System and method for automatically and selectively promoting object variables to method fields and variables in a digital computer system

• US 6,308,315 B1
• Filed: 10/14/1998
• Issued: 10/23/2001
• Est. Priority Date: 10/14/1998
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Mann, Ronald J., Herrick, Andrew F., Dice, David
• Primary Examiner(s): Chaki, Kakali
• Assistant Examiner(s): Khatri, Anil
• Application Number:
  US09/172,153
• Time in Patent Office: 1,105 Days
• Field of Search: 717/2, 717/3, 717/4, 717/5, 345/326, 345/327
• US Class Current: 717/106
• CPC Class Codes: G06F 8/433 Dependency analysis; Data or control flow analysis
• CPC Class Codes: G06F 8/443 Optimisation
• CPC Class Codes: G06F 9/4488 Object-oriented

Abstract

A code generating system generates, from code in a program, native code that is executable by a computer system. The computer system includes a memory subsystem including a heap in which objects are stored and a stack in which method variables are stored. The code generating system may be included in a just-in-time compiler used to generate native code that is executable by a computer system, from a program in Java Byte Code form, and specifically determines, in response to Java Byte Code representative of an operator for enabling instantiation of a new object, whether the object to be instantiated contains a variable to be used in processing of the received program code portion which can be promoted to a method variable, and, if so, generates native code to enable said variable to be instantiated on the stack.

Claims

1. A code generator for generating, from code in a program, native code executable by a computer system, the computer system including a memory subsystem including a heap in which objects are stored and a stack in which method variables are stored, the code generator comprising:

A. a code portion receiver configured to receive a portion of the program code for which the native executable code is to be generated;

B. an object instantiation detector configured to determine whether the received program code portion includes an operator for enabling instantiation of a new object;

C. a variable promotion eligibility detector configured to, in response to a positive determination by said object instantiation detector, determine whether the object to be instantiated contains a variable to be used in processing of the received program code portion which can be promoted to a method variable, and

D. a native code generator configured to, in response to positive determination by said variable promotion eligibility detector, generate native code to enable said variable to be instantiated on the stack.

2. A code generator as defined in claim 1 in which the program includes instructions in Java Byte Code.

3. A code generator as defined in claim 1 in which the native code generator is in the form of a just-in-time compiler.

4. A code generator as defined in claim 1 in which the variable promotion eligibility detector is configured to make a negative determination if the lifetime of the object to be instantiated is shorter than the time during which the program code portion is to be executed.

5. A code generator as defined in claim 1 in which the variable promotion eligibility detector is configured to make a negative determination if the operator that enables instantiation of the object can, during execution of the program code portion, be executed an indeterminate number of times.

6. A code generator as defined in claim 1 in which the variable promotion eligibility detector is configured to make a negative determination if the program code portion stores a reference to the object to be instantiated in a storage location maintained by the computer system except a location in the stack.

7. A code generator as defined in claim 1 in which the native code generator is configured to, in response to a negative determination by said variable promotion eligibility detector, generate native code to enable said object to be instantiated in the heap.

8. A code generation method for generating, from code in a program, native code executable by a computer system, the computer system including a memory subsystem including a heap in which objects are stored and a stack in which method variables are stored, method comprising the steps of:

A. receiving a portion of the program code for which the native executable code is to be generated;

B. determining whether the received program code portion includes an operator for enabling instantiation of a new object;

C. in response to a positive determination by said object instantiation detector, determining whether the object to be instantiated contains a variable to be used in processing of the received program code portion which can be promoted to a method variable, and

D. in response to positive determination by said variable promotion eligibility detector, generating native code to enable said variable to be instantiated on the stack.

9. A method as defined in claim 8 in which the program includes instructions in Java Byte Code.

10. A method as defined in claim 8 in which the native code generating step includes the step of using a just-in-time compiler.

11. A method as defined in claim 8 in which the variable promotion eligibility detection step includes the step of making a negative determination if the lifetime of the object to be instantiated is shorter than the time during which the program code portion is to be executed.

12. A method as defined in claim 8 in which the variable promotion eligibility detection step includes the step of making a negative determination if the operator that enables instantiation of the object can, during execution of the program code portion, be executed an indeterminate number of times.

13. A method as defined in claim 8 in which the variable promotion eligibility detection step includes the step of making a negative determination if the program code portion stores a reference to the object to be instantiated in a storage location maintained by the computer system except a location in the stack.

14. A method as defined in claim 8 in which the native code generating step includes the step of in response to a negative determination during the variable promotion eligibility detection step, generating native code to enable said object to be instantiated in the heap.

15. A computer program product for use in connection with a computer to provide a code generator for generating, from code in a program, native code executable by a computer system, the computer system including a memory subsystem including a heap in which objects are stored and a stack in which method variables are stored, the computer program product comprising a computer-readable medium having encoded thereon:

A. a code portion receiver module configured to enable the computer to receive a portion of the program code for which the native executable code is to be generated;

B. an object instantiation detector module configured to enable the computer to determine whether the received program code portion includes an operator for enabling instantiation of a new object;

C. a variable promotion eligibility detector module configured to enable the computer to, in response to a positive determination by said object instantiation detector, determine whether the object to be instantiated contains a variable to be used in processing of the received program code portion which can be promoted to a method variable, and

D. a native code generator module configured to enable the computer to, in response to positive determination by said variable promotion eligibility detector, generate native code to enable said variable to be instantiated on the stack.

16. A computer program product as defined in claim 15 in which the program includes instructions in Java Byte Code.

17. A computer program product as defined in claim 15 in which the native code generator module is in the form of a just-in-time compiler.

18. A computer program product as defined in claim 15 in which the variable promotion eligibility detector module is configured to enable the computer to make a negative determination if the lifetime of the object to be instantiated is shorter than the time during which the program code portion is to be executed.

19. A computer program product as defined in claim 15 in which the variable promotion eligibility detector module is configured to enable the computer to make a negative determination if the operator that enables instantiation of the object can, during execution of the program code portion, be executed an indeterminate number of times.

20. A computer program product as defined in claim 15 in which the variable promotion eligibility detector module is configured to enable the computer to make a negative determination if the program code portion stores a reference to the object to be instantiated in a storage location maintained by the computer system except a location in the stack.

21. A as defined in claim 15 in which the native code generator module is configured to enable the computer to, in response to a negative determination by said variable promotion eligibility detector module, generate native code to enable said object to be instantiated in the heap.