Implement combinatorial UDPs

Using a `with .. select' statement

tgt-vhdl/logic.cc

@@ -120,9 +120,10 @@ static void udp_logic(vhdl_arch *arch, ivl_net_logic_t log)
    vhdl_signal_decl *tmp_decl =
       new vhdl_signal_decl(ss.str().c_str(), tmp_type);
    arch->get_scope()->add_decl(tmp_decl);
-   
+
+   int nin = ivl_udp_nin(udp);
    vhdl_expr *tmp_rhs;
-   if (ivl_udp_nin(udp) == 1) {
+   if (nin == 1) {
       tmp_rhs = nexus_to_var_ref(arch->get_scope(), ivl_logic_pin(log, 1));
       tmp_rhs = tmp_rhs->cast(tmp_type);
    }
@@ -137,7 +138,29 @@ static void udp_logic(vhdl_arch *arch, ivl_net_logic_t log)
    vhdl_var_ref *tmp_ref =
       new vhdl_var_ref(tmp_decl->get_name().c_str(), NULL);
    arch->add_stmt(new vhdl_cassign_stmt(tmp_ref, tmp_rhs));
+
+   // Now we can implement the UDP as a `with .. select' statement
+   // by reading values out of the table
+   ivl_nexus_t output_nex = ivl_logic_pin(log, 0);
+   vhdl_var_ref *out = nexus_to_var_ref(arch->get_scope(), output_nex);
+   vhdl_with_select_stmt *ws =
+      new vhdl_with_select_stmt(new vhdl_var_ref(*tmp_ref), out);
    
+   int nrows = ivl_udp_rows(udp);
+   for (int i = 0; i < nrows; i++) {
+      const char *row = ivl_udp_row(udp, i);
+      
+      vhdl_expr *value = new vhdl_const_bit(row[nin]);
+      vhdl_expr *cond = new vhdl_const_bits(row, nin, false);
+
+      ws->add_condition(value, cond);
+   }
+
+   ss.str("");
+   ss << "UDP " << ivl_udp_name(udp);
+   ws->set_comment(ss.str());
+
+   arch->add_stmt(ws);
 }
 
 static vhdl_expr *translate_logic_inputs(vhdl_scope *scope, ivl_net_logic_t log)

tgt-vhdl/vhdl_syntax.cc

@@ -892,6 +892,7 @@ void vhdl_param_decl::emit(std::ostream &of, int level) const
 vhdl_with_select_stmt::~vhdl_with_select_stmt()
 {
    delete test_;
+   delete out_;
 
    for (when_list_t::const_iterator it = whens_.begin();
         it != whens_.end();
@@ -903,15 +904,21 @@ vhdl_with_select_stmt::~vhdl_with_select_stmt()
 
 void vhdl_with_select_stmt::emit(std::ostream &of, int level) const
 {
-   emit_comment(of, level);
-   
    of << "with ";
    test_->emit(of, level);
    of << " select";
+   emit_comment(of, level, true);   
    newline(of, indent(level));
 
+   out_->emit(of, level);
+   of << " <= ";      
+   
    when_list_t::const_iterator it = whens_.begin();
    while (it != whens_.end()) {
+      (*it).value->emit(of, level);
+      of << " when ";
+      (*it).cond->emit(of, level);
+      
       if (++it != whens_.end()) {
          of << ",";
          newline(of, indent(level));

tgt-vhdl/vhdl_syntax.hh

@@ -288,13 +288,15 @@ private:
 
 class vhdl_with_select_stmt : public vhdl_conc_stmt {
 public:
-   vhdl_with_select_stmt(vhdl_expr *test) : test_(test) {}
+   vhdl_with_select_stmt(vhdl_expr *test, vhdl_var_ref *out)
+      : test_(test), out_(out) {}
    ~vhdl_with_select_stmt();
    
    void emit(std::ostream &of, int level) const;
    void add_condition(vhdl_expr *value, vhdl_expr *cond);
 private:
    vhdl_expr *test_;
+   vhdl_var_ref *out_;
    when_list_t whens_;
 };