Open Source Summit Europe 2024

The C runtime offers a range of string processing routines, such as strcmp() and strlen(). The throughput of these routines has a significant impact on many applications and benchmarks, so they are one of the many optimization targets of toolchain developers. Unfortunately, these functions have certain properties and corner cases that limit the optimization opportunities. This talk makes a journey through common optimization techniques ranging from utilization of alignment information in the compiler. It ends with specific instructions that speed up string processing (RISC-V’s orc.b instruction). Further, the talk will show how these optimizations can boost the throughput on real HW by orders of magnitudes in synthetic benchmarks and the impact on the SPEC CPU 2017 benchmark suite. The presentation will include assembly listings, so basic assembly knowledge will help follow the talk.