[InsertDWC] use impl_style=vivado if widths not divisible

src/finn/transformation/fpgadataflow/insert_dwc.py

@@ -81,6 +81,12 @@ class InsertDWC(Transformation):
                             dwc_in_width = n0.get_outstream_width()
                             # determine dwc outwidth
                             dwc_out_width = n1.get_instream_width()
+                            larger_width = max(dwc_in_width, dwc_out_width)
+                            smaller_width = min(dwc_in_width, dwc_out_width)
+                            if larger_width % smaller_width == 0:
+                                impl_style = "hls"
+                            else:
+                                impl_style = "vivado"
 
                             # determine shape for dwc
                             dwc_shape = n0.get_normal_output_shape()
@@ -105,6 +111,7 @@ class InsertDWC(Transformation):
                                 inWidth=dwc_in_width,
                                 outWidth=dwc_out_width,
                                 dataType=str(dtype.name),
+                                impl_style=impl_style,
                             )
                             # insert dwc
                             graph.node.insert(node_ind + 1, dwc_node)