From: whitequark <whitequark@whitequark.org>
Date: Fri, 3 Apr 2020 05:20:42 +0000 (+0000)
Subject: back.pysim: fix emission of undriven traces to VCD files.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=c89bca6042910eb0e84b11b2bdfee962001bda1c;p=nmigen.git

back.pysim: fix emission of undriven traces to VCD files.

This has been originally implemented in commit d3775eed (which fixed
`write_vcd(traces=)` to do something at all), but had a flaw where
undriven traces would not be correctly placed in hierarchy. This
used to produce incorrect results on pyvcd 0.1, but started causing
assertion failures on pyvcd 0.2.

Fixes #345.
---

diff --git a/nmigen/back/pysim.py b/nmigen/back/pysim.py
index 96e98e7..398266e 100644
--- a/nmigen/back/pysim.py
+++ b/nmigen/back/pysim.py
@@ -93,7 +93,7 @@ class _VCDWaveformWriter(_WaveformWriter):
         trace_names = SignalDict()
         for trace in traces:
             if trace not in signal_names:
-                trace_names[trace] = trace.name
+                trace_names[trace] = {("top", trace.name)}
             self.traces.append(trace)
 
         if self.vcd_writer is None: