adding Context Length Specialization (CCL)

[vjanfaza]

Compute-Context-Length (CCL) technique optimizes the throughput of large language models (LLMs) on Qualcomm devices when handling very large context lengths. The current Ahead Of Time (AOT) compilation on Qualcomm devices doesn't predict the number of tokens needed, leading to significant throughput drops during the prefilling and the decoding phases. This happens because the system performs attention calculations based on large context length. To address this issue, we introduce Compute Context Length (CCL), an additional ONNX variable that allows for dynamic context-length specialization. By generating tokens using smaller, more manageable context lengths (CCL), we optimize memory reads and attention calculations, thereby improving throughput.