The growing gap between the advanced capabilities of static compilers as reflected in benchmarking results and the actual performance that users experience in real-life scenarios makes client-side dynamic optimization technologies imperative to the domain of static languages. Dynamic optimization of software distributed in the form of a platform-agnostic Intermediate- Representation (IR) has been very successful in the domain of managed languages, greatly improving upon interpreted code, especially when online profiling is used. However, can such feedback-directed IR-based dynamic code generation be viable in the domain of statically compiled, rather than interpreted, languages? We show that fat binaries, which combine the IR together with the statically compiled executable, can provide a practical solution for software vendors, allowing their software to be dynamically optimized without the limitation of binary-level approaches, which lack the high-level IR of the program, and without the warm-up costs associated with the IR-only software distribution approach. We describe and evaluate the fat-binary-based runtime compilation approach using SPECint2006, demonstrating that the overheads it incurs are low enough to be successfully surmounted by dynamic optimization. Building on Java JIT technologies, our results already improve upon common real-world usage scenarios, including very small workloads. © 2013 ACM.