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diff --git a/passes/techmap/abc9.cc b/passes/techmap/abc9.cc
index 4a6ec3a47ee254550ec1a24a9ef4bbcab0c04574..658bb1225cef370d02bfbb08fb8ee6a2c76374b3 100644 (file)
--- a/passes/techmap/abc9.cc
+++ b/passes/techmap/abc9.cc
@@ -787,6 +787,11 @@ void abc9_module(RTLIL::Design *design, RTLIL::Module *current_module, std::stri
                                sink_cell->setParam("\\LUT", mask);
                        }
 
+                       // Since we have rewritten all sinks (which we know
+                       // to be only LUTs) to be after the inverter, we can
+                       // go ahead and clone the LUT with the expectation
+                       // that the original driving LUT will become dangling
+                       // and get cleaned away
 clone_lut:
                        driver_mask = driver_lut->getParam("\\LUT");
                        for (auto &b : driver_mask.bits) {