This PhD thesis , awarded with the SPEC Distinguished Dissertation Award 2011, proposes and studies three workload generation and reduction techniques for microprocessor performance evaluation. (1) The thesis proposes code mutation, a novel methodology for hiding proprietary information from computer programs while maintaining representative behavior; code mutation enables dissemination of proprietary applications as benchmarks to third parties in both academia and industry. (2) It contributes to sampled simulation by proposing NSL-BLRL, a novel warm-up technique that reduces simulation time by an order of magnitude over state-of-the-art. (3) It presents a benchmark synthesis framework for generating synthetic benchmarks from a set of desired program statistics. The benchmarks are generated in a high-level programming language, which enables both compiler and hardware exploration.