3.6.3.40 SHLS-99

Message

Error:   (SHLS-99) SW/HW co-simulation for function pipelining with arrays as top-level inputs/outputs is not supported. The program uses the array '{array}' in function '{function}' as a top-level input/output. Please create a custom RTL testbench to simulate this hardware.

/*****************************************************************
 *  This example is expected to result in
 *  - Code    : SHLS-99
 *  - Type    : Error
 *  - Command : SW/HW Co-Simulation (shls cosim)
 *  - Cause   : Co-simulation is attempted on function pipelined
 *              design that includes top-level interface I/O
 *              derived from global array variables.
 *****************************************************************/
#include "hls/streaming.hpp"

hls::FIFO<int> in_fifo;
hls::FIFO<int> out[2];

void DUT() {
    #pragma HLS function top pipeline

    int r = in_fifo.read();

    out[0].write(r+2);
    out[1].write(r*3);
}

int main() {
    int in = 2;

    in_fifo.write(in);
    DUT();
    int out0 = out[0].read();
    int out1 = out[1].read();

    return (out0 != in+2) || (out1 != in*3);
}

To prevent this error, users are advised to pass the affected global array variables as function arguments. For example, to avoid encountering code SHLS-99 in the example above, the code can be rewritten as follows:

#include "hls/streaming.hpp"

hls::FIFO<int> in_fifo;

void DUT(hls::FIFO<int> out[2]) {
    #pragma HLS function top pipeline

    int r = in_fifo.read();

    out[0].write(r+2);
    out[1].write(r*3);
}

int main() {
    hls::FIFO<int> out[2];

    int in = 2;

    in_fifo.write(in);
    DUT(out);
    int out0 = out[0].read();
    int out1 = out[1].read();

    return (out0 != in+2) || (out1 != in*3);
}

Related to: Simulate HLS Hardware (SW/HW Co-Simulation), Pipeline Function