CISim: ISA-Agnostic Custom Instruction Simulation for General-Purpose Processor
2026 Design, Automation & Test in Europe Conference (DATE), 2026
@inproceedings{hao2026cisim,
author = {Hao, Xiaoyu and Zhang, Sen and Qiao, Liang and Shi, Jun and Chen, Junshi and An, Hong},
title = {CISim: ISA-Agnostic Custom Instruction Simulation for General-Purpose Processor},
year = {2026},
isbn = {979-8-3315-0601-8},
publisher = {Institute of Electrical and Electronics Engineers (IEEE)},
doi = {10.23919/date69613.2026.11539409},
url = {https://doi.org/10.23919/date69613.2026.11539409},
booktitle = {2026 Design, Automation \& Test in Europe Conference (DATE)},
pages = {1-7},
numpages = {7},
location = {Verona, Italy},
series = {DATE '26}
}
Abstract
Pre-RTL ISA-agnostic simulators have been established for designing heterogeneous systems, but few of them are suitable for evaluating a general-purpose processor (GPP) with custom instructions (CIs). MosaicSim [1], a state-of-the-art ISA-agnostic simulator, still has several limitations for CI design and simulation. First, it shows inaccuracy in simulating GPPs due to an oversimplified performance model. Second, as designed for kernel simulation, it lacks support for running complex real-world benchmarks. Third, it cannot evaluate fine-grained irregular CIs due to the lack of the ability to represent or define them in benchmarks. To this end, we propose CISim, a new ISA-agnostic simulation framework containing an offloader that generates and integrates CIs into benchmarks, along with a simulator capable of executing benchmarks with CIs. Evaluations show that CISim is accurate by validating against Gem5 [2] and achieves higher accuracy than MosaicSim. A case study evaluating CI exploration methods highlights the strength and flexibility of CISim.