minimal addition to rewrite bit-vector to character conversion using constant folding.

src/ast/rewriter/CMakeLists.txt

@@ -9,6 +9,7 @@ z3_add_component(rewriter
     bv_elim.cpp
     bv_rewriter.cpp
     cached_var_subst.cpp
+    char_rewriter.cpp
     datatype_rewriter.cpp
     der.cpp
     distribute_forall.cpp

src/ast/rewriter/char_rewriter.cpp

@@ -0,0 +1,62 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    char_rewriter.cpp
+
+Abstract:
+
+    Basic rewriting rules for character constraints
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2015-12-5
+
+--*/
+
+#include "util/debug.h"
+#include "ast/rewriter/char_rewriter.h"
+#include "ast/bv_decl_plugin.h"
+
+char_rewriter::char_rewriter(ast_manager& m):
+    m(m) {
+    m_char = static_cast<char_decl_plugin*>(m.get_plugin(m.mk_family_id("char")));
+}
+
+family_id char_rewriter::get_fid() {
+    return m_char->get_family_id();
+}
+
+br_status char_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result) {
+    SASSERT(f->get_family_id() == get_fid());
+    br_status st = BR_FAILED;
+    switch (f->get_decl_kind()) {
+    case OP_CHAR_CONST:
+        break;
+    case OP_CHAR_LE:
+        break;
+    case OP_CHAR_TO_INT:
+        break;
+    case OP_CHAR_TO_BV:
+        break;
+    case OP_CHAR_FROM_BV:
+        st = mk_char_from_bv(args[0], result);
+        break;
+    case OP_CHAR_IS_DIGIT:
+        break;
+    }
+    return st;
+}
+
+br_status char_rewriter::mk_char_from_bv(expr* e, expr_ref& result) {
+    bv_util bv(m);
+    rational n;
+    if (bv.is_numeral(e, n) && n.is_unsigned()) {
+        if (n > m_char->max_char())
+            return BR_FAILED;
+        result = m_char->mk_char(n.get_unsigned());
+        return BR_DONE;
+    }
+    return BR_FAILED;
+}

src/ast/rewriter/char_rewriter.h

@@ -0,0 +1,54 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    char_rewriter.h
+
+Abstract:
+
+    Basic rewriting rules for characters constraints.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2022-03-10
+
+Notes:
+
+--*/
+#pragma once
+
+#include "ast/char_decl_plugin.h"
+#include "ast/rewriter/rewriter_types.h"
+#include "util/params.h"
+#include "util/lbool.h"
+
+
+/**
+   \brief Cheap rewrite rules for character constraints
+*/
+class char_rewriter {
+    ast_manager& m;
+    char_decl_plugin* m_char;
+
+    br_status mk_char_from_bv(expr* e, expr_ref& result);
+public:
+
+    char_rewriter(ast_manager& m);
+
+    family_id get_fid();
+
+    br_status mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result);
+
+    expr_ref mk_app(func_decl* f, expr_ref_vector const& args) { return mk_app(f, args.size(), args.data()); }
+
+    expr_ref mk_app(func_decl* f, unsigned n, expr* const* args) { 
+        expr_ref result(m);
+        if (f->get_family_id() != get_fid() ||
+            BR_FAILED == mk_app_core(f, n, args, result))
+            result = m.mk_app(f, n, args);
+        return result;
+    }
+
+};
+

src/ast/rewriter/th_rewriter.cpp

@@ -21,6 +21,7 @@ Notes:
 #include "ast/rewriter/bool_rewriter.h"
 #include "ast/rewriter/arith_rewriter.h"
 #include "ast/rewriter/bv_rewriter.h"
+#include "ast/rewriter/char_rewriter.h"
 #include "ast/rewriter/datatype_rewriter.h"
 #include "ast/rewriter/array_rewriter.h"
 #include "ast/rewriter/fpa_rewriter.h"
@@ -48,6 +49,7 @@ struct th_rewriter_cfg : public default_rewriter_cfg {
     dl_rewriter         m_dl_rw;
     pb_rewriter         m_pb_rw;
     seq_rewriter        m_seq_rw;
+    char_rewriter       m_char_rw;
     recfun_rewriter     m_rec_rw;
     arith_util          m_a_util;
     bv_util             m_bv_util;
@@ -247,6 +249,8 @@ struct th_rewriter_cfg : public default_rewriter_cfg {
             return m_pb_rw.mk_app_core(f, num, args, result);
         if (fid == m_seq_rw.get_fid())
             return m_seq_rw.mk_app_core(f, num, args, result);
+        if (fid == m_char_rw.get_fid())
+            return m_char_rw.mk_app_core(f, num, args, result);        
         if (fid == m_rec_rw.get_fid())
             return m_rec_rw.mk_app_core(f, num, args, result);
         return BR_FAILED;
@@ -802,6 +806,7 @@ struct th_rewriter_cfg : public default_rewriter_cfg {
         m_dl_rw(m),
         m_pb_rw(m),
         m_seq_rw(m),
+        m_char_rw(m),
         m_rec_rw(m),
         m_a_util(m),
         m_bv_util(m),