Abstract

Bottom-up tree rewriting has become the technique of choice for code selection in compilers. The technique is based on dynamic programming, and can select optimal code on trees. Several tools exist which are able to automatically produce bottom up tree rewriters from grammar specifications. We describe one such tool, MBURG, and introduce two innovations: incremental labelling, and forced reductions. Early experience with MBURG shows that it can produce code superior to that from carefully hand-tuned stack automata, by selecting optimal address modes for its emitted instructions. It is shown that the technique can be generalised to recognise tree idioms and perform some surprising code improvements. Keywords: code-generation, compilers, tree rewriting. 1

Citations