We consider a class of constraint logic programs including negation that can be executed bottom up without constraint solving, by replacing constraints with tests and assignments. We show how to optimize the bottom-up evaluation of queries for such programs using transformations based on analysis obtained using abstract interpretation. Although the paper concentrates on a class of efficiently executable programs the optimizations we describe are correct and applicable for arbitrary constraint programs. Our approach generalizes earlier work on constraint propagation.

The pure logic programming language Mercury is very well suited to the development of sophisticated program transformations due to its clean semantics and strong type, mode and determinism systems. We describe the design and implementation of some of the high-level optimization passes of the Mercury compiler, including deforestation, constraint propagation and type specialization. Mercury's mode system allows programmers to specify when a data structure can have only one reference. We present the implementation of an optimization pass to exploit this information to reuse dead cells or insert calls to place them on a free list. Contents 1 Introduction 1 2 Mercury 1 2.1 Super-homogeneous form : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 2.2 Quantification : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 2.3 Type checking : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 2.4 Mode analysis : : : : : : : : :...