Fixed a bug in opt_muxtree for "mux forests"

diff --git a/passes/opt/opt_muxtree.cc b/passes/opt/opt_muxtree.cc
index fa91d4537b4412feda39c6085e7c57de4c9690b7..33dd12a03fa9b2aeeb0018bc59cdadbd712ca62f 100644 (file)
--- a/passes/opt/opt_muxtree.cc
+++ b/passes/opt/opt_muxtree.cc
@@ -69,6 +69,8 @@ struct OptMuxtreeWorker
 
        std::vector<muxinfo_t> mux2info;
 
+       std::set<int> root_muxes;
+
        OptMuxtreeWorker(RTLIL::Design *design, RTLIL::Module *module) :
                        design(design), module(module), assign_map(module), removed_count(0)
        {
@@ -159,15 +161,26 @@ struct OptMuxtreeWorker
 
                log("  Evaluating internal representation of mux trees.\n");
 
-               std::set<int> root_muxes;
+               dict<int, pool<int>> mux_to_users;
+
                for (auto &bi : bit2info) {
+                       for (int i : bi.mux_drivers)
+                               for (int j : bi.mux_users)
+                                       mux_to_users[i].insert(j);
                        if (!bi.seen_non_mux)
                                continue;
                        for (int mux_idx : bi.mux_drivers)
                                root_muxes.insert(mux_idx);
                }
-               for (int mux_idx : root_muxes)
+
+               for (auto &it : mux_to_users)
+                       if (GetSize(it.second) > 1)
+                               root_muxes.insert(it.first);
+
+               for (int mux_idx : root_muxes) {
+                       log("    Root of a mux tree: %s\n", log_id(mux2info[mux_idx].cell));
                        eval_root_mux(mux_idx);
+               }
 
                log("  Analyzing evaluation results.\n");
 
@@ -317,7 +330,8 @@ struct OptMuxtreeWorker
                        parent_muxes.push_back(m);
                }
                for (int m : parent_muxes)
-                       eval_mux(knowledge, m);
+                       if (!root_muxes.count(m))
+                               eval_mux(knowledge, m);
                for (int m : parent_muxes)
                        knowledge.visited_muxes.erase(m);
 
@@ -355,7 +369,7 @@ struct OptMuxtreeWorker
                }
 
                if (did_something) {
-                       log("    Replacing known input bits on port %s of cell %s: %s -> %s\n", log_id(portname),
+                       log("      Replacing known input bits on port %s of cell %s: %s -> %s\n", log_id(portname),
                                        log_id(muxinfo.cell), log_signal(muxinfo.cell->getPort(portname)), log_signal(sig));
                        muxinfo.cell->setPort(portname, sig);
                }