problem:HLS stream_data with default size is used in a non-dataflow region

solution:

In dataflow design, vivado hls have the "config_dataflow -fifo_depth <default depth>" command to config the default depth, and the default depth will be used if you do not specify the depth in the stream directive.

However, if you use stream directive in nondataflow design without depth, vivado hls do not known how to figure out a reasonable default depth for you, because the config_dataflow dosen't apply here. (Actually it just use 1 as default depth).