uio: support generator trampolining in simulation

migen/uio/ioo.py

@@ -1,6 +1,7 @@
 from migen.fhdl.structure import *
 from migen.flow.actor import *
 from migen.bus import wishbone
+from migen.uio.trampoline import Trampoline
 
 class UnifiedIOObject(Actor):
 	def __init__(self, dataflow=None, buses={}):
@@ -12,7 +13,7 @@ class UnifiedIOObject(Actor):
 
 class UnifiedIOSimulation(UnifiedIOObject):
 	def __init__(self, generator, dataflow=None, buses={}):
-		self.generator = generator
+		self.generator = Trampoline(generator)
 		super().__init__(dataflow, buses)
 		
 		self.callers = []

migen/uio/trampoline.py

@@ -0,0 +1,23 @@
+import types
+
+class Trampoline:
+	def __init__(self, g):
+		self.stack = [g]
+	
+	def __iter__(self):
+		return self
+	
+	def __next__(self):
+		while True:
+			while True:
+				try:
+					r = next(self.stack[-1])
+					break
+				except StopIteration:
+					self.stack.pop()
+					if not self.stack:
+						raise
+			if isinstance(r, types.GeneratorType):
+				self.stack.append(r)
+			else:
+				return r