pytholite/compiler: SymbolStack

migen/pytholite/compiler.py

@@ -55,13 +55,35 @@ class _Register:
 		sync = [Case(self.sel, *cases)]
 		return Fragment(sync=sync)
 
+class _SymbolStack:
+	def __init__(self):
+		self.stack = []
+	
+	def push(self, init={}):
+		self.stack.append(init)
+	
+	def pop(self):
+		return self.stack.pop()
+	
+	def __setitem__(self, key, value):
+		self.stack[-1][key] = value
+	
+	def __getitem__(self, key):
+		for frame in reversed(self.stack):
+			try:
+				return frame[key]
+			except KeyError:
+				pass
+		raise KeyError
+		
 class _AbstractNextState:
 	def __init__(self, target_state):
 		self.target_state = target_state
 
 class _Compiler:
 	def __init__(self, symdict, registers):
-		self.symdict = symdict
+		self.symdict = _SymbolStack()
+		self.symdict.push(symdict)
 		self.registers = registers
 		self.targetname = ""