migen/test/test_signed: add a (currently failing) signed comparison testcase

migen/test/test_signed.py

@@ -0,0 +1,45 @@
+import unittest
+
+from migen.fhdl.std import *
+from migen.test.support import SimCase, SimBench
+
+class SignedCase(SimCase, unittest.TestCase):
+	class TestBench(SimBench):
+		def __init__(self):
+			self.a = Signal((3, True))
+			self.b = Signal((4, True))
+			comps = [
+					lambda p, q: p > q,
+					lambda p, q: p >= q,
+					lambda p, q: p < q,
+					lambda p, q: p <= q,
+					lambda p, q: p == q,
+					lambda p, q: p != q,
+					]
+			self.vals = []
+			for asign in 1, -1:
+				for bsign in 1, -1:
+					for f in comps:
+						r = Signal()
+						r0 = f(asign*self.a, bsign*self.b)
+						self.comb += r.eq(r0)
+						self.vals.append((asign, bsign, f, r, r0.op))
+
+	def test_comparisons(self):
+		values = range(-4, 4)
+		agen = iter(values)
+		bgen = iter(values)
+		def cb(tb, s):
+			try:
+				s.wr(self.tb.a, next(agen))
+				s.wr(self.tb.b, next(bgen))
+			except StopIteration:
+				s.interrupt = True
+			a = s.rd(self.tb.a)
+			b = s.rd(self.tb.b)
+			for asign, bsign, f, r, op in self.tb.vals:
+				r, r0 = s.rd(r), f(asign*a, bsign*b)
+				self.assertEqual(r, int(r0),
+						"got {}, want {}*{} {} {}*{} = {}".format(
+							r, asign, a, op, bsign, b, r0))
+		self.run_with(cb)