Digital Equipment Corporation

David S Blickstein

Steven O Hobbs

Robert Neil Faiman, Jr

A compiler framework comprises a generic compiler back end which may be used by a plurality of front ends to generate object code for a target computer system. Each front end scans and parses a source module containing source code for a programming language, and generates an intermediate language representation that describes the source code. The intermediate language representation is input to the generic compiler back end which performs optimization and code generation for a plurality of target computer systems. A plurality of optimizations are performed by the generic compiler back end using induction variables. Induction variables are commonly used in performing optimizations such as loop unrolling. An efficient method for determining a set of induction variables for a programming loop construct uses effect and dependency information. Typically, effect and dependency information is used for another purpose besides detecting induction variables, for example, to validate other code optimizations. The method for determining the set of induction variables reuses this information as a shortcut to determine induction variables.

Analyzing inductive expressions in a multilanguage optimizing compiler

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.

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Hudson, NH, United States of America

David S Blickstein