dsp/tools: unittest sat_add

artiq/gateware/test/dsp/test_satadd.py

@@ -0,0 +1,69 @@
+import unittest
+import migen as mg
+
+from artiq.gateware.dsp.tools import SatAddMixin
+
+
+class DUT(mg.Module, SatAddMixin):
+    def __init__(self, width):
+        self.o = mg.Signal((width, True))
+        self.i0 = mg.Signal.like(self.o)
+        self.i1 = mg.Signal.like(self.o)
+        self.l0 = mg.Signal.like(self.o)
+        self.l1 = mg.Signal.like(self.o)
+        self.c = mg.Signal(2)
+        self.comb += self.o.eq(self.sat_add(self.i0, self.i1,
+            limits=(self.l0, self.l1), clipped=self.c))
+
+
+class SatAddTest(unittest.TestCase):
+    def setUp(self):
+        self.dut = DUT(width=4)
+
+    def _sweep(self):
+        def gen():
+            for i0 in range(-8, 8):
+                yield self.dut.i0.eq(i0)
+                for i1 in range(-8, 8):
+                    yield self.dut.i1.eq(i1)
+                    yield
+
+        def rec():
+            l0 = yield self.dut.l0
+            l1 = yield self.dut.l1
+            for i in range(1 << 8):
+                i0 = yield self.dut.i0
+                i1 = yield self.dut.i1
+                o = yield self.dut.o
+                c = yield self.dut.c
+
+                full = i0 + i1
+                lim = full
+                if full < l0:
+                    lim = l0
+                if full > l1:
+                    lim = l1
+                if l1 < full < l0:
+                    lim = 0
+                clip = int(full < l0) | (int(full > l1) << 1)
+                with self.subTest(i0=i0, i1=i1):
+                    self.assertEqual(lim, o)
+                    self.assertEqual(clip, c)
+                yield
+
+        mg.run_simulation(self.dut, (gen(), rec()))
+
+    def test_inst(self):
+        pass
+
+    def test_run(self):
+        self._sweep()
+
+    def test_limits(self):
+        for l0 in -8, 0, 1, 7:
+            for l1 in -8, 0, 1, 7:
+                self.setUp()
+                self.dut.l0.reset = l0
+                self.dut.l1.reset = l1
+                with self.subTest(l0=l0, l1=l1):
+                    self._sweep()