A compiler transforms source code into intermediate code and provides the intermediate code to a profiler. The profiler executes the intermediate code. The profiler generates a performance profile that indicates the performance of the intermediate code, and annotates the intermediate code based, at least in part, on data from the performance profile. The compiler receives annotated intermediate code from the profiler and transforms the annotated intermediate code into machine code. Alternatively, the compiler transforms intermediate code to machine code and provides the machine code to a profiler. The profiler executes the machine code and generates a data file that indicates the performance of the machine code. The compiler receives the data file, and modifies the machine code based on the data file.