Add VHDL flag to specify maximum module depth

Specifying -pdepth=N only outputs entities that correspond
to Verilog modules found at depth < N in the hierarchy.

Setting -pdepth=0 (the default) outputs all entities.

This is for feature request 2391457

tgt-vhdl/scope.cc

@@ -642,7 +642,7 @@ static int draw_task(ivl_scope_t scope, ivl_scope_t parent)
 /*
  * Create an empty VHDL entity for a Verilog module.
  */
-static void create_skeleton_entity_for(ivl_scope_t scope)
+static void create_skeleton_entity_for(ivl_scope_t scope, int depth)
 {
    assert(ivl_scope_type(scope) == IVL_SCT_MODULE);
 
@@ -658,7 +658,7 @@ static void create_skeleton_entity_for(ivl_scope_t scope)
    // with the entity for convenience (this also means that we
    // retain a 1-to-1 mapping of scope to VHDL element)
    vhdl_arch *arch = new vhdl_arch(tname, "FromVerilog");
-   vhdl_entity *ent = new vhdl_entity(tname, derived_from, arch);
+   vhdl_entity *ent = new vhdl_entity(tname, derived_from, arch, depth);
 
    // Build a comment to add to the entity/architecture
    ostringstream ss;
@@ -676,13 +676,16 @@ static void create_skeleton_entity_for(ivl_scope_t scope)
  * A first pass through the hierarchy: create VHDL entities for
  * each unique Verilog module type.
  */
-static int draw_skeleton_scope(ivl_scope_t scope, void *_parent)
+static int draw_skeleton_scope(ivl_scope_t scope, void *_unused)
 {
-   debug_msg("Initial visit to scope %s", ivl_scope_name(scope));
+   static int depth = 0;
+   
+   debug_msg("Initial visit to scope %s at depth %d",
+             ivl_scope_name(scope), depth);
    
    switch (ivl_scope_type(scope)) {
    case IVL_SCT_MODULE:
-      create_skeleton_entity_for(scope);
+      create_skeleton_entity_for(scope, depth);
       break;
    case IVL_SCT_GENERATE:
       error("No translation for generate statements yet");
@@ -694,8 +697,11 @@ static int draw_skeleton_scope(ivl_scope_t scope, void *_parent)
       // The other scope types are expanded later on
       break;
    }
-      
-   return ivl_scope_children(scope, draw_skeleton_scope, scope);
+
+   ++depth;
+   int rc = ivl_scope_children(scope, draw_skeleton_scope, NULL);
+   --depth;
+   return rc;
 }
 
 static int draw_all_signals(ivl_scope_t scope, void *_parent)

tgt-vhdl/vhdl.cc

@@ -28,6 +28,7 @@
 #include <cstdio>
 #include <cassert>
 #include <cstring>
+#include <cstdlib>
 #include <list>
 #include <map>
 #include <set>
@@ -210,13 +211,21 @@ extern "C" int target_design(ivl_design_t des)
               << "-- Icarus Verilog VHDL Code Generator " VERSION
                  " (" VERSION_TAG ")" << endl << endl;
 
+      // If the user passed -pdepth=N then only emit entities with
+      // depth < N
+      // I.e. -pdepth=1 emits only the top-level entity
+      // If max_depth is zero then all entities will be emitted
+      // (This is handy since it means we can use atoi ;-)
+      int max_depth = std::atoi(ivl_design_flag(des, "depth"));
+
       // Make sure we only emit one example of each type of entity
       set<string> seen_entities;
       
       for (entity_list_t::iterator it = g_entities.begin();
            it != g_entities.end();
            ++it) {
-         if (seen_entities.find((*it)->get_name()) == seen_entities.end()) {
+         if (seen_entities.find((*it)->get_name()) == seen_entities.end()
+             && (max_depth == 0 || (*it)->depth < max_depth)) {
             (*it)->emit(outfile);
             seen_entities.insert((*it)->get_name());
          }

tgt-vhdl/vhdl_syntax.cc

@@ -87,8 +87,8 @@ vhdl_scope *vhdl_scope::get_parent() const
 }
 
 vhdl_entity::vhdl_entity(const char *name, const char *derived_from,
-                         vhdl_arch *arch)
-   : name_(name), arch_(arch), derived_from_(derived_from)
+                         vhdl_arch *arch, int depth)
+   :  depth(depth), name_(name), arch_(arch), derived_from_(derived_from)
 {
    arch->get_scope()->set_parent(&ports_);
 }

tgt-vhdl/vhdl_syntax.hh

@@ -797,7 +797,7 @@ private:
 class vhdl_entity : public vhdl_element {
 public:
    vhdl_entity(const char *name, const char *derived_from,
-               vhdl_arch *arch);
+               vhdl_arch *arch, int depth=0);
    virtual ~vhdl_entity();
 
    void emit(std::ostream &of, int level=0) const;
@@ -807,6 +807,11 @@ public:
    const std::string &get_derived_from() const { return derived_from_; }
 
    vhdl_scope *get_scope() { return &ports_; }
+   
+   // Each entity has an associated depth which is how deep in
+   // the Verilog module hierarchy it was found
+   // This is used to limit the maximum depth of modules emitted
+   const int depth;
 private:
    std::string name_;
    vhdl_arch *arch_;  // Entity may only have a single architecture