Add simplification customization for SMTLIB2

Add the ability to customize incremental pre-processing simplification for the SMTLIB2 front-end. The main new capability is to use pre-processing tactics in incremental mode that were previously not available. The main new capabilities are
- solve-eqs
- reduce-args
- elim-unconstrained
There are several more. Documentation and exposed simplifiers are populated incrementally. The current set of supported simplifiers can be inspected by using z3 with the --simplifiers flag or referring to https://microsoft.github.io/z3guide/docs/strategies/simplifiers

Some pending features are:
- add the ability to update parameters to simplifiers similar to how tactics can be controlled using parameters.
- expose simplification solvers over the binary API.

src/shell/main.cpp

@@ -98,6 +98,7 @@ void display_usage() {
     std::cout << "  -pmmd:name  display Z3 module ('name') parameters in Markdown format.\n";
     std::cout << "  -pp:name    display Z3 parameter description, if 'name' is not provided, then all module names are listed.\n";
     std::cout << "  -tactics[:name]  display built-in tactics or if argument is given, display detailed information on tactic.\n";
+    std::cout << "  -simplifiers[:name]  display built-in simplifiers or if argument is given, display detailed information on simplifier.\n";
     std::cout << "  -probes     display avilable probes.\n";
     std::cout << "  --"      << "          all remaining arguments are assumed to be part of the input file name. This option allows Z3 to read files with strange names such as: -foo.smt2.\n";
     std::cout << "\nResources:\n";
@@ -295,6 +296,12 @@ static void parse_cmd_line_args(std::string& input_file, int argc, char ** argv)
                 else
                     help_tactic(opt_arg, false);
             }
+            else if (strcmp(opt_name, "simplifiers") == 0) {
+                if (!opt_arg)
+                    help_simplifiers();
+                else
+                    help_simplifier(opt_arg, false);
+            }
             else if (strcmp(opt_name, "tacticsmd") == 0 && opt_arg) 
                 help_tactic(opt_arg, true);
             else if (strcmp(opt_name, "probes") == 0) 

src/shell/smtlib_frontend.cpp

@@ -88,6 +88,22 @@ void help_tactics() {
         std::cout << "- " << cmd->get_name() << " " << cmd->get_descr() << "\n";
 }
 
+void help_simplifiers() {
+    struct cmp {
+        bool operator()(simplifier_cmd* a, simplifier_cmd* b) const {
+            return a->get_name().str() < b->get_name().str();
+        }
+    };
+    cmd_context ctx;
+    ptr_vector<simplifier_cmd> cmds;
+    for (auto cmd : ctx.simplifiers()) 
+        cmds.push_back(cmd);
+    cmp lt;
+    std::sort(cmds.begin(), cmds.end(), lt);
+    for (auto cmd : cmds) 
+        std::cout << "- " << cmd->get_name() << " " << cmd->get_descr() << "\n";
+}
+
 void help_tactic(char const* name, bool markdown) {
     cmd_context ctx;
     for (auto cmd : ctx.tactics()) {
@@ -103,6 +119,25 @@ void help_tactic(char const* name, bool markdown) {
     }
 }
 
+void help_simplifier(char const* name, bool markdown) {
+    cmd_context ctx;
+    for (auto cmd : ctx.simplifiers()) {
+        if (cmd->get_name() == name) {
+            auto fac = cmd->factory();
+            param_descrs descrs;
+            ast_manager& m = ctx.m();
+            default_dependent_expr_state st(m);
+            params_ref p;
+            scoped_ptr<dependent_expr_simplifier> s = fac(m, p, st);
+            s->collect_param_descrs(descrs);
+            if (markdown)
+                descrs.display_markdown(std::cout);
+            else
+                descrs.display(std::cout, 4);
+        }
+    }
+}
+
 void help_probes() {
     struct cmp {
         bool operator()(probe_info* a, probe_info* b) const {

src/shell/smtlib_frontend.h

@@ -21,7 +21,9 @@ Revision History:
 unsigned read_smtlib_file(char const * benchmark_file);
 unsigned read_smtlib2_commands(char const * command_file);
 void help_tactics();
+void help_simplifiers();
 void help_probes();
 void help_tactic(char const* name, bool markdown);
+void help_simplifier(char const* name, bool markdown);