Debugging of Globally Optimized Programs Using Data Flow Analysis

Abstract

Advanced processor and machine architectures need optimizing compilers to be efficiently programmed in high level languages. Therefore the need for source level debuggers that can handle optimized programs is rising. One difficulty in debugging optimized code arises from the problem to determine the values of source code variables. To ensure correct debugger behaviour with optimized programs, the debugger not only has to determine the variable's storage location or associated register. It must also verify that the variable is current, i.e. the value determined from that location is really the value that the variable would have in unoptimized code. We will deduce requirements on algorithms for currentness determination and present an algorithm meeting this requirements that is more general than previous work. We will also give first experiences with an implementation. To our knowledge this is the first implementation of a currentness determination algorithm for globally optimized code.