Xilinx OpenCL Pipes lead to error: Global program variables are not supported.

[Mellich]

Hi everyone,

I tried to synthesize and execute an OpenCL design that makes use of pipes with Vitis 2020.2 and XRT 2.9 for the platform xilinx_u280_xdma_201920_3.

Execution of the kernels throws the error [XRT] ERROR: Global program variables are not supported.. The very same design worked with Vitis 2019.2 and (I think) XRT 2.3. In the XRT Changelog it is mentioned for version 2.9, that the implementation of OpenCL changed to use native XRT APIs. May this be the reason for this changed behavior? Unfortunately, I can not test my design with older XRT versions to verify this or get a working setup again.

Is this a bug or does this mean pipes are not supported by XRT anymore?

Thanks in advance!

[stsoe]

@Mellich Looks like our documentation is not quite accurate and that example links should be updated. We no longer support pipes, the recommended approach is to use hls::stream for kernel-to-kernel streaming. You will find several such examples under https://github.com/Xilinx/Vitis_Accel_Examples, e.g. https://github.com/Xilinx/Vitis_Accel_Examples/blob/master/cpp_kernels/dataflow_stream/src/adder.cpp

[uday610]

We will update ug1393 to remove/deprecate OpenCL kernel development section.

[Mellich]

@stsoe Thank you for the clarification.