Method of constructing a constant-folding mechanism in a multilanguage optimizing compiler

A method performed in a host computer system having a memory for compiling source code and producing a corresponding object module, the method comprising the steps of:

• generating a first flow graph that is stored in said memory by performing an execution flow analysis of said source code, said first flow graph representing said source code in an intermediate language, said intermediate language being a universal language used by a plurality of compiler front ends to represent source code and including operators and data types used to described said source code, each of said plurality of compiler front ends corresponding to a different programming language;
• generating a second flow graph that contains an optimized representation of said first flow graph by detecting a constant expression in said first flow graph and executing a constant-folding routine which evaluates said constant expression and replaces said constant expression with an equivalent expression yielding a same result as said constant expression, said constant expression including at least one of said operators or said data types, said second flow graph being stored in said memory;
• and
• producing said corresponding object module by using said second flow graph as input to a code generator that produces said corresponding object module for a target computer system, said corresponding object module including machine instructions for execution in said target computer system, said code generator being a common code generator used by a plurality of front ends to generate an object module using a flow graph;
• and wherein said constant-folding routine is produced by performing the steps of:
• generating, using a compiler front end and an intermediate language input to said compiler front end, a third flow graph that represents said constant-folding routine in said intermediate language, said intermediate language input describing said intermediate language and comprising said operators and said data types of said intermediate language, said compiler front end being one of said plurality of compiler front ends;
• and
• producing a constant-folding object module using said third flow graph as an input to said code generator.

An apparatus for use in a host computer system having a memory for compiling source code and producing a corresponding object module, the apparatus comprising:

• A) a first compiler front end performing an execution flow analysis of said source code and producing a first flow graph that is stored in said memory, said first flow graph representing said source code in an intermediate language including operators and data types used to describe said source code;
• B) a compiler back end, coupled to said first compiler front end, said compiler back-end comprising:
• i) optimizing means that uses said first flow graph as input for producing a second flow graph that contains an optimized representation of said first flow graph, said second flow graph representing said source code in said intermediate language and being stored in said memory;
• and
• ii) code generator means, coupled to said optimizing means, for generating said corresponding object module using said second flow graph as input;
• said optimizing means comprising constant-folding means executing a constant-folding routine for detecting and evaluating a constant expression in said second flow graph and replacing said constant expression with an equivalent expression yielding a same result as said constant expression, said constant expression being comprised of at least one of said operators or said data types, said corresponding object module comprising machine instructions for execution in said target computer system;
• and
• C) means for generating said constant-folding routine comprising:
• i) a second compiler front end for generating a third flow graph that represents said constant-folding routine in said intermediate language, said third flow graph being generated using said operators of said intermediate language as input;
• and
• ii) said compiler back end, using said third flow graph as input and coupled to said second compiler front end, for generating an object file containing machine instructions for said constant-folding routine.

An apparatus for compiling source code in a host computer system with a memory and producing a corresponding object module, the apparatus comprising:

• generating means for generating a first flow graph that is stored in said memory by performing an execution flow analysis of said source code, said first flow graph representing said source code in an intermediate language, said intermediate language being a universal language used by a plurality of compiler front ends to represent source code and including operators and data types used to described said source code, each of said plurality of compiler front ends corresponding to a different programming language;
• generating means for generating a second flow graph that contains an optimized representation of said first flow graph by detecting a constant expression in said first flow graph and executing a constant-folding routine which evaluates and replaces said constant expression with an equivalent expression yielding a same result as said constant expression, said constant expression being comprised of at least one of said operators or said data types, said third flow graph being stored in said memory;
• and
• producing means for producing said corresponding object module by using said second flow graph as input to a code generator that produces said corresponding object module for a target computer system, said corresponding object module including machine instructions for execution in said target computer system, said code generator being a common code generator used by a plurality of front ends to generate an object module using a flow graph;
• and wherein said constant-folding routine is produced using:
• a compiler front end and an intermediate language input to said compiler front end for generating a third flow graph that represents said constant-folding routine in said intermediate language, said intermediate language input describing said intermediate language and comprising said operators and said data types of said intermediate language;
• and
• said code generator, using said third flow graph as an input, for generating a constant-folding object module comprising machine instructions for said constant-folding routine.