The Mahler experience: using an intermediate language as the machine description

Abstract

Division of a compiler into a front end and a back end that communicate via an intermediate language is a well-known technique. We go farther and use the intermediate language as the official description of a family of machines with simple instruction sets and addressing capabilities, hiding some of the inconvenient details of the real machine from the users and the front end compilers.To do this credibly, we have had to hide not only the existence of the details but also the performance consequences of hiding them. The back end that compiles and links the intermediate language tries to produce code that does not suffer a performance penalty because of the details that were hidden from the front end compiler. To accomplish this, we have used a number of link-time optimizations, including instruction scheduling and interprocedural register allocation, to hide the existence of such idiosyncracies as delayed branches and non-infinite register sets. For the most part we have been sucessful.