We present TAFFO, a framework that automatically performs precision tuning to exploit the perfor-mance/accuracy trade-off. In order to avoid expensive dynamic analyses, TAFFO leverages programmer annotations which encapsulate domain knowledge about the conditions under which the software being optimized will run. As a result, TAFFO is easy to use and provides state-of-the-art optimization efficacy in a variety of hardware configurations and application domains. We provide guidelines for the effective exploitation of TAFFO by showing a typical example of usage on a simple application, achieving a speedup up to 60% at the price of an absolute error of 3.53x10-5. TAFFO is modular and based on the solid LLvm technology, which allows extensibility to improved analysis techniques, and comprehensive support for the most common precision-reduced data types and programming languages. As a result, the TAFFO technology has been selected as the precision tuning tool of the European Training Network on Approximate Computing.