Basic Pointers - 2021.2 English

Vitis High-Level Synthesis User Guide (UG1399)

Document ID
UG1399
ft:locale
English (United States)
Release Date
2021-12-15
Version
2021.2 English

A function with basic pointers on the top-level interface, such as shown in the following code example, produces no issues for Vitis HLS. The pointer can be synthesized to either a simple wire interface or an interface protocol using handshakes.

Tip: To be synthesized as a FIFO interface, a pointer must be read-only or write-only.
#include "pointer_basic.h"

void pointer_basic (dio_t *d) {
 static dio_t acc = 0;

 acc += *d;
 *d  = acc;
}

The pointer on the interface is read or written only once per function call. The test bench shown in the following code example.

#include "pointer_basic.h"

int main () {
 dio_t d;
 int i, retval=0;
 FILE *fp;

 // Save the results to a file
 fp=fopen(result.dat,w);
 printf( Din Dout\n, i, d);

 // Create input data
 // Call the function to operate on the data
 for (i=0;i<4;i++) {
    d = i;
    pointer_basic(&d);
    fprintf(fp, %d \n, d);
    printf(  %d   %d\n, i, d);
 }
 fclose(fp);

 // Compare the results file with the golden results
 retval = system(diff --brief -w result.dat result.golden.dat);
 if (retval != 0) {
    printf(Test failed!!!\n); 
    retval=1;
 } else {
    printf(Test passed!\n);
 }

 // Return 0 if the test
 return retval;
}

C and RTL simulation verify the correct operation (although not all possible cases) with this simple data set:

Din Dout
  0   0
  1   1
  2   3
  3   6
Test passed!