We present the wamcc system, a Prolog compiler that translates Prolog to C via the WAM. This approach has some interesting consequences: simplicity, efficiency, portability, extensibility and modularity. Indeed the system does not incorporate complex optimizations but is as efficient as Quintus Prolog 2.5 (based on an emulator written in assembly language) and only 30 % slower than Sicstus Prolog (compiling to native code). It is instantly portable to any machine with a C compiler and easily expandable with various extensions, such as constraints, as shown by the clp(FD) system which is based on wamcc. It also incorporates a simple but efficient handling of modularity thanks to the use of C modularity.

Program specialization is normally supported by global analysis of the program. Compilers use the information deduced to generate more efficient, specialized implementations of the program. This specialization can be single or multiple, depending if each procedure of the program is specialized into one or more versions. We present a Prolog compiler that does multiple specialization, using an algorithm that works over the WAM code, deducing the reachable procedure activations based on local analysis. The idea is to use the analysis that is done in the Prolog to WAM compilation, and that generates local specialized instructions, and to propagate this information through the entire program. The creation of multiple versions of predicates allows the propagation to be inter-procedural, and to achieve global program specialization. Results from an implementation generating C code as target language are presented, showing a performance comparable to native code Prolog compilers. Keywords: P...