TRACKING VARIABLE INFORMATION IN OPTIMIZED CODE

• US 20110307875A1
• Filed: 06/10/2010
• Published: 12/15/2011
• Est. Priority Date: 06/10/2010
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Hu, Weiping, Xu, Lin, Zhu, Yongkang
• Granted Patent: US 8,656,377 B2
• Time in Patent Office: Days
• US Class Current: 717/151
• CPC Class Codes: G06F 8/437 Type checking

Abstract

Embodiments are directed to tracking variable location information in optimized code and efficiently collecting and storing reaching definition information. A computer system receives a portion of source code at a compiler, where the compiler is configured to compile and optimize the source code for execution. The computer system tags selected variables in the source code with a tag, where the tag is configured to provide location information for the variable. The computer system optimizes the received portion of source code including changing at least one of the tagged variables. The computer system also tracks the tagged variables as the variables are changed by the compiler during code optimization and persists the variable location information, so that the persisted variable location information is available to other compiler components.

Claims

1. At a computer system including a processor and a memory, a computer-implemented method for tracking variable location information in optimized code, the method comprising:

an act of receiving a portion of source code at a compiler, wherein the compiler is configured to compile and optimize the source code for execution;

an act of tagging one or more selected variables in the source code with a tag, wherein the tag is configured to provide location information for the variable;

an act of the compiler optimizing the received portion of source code, wherein optimizing at least includes changing one or more of the tagged variables;

an act of tracking the tagged variables as the variables are changed by the compiler during code optimization; and

an act of persisting the variable location information, such that the persisted variable location information is available to one or more other compiler components.

2. The method of claim 1, further comprising an act of a user selecting which variables are to be tagged.

3. The method of claim 1, further comprising an act of compressing the persisted variable location information using a domain-specific compression algorithm.

4. The method of claim 3, further comprising an act of a debugger decompressing the compressed variable location information.

5. The method of claim 4, further comprising an act of the debugger displaying the decompressed variable location information to a user.

6. The method of claim 1, wherein the variable location information includes at least one of a memory address and a register identifier.

7. The method of claim 6, wherein at least one of the variables changes locations during code optimization.

8. The method of claim 6, wherein the compiler is configured to determine, for each memory address, which variable is currently stored at each address and how long the variable has been stored there.

9. The method of claim 6, wherein the persisted variable location information includes at least one mapping between a variable named in the source code and one or more variables created during optimization.

10. The method of claim 1, wherein the persisted variable location information is implemented by at least one of the following:

code analysis tools, code instrumentation tools, code coverage tools and automated bug analysis tools.

11. A computer program product for implementing a method for efficiently collecting and storing reaching definition information, the computer program product comprising one or more computer-readable storage media having stored thereon computer-executable instructions that, when executed by one or more processors of the computing system, cause the computing system to perform the method, the method comprising:

an act of accessing at least a portion of persisted variable location information;

an act of calculating one or more reaching definitions for one or more different variables implemented by a compiler during code optimization, wherein the reaching definitions comprise sets of instructions for which the variables possess an indicated location, such that each variable that is written to is represented by its reaching definition;

an act of compressing at least one of the calculated reaching definitions using a domain-specific compression algorithm; and

an act of sending the compressed reaching definitions from the compiler to the debugger for display to the user.

12. The computer program product of claim 11, wherein at least one of the variables is generated by the compiler during code optimization.

13. The computer program product of claim 12, wherein the compiler-generated variable comprises at least one of a temporary variable and a merged variable.

14. The computer program product of claim 11, wherein at least one of the variables'"'"' names is altered by the compiler during code optimization.

15. The computer program product of claim 11, wherein the domain-specific algorithm includes the following:

merging variable location information;

dropping at least a portion of irrelevant variable location information; and

compressing at least a portion of the reaching definitions in a lossless manner.

16. The computer program product of claim 11, wherein the variable location information was generated without any direct knowledge of what code optimizations were made during code optimization.

17. The computer program product of claim 11, wherein the variable location information is generated when one or more member fields of a structure are promoted to registers.

18. The computer program product of claim 11, wherein the variable location information is generated depending on runtime state.

19. The computer program product of claim 18, wherein a memory location is owned by different variables depending on runtime behavior.

20. A computer system comprising the following:

one or more processors;

system memory;

one or more computer-readable storage media having stored thereon computer-executable instructions that, when executed by the one or more processors, causes the computing system to perform a method for tracking variable location information in optimized code, the method comprising the following;

an act of receiving a portion of source code at a compiler, wherein the compiler is configured to compile and optimize the source code for execution;

an act of tagging one or more selected variables in the source code with a tag, wherein the tag is configured to provide location information for the variable;

an act of the compiler optimizing the received portion of source code, wherein optimizing at least includes changing one or more of the tagged variables;

an act of tracking the tagged variables as the variables are changed by the compiler during code optimization;

an act of persisting the variable location information, such that the persisted variable location information is available to one or more other compiler components;

an act of compressing the persisted variable location information using a domain-specific compression algorithm;

an act of a debugger decompressing the compressed variable location information; and

an act of the debugger displaying the decompressed variable location information to a user.