Add attributes to the hierarchical cells (#1405)

* Adds attributes to the hierarchical cells

* python: add binding for hierarchical cells attributes

* frontend/base: import hierarchical cells attributes

common/kernel/nextpnr_types.h

@@ -519,6 +519,8 @@ struct HierarchicalCell
     dict<IdString, HierarchicalPort> ports;
     // Name inside cell instance -> global name
     dict<IdString, IdString> hier_cells;
+    // Cell attributes
+    dict<IdString, Property> attrs;
 };
 
 NEXTPNR_NAMESPACE_END

common/kernel/pybindings.cc

@@ -283,6 +283,9 @@ PYBIND11_EMBEDDED_MODULE(MODULE_NAME, m)
                      wrap_context<IdIdMap &>>::def_wrap(hierarchy_cls, "nets");
     readonly_wrapper<HierarchicalCell &, decltype(&HierarchicalCell::hier_cells), &HierarchicalCell::hier_cells,
                      wrap_context<IdIdMap &>>::def_wrap(hierarchy_cls, "hier_cells");
+    readonly_wrapper<HierarchicalCell &, decltype(&HierarchicalCell::attrs), &HierarchicalCell::attrs,
+                     wrap_context<AttrMap &>>::def_wrap(hierarchy_cls, "attrs");
+
     WRAP_MAP(m, AttrMap, conv_to_str<Property>, "AttrMap");
     WRAP_MAP(m, PortMap, wrap_context<PortInfo &>, "PortMap");
     WRAP_MAP(m, IdIdMap, conv_to_str<IdString>, "IdIdMap");

frontend/frontend_base.h

@@ -535,6 +535,9 @@ template <typename FrontendType> struct GenericFrontend
         // Do the submodule import
         auto type = impl.get_cell_type(cd);
         import_module(submod, name, type, mod_refs.at(type));
+        // Add current cell attributes to the imported module
+        impl.foreach_attr( cd, [&](const std::string &name, const Property &value)
+              { ctx->hierarchy[submod.path].attrs[ctx->id(name)] = value; } );
     }
 
     // Import the cells section of a module