Efficiency, Expressivity, and Extensibility in a Close-to-Metal NPU Programming Interface

Abstract

Conference Title: 2025 IEEE 33rd Annual International Symposium on Field-Programmable Custom Computing Machines (FCCM)

Conference Start Date: 2025 May 4

Conference End Date: 2025 May 7

Conference Location: Fayetteville, AR, USA

Accelerators such as neural processing units (NPUs) deliver an enticing balance of performance and efficiency compared to general purpose compute architectures. However, effectively leveraging accelerator capabilities is not always simple: low-level programming toolkits may require substantial developer effort while high-level programming toolkits may abstract critical optimization features. This work aims to increase efficiency of designers using IRON, a toolkit for close-to-metal NPU performance engineers. We provide an updated programmer interface to IRON containing new and refined programming constructs. The new interface includes extensible features for placement and data transformation. These contributions are evaluated in terms of 1) efficiency, with analysis showing ~ 26% average reduction in lines of code and decreases in Halstead metrics for a variety of designs; 2) expressivity, demonstrating the new interface supports the wide range of features and patterns already supported by IRON; and 3) extensibility, illustrating the new tooling for placement and tiling can be extended to accommodate common use-cases.