Various signal naming fixes for VHDL target

This avoids generating invalid VHDL signal names in the
following cases:
	- The name begins or ends with an underscore
	- The name contains two consecutive underscores
	- The name is the same as a component declaration
	- The name differs from another only in case

tgt-vhdl/scope.cc

@@ -384,10 +384,28 @@ static void declare_logic(vhdl_arch *arch, ivl_scope_t scope)
  */
 static string make_safe_name(ivl_signal_t sig)
 {
-   const char *base = ivl_signal_basename(sig);      
-   if (base[0] == '_')
-      return string("VL") + base;
+   string base(ivl_signal_basename(sig));
 
+   if (ivl_signal_local(sig))
+      base = "Tmp" + base;
+   
+   if (base[0] == '_')
+      base = "Sig" + base;
+
+   if (*base.rbegin() == '_')
+      base += "Sig";
+
+   // Can't have two consecutive underscores
+   size_t pos = base.find("__");
+   while (pos != string::npos) {
+      base.replace(pos, 2, "_");
+      pos = base.find("__");
+   }
+   
+   // A signal name may not be the same as a component name
+   if (find_entity(base) != NULL)
+      base += "_Sig";
+   
    // This is the complete list of VHDL reserved words
    const char *vhdl_reserved[] = {
       "abs", "access", "after", "alias", "all", "and", "architecture",
@@ -407,14 +425,32 @@ static string make_safe_name(ivl_signal_t sig)
    };
 
    for (const char **p = vhdl_reserved; *p != NULL; p++) {
-      if (strcasecmp(*p, base) == 0) {
-         return string("VL_") + base;
+      if (strcasecmp(*p, base.c_str()) == 0) {
+         return "Sig_" + base;
          break;
       }
    }
    return string(base);
 }
 
+// Check if `name' differs from an existing name only in case and
+// make it unique if it does.
+static void avoid_name_collision(string& name, vhdl_scope* scope)
+{
+   if (scope->name_collides(name)) {
+      name += "_";
+      ostringstream ss;
+      int i = 1;
+      do {
+         // Keep adding an extra number until we get a unique name
+         ss.str("");
+         ss << name << i++;
+      } while (scope->name_collides(ss.str()));
+      
+      name = ss.str();
+   }
+}
+
 /*
  * Declare all signals and ports for a scope.
  */
@@ -428,6 +464,8 @@ static void declare_signals(vhdl_entity *ent, ivl_scope_t scope)
       remember_signal(sig, ent->get_arch()->get_scope());
 
       string name(make_safe_name(sig));
+      avoid_name_collision(name, ent->get_arch()->get_scope());
+      
       rename_signal(sig, name);
       
       vhdl_type *sig_type;
@@ -977,7 +1015,11 @@ static int draw_hierarchy(ivl_scope_t scope, void *_parent)
       
       loc = inst_name.find(']', 0);
       if (loc != string::npos)
-         inst_name.erase(loc, 1);         
+         inst_name.erase(loc, 1);
+
+      // Make sure the name doesn't collide with anything we've
+      // already declared
+      avoid_name_collision(inst_name, parent_arch->get_scope());
       
       vhdl_comp_inst *inst =
          new vhdl_comp_inst(inst_name.c_str(), ent->get_name().c_str());

tgt-vhdl/state.cc

@@ -149,6 +149,19 @@ struct cmp_ent_name {
    const string& name_;
 };
 
+// Find an entity given its name.
+vhdl_entity* find_entity(const string& name)
+{
+   entity_list_t::const_iterator it
+      = find_if(g_entities.begin(), g_entities.end(),
+                cmp_ent_name(name));
+
+   if (it != g_entities.end())
+      return *it;
+   else
+      return NULL;
+}
+
 // Find a VHDL entity given a Verilog module scope. The VHDL entity
 // name should be the same as the Verilog module type name.
 // Note that this will return NULL if no entity has been recorded
@@ -157,14 +170,7 @@ vhdl_entity* find_entity(const ivl_scope_t scope)
 {
    assert(ivl_scope_type(scope) == IVL_SCT_MODULE);
 
-   entity_list_t::const_iterator it
-      = find_if(g_entities.begin(), g_entities.end(),
-                cmp_ent_name(ivl_scope_tname(scope)));
-
-   if (it != g_entities.end())
-      return *it;
-   else
-      return NULL;
+   return find_entity(ivl_scope_tname(scope));
 }
 
 // Add an entity/architecture pair to the list of entities to emit.

tgt-vhdl/state.hh

@@ -39,7 +39,8 @@ ivl_signal_t find_signal_named(const std::string &name, const vhdl_scope *scope)
 
 // Manage the set of VHDL entities
 void remember_entity(vhdl_entity *ent);
-vhdl_entity *find_entity(const ivl_scope_t scope);
+vhdl_entity* find_entity(const ivl_scope_t scope);
+vhdl_entity* find_entity(const std::string& name);
 void emit_all_entities(std::ostream& os, int max_depth);
 void free_all_vhdl_objects();
 

tgt-vhdl/vhdl_syntax.cc

@@ -74,6 +74,16 @@ bool vhdl_scope::have_declared(const std::string &name) const
    return get_decl(name) != NULL;
 }
 
+// True if `name' differs in all but case from another declaration
+bool vhdl_scope::name_collides(const string& name) const
+{
+   const vhdl_decl* decl = get_decl(name);
+   if (decl)
+      return decl->get_name() != name;
+   else
+      return false;
+}
+
 bool vhdl_scope::contained_within(const vhdl_scope *other) const
 {
    if (this == other)

tgt-vhdl/vhdl_syntax.hh

@@ -719,6 +719,7 @@ public:
    void add_forward_decl(vhdl_decl *decl);
    vhdl_decl *get_decl(const std::string &name) const;
    bool have_declared(const std::string &name) const;
+   bool name_collides(const string& name) const;
    bool contained_within(const vhdl_scope *other) const;
    vhdl_scope *get_parent() const;