The author describes replacing a 1392-line linear scan register allocator in their rat compiler backend with a 584-line priority bin-packing allocator that produces better code. The new allocator orders live ranges by importance and assigns each to the first register where it fits, drawing inspiration from LLVM's greedy allocator while remaining much simpler.
Background
Register allocation is a classic compiler optimization problem that maps virtual registers to a limited set of physical registers, spilling excess values to memory. Linear scan was long the go-to heuristic for its simplicity, but bin-packing approaches can produce higher-quality code.
- Source
- Lobsters
- Published
- Oct 8, 2026 at 02:01 AM
- Score
- 6.0 / 10