Abstract: Multiple classifier models are applied to features of a circuit design after processing the design through a first phase of an implementation flow. Each classifier model is associated with one of multiple directives, the directives are associated with a second phase of the implementation flow, and each classifier model returns a value indicative of likelihood of improving a quality metric. Regressor models of each set of a plurality of sets of regressor models are applied to the features. Each directive is associated with one of the sets of regressor models, and a combined score from each set of regressor models indicates a likelihood of satisfying a constraint. The directives are ranked based on the values indicated by the classifier models and scores from the sets of regressor models, and the circuit design is processed n the second phase of the implementation flow by the design tool using the directive having the highest rank.