fix sim model generation for circuits with dangling nodes

src/kyupy/sim.py

@@ -188,10 +188,10 @@ class SimOps:
         levels = []
 
         ppio2idx = dict((n, i) for i, n in enumerate(circuit.s_nodes))
-        ppos = set([n for n in circuit.s_nodes if len(n.ins) > 0])
+        root_nodes = set([n for n in circuit.s_nodes if len(n.ins) > 0] + [n for n in circuit.nodes if len(n.outs) == 0])  # start from POs, PPOs, and any dangling nodes
-        readers = np.array([1 if l.reader in ppos else len(l.reader.outs) for l in circuit.lines], dtype=np.int32)  # for ref-counting forks
+        readers = np.array([1 if l.reader in root_nodes else len(l.reader.outs) for l in circuit.lines], dtype=np.int32)  # for ref-counting forks
 
-        level_lines = [n.ins[0] for n in ppos]  # start from PPOs
+        level_lines = [n.ins[0] for n in root_nodes]
         # FIXME: Should probably instanciate buffers for PPOs and attach DFF clocks
 
         while len(level_lines) > 0:  # traverse the circuit level-wise back towards (P)PIs

tests/test_logic_sim.py

@@ -3,6 +3,22 @@ import numpy as np
 from kyupy.logic_sim import LogicSim, LogicSim2V, LogicSim4V, LogicSim6V
 from kyupy import bench, logic, sim, verilog
 from kyupy.logic import mvarray, bparray, bp_to_mv, mv_to_bp
+from kyupy.techlib import SAED90
+
+def test_dangling():
+    c = verilog.parse('''
+        module test(i, o);
+            input i; output o; wire dangling;
+            INVX0 dff1 (.INP(i),.ZN(o));
+            assign dangling=o;
+        endmodule
+    ''', tlib=SAED90)
+    c.resolve_tlib_cells(SAED90)
+    sim = LogicSim2V(c)
+    p = sim.allocate()
+    p[...] = 0
+    sim.simulate(p)
+    assert p[1,0] == logic.ONE
 
 def assert_equal_shape_and_contents(actual, desired):
     desired = np.array(desired, dtype=np.uint8)