Efficient Calling Conventions for Irregular Architectures

TL;DR

This paper empirically evaluates various C calling conventions on irregular microcontroller architectures, demonstrating significant improvements in code size and speed that led to changes in SDCC's default calling convention.

Contribution

It introduces optimized calling conventions tailored for irregular architectures, showing substantial performance and size benefits over previous standards.

Findings

Significant reduction in code size and execution time.

SDCC adopted new calling conventions based on findings.

Potential for further optimization in embedded compiler design.

Abstract

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.