Partial Translation: Towards a Portable and Efficient Prolog Implementation Technology

We describe a new language translation framework (partial translation) and the application of one of its instances: the C-iication of Binary Prolog. Our partial translation framework compiles selected sequences of em-ulator instructions down to native code. The technique can be seen as an automatic specialization with respect to a given program of the traditional instruction folding techniques used to speed-up emulators. In our implementation, the complex control structure, some large instructions and the management of the symbol table are left to the emulator while the translated code deals with relatively long sequences of simple instructions. After compilation, the generated code is linked with a target language representation of the emulator's byte-code and the emulator itself to form a stand-alone application. The composite run-time system's behavior can be seen as a form of`coroutining' between emulated and native code. The framework supports modular compilation, allows programmer control of the speed vs. size optimization, is fully portable and has a performance that ranges between the performance of emulated code and that of native code. Our design has been proven practical in the implementation of the C-code generator of a fairly complete multi-platform Prolog system (BinProlog) available by ftp at clement.info.umoncton.ca.