[VTA] Fix VTA function Vivado Compile Error.

[huajsj]

Issue:
when using vivado compile vta.cc with top function 'vta', vivado
report deadlock error like '...with default size is used in a non -dataflow
region, which may result in deadlock Please consider to resize the
stream using the directive ‘set_directive_stream’ or the ‘HL S stream’
pragma.'

Solution:
give the queue a default size as 8. after fix, compile error gone, we can run test bench with this 'vta' function and get correct result.

[huajsj]

@tmoreau89 could help to review this patch?

[tmoreau89]

Which version of Vivado were you using @huajsj

[tmoreau89]

And could you provide more details on reproducing the bug?

[huajsj]

@tmoreau89 following are the detailed information about the reproduce and vivado_hls information.

1. vivado_hls version is 2018.2

2. Reproduce as following
   2.1 run vivado_hls 2018.2
   2.2 add vta.cc and vta.h into source
   2.3 copy vta_config.json macro define into hw_spec.h to fix macro not existing issue when do
   synthesis.
   2.4. run sysnthesis
   2.5. saw the vivado_hls compile error.

      ERROR: [XFORM 203-733] An internal stream 'tmp_load_queue.V.V' (vm/vta/hardware/xilinx/src/vta.cc:588) with default size is used in a non-dataflow region, which may result in deadlock. Please consider to resize the stream using the directive 'set_directive_stream' or the 'HLS stream' pragma.
   

ERROR: [HLS 200-70] Pre-synthesis failed.

[tmoreau89]

Thanks for the details; I believe we should migrate to 2019.1 (I'll issue a PR for this). Could you check that this fix also works in 2019.1?

Thanks

[huajsj]

@tmoreau89 , about 2019.1, just verified, the fix work good under 2019.1, steps as following.
#1. using vivado_hls 2019.1 create solution add vta.cc and vta.h, fix header file path/macro issue.
#2. compile , saw the deadlock error and synthesis failed.
#3 apply this patch, issue go away.

[tmoreau89]

LGTM