mold: A Parallel Linker That Links Multi-Gigabyte Binaries in Under a Second

Linking is a critical step in the software build process, yet it remains a bottleneck, especially for large C++ programs. Existing linkers exploit limited parallelism, leaving CPU cores idle. This paper presents mold, a Unix/Linux linker that applies data parallelism across the entire linking pipeline. By decoupling symbol resolution and archive processing, mold achieves 2.4–16.1x speedup over lld and up to 112x over GNU ld, linking multi-gigabyte debug binaries in seconds. An ablation study shows the speedup comes from cumulative parallelization, not a single optimization.