fhdl/tools: use NodeTransformer to lower arrays

migen/fhdl/tools.py

@@ -1,8 +1,6 @@
-from copy import copy
-
 from migen.fhdl.structure import *
 from migen.fhdl.structure import _Operator, _Slice, _Assign, _ArrayProxy
-from migen.fhdl.visit import NodeVisitor
+from migen.fhdl.visit import NodeVisitor, NodeTransformer
 
 class _SignalLister(NodeVisitor):
 	def __init__(self):
@@ -144,100 +142,32 @@ def value_bv(v):
 	else:
 		raise TypeError
 
-def _lower_arrays_values(vl):
-	r = []
-	extra_comb = []
-	for v in vl:
-		v2, e = _lower_arrays_value(v)
-		extra_comb += e
-		r.append(v2)
-	return r, extra_comb
+class _ArrayLowerer(NodeTransformer):
+	def __init__(self):
+		self.comb = []
 	
-def _lower_arrays_value(v):
-	if isinstance(v, Constant):
-		return v, []
-	elif isinstance(v, Signal):
-		return v, []
-	elif isinstance(v, _Operator):
-		op2, e = _lower_arrays_values(v.operands)
-		return _Operator(v.op, op2), e
-	elif isinstance(v, _Slice):
-		v2, e = _lower_arrays_value(v.value)
-		return _Slice(v2, v.start, v.stop), e
-	elif isinstance(v, Cat):
-		l2, e = _lower_arrays_values(v.l)
-		return Cat(*l2), e
-	elif isinstance(v, Replicate):
-		v2, e = _lower_arrays_value(v.v)
-		return Replicate(v2, v.n), e
-	elif isinstance(v, _ArrayProxy):
-		choices2, e = _lower_arrays_values(v.choices)
-		array_muxed = Signal(value_bv(v))
-		cases = [[Constant(n), _Assign(array_muxed, choice)]
-			for n, choice in enumerate(choices2)]
-		cases[-1][0] = Default()
-		e.append(Case(v.key, *cases))
-		return array_muxed, e
-
-def _lower_arrays_assign(l, r):
-	extra_comb = []
-	if isinstance(l, _ArrayProxy):
-		k, e = _lower_arrays_value(l.key)
-		extra_comb += e
+	def visit_Assign(self, node):
+		if isinstance(node.l, _ArrayProxy):
+			k = self.visit(node.l.key)
 			cases = []
-		for n, choice in enumerate(l.choices):
-			assign, e = _lower_arrays_assign(choice, r)
-			extra_comb += e
+			for n, choice in enumerate(node.l.choices):
+				assign = self.visit_Assign(_Assign(choice, node.r))
 				cases.append([Constant(n), assign])
 			cases[-1][0] = Default()
-		return Case(k, *cases), extra_comb
+			return Case(k, *cases)
 		else:
-		return _Assign(l, r), extra_comb
+			return super().visit_Assign(node)
 	
-def _lower_arrays_sl(sl):
-	rs = []
-	extra_comb = []
-	for statement in sl:
-		if isinstance(statement, _Assign):
-			r, e = _lower_arrays_value(statement.r)
-			extra_comb += e
-			r, e = _lower_arrays_assign(statement.l, r)
-			extra_comb += e
-			rs.append(r)
-		elif isinstance(statement, If):
-			cond, e = _lower_arrays_value(statement.cond)
-			extra_comb += e
-			t, e = _lower_arrays_sl(statement.t)
-			extra_comb += e
-			f, e = _lower_arrays_sl(statement.f)
-			extra_comb += e
-			i = If(cond)
-			i.t = t
-			i.f = f
-			rs.append(i)
-		elif isinstance(statement, Case):
-			test, e = _lower_arrays_value(statement.test)
-			extra_comb += e
-			c = Case(test)
-			for cond, csl in statement.cases:
-				stmts, e = _lower_arrays_sl(csl)
-				extra_comb += e
-				c.cases.append((cond, stmts))
-			if statement.default is not None:
-				c.default, e = _lower_arrays_sl(statement.default)
-				extra_comb += e
-			rs.append(c)
-		elif statement is not None:
-			raise TypeError
-	return rs, extra_comb
+	def visit_ArrayProxy(self, node):
+		array_muxed = Signal(value_bv(node))
+		cases = [[Constant(n), _Assign(array_muxed, self.visit(choice))]
+			for n, choice in enumerate(node.choices)]
+		cases[-1][0] = Default()
+		self.comb.append(Case(self.visit(node.key), *cases))
+		return array_muxed
 
 def lower_arrays(f):
-	f = copy(f)
-	f.comb, ec1 = _lower_arrays_sl(f.comb)
-	f.comb += ec1
-	newsync = dict()
-	for k, v in f.sync.items():
-		newsync[k], ec2 = _lower_arrays_sl(v)
-		f.comb += ec2
-	f.sync = newsync
-	return f
+	al = _ArrayLowerer()
+	f2 = al.visit(f)
+	f2.comb += al.comb
+	return f2