[FRONTEND] Added support for element-wise function defined in external LLVM bitcode (e.g., libdevice) (#562)

lib/ir/builder.cc

@@ -379,6 +379,19 @@ value *builder::create_globaltimer() {
   return insert(globaltimer_inst::create(ctx_));
 }
 
+//===----------------------------------------------------------------------===//
+//                               externs
+//===----------------------------------------------------------------------===//
+
+value *builder::create_extern_elementwise(const std::string &lib_name,
+                                          const std::string &lib_path,
+                                          const std::string &symbol_name,
+                                          const std::vector<value *> &args,
+                                          type *ret_ty) {
+  return insert(extern_elementwise_inst::create(ctx_, args, ret_ty, lib_name,
+                                                lib_path, symbol_name));
+}
+
 //===----------------------------------------------------------------------===//
 //                               built-in instructions
 //===----------------------------------------------------------------------===//