ROM Optimization - 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

The following shows a code example in which Vitis HLS implements a ROM even though the array is not specified with a static or const qualifier. This demonstrates how Vitis HLS analyzes the design, and determines the most optimal implementation. The qualifiers guide the tool, but do not dictate the final RTL.

#include "array_ROM.h"

dout_t array_ROM(din1_t inval, din2_t idx)
{
 din1_t lookup_table[256];
 dint_t i;

 for (i = 0; i < 256; i++) {
 lookup_table[i] = 256 * (i - 128);
 }

 return (dout_t)inval * (dout_t)lookup_table[idx];
}

In this example, the tool is able to determine that the implementation is best served by having the variable lookup_table as a memory element in the final RTL.