Introduction to BOLT

Binary optimization and layout tool (BOLT) is a post-link optimizer based on the LLVM framework. By using perf or instrumentation, running information is collected to guide binary code layout optimization to improve performance. For details, see README on GitHub. It is designed to improve application performance by laying out code in a way that helps the CPU better utilize its cache and branch prediction resources. The applications that benefit most from BOLT optimizations are programs with many I-cache and iTLB misses, typically large applications over hundreds of megabytes in size. BOLT complements traditional compiler optimizations by further improving program performance with sampling files based on highly optimized binary files built with FDO and LTO.