Interface for symbol table construction in a multilanguage optimizing compiler

• US 5,659,753 A
• Filed: 12/27/1994
• Issued: 08/19/1997
• Est. Priority Date: 02/27/1991
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Digital Equipment Corporation (HP Inc.)
• Inventors: Murphy, Dennis Joseph, Faiman, Robert Neil Jr.
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Alam, Hosain T.
• Application Number:
  US08/364,437
• Time in Patent Office: 966 Days
• Field of Search: 395/700, 395/600, 395/705, 395/708
• US Class Current: 717/147
• CPC Class Codes: G06F 8/433 Dependency analysis; Data or control flow analysis
• CPC Class Codes: G06F 8/437 Type checking
• CPC Class Codes: G06F 8/443 Optimisation
• CPC Class Codes: G06F 8/47 Retargetable compilers

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 the type definition (TD) mechanism, referred to a the TD module. This module provides mechanisms used by the front end and the compiler of the back end in constructing program "type-information" to be incorporated in an object module for use by a linker or debugger. The creation of "type-information" takes place in the context of symbol table creation and allows a front end to specify to the back end an abstract representation of program type information. The TD module provides service routines that allow a front end to describe basic types and abstract types.

Claims

1. A method, executed in a computer system, for providing type information about a source program, the method comprising the steps of:

producing a type node by a compiler front end calling a service routine that creates and stores the type node at a first address in a memory, said compiler front end performing syntactic and semantic processing of a programming language, said type node describing a data type that belongs to said programming language and is used in a source program that is stored in the memory and includes one or more source statements written in said programming language, said service routine being a routine in a compiler back end and being called by a plurality of different compiler front ends, each of said different compiler front ends performing syntactic and semantic processing of a different programming language;

generating, using the source program and the compiler front end, a symbol table that includes said type node; and

generating, using said symbol table and said compiler back end, type information that is described by said type node and an object module for use in a target computer system, said object module and said type information being used in producing a machine executable program for said target computer system, said type information and said object module corresponding to said source program.

2. The method of claim 1, wherein said compiler back end produces code for one of a plurality of different target computer systems and includes an object module emitter that produces said object module, and wherein said object module includes said type information, and the method further comprises the step of:

linking, using a linker, said object module and producing a machine-executable program that comprises said type information.

3. The method of claim 1 wherein said type node is a first type node, said compiler front end is a first compiler front end, said address is a first address, said programming language is a first programming language, said source program is a first source program, said symbol table is a first symbol table, said data type is a first data type, said target computer system is a first target computer system, and the method further comprising the steps of:

producing a second type node by a second compiler front end, said second compiler front end calling said service routine that creates and stores said second type node at a second address in said memory, said second compiler front end performing syntactic and semantic processing of said second programming language, said second type node describing a second data type which belongs to said second programming language and which is used in a second source program;

generating, using said second source program and said second compiler front end, a second symbol table that includes said second type node; and

generating, using said second symbol table and said compiler back end, other type information that is described by said second type node and another object module for a second target computer system, said other type information and said other object module being used to produce another machine executable program for said second target computer system, said other type information and said other object module corresponding to said second source program.

4. The method of claim 1, further comprising the step of generating an intermediate language graph that represents said source program in an intermediate language, and wherein said step of generating type information and an object module uses said intermediate language graph to generate said object module.

5. The method of claim 1, wherein said symbol table further includes a symbol node that represents a program symbol in said source program and a block node that corresponds to a portion of the source program in which said program symbol is used, said program symbol being of said data type, said type node being associated with said symbol node identifying said program symbol as said data type, said block node including type list information denoting a first list that includes said type node and that represents data types used within said portion of said source program, a second list comprising one or more symbol nodes is associated with said block node, said second list representing program symbols declared within said portion of said source program and said second list including said first symbol node, and said type information includes information that represents said program symbol being of said data type.

6. The method of claim 5, wherein said address is a first address and said service routine creates said type node as a data structure stored at said address and said service routine returns to said compiler front end an address handle corresponding to said address in said memory, said service routine constructing and managing said first list of type nodes at a second address in said memory, said type list information of said block node denoting said second address, and said first symbol node including said address handle.

7. The method of claim 5, wherein said program symbol is a user-defined programming variable, and said portion of said source program comprises a source language statement assigning a value to said program symbol.

8. The method of claim 5, wherein said symbol node comprises said address of said type node being associated with said symbol node.

9. The method of claim 1, wherein said step of generating said type information and said object module further comprises generating, using said symbol table, a debug symbol table that comprises debug type information as described in said symbol table, said debug type information used for debugging said source program.

10. The method of claim 1, wherein said data type is one of a basic type describing a type of said programing language common to other programming languages, an abstract type describing a type specific to said programming language, or a user-defined type as defined in said source program.

11. The method of claim 10, wherein said basic type is one of an integer data type, a floating-point data type or a character data type.

12. A memory comprising:

a compiler front end that performs syntactic and semantic processing of a programming language;

producing means, coupled to said compiler front end, for producing a type node which describes a data type that belongs to said programming language and that is used in a source program including one or more source statements written in said programming language, said producing means including a service routine that is included in a compiler back end and that is called by said compiler front end to create said type node;

means for generating, using said source program and said compiler front end, a symbol table that includes said type node; and

means for generating, using said symbol table and said compiler back end, type information that is described by said type node and an object module used in a target computer system, said object module and said type information being used to produce a machine executable program for said target computer system, said type information and said object module corresponding to said source program.

13. The memory of claim 12, wherein said means for generating said symbol table generates an intermediate language graph that represents said source program in an intermediate language, and wherein said means for generating said type information and said object module use said intermediate language graph to generate said object module.

14. The memory of claim 12 wherein said compiler front end is a first compiler front end, said programming language is a first programming language, said source program is a first source program, said type node is a first type node, said data type is a first data type, and the memory further comprising:

a second compiler front end that performs syntactic and semantic processing of a second programming language, and wherein said producing means for producing a type node, coupled to said second compiler front end, produces a second type node that represents a second data type in said second programming language, and the memory further includes;

means for generating, using a second source program written in said second programming language and said second compiler front end, another symbol table that comprises said second type node.

15. The apparatus of claim 14, wherein said service routine is called by said first and second compiler front ends and creates said first and said second type nodes which represent, respectively, said first and second data types.

16. The memory of claim 15, wherein said compiler back end includes an object module emitter that generates an object module for one of a plurality of different target computer systems, and wherein said object module comprises said type information.

17. A method, executed in a computer system, of producing debug type information, the method comprising the steps of:

producing, using a compiler front end that performs syntactic and semantic processing of a first programming language, a type node describing a data type of said programming language, said compiler front end calling a service routine that creates said type node as a first data structure in a memory at a first memory location and returns to said compiler front end an address handle corresponding to said first memory location, said service routine constructing and managing a list of type nodes that it has created in response to calls from said compiler front end, said list being stored in said memory at a second memory location;

generating, using said source program and said compiler front end, a symbol table that includes a symbol node that is a second data structure and represents a program symbol in said source program, said symbol table includes a block node that is a third data structure and corresponds to a portion of said source program in which said program symbol is used, said program symbol being of said data type described by said the node and said symbol node including said first address handle, said type node is associated with said symbol node identifying said program symbol as being said data type, said block node comprising a list address handle denoting said second memory location; and

generating, using said symbol table, a debug symbol table that includes debug type information about said source program, said debug type information being described by said type node and representing said program symbol being of said data type.

18. The method of claim 17, wherein said list comprises a first marker element denoting the front of the list and a second marker element denoting the end of the list.

19. The method of claim 17, wherein said step of generating a debug symbol table generates, using an object module emitter and said symbol table, an object module that includes said debug symbol table.

20. The method of claim 19 further comprising the step of:

linking said object module and producing a machine executable program that uses said debug type information comprising said debug symbol table for debugging first source program.

21. The method of claim 17, wherein said compiler front end is a first compiler front end, said source program is a first source program, said programming language is a first programming language, said type node is a first type node, said data type is a first data type, said address handle is a first address handle, and the method further comprising the step of:

producing, using a second compiler front end that performs syntactic and semantic processing of a second programming language different from said first programming language, a second type node describing a second data type of said second programming language, said second front end calling said service routine that creates said second type node as a fourth data structure in said memory at a third memory location and returns to said second compiler front end a second address handle corresponding to said third memory location, said service routine constructing and managing another list of type nodes it has created in response to calls made by said second compiler front end, said second data type being a data type of another program symbol in a second source program that includes statements written in said second programming language.