gen/sim: hack to update vcd output file during simulation (allow visualizing progress directly and having a vcd file even when simulation fails or doesn't stop)

litex/gen/sim/core.py

@@ -39,7 +39,7 @@ class TimeManager:
             else:
                 high = False
             self.clocks[k] = ClockState(high, half_period, half_period - phase)
-    
+
     def tick(self):
         rising = set()
         falling = set()
@@ -62,14 +62,14 @@ str2op = {
     "+": operator.add,
     "-": operator.sub,
     "*": operator.mul,
-    
+
     ">>>": operator.rshift,
     "<<<": operator.lshift,
-    
+
     "&": operator.and_,
     "^": operator.xor,
     "|": operator.or_,
-    
+
     "<": operator.lt,
     "<=": operator.le,
     "==": operator.eq,
@@ -279,6 +279,7 @@ class Simulator:
                     signals.add(cd.rst)
             for memory_array in mta.replacements.values():
                 signals |= set(memory_array)
+            self.vcd.init(signals)
             for signal in sorted(signals, key=lambda x: x.duid):
                 self.vcd.set(signal, signal.reset.value)
 

litex/gen/sim/vcd.py

@@ -21,8 +21,7 @@ def vcd_codes():
 class VCDWriter:
     def __init__(self, filename):
         self.filename = filename
-        self.buffer_file = tempfile.TemporaryFile(
+        self.out_file = open(self.filename, "w")
-            dir=os.path.dirname(filename), mode="w+")
         self.codegen = vcd_codes()
         self.codes = OrderedDict()
         self.signal_values = dict()
@@ -36,45 +35,49 @@ class VCDWriter:
             fmtstr = "b{:0" + str(l) + "b} {}\n"
         else:
             fmtstr = "{}{}\n"
-        try:
+        code = self.codes[signal]
-            code = self.codes[signal]
-        except KeyError:
-            code = next(self.codegen)
-            self.codes[signal] = code
         f.write(fmtstr.format(value, code))
 
+    def init(self, signals):
+        # generate codes
+        for signal in signals:
+            try:
+                code = self.codes[signal]
+            except KeyError:
+                code = next(self.codegen)
+                self.codes[signal] = code
+
+        # write vcd header
+        out = self.out_file
+        ns = build_namespace(self.codes.keys())
+        for signal, code in self.codes.items():
+            name = ns.get_name(signal)
+            out.write("$var wire {len} {code} {name} $end\n"
+                      .format(name=name, code=code, len=len(signal)))
+        out.write("$dumpvars\n")
+        for signal in self.codes.keys():
+            self._write_value(out, signal, signal.reset.value)
+        out.write("$end\n")
+        out.write("#0\n")
+
     def set(self, signal, value):
         if (signal not in self.signal_values
                 or self.signal_values[signal] != value):
-            self._write_value(self.buffer_file, signal, value)
+            self._write_value(self.out_file, signal, value)
             self.signal_values[signal] = value
 
     def delay(self, delay):
         self.t += delay
-        self.buffer_file.write("#{}\n".format(self.t))
+        self.out_file.write("#{}\n".format(self.t))
 
     def close(self):
-        out = open(self.filename, "w")
+        self.out_file.close()
-        try:
-            ns = build_namespace(self.codes.keys())
-            for signal, code in self.codes.items():
-                name = ns.get_name(signal)
-                out.write("$var wire {len} {code} {name} $end\n"
-                          .format(name=name, code=code, len=len(signal)))
-            out.write("$dumpvars\n")
-            for signal in self.codes.keys():
-                self._write_value(out, signal, signal.reset.value)
-            out.write("$end\n")
-            out.write("#0\n")
-
-            self.buffer_file.seek(0)
-            shutil.copyfileobj(self.buffer_file, out)
-            self.buffer_file.close()
-        finally:
-            out.close()
 
 
 class DummyVCDWriter:
+    def init(self):
+        pass
+
     def set(self, signal, value):
         pass