Be slightly less aggressive in "deminout" pass

Signed-off-by: Clifford Wolf <clifford@clifford.at>

diff --git a/passes/techmap/deminout.cc b/passes/techmap/deminout.cc
index ed4e457621379b61bee75c41a3cefc204cc608e3..0b8fd5246704cc85013bd13b965eb68ea96ec1c3 100644 (file)
--- a/passes/techmap/deminout.cc
+++ b/passes/techmap/deminout.cc
@@ -57,7 +57,7 @@ struct DeminoutPass : public Pass {
                        for (auto module : design->selected_modules())
                        {
                                SigMap sigmap(module);
-                               pool<SigBit> bits_written, bits_used, bits_inout;
+                               pool<SigBit> bits_written, bits_used, bits_inout, bits_tribuf;
                                dict<SigBit, int> bits_numports;
 
                                for (auto wire : module->wires())
@@ -82,6 +82,25 @@ struct DeminoutPass : public Pass {
                                        if (cellport_in)
                                                for (auto bit : sigmap(conn.second))
                                                        bits_used.insert(bit);
+
+                                       if (conn.first == "\\Y" && cell->type.in("$mux", "$pmux", "$_MUX_", "$_TBUF_"))
+                                       {
+                                               bool tribuf = (cell->type == "$_TBUF_");
+
+                                               if (!tribuf) {
+                                                       for (auto &c : cell->connections()) {
+                                                               if (!c.first.in("\\A", "\\B"))
+                                                                       continue;
+                                                               for (auto b : sigmap(c.second))
+                                                                       if (b == State::Sz)
+                                                                               tribuf = true;
+                                                       }
+                                               }
+
+                                               if (tribuf)
+                                                       for (auto bit : sigmap(conn.second))
+                                                               bits_tribuf.insert(bit);
+                                       }
                                }
 
                                for (auto wire : module->selected_wires())
@@ -95,10 +114,15 @@ struct DeminoutPass : public Pass {
                                                        if (bits_numports[bit] > 1 || bits_inout.count(bit))
                                                                new_input = true, new_output = true;
 
-                                                       if (bits_written.count(bit))
+                                                       if (bits_written.count(bit)) {
                                                                new_output = true;
-                                                       else if (bits_used.count(bit))
-                                                               new_input = true;
+                                                               if (bits_tribuf.count(bit))
+                                                                       goto tribuf_bit;
+                                                       } else {
+                                               tribuf_bit:
+                                                               if (bits_used.count(bit))
+                                                                       new_input = true;
+                                                       }
                                                }
 
                                                if (new_input != new_output) {