abc9_ops -prep_times: update comment

diff --git a/passes/techmap/abc9_ops.cc b/passes/techmap/abc9_ops.cc
index 4d49bb4d2674847912c753eca3a9807f8d9617b6..14b3f6c43b67b57ba66824037d32608d61424952 100644 (file)
--- a/passes/techmap/abc9_ops.cc
+++ b/passes/techmap/abc9_ops.cc
@@ -485,9 +485,9 @@ void prep_times(RTLIL::Design *design)
                                continue;
                        if (!inst_module->get_blackbox_attribute())
                                continue;
-                       // Flop inputs cannot have required times
-                       //   (required time should be captured by flop box)
-                       // TODO: enforce this
+                       // Only flop boxes are not combinatorial and may have required times,
+                       //   however those times are captured by this flop box, no need to
+                       //   add delay boxes
                        if (cell->attributes.count(ID(abc9_box_id)))
                                continue;
                        boxes.emplace_back(cell);
@@ -566,6 +566,7 @@ void write_box(RTLIL::Module *module, const std::string &src, const std::string
                        ofs << "$__ABC9_DELAY@" << d << " " << ABC9_DELAY_BASE_ID + d << " 0 1 1" << std::endl;
                        ofs << d << std::endl;
                }
+               module->attributes.erase(it);
        }
 
        ofs.close();