json: Add support for memories.

Previously, memories were silently discarded by the JSON backend, making
round-tripping modules with them crash.

Since there are already some users using JSON to implement custom
external passes that use memories (and infer width/size from memory
ports), let's fix this by just making JSON backend and frontend support
memories as first-class objects.

Processes are still not supported, and will now cause a hard error.

Fixes #1908.

2 files changed, 88 insertions, 0 deletions

diff --git a/backends/json/json.cc b/backends/json/json.cc
index eeadc1b89..b13105f64 100644
--- a/backends/json/json.cc
+++ b/backends/json/json.cc
@@ -135,6 +135,10 @@ struct JsonWriter
 		// reserve 0 and 1 to avoid confusion with "0" and "1"
 		sigidcounter = 2;
 
+		if (module->has_processes()) {
+			log_error("Module %s contains processes, which are not supported by JSON backend.\n", log_id(module));
+		}
+
 		f << stringf("    %s: {\n", get_name(module->name).c_str());
 
 		f << stringf("      \"attributes\": {");
@@ -216,6 +220,27 @@ struct JsonWriter
 		}
 		f << stringf("\n      },\n");
 
+		if (!module->memories.empty()) {
+			f << stringf("      \"memories\": {");
+			first = true;
+			for (auto &it : module->memories) {
+				if (use_selection && !module->selected(it.second))
+					continue;
+				f << stringf("%s\n", first ? "" : ",");
+				f << stringf("        %s: {\n", get_name(it.second->name).c_str());
+				f << stringf("          \"hide_name\": %s,\n", it.second->name[0] == '$' ? "1" : "0");
+				f << stringf("          \"attributes\": {");
+				write_parameters(it.second->attributes);
+				f << stringf("\n          },\n");
+				f << stringf("          \"width\": %d,\n", it.second->width);
+				f << stringf("          \"start_offset\": %d,\n", it.second->start_offset);
+				f << stringf("          \"size\": %d\n", it.second->size);
+				f << stringf("        }");
+				first = false;
+			}
+			f << stringf("\n      },\n");
+		}
+
 		f << stringf("      \"netnames\": {");
 		first = true;
 		for (auto w : module->wires()) {
@@ -332,6 +357,10 @@ struct JsonBackend : public Backend {
 		log("            <cell_name>: <cell_details>,\n");
 		log("            ...\n");
 		log("          },\n");
+		log("          \"memories\": {\n");
+		log("            <memory_name>: <memory_details>,\n");
+		log("            ...\n");
+		log("          },\n");
 		log("          \"netnames\": {\n");
 		log("            <net_name>: <net_details>,\n");
 		log("            ...\n");
@@ -379,6 +408,19 @@ struct JsonBackend : public Backend {
 		log("      },\n");
 		log("    }\n");
 		log("\n");
+		log("And <memory_details> is:\n");
+		log("\n");
+		log("    {\n");
+		log("      \"hide_name\": <1 | 0>,\n");
+		log("      \"attributes\": {\n");
+		log("        <attribute_name>: <attribute_value>,\n");
+		log("        ...\n");
+		log("      },\n");
+		log("      \"width\": <memory width>\n");
+		log("      \"start_offset\": <the lowest valid memory address>\n");
+		log("      \"size\": <memory size>\n");
+		log("    }\n");
+		log("\n");
 		log("And <net_details> is:\n");
 		log("\n");
 		log("    {\n");
diff --git a/frontends/json/jsonparse.cc b/frontends/json/jsonparse.cc
index 312f6d3be..d897ac20b 100644
--- a/frontends/json/jsonparse.cc
+++ b/frontends/json/jsonparse.cc
@@ -539,6 +539,52 @@ void json_import(Design *design, string &modname, JsonNode *node)
 				json_parse_attr_param(cell->parameters, cell_node->data_dict.at("parameters"));
 		}
 	}
+
+	if (node->data_dict.count("memories"))
+	{
+		JsonNode *memories_node = node->data_dict.at("memories");
+
+		if (memories_node->type != 'D')
+			log_error("JSON memories node is not a dictionary.\n");
+
+		for (auto &memory_node_it : memories_node->data_dict)
+		{
+			IdString memory_name = RTLIL::escape_id(memory_node_it.first.c_str());
+			JsonNode *memory_node = memory_node_it.second;
+
+			RTLIL::Memory *mem = new RTLIL::Memory;
+			mem->name = memory_name;
+
+			if (memory_node->type != 'D')
+				log_error("JSON memory node '%s' is not a dictionary.\n", log_id(memory_name));
+
+			if (memory_node->data_dict.count("width") == 0)
+				log_error("JSON memory node '%s' has no width attribute.\n", log_id(memory_name));
+			JsonNode *width_node = memory_node->data_dict.at("width");
+			if (width_node->type != 'N')
+				log_error("JSON memory node '%s' has a non-number width.\n", log_id(memory_name));
+			mem->width = width_node->data_number;
+
+			if (memory_node->data_dict.count("size") == 0)
+				log_error("JSON memory node '%s' has no size attribute.\n", log_id(memory_name));
+			JsonNode *size_node = memory_node->data_dict.at("size");
+			if (size_node->type != 'N')
+				log_error("JSON memory node '%s' has a non-number size.\n", log_id(memory_name));
+			mem->size = size_node->data_number;
+
+			mem->start_offset = 0;
+			if (memory_node->data_dict.count("start_offset") != 0) {
+				JsonNode *val = memory_node->data_dict.at("start_offset");
+				if (val->type == 'N')
+					mem->start_offset = val->data_number;
+			}
+
+			if (memory_node->data_dict.count("attributes"))
+				json_parse_attr_param(mem->attributes, memory_node->data_dict.at("attributes"));
+
+			module->memories[mem->name] = mem;
+		}
+	}
 }
 
 struct JsonFrontend : public Frontend {