Achieve Latency-Efficient Temporal-Coding Spiking LLMs via Discretization-Aware Conversion

Large language models (LLMs) have achieved remarkable success while introducing critical energy bottlenecks that challenge sustainable deployment. Spiking neural networks (SNNs) provide a promising approach for energy-efficient spiking LLMs via ANN-to-SNN (A2S) conversion. Among various spike coding methods, time-to-first-spike (TTFS) coding is particularly appealing as it conveys information with a single spike, further reducing energy consumption. However, existing TTFS-based A2S conversion relies on continuous-time assumptions, requiring prohibitively large latencies (e.g., 4096 time steps) to approximate ANN's continuous values. This dependency leads to unacceptable inference delays in LLMs, posing significant challenges for developing practical temporal-coding spiking LLMs. In this paper, we propose a discrete analysis framework for TTFS-based LLMs, reformulating TTFS-based A2S conversion from continuous lossless conversion into discrete error-aware representation. Building on this analysis, we establish an equivalence between discrete TTFS-based SNNs and static quantized ANNs, allowing TTFS conversion to be handled through quantization techniques. Motivated by this equivalence, we introduce Quantization-Consistent ANN-to-SNN (QC-A2S) conversion, which combines static quantization with discretization-compatible TTFS neurons to achieve latency-efficient and high-performance temporal-coding spiking LLMs. Extensive evaluations on representative LLMs across multiple benchmarks demonstrate competitive performance with substantially reduced inference latency.