btor: add support for $pos cell

diff --git a/backends/btor/btor.cc b/backends/btor/btor.cc
index 5be9bf324c33e18c96cb07e15f182a7c2062e1ea..7dec70545bd13d844e85b93a57f806cf0969c0a4 100644 (file)
--- a/backends/btor/btor.cc
+++ b/backends/btor/btor.cc
@@ -446,25 +446,28 @@ struct BtorWorker
                        goto okay;
                }
 
-               if (cell->type.in(ID($not), ID($neg), ID($_NOT_)))
+               if (cell->type.in(ID($not), ID($neg), ID($_NOT_), ID($pos)))
                {
                        string btor_op;
                        if (cell->type.in(ID($not), ID($_NOT_))) btor_op = "not";
                        if (cell->type == ID($neg)) btor_op = "neg";
-                       log_assert(!btor_op.empty());
 
                        int width = std::max(GetSize(cell->getPort(ID::A)), GetSize(cell->getPort(ID::Y)));
 
                        bool a_signed = cell->hasParam(ID::A_SIGNED) ? cell->getParam(ID::A_SIGNED).as_bool() : false;
-
-                       int sid = get_bv_sid(width);
                        int nid_a = get_sig_nid(cell->getPort(ID::A), width, a_signed);
-
-                       int nid = next_nid++;
-                       btorf("%d %s %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, getinfo(cell).c_str());
-
                        SigSpec sig = sigmap(cell->getPort(ID::Y));
 
+                       // the $pos cell just passes through, all other cells need an actual operation applied
+                       int nid = nid_a;
+                       if (cell->type != ID($pos))
+                       {
+                               log_assert(!btor_op.empty());
+                               int sid = get_bv_sid(width);
+                               nid = next_nid++;
+                               btorf("%d %s %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, getinfo(cell).c_str());
+                       }
+
                        if (GetSize(sig) < width) {
                                int sid = get_bv_sid(GetSize(sig));
                                int nid2 = next_nid++;