We empirically evaluated thousands of different C calling conventions for irregular microcontroller architectures, and found potential for improvement over the calling conventions previously used in the Small Device C Compiler (SDCC). The improvements in code size and speed are substantial enough that SDCC made changes to its default calling convention, breaking ABI compatibility.
Cite
@article{arxiv.2112.01397,
title = {Efficient Calling Conventions for Irregular Architectures},
author = {Philipp K. Krause},
journal= {arXiv preprint arXiv:2112.01397},
year = {2022}
}