Add comment, use sigmap

diff --git a/backends/aiger/xaiger.cc b/backends/aiger/xaiger.cc
index 8b809b2e22cf7f7e9f957a83af2c739e889a6f07..e05b6cc6085f19fd3a993da9e0961a3a291b6764 100644 (file)
--- a/backends/aiger/xaiger.cc
+++ b/backends/aiger/xaiger.cc
@@ -198,11 +198,11 @@ struct XAigerWriter
                        }
                }
 
+               // Cannot fold into above due to use of sigmap
                for (auto bit : input_bits)
                        undriven_bits.erase(sigmap(bit));
                for (auto bit : output_bits)
-                       if (!bit.wire->port_input)
-                               unused_bits.erase(bit);
+                       unused_bits.erase(sigmap(bit));
 
                // TODO: Speed up toposort -- ultimately we care about
                //       box ordering, but not individual AIG cells