transform/unroll: support for variables

examples/basic/multi_accumulator.py

@@ -4,16 +4,20 @@ from migen.fhdl import verilog
 
 x = Signal(BV(4))
 y = Signal(BV(4))
-acc = Signal(BV(4))
+acc = Signal(BV(4), variable=True)
+z = Signal()
 
 sync = [
-	acc.eq(acc + x + y)
+	If(acc == 2, acc.eq(3)),
+	acc.eq(acc + x + y),
+	z.eq(acc == 0)
 ]
 
 n = 5
 xs = [Signal(BV(4)) for i in range(n)]
 ys = [Signal(BV(4)) for i in range(n)]
 accs = [Signal(BV(4)) for i in range(n)]
+zs = [Signal() for i in range(n)]
 
-sync_u = unroll_sync(sync, {x: xs, y: ys}, {acc: accs})
-print(verilog.convert(Fragment(sync=sync_u), ios=set(xs+ys+accs)))
+sync_u = unroll_sync(sync, {x: xs, y: ys}, {acc: accs, z: zs})
+print(verilog.convert(Fragment(sync=sync_u), ios=set(xs+ys+zs)))

migen/transform/unroll.py

@@ -80,15 +80,27 @@ def _variable_for(s, n):
 def unroll_sync(sync, inputs, outputs):
 	sd_in = _list_step_dicts(inputs)
 	sd_out = _list_step_dicts(outputs)
-	
-	do_var_old = sd_out[-1]
+
 	r = []
+	io_var_dict = sd_out[-1].copy()
 	for n, (di, do) in enumerate(zip(sd_in, sd_out)):
 		do_var = dict((k, _variable_for(v, n)) for k, v in do.items())
-		di_plus_do_var_old = di.copy()
-		di_plus_do_var_old.update(do_var_old)
-		r += _replace(sync, di_plus_do_var_old, do_var)
+		
+		# initialize variables
+		for k, v in io_var_dict.items():
+			if k.variable:
+				r.append(do_var[k].eq(io_var_dict[k]))
+				io_var_dict[k] = do_var[k]
+			
+		
+		# replace signals with intermediate variables and copy statements
+		io_var_dict.update(di)
+		r += _replace(sync, io_var_dict, do_var)
+		
+		# assign to output signals
 		r += [v.eq(do_var[k]) for k, v in do.items()]
-		do_var_old = do_var
+		
+		# prepare the next i+o dictionary
+		io_var_dict = do_var.copy()
 	
 	return r