Noriyasu Nakayama

Incremental high-level synthesis

The widespread acceptance of High-level synthesis as a mainstream tool mostly depends on its tight integration with the following RTL-to-GDSII design flow. A key aspect is the handling of so-called Engineering Change Orders (ECOs), i.e. minor changes required to fix small functional bugs or meet performance requirements late in the design cycle. Traditional high-level synthesis has attempted to optimize at best the output logic. However, in the ECO scenario the goal is to implement the required change with as few modifications as possible to the RTL, logic netlist, placed netlist and layout. In this paper we show how, by judiciously changing the internal databases used by the tool to match as much as possible the original design, one can achieve minimal impact and implement ECOs in truly incremental mode, while full-blow re-synthesis would lead to massive unnecessary downstream changes. The tool essentially matches source constructs between the original and the ECO design, and copies as many synthesis decisions as possible from the original design to the ECO design.