapping.size(), var_mapping.data()));
167 }
168 for (unsigned i = 0; i < num_no_patterns; i++) {
169 new_no_patterns.push_back(m_subst(q->get_no_pattern(i), var_mapping.size(), var_mapping.data()));
170 }
171
172 result = m.mk_quantifier(q->get_kind(),
173 used_decl_sorts.size(),
174 used_decl_sorts.data(),
175 used_decl_names.data(),
176 new_expr,
177 q->get_weight(),
178 q->get_qid(),
179 q->get_skid(),
180 num_patterns,
181 new_patterns.data(),
182 num_no_patterns,
183 new_no_patterns.data());
184 to_quantifier(result)->set_no_unused_vars();
185 SASSERT(is_well_sorted(m, result));
186 return result;
187 }
188
elim_unused_vars(ast_manager & m,quantifier * q,params_ref const & params)189 expr_ref elim_unused_vars(ast_manager & m, quantifier * q, params_ref const & params) {
190 unused_vars_eliminator el(m, params);
191 expr_ref result = el(q);
192 TRACE("elim_unused_vars", tout << expr_ref(q, m) << " -> " << result << "\n";);
193 return result;
194 }
195
instantiate(ast_manager & m,quantifier * q,expr * const * exprs)196 expr_ref instantiate(ast_manager & m, quantifier * q, expr * const * exprs) {
197 var_subst subst(m);
198 expr_ref new_expr(m), result(m);
199 new_expr = subst(q->get_expr(), q->get_num_decls(), exprs);
200 TRACE("var_subst", tout << mk_pp(q, m) << "\n" << new_expr << "\n";);
201 inv_var_shifter shift(m);
202 shift(new_expr, q->get_num_decls(), result);
203 SASSERT(is_well_sorted(m, result));
204 TRACE("instantiate_bug", tout << mk_ismt2_pp(q, m) << "\nusing\n";
205 for (unsigned i = 0; i < q->get_num_decls(); i++) tout << mk_ismt2_pp(exprs[i], m) << "\n";
206 tout << "\n----->\n" << mk_ismt2_pp(result, m) << "\n";);
207 return result;
208 }
209
get_free_vars_offset(expr_sparse_mark & mark,ptr_vector<expr> & todo,unsigned offset,expr * e,ptr_vector<sort> & sorts)210 static void get_free_vars_offset(expr_sparse_mark& mark, ptr_vector<expr>& todo, unsigned offset, expr* e, ptr_vector<sort>& sorts) {
211 todo.push_back(e);
212 while (!todo.empty()) {
213 e = todo.back();
214 todo.pop_back();
215 if (mark.is_marked(e)) {
216 continue;
217 }
218 mark.mark(e, true);
219 switch(e->get_kind()) {
220 case AST_QUANTIFIER: {
221 quantifier* q = to_quantifier(e);
222 expr_sparse_mark mark1;
223 ptr_vector<expr> todo1;
224 get_free_vars_offset(mark1, todo1, offset+q->get_num_decls(), q->get_expr(), sorts);
225 break;
226 }
227 case AST_VAR: {
228 var* v = to_var(e);
229 if (v->get_idx() >= offset) {
230 unsigned idx = v->get_idx()-offset;
231 if (sorts.size() <= idx) {
232 sorts.resize(idx+1);
233 }
234 if (!sorts[idx]) {
235 sorts[idx] = v->get_sort();
236 }
237 SASSERT(sorts[idx] == v->get_sort());
238 }
239 break;
240 }
241 case AST_APP: {
242 for (expr* arg : *to_app(e))
243 todo.push_back(arg);
244 break;
245 }
246 default:
247 UNREACHABLE();
248 }
249 }
250 }
251
252
get_free_vars(expr * e,ptr_vector<sort> & sorts)253 void get_free_vars(expr* e, ptr_vector<sort>& sorts) {
254 expr_sparse_mark mark;
255 ptr_vector<expr> todo;
256 get_free_vars_offset(mark, todo, 0, e, sorts);
257 }
258
get_free_vars(expr_sparse_mark & mark,ptr_vector<expr> & todo,expr * e,ptr_vector<sort> & sorts)259 void get_free_vars(expr_sparse_mark& mark, ptr_vector<expr>& todo, expr* e, ptr_vector<sort>& sorts) {
260 get_free_vars_offset(mark, todo, 0, e, sorts);
261 }
262
reset()263 void expr_free_vars::reset() {
264 m_mark.reset();
265 m_sorts.reset();
266 SASSERT(m_todo.empty());
267 }
268
set_default_sort(sort * s)269 void expr_free_vars::set_default_sort(sort *s) {
270 for (unsigned i = 0; i < m_sorts.size(); ++i) {
271 if (!m_sorts[i]) m_sorts[i] = s;
272 }
273 }
274
operator ()(expr * e)275 void expr_free_vars::operator()(expr* e) {
276 reset();
277 get_free_vars_offset(m_mark, m_todo, 0, e, m_sorts);
278 }
279
accumulate(expr * e)280 void expr_free_vars::accumulate(expr* e) {
281 SASSERT(m_todo.empty());
282 get_free_vars_offset(m_mark, m_todo, 0, e, m_sorts);
283 }
284