yosys-witness concat yw trace files

Intended for use with SCY to combine sequential cover traces.
Arbitrary number of inputs, will load all and attempt to join them.  Each trace will be replayed one after the other, in the same order as the files are provided.
Mismatch in init_only fields seems to work fine, with values in subsequent traces being assigned in the initial only if they weren't previously defined.
Uncertain if a mismatch in non init_only fields will cause problems.
Fixes WitnessSig.__eq__().
Adds helper functions to WitnessValues and ReadWitness classes.

backends/smt2/witness.py

@@ -84,26 +84,48 @@ def stats(input):
 Transform a Yosys witness trace.
 
 Currently no transformations are implemented, so it is only useful for testing.
+If two or more inputs are provided they will be concatenated together into the output.
 """)
-@click.argument("input", type=click.File("r"))
+@click.argument("inputs", type=click.File("r"), nargs=-1)
 @click.argument("output", type=click.File("w"))
-def yw2yw(input, output):
-    click.echo(f"Copying yosys witness trace from {input.name!r} to {output.name!r}...")
-    inyw = ReadWitness(input)
+def yw2yw(inputs, output):
     outyw = WriteWitness(output, "yosys-witness yw2yw")
+    join_inputs = len(inputs) > 1
+    inyws = {}
+    for input in inputs:
+        if (join_inputs):
+            click.echo(f"Loading signals from yosys witness trace {input.name!r}...")
+        inyw = ReadWitness(input)
+        inyws[input] = inyw
+        for clock in inyw.clocks:
+            if clock not in outyw.clocks:
+                outyw.add_clock(clock["path"], clock["offset"], clock["edge"])
 
-    for clock in inyw.clocks:
-        outyw.add_clock(clock["path"], clock["offset"], clock["edge"])
+        for sig in inyw.signals:
+            if sig not in outyw.signals:
+                outyw.add_sig(sig.path, sig.offset, sig.width, sig.init_only)
 
-    for sig in inyw.signals:
-        outyw.add_sig(sig.path, sig.offset, sig.width, sig.init_only)
+    init_values = sum([inyw.init_step() for inyw in inyws.values()], start=WitnessValues())
 
-    for t, values in inyw.steps():
-        outyw.step(values)
+    first_witness = True
+    for (input, inyw) in inyws.items():
+        click.echo(f"Copying yosys witness trace from {input.name!r} to {output.name!r}...")
+
+        if first_witness:
+            outyw.step(init_values)
+        else:
+            outyw.step(inyw.first_step())
+
+        for t, values in inyw.steps(1):
+            outyw.step(values)
+
+        click.echo(f"Copied {t + 1} time steps.")
+        first_witness = False
 
     outyw.end_trace()
 
-    click.echo(f"Copied {outyw.t + 1} time steps.")
+    if join_inputs:
+        click.echo(f"Copied {outyw.t} total time steps.")
 
 
 class AigerMap:

backends/smt2/ywio.py

@@ -165,8 +165,8 @@ class WitnessSig:
         else:
             return f"{pretty_path(self.path)}[{self.offset}]"
 
-    def __eq__(self):
-        return self.sort_key
+    def __eq__(self, other):
+        return self.sort_key == other.sort_key
 
     def __hash__(self):
         return hash(self.sort_key)
@@ -294,6 +294,16 @@ class WitnessValues:
 
         return sorted(signals), missing_signals
 
+    def __add__(self, other: "WitnessValues"):
+        new = WitnessValues()
+        new += self
+        new += other
+        return new
+
+    def __iadd__(self, other: "WitnessValues"):
+        for key, value in other.values.items():
+            self.values.setdefault(key, value)
+        return self
 
 class WriteWitness:
     def __init__(self, f, generator):
@@ -380,13 +390,24 @@ class ReadWitness:
 
         self.bits = [step["bits"] for step in data["steps"]]
 
+    def init_step(self):
+        return self.step(0)
+    
+    def first_step(self):
+        values = WitnessValues()
+        if len(self.bits) <= 1:
+            raise NotImplementedError("ReadWitness.first_step() not supported for less than 2 steps")
+        non_init_bits = len(self.bits[1])
+        values.unpack(WitnessSigMap([sig for sig in self.signals if not sig.init_only]), self.bits[0][-non_init_bits:])
+        return values
+
     def step(self, t):
         values = WitnessValues()
         values.unpack(self.sigmap, self.bits[t])
         return values
 
-    def steps(self):
-        for i in range(len(self.bits)):
+    def steps(self, start=0):
+        for i in range(start, len(self.bits)):
             yield i, self.step(i)
 
     def __len__(self):