Compiler back end calling predetermined front end routines that use effect and dependency indicators to provide information to the compiler to determine the validity of an optimization

摘要

A compiler framework uses a generic "shell" and a generic back end (where the code generator is target-specific). The generic back end provides the functions of optimization, register and memory allocation, and code generation. The code generation function of the back end may be targeted for any of a number of computer architectures. A front end is tailored for each different source language, such as Cobol, Fortran, Pascal, C, C++, etc. The front end scans and parses the source code modules, and generates from them an intermediate language representation of the source code programs expressed in the source code. The intermediate language represents any of the source code languages in a universal manner, so the interface between the front end and back end is of a standard format, and need not be rewritten for each language- specific front end. A feature is a mechanism for representing effects and dependencies in the interface between front end and back end. An element has an effect if it writes to memory, and has a dependency if it reads from a location which some other node may write to. A mechanism which is independent of source language is provided for describing the effects of program execution.