From e1075a962ceebdb993d67e7d1a8d0c9b29809c0f Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sebastien@milkymist.org>
Date: Fri, 9 Nov 2012 19:37:52 +0100
Subject: [PATCH] pytholite/compiler: support if statements

---
 migen/pytholite/compiler.py | 44 +++++++++++++++++++++++++++++++------
 1 file changed, 37 insertions(+), 7 deletions(-)

diff --git a/migen/pytholite/compiler.py b/migen/pytholite/compiler.py
index acac97387..a46176a7c 100644
--- a/migen/pytholite/compiler.py
+++ b/migen/pytholite/compiler.py
@@ -54,6 +54,10 @@ class _Register:
 		sync = [Case(self.sel, *cases)]
 		return Fragment(sync=sync)
 
+class _AbstractNextState:
+	def __init__(self, target_state):
+		self.target_state = target_state
+
 class _Compiler:
 	def __init__(self, symdict, registers):
 		self.symdict = symdict
@@ -76,6 +80,15 @@ class _Compiler:
 				op = self.visit_assign(statement)
 				if op:
 					states.append(op)
+			elif isinstance(statement, ast.If):
+				test = self.visit_expr(statement.test)
+				states_t = self.visit_block(statement.body)
+				states_f = self.visit_block(statement.orelse)
+				test_state_stmt = If(test, _AbstractNextState(states_t[0]))
+				if states_f:
+					test_state_stmt.Else(_AbstractNextState(states_f[0]))
+				states.append([test_state_stmt])
+				states += states_t + states_f
 			else:
 				raise NotImplementedError
 		return states
@@ -163,10 +176,10 @@ class _Compiler:
 			raise NotImplementedError
 	
 	def visit_expr_compare(self, node):
-		test = visit_expr(node.test)
+		test = self.visit_expr(node.left)
 		r = None
 		for op, rcomparator in zip(node.ops, node.comparators):
-			comparator = visit_expr(rcomparator)
+			comparator = self.visit_expr(rcomparator)
 			if isinstance(op, ast.Eq):
 				comparison = test == comparator
 			elif isinstance(op, ast.NotEq):
@@ -197,15 +210,32 @@ class _Compiler:
 	def visit_expr_num(self, node):
 		return node.n
 
+# like list.index, but using "is" instead of comparison
+def _index_is(l, x):
+	for i, e in enumerate(l):
+		if e is x:
+			return i
+
+class _LowerAbstractNextState(fhdl.NodeTransformer):
+	def __init__(self, fsm, states, stnames):
+		self.fsm = fsm
+		self.states = states
+		self.stnames = stnames
+		
+	def visit_unknown(self, node):
+		if isinstance(node, _AbstractNextState):
+			index = _index_is(self.states, node.target_state)
+			estate = getattr(self.fsm, self.stnames[index])
+			return self.fsm.next_state(estate)
+		else:
+			return node
+
 def _create_fsm(states):
 	stnames = ["S" + str(i) for i in range(len(states))]
 	fsm = FSM(*stnames)
+	lans = _LowerAbstractNextState(fsm, states, stnames)
 	for i, state in enumerate(states):
-		if i == len(states) - 1:
-			actions = []
-		else:
-			actions = [fsm.next_state(getattr(fsm, stnames[i+1]))]
-		actions += state
+		actions = lans.visit(state)
 		fsm.act(getattr(fsm, stnames[i]), *actions)
 	return fsm