verilog: split comb block, use assign statements

migen/fhdl/tools.py

@@ -63,8 +63,6 @@ def list_targets(node):
 	elif isinstance(node, Cat):
 		l = list(map(list_targets, node.l))
 		return set().union(*l)
-	elif isinstance(node, Replicate):
-		return list_targets(node.v)
 	elif isinstance(node, _Assign):
 		return list_targets(node.l)
 	elif isinstance(node, _StatementList):
@@ -80,6 +78,21 @@ def list_targets(node):
 	else:
 		raise TypeError
 
+def group_by_targets(sl):
+	groups = []
+	for statement in sl.l:
+		targets = list_targets(statement)
+		processed = False
+		for g in groups:
+			if not targets.isdisjoint(g[0]):
+				g[0].update(targets)
+				g[1].append(statement)
+				processed = True
+				break
+		if not processed:
+			groups.append((targets, [statement]))
+	return groups
+
 def list_inst_outs(i):
 	if isinstance(i, Fragment):
 		return list_inst_outs(i.instances)

migen/fhdl/verilog.py

@@ -46,42 +46,57 @@ def _printexpr(ns, node):
 	else:
 		raise TypeError
 
-def _printnode(ns, is_sync, level, node):
+(_AT_BLOCKING, _AT_NONBLOCKING, _AT_SIGNAL) = range(3)
+
+def _printnode(ns, at, level, node):
 	if isinstance(node, _Assign):
-		if is_sync and is_variable(node.l):
+		if at == _AT_BLOCKING:
+			assignment = " = "
+		elif at == _AT_NONBLOCKING:
+			assignment = " <= "
+		elif is_variable(node.l):
 			assignment = " = "
 		else:
 			assignment = " <= "
 		return "\t"*level + _printexpr(ns, node.l) + assignment + _printexpr(ns, node.r) + ";\n"
 	elif isinstance(node, _StatementList):
-		return "".join(list(map(partial(_printnode, ns, is_sync, level), node.l)))
+		return "".join(list(map(partial(_printnode, ns, at, level), node.l)))
 	elif isinstance(node, If):
 		r = "\t"*level + "if (" + _printexpr(ns, node.cond) + ") begin\n"
-		r += _printnode(ns, is_sync, level + 1, node.t)
+		r += _printnode(ns, at, level + 1, node.t)
 		if node.f.l:
 			r += "\t"*level + "end else begin\n"
-			r += _printnode(ns, is_sync, level + 1, node.f)
+			r += _printnode(ns, at, level + 1, node.f)
 		r += "\t"*level + "end\n"
 		return r
 	elif isinstance(node, Case):
 		r = "\t"*level + "case (" + _printexpr(ns, node.test) + ")\n"
 		for case in node.cases:
 			r += "\t"*(level + 1) + _printexpr(ns, case[0]) + ": begin\n"
-			r += _printnode(ns, is_sync, level + 2, case[1])
+			r += _printnode(ns, at, level + 2, case[1])
 			r += "\t"*(level + 1) + "end\n"
 		if node.default.l:
 			r += "\t"*(level + 1) + "default: begin\n"
-			r += _printnode(ns, is_sync, level + 2, node.default)
+			r += _printnode(ns, at, level + 2, node.default)
 			r += "\t"*(level + 1) + "end\n"
 		r += "\t"*level + "endcase\n"
 		return r
 	else:
 		raise TypeError
 
+def _list_comb_wires(f):
+	r = set()
+	groups = group_by_targets(f.comb)
+	for g in groups:
+		if len(g[1]) == 1 and isinstance(g[1][0], _Assign):
+			r |= g[0]
+	return r
+
 def _printheader(f, ios, name, ns):
 	sigs = list_signals(f)
 	targets = list_targets(f)
 	instouts = list_inst_outs(f)
+	wires = _list_comb_wires(f)
 	r = "module " + name + "(\n"
 	firstp = True
 	for sig in ios:
@@ -89,14 +104,17 @@ def _printheader(f, ios, name, ns):
 			r += ",\n"
 		firstp = False
 		if sig in targets:
-			r += "\toutput reg " + _printsig(ns, sig)
+			if sig in wires:
+				r += "\toutput " + _printsig(ns, sig)
+			else:
+				r += "\toutput reg " + _printsig(ns, sig)
 		elif sig in instouts:
 			r += "\toutput " + _printsig(ns, sig)
 		else:
 			r += "\tinput " + _printsig(ns, sig)
 	r += "\n);\n\n"
 	for sig in sigs - ios:
-		if sig in instouts:
+		if sig in wires or sig in instouts:
 			r += "wire " + _printsig(ns, sig) + ";\n"
 		else:
 			r += "reg " + _printsig(ns, sig) + ";\n"
@@ -110,37 +128,39 @@ def _printcomb(f, ns):
 		# to run the combinatorial process once at the beginning.
 		syn_off = "// synthesis translate off\n"
 		syn_on = "// synthesis translate on\n"
-		dummy_s = Signal(name="dummy_s")
-		dummy_d = Signal(name="dummy_d")
+		dummy_s = Signal()
 		r += syn_off
 		r += "reg " + _printsig(ns, dummy_s) + ";\n"
-		r += "reg " + _printsig(ns, dummy_d) + ";\n"
 		r += "initial " + ns.get_name(dummy_s) + " <= 1'b0;\n"
-		r += syn_on + "\n"
-		
-		r += "always @(*) begin\n"
-		to_reset = list_targets(f.comb)
-		# do not reset signals with obvious unconditional assignments
-		for s in f.comb.l:
-			if isinstance(s, _Assign) and isinstance(s.l, Signal):
-				try:
-					to_reset.remove(s.l)
-				except KeyError:
-					pass
-		for t in to_reset:
-			r += "\t" + ns.get_name(t) + " <= " + str(t.reset) + ";\n"
-		r += _printnode(ns, False, 1, f.comb)
-		r += syn_off
-		r += "\t" + ns.get_name(dummy_d) + " <= " + ns.get_name(dummy_s) + ";\n"
 		r += syn_on
-		r += "end\n\n"
+		
+		groups = group_by_targets(f.comb)
+		
+		for g in groups:
+			if len(g[1]) == 1 and isinstance(g[1][0], _Assign):
+				r += "assign " + _printnode(ns, _AT_BLOCKING, 0, g[1][0])
+			else:
+				dummy_d = Signal()
+				r += "\n" + syn_off
+				r += "reg " + _printsig(ns, dummy_d) + ";\n"
+				r += syn_on
+				
+				r += "always @(*) begin\n"
+				for t in g[0]:
+					r += "\t" + ns.get_name(t) + " <= " + str(t.reset) + ";\n"
+				r += _printnode(ns, _AT_NONBLOCKING, 1, _StatementList(g[1]))
+				r += syn_off
+				r += "\t" + ns.get_name(dummy_d) + " <= " + ns.get_name(dummy_s) + ";\n"
+				r += syn_on
+				r += "end\n"
+	r += "\n"
 	return r
 
 def _printsync(f, ns, clk_signal, rst_signal):
 	r = ""
 	if f.sync.l:
 		r += "always @(posedge " + ns.get_name(clk_signal) + ") begin\n"
-		r += _printnode(ns, True, 1, insert_reset(rst_signal, f.sync))
+		r += _printnode(ns, _AT_SIGNAL, 1, insert_reset(rst_signal, f.sync))
 		r += "end\n\n"
 	return r