record: support aligned flattening

examples/using_record.py

@@ -2,16 +2,17 @@
 from migen.corelogic.record import *
 
 L = [
-	("x", BV(10)),
-	("y", BV(10)),
+	("x", BV(10), 8),
+	("y", BV(10), 8),
 	("level2", [
-		("a", BV(5)),
-		("b", BV(5))
+		("a", BV(5), 32),
+		("b", BV(5), 16)
 	])
 ]
 
 myrec = Record(L)
 print(myrec.flatten())
+print(myrec.flatten(True))
 s = myrec.subrecord("level2/a", "x")
 print(s.flatten())
 print(s.level2.layout())

migen/corelogic/record.py

@@ -15,24 +15,30 @@ def __init__(self, layout, name=None):
 					setattr(self, f[0], Record(f[1], self.name + "_" + f[0]))
 				else:
 					raise TypeError
-				self.field_order.append(f[0])
+				if len(f) == 3:
+					self.field_order.append((f[0], f[2]))
+				else:
+					self.field_order.append((f[0], 1))
 			else:
 				setattr(self, f, Signal(BV(1), self.name + "_" + f))
-				self.field_order.append(f)
+				self.field_order.append((f, 1))
 
 	def layout(self):
 		l = []
-		for key in self.field_order:
+		for key, alignment in self.field_order:
 			e = self.__dict__[key]
 			if isinstance(e, Signal):
-				l.append((key, e.bv))
+				l.append((key, e.bv, alignment))
 			elif isinstance(e, Record):
-				l.append((key, e.layout()))
+				l.append((key, e.layout(), alignment))
 		return l
 
 	def copy(self, name=None):
 		return Record(self.layout(), name or _make_signal_name())
 
+	def get_alignment(self, name):
+		return list(filter(lambda x: x[0] == name, self.field_order))[0][1]
+
 	def subrecord(self, *descr):
 		fields = []
 		for item in descr:
@@ -53,22 +59,33 @@ def subrecord(self, *descr):
 					raise ValueError
 			if len(list(filter(lambda x: x[0] == last, pos_fields))) > 0:
 				raise ValueError
-			pos_fields.append((last, getattr(pos_self, last)))
+			pos_fields.append((last, getattr(pos_self, last), pos_self.get_alignment(last)))
 		return Record(fields, "subrecord")
 
 	def compatible(self, other):
 		tpl1 = self.flatten()
 		tpl2 = other.flatten()
 		return len(tpl1) == len(tpl2)
 
-	def flatten(self):
+	def flatten(self, align=False, offset=0):
 		l = []
-		for key in self.field_order:
+		for key, alignment in self.field_order:
+			if align:
+				pad_size = alignment - (offset % alignment)
+				if pad_size < alignment:
+					l.append(Constant(0, BV(pad_size)))
+					offset += pad_size
+
 			e = self.__dict__[key]
 			if isinstance(e, Signal):
-				l.append(e)
+				added = [e]
 			elif isinstance(e, Record):
-				l += e.flatten()
+				added = e.flatten(align, offset)
+			else:
+				raise TypeError
+			for x in added:
+				offset += x.bv.width
+			l += added
 		return l
 
 	def __repr__(self):