US 5,493,675 AGranted

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

AssigneeDigital Equipment Corporation

InventorsRobert N. Faiman, Jr., David S. Blickstein, Steven O. Hobbs

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Abstract

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.

Claims10

Dependent claims

A method executed in a computer system, the method comprising the steps:

generating a flow graph for a source program that is being compiled using a compiler front end which performs syntactic and semantic processing of a programing language, said flow graph comprising tuples, each tuple representing a single expression in said source program, said flow graph being a representation of said source program in an intermediate language;
determining, by said compiler front end for each tuple which can have an effect on another tuple and which is included in said first flow graph, an effect indicator that represents an effect said each tuple has on said another tuple, said effect indicator being associated with said each tuple;
determining, by said compiler front end for each tuple which can have a dependency on another tuple and which is included in said flow graph, a dependency indicator that represents a dependency said each tuple on said another tuple, said dependency indicator being associated with said each tuple;
and
optimizing said flow graph by a compiler back end calling one or more predetermined routines in said compiler front end, said predetermined routines using effect and dependency information from said determining effect and said determining dependency steps to provide return information to said compiler back end wherein said compiler back end uses said return information to determine whether an optimization is valid for one of said tuples comprising said flow graph.

2 more elements

A memory for use in a computer system, said memory comprising:

means for generating, using a first compiler front end, a first flow graph for a first source program, said first source program being compiled using said first compiler front end which performs syntactic and semantic processing of a first programming language, said first flow graph comprising tuples, each tuple representing a single expression in said first source program, said first flow graph being a representation of said first source program in an intermediate language;
means for determining using said compiler front end an effect indicator for each tuple which can have an effect on another tuple and which is included in said first flow graph, said effect indicator representing an effect said each tuple has on said another tuple and being associated with said each tuple;
means for determining, by said compiler front end a dependency indicator for each tuple which can have a dependency on another tuple and which is included in said first flow graph, said dependency indicator representing a dependence of said each tuple has on said another tuple and being associated with said each tuple;
means for optimizing, coupled to said first and second determining means, said first flow graph by a compiler back end calling one or more predetermine routines in said compiler front end, said predetemined routines using effect and dependency information from said effect determining means and said dependency determining means to provide return information to said compiler back end wherein said compiler back end uses said return information to determine whether an optimization is valid for one of said tuples comprising said flow graph.

1 more element

Dependencies are inferred from the claim text.