nixpkgs/pkgs/development/compilers/yosys/plugin-search-dirs.patch

diff --git a/passes/cmds/plugin.cc b/passes/cmds/plugin.cc
index 3ed19497..f9534bd0 100644
--- a/passes/cmds/plugin.cc
+++ b/passes/cmds/plugin.cc
@@ -75,8 +75,27 @@ void load_plugin(std::string filename, std::vector<std::string> aliases)
 		#endif
 
 		void *hdl = dlopen(filename.c_str(), RTLD_LAZY|RTLD_LOCAL);
-		if (hdl == NULL && orig_filename.find('/') == std::string::npos)
-			hdl = dlopen((proc_share_dirname() + "plugins/" + orig_filename + ".so").c_str(), RTLD_LAZY|RTLD_LOCAL);
+		if (hdl == NULL && orig_filename.find('/') == std::string::npos) {
+			std::string install_dir = proc_share_dirname() + "plugins";
+
+			vector<string> all_dirs;
+			all_dirs.push_back(install_dir);
+
+			char* plugin_dirs = getenv("NIX_YOSYS_PLUGIN_DIRS");
+			if (plugin_dirs != NULL) {
+				std::string p(plugin_dirs), t;
+				std::stringstream ss(p);
+
+				while(std::getline(ss, t, ':')) {
+					all_dirs.push_back(t);
+				}
+			}
+
+			for (auto dir : all_dirs) {
+				hdl = dlopen((dir + "/" + orig_filename + ".so").c_str(), RTLD_LAZY|RTLD_LOCAL);
+				if (hdl != NULL) break;
+			}
+		}
 		if (hdl == NULL)
 			log_cmd_error("Can't load module `%s': %s\n", filename.c_str(), dlerror());
 		loaded_plugins[orig_filename] = hdl;