lib.fifo: port sync FIFO queues from Migen.

nmigen/test/test_lib_fifo.py

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+from .tools import *
+from ..hdl.ast import *
+from ..hdl.dsl import *
+from ..back.pysim import *
+from ..lib.fifo import *
+
+
+class FIFOSmokeTestCase(FHDLTestCase):
+    def assertSyncFIFOWorks(self, fifo):
+        with Simulator(fifo) as sim:
+            sim.add_clock(1e-6)
+            def process():
+                yield from fifo.write(1)
+                yield from fifo.write(2)
+                yield
+                self.assertEqual((yield from fifo.read()), 1)
+                self.assertEqual((yield from fifo.read()), 2)
+            sim.add_sync_process(process)
+            sim.run()
+
+    def test_sync_fwft(self):
+        fifo = SyncFIFO(width=8, depth=4, fwft=True)
+        self.assertSyncFIFOWorks(SyncFIFO(width=8, depth=4))
+
+    def test_sync_not_fwft(self):
+        fifo = SyncFIFO(width=8, depth=4, fwft=False)
+        self.assertSyncFIFOWorks(SyncFIFO(width=8, depth=4))
+
+    def test_sync_buffered(self):
+        fifo = SyncFIFO(width=8, depth=4, fwft=True)
+        self.assertSyncFIFOWorks(SyncFIFOBuffered(width=8, depth=4))