As optimizing compilers become more sophisticated, the problem of debugging the source code of an application becomes more difficult. In order to investigate this problem, we implemented DOC, a prototype solution for Debugging Optimized Code. DOC is a modification of the existing C compiler and source-level symbolic debugger for the HP9000 Series 800. This paper describes our experiences in this effort. We show in an actual implementation that source-level debugging of globally optimized code is viable.

All optimizing compilers must deal with the problem of aliases arising due to the presence of multiple names that reference the same memory areas. Presented in this paper is a staged, high-level alias analysis methodology that provides detailed alias information to a global optimizer implemented at any level in the compilation process. The framework provides easy portability of optimizing compilers to new architectures, as well as the easy addition, of new compilers to an already existing family of optimizing compilers. The method involves the application of a set of language-specific alias rules to the source code in order to gather alias information. A language-independent component then performs a transitive closure of this information and transforms it into a presentation more suitable for use by a global optimizer. Each stage of the methodology is detailed. Results are given for an implemented family of compilers targeted for a reduced instruction set computer.