back.pysim: squash one level of hierarchy.

There's really no point in the "top" node.

diff --git a/nmigen/back/pysim.py b/nmigen/back/pysim.py
index fb234b511c59a3d2f30e38c962f0bf7c0ed67775..47d84fae640ec8000256a81856cd7c5276da5559 100644 (file)
--- a/nmigen/back/pysim.py
+++ b/nmigen/back/pysim.py
@@ -295,7 +295,7 @@ class Simulator:
             self._domain_signals[domain] = ValueSet()
 
         hierarchy = {}
-        def add_fragment(fragment, scope=("top",)):
+        def add_fragment(fragment, scope=()):
             hierarchy[fragment] = scope
             for subfragment, name in fragment.subfragments:
                 add_fragment(subfragment, (*scope, name))