AMD recommends that you separate the
top-level function for synthesis from the test bench, and that you use header files. The
following code example shows a design in which the top-level function for the HLS project,
hier_func
, calls two sub-functions:
-
sumsub_func
performs addition and subtraction. -
shift_func
performs shift.
The data types are defined in the header file (hier_func.h). The code for the function follows:
#include "hier_func.h"
int sumsub_func(din_t *in1, din_t *in2, dint_t *outSum, dint_t *outSub)
{
*outSum = *in1 + *in2;
*outSub = *in1 - *in2;
}
int shift_func(dint_t *in1, dint_t *in2, dout_t *outA, dout_t *outB)
{
*outA = *in1 >> 1;
*outB = *in2 >> 2;
}
void hier_func(din_t A, din_t B, dout_t *C, dout_t *D)
{
dint_t apb, amb;
sumsub_func(&A,&B,&apb,&amb);
shift_func(&apb,&amb,C,D);
}
As shown, the top-level function can contain multiple sub-functions. There can only be one top-level function for synthesis. To synthesize multiple functions, group them as sub-functions of a single top-level function.
The header file (hier_func.h
), shown below,
demonstrates how to use macros and how typedef
statements can
make the code more portable and readable.
typedef
statement allows the types and therefore the
bit-widths of the variables to be refined for both area and performance improvements in the
final FPGA implementation.#ifndef _HIER_FUNC_H_
#define _HIER_FUNC_H_
#include <stdio.h>
#define NUM_TRANS 40
typedef int din_t;
typedef int dint_t;
typedef int dout_t;
void hier_func(din_t A, din_t B, dout_t *C, dout_t *D);
#endif
The header file above includes some #define
statements, such
as NUM_TRANS
, that are not required by the hier_func
function, but are provided for the test bench, which also
includes the same header file.
The following code defines a test bench for the hier_func
design:
#include "hier_func.h"
int main() {
// Data storage
int a[NUM_TRANS], b[NUM_TRANS];
int c_expected[NUM_TRANS], d_expected[NUM_TRANS];
int c[NUM_TRANS], d[NUM_TRANS];
//Function data (to/from function)
int a_actual, b_actual;
int c_actual, d_actual;
// Misc
int retval=0, i, i_trans, tmp;
FILE *fp;
// Load input data from files
fp=fopen(tb_data/inA.dat,r);
for (i=0; i<NUM_TRANS; i++){
fscanf(fp, %d, &tmp);
a[i] = tmp;
}
fclose(fp);
fp=fopen(tb_data/inB.dat,r);
for (i=0; i<NUM_TRANS; i++){
fscanf(fp, %d, &tmp);
b[i] = tmp;
}
fclose(fp);
// Execute the function multiple times (multiple transactions)
for(i_trans=0; i_trans<NUM_TRANS-1; i_trans++){
//Apply next data values
a_actual = a[i_trans];
b_actual = b[i_trans];
hier_func(a_actual, b_actual, &c_actual, &d_actual);
//Store outputs
c[i_trans] = c_actual;
d[i_trans] = d_actual;
}
// Load expected output data from files
fp=fopen(tb_data/outC.golden.dat,r);
for (i=0; i<NUM_TRANS; i++){
fscanf(fp, %d, &tmp);
c_expected[i] = tmp;
}
fclose(fp);
fp=fopen(tb_data/outD.golden.dat,r);
for (i=0; i<NUM_TRANS; i++){
fscanf(fp, %d, &tmp);
d_expected[i] = tmp;
}
fclose(fp);
// Check outputs against expected
for (i = 0; i < NUM_TRANS-1; ++i) {
if(c[i] != c_expected[i]){
retval = 1;
}
if(d[i] != d_expected[i]){
retval = 1;
}
}
// Print Results
if(retval == 0){
printf( *** *** *** *** \n);
printf( Results are good \n);
printf( *** *** *** *** \n);
} else {
printf( *** *** *** *** \n);
printf( Mismatch: retval=%d \n, retval);
printf( *** *** *** *** \n);
}
// Return 0 if outputs are corre
return retval;
}