SLOTHY – Super Lazy Optimization of Tricky Handwritten assemblY – is a fixed-instruction assembly superoptimizer based on constraint solving. It takes handwritten assembly as input and simultaneously super-optimizes:

• Instruction scheduling
• Register allocation
• Software pipelining

SLOTHY enables a development workflow where developers write ‘clean’ assembly by hand, emphasizing the logic of the computation, while SLOTHY automates microarchitecture-specific micro-optimizations. Since SLOTHY does not change instructions, and scheduling/allocation optimizations are tightly controlled through configurable and extensible constraints, the developer keeps close control over the final assembly, while being freed from tedious micro-optimizations.

See also FAQ

Architecture/Microarchitecture support

SLOTHY is generic in the target architecture and microarchitecture. It currently supports Cortex-M55 and Cortex-M85 implementing Armv8.1-M + Helium, and Cortex-A55 and Cortex-A72 implementing Armv8-A + Neon. Moreover, there is an experimental model for Cortex-X/Neoverse-V cores.

Paper

SLOTHY is described in detail in the CHES 2024 paper Fast and Clean: Auditable high-performance assembly via constraint solving.