[FIFO] remove exceptions/warnings about first FIFO, no longer valid

src/finn/transformation/fpgadataflow/create_stitched_ip.py

@@ -291,14 +291,6 @@ def apply(self, model):
                 behavior. It is strongly recommended to insert FIFOs prior to
                 calling CreateStitchedIP."""
             )
-        if model.graph.node[0].op_type == "StreamingFIFO":
-            firstfifo = getCustomOp(model.graph.node[0])
-            if firstfifo.get_nodeattr("impl_style") == "vivado":
-                warnings.warn(
-                    """First FIFO has impl_style=vivado, which may cause
-                    simulation glitches (e.g. dropping the first input sample
-                    after reset)."""
-                )
         for node in model.graph.node:
             # ensure that all nodes are fpgadataflow, and that IPs are generated
             assert is_fpgadataflow_node(node), "All nodes must be FINN fpgadataflow nodes."

src/finn/transformation/fpgadataflow/set_fifo_depths.py

@@ -404,13 +404,8 @@ def apply(self, model):
                 node_inst = getCustomOp(node)
                 node_inst.set_nodeattr("depth", depth)
                 node_inst.set_nodeattr("depth_monitor", 0)
-                # exception for top-level IO FIFOs which cause a bug in simulation
-                # (top-level IOs should not have impl_style=vivado)
-                toplevel_in = node.input[0] in [x.name for x in model.graph.input]
-                toplevel_out = node.output[0] in [x.name for x in model.graph.output]
-                toplevel_style_exception = toplevel_in or toplevel_out
                 # Set FIFO implementation/ram styles
-                if (depth > self.max_qsrl_depth) and (not toplevel_style_exception):
+                if (depth > self.max_qsrl_depth):
                     node_inst.set_nodeattr("impl_style", "vivado")
                     node_inst.set_nodeattr("ram_style", self.vivado_ram_style)
                 else: