1 Introduction
Code Large Language Models (Code LLMs) have attracted sub-stantial attention in the industry owing to their vast applications throughout the entire software engineering lifecycle. The release of Copilot, empowered by Codex [7], served as a significant testament to the imminent arrival of the era of intelligent code. One astonishing application, ChatGPT [6], [27], has captivated an incredible user base of over 100 million in two months since its launch. In recent code models such as AlphaCode[21], InCoder[13], SantaCoder[1], StarCoder[20], and Code Llama[30], the incorporation of fill-in-the-middle capabilities has proven to be particularly valuable for practical code completion scenarios.