A single intermediate language that supports multiple implementations of exceptions

We present mechanisms that enable our compiler-target language, C--, to exp ress four of the best known techniques for implementing exceptions, all wit hin a single, uniform framework. We define the mechanisms precisely, using a formal operational semantics. We also show that exceptions need not requi re special treatment in the optimizer; by introducing extra dataflow edges, we make standard optimization techniques work even on programs that use ex ceptions. Our approach clarifies the design space of exception-handling tec hniques, and it allows a single optimizer to handle a variety of implementa tion techniques. Our ultimate goal is to allow a source-language compiler t he freedom to choose its exception-handling policy, while encapsulating the architecture-dependent mechanisms and their optimization in an implementat ion of C-- that can be used by compilers for many source languages.