From: whitequark <cz@m-labs.hk>
Date: Fri, 14 Dec 2018 09:12:38 +0000 (+0000)
Subject: back.pysim: undriven comb signals should return to reset value.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=f3f3f05154aa39d18bfa252b067df2e8f63a7477;p=nmigen.git

back.pysim: undriven comb signals should return to reset value.
---

diff --git a/nmigen/back/pysim.py b/nmigen/back/pysim.py
index 9716ff2..c228611 100644
--- a/nmigen/back/pysim.py
+++ b/nmigen/back/pysim.py
@@ -326,8 +326,13 @@ class Simulator:
                     self._sync_signals.update(signals)
                     self._domain_signals[domain].update(signals)
 
+            statements = []
+            for signal in fragment.iter_comb():
+                statements.append(signal.eq(signal.reset))
+            statements += fragment.statements
+
             compiler = _StatementCompiler()
-            funclet  = compiler(fragment.statements)
+            funclet  = compiler(statements)
             for signal in compiler.sensitivity:
                 self._add_funclet(signal, funclet)
             for domain, cd in fragment.domains.items():
diff --git a/nmigen/fhdl/ir.py b/nmigen/fhdl/ir.py
index 8c8b7a9..493aa2f 100644
--- a/nmigen/fhdl/ir.py
+++ b/nmigen/fhdl/ir.py
@@ -39,7 +39,8 @@ class Fragment:
                 yield domain, signal
 
     def iter_comb(self):
-        yield from self.drivers[None]
+        if None in self.drivers:
+            yield from self.drivers[None]
 
     def iter_sync(self):
         for domain, signals in self.drivers.items():