Data processing: software development – installation – and managem – Software program development tool – Testing or debugging
Reexamination Certificate
1999-04-23
2003-04-22
Morse, Gregory (Department: 2122)
Data processing: software development, installation, and managem
Software program development tool
Testing or debugging
C717S124000, C717S125000, C717S126000, C717S127000, C717S128000, C717S130000, C717S131000, C717S132000, C717S133000
Reexamination Certificate
active
06553565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to methods and apparatus for improving the performance of software applications. More particularly, the present invention relates to methods and apparatus for providing a debugging system with sufficient information to effectively debug optimized code.
2. Description of the Related Art
In an effort to increase the efficiency associated with the execution of computer programs, many computer programs are “optimized.” Optimizing a computer program generally serves to eliminate portions of computer code which are essentially unused. In addition, optimizing a computer program may restructure computational operations to allow overall computations to be performed more efficiently, thereby consuming fewer computer resources.
An optimizer is arranged to effectively transform a computer program, e.g., a computer program written in a programming language such as C++, FORTRAN, or Java Bytecodes into a faster program. The faster, or optimized, program generally includes substantially all the same, observable behaviors as the original, or pre-converted, computer program. Specifically, the optimized program includes the same mathematical behavior has its associated original program. However, the optimized program generally recreates the same mathematical behavior with fewer computations.
Typically, an optimizer includes a register allocator and a core optimizer. As will be appreciated by those skilled in the art, a register allocator moves computations from memory space into register space, while the core optimizer implements mathematical computations associated with the optimized program. In the course of creating an optimized program, an optimizer eliminates unused code. For example, codes associated with variables in an original program that are not used outside of a loop are generally eliminated. Such variables may include, but are not limited to, counter variables used as indexes within loops.
When an optimizer transforms a computer program, the optimizer often creates an internal representation of the computer program. The internal representation may then be used to generate machine code that is a computational equivalent of the computer program.
FIG. 1
is a diagrammatic representation of an optimizer which transforms a computer program into an optimized computer program. A computer program
104
, which may be written in any suitable computer programming language, is provided to an optimizer
110
. As shown, computer program
104
includes a “for” loop
106
that includes a variable “i.”
Optimizer
110
, which is effectively a compiler, includes an internal representation generator
114
and a machine code generator
118
. Internal representation generator
114
takes computer program
104
as input, and produces an internal representation
122
of computer program
104
. Internal representation generator
114
typically removes unused code, e.g., index variables such as variable “i,” such that internal representation
122
has no references to the unused code.
Internal representation
122
is provided as input to machine code generator
118
, which produces machine code
126
, i.e., a transformed computational equivalent of computer program
104
. As internal representation
122
does not include references to the unused code, it should be appreciated that machine code
126
also does not include references to the unused code. By eliminating the unused code, machine code
126
may execute more efficiently than it would if the unused code were included.
Machine code
126
, which represents a transformed or optimized version of computer program
104
, is typically accessed by a debugger when machine code is to be debugged. While optimized code may be debugged for a variety of different reasons, optimized code is often debugged in order to identify errors which are only manifested in optimized code. Debugging may also occur to identify internal states associated with the code, as will be appreciated by those skilled in the art.
FIG. 2
is a process flow diagram which illustrates the steps associated with optimizing a program and debugging the optimized program. A process
200
of optimizing and debugging a program begins at step
202
in which program code that contains an unused value, or variable, is obtained by an optimizer. Once the program code is obtained, an internal representation of the program code is generated in step
204
. Generating an internal representation of the program code typically entails removing references to the unused value, as previously mentioned.
After the internal representation of the program code is created, machine code is generated from the internal representation in step
206
. A debugger then accesses the machine code in step
208
, and obtains available debugging information from the machine code. In general, debugging information includes state information at different points in the machine code. Such debugging information is generated by “de-optimizing” the optimized code. When unused code, e.g., a dead variable, is removed from an optimized program, that unused code generally may not be re-obtained during a debugging process. As such, a precise relationship between debugged code and optimized code either may not be obtained, or may be incorrect, as will be understood by those skilled in the art. In other words, the debugging information obtained may be inaccurate. Once the debugging information is obtained, the process of optimizing code and debugging the optimized code is completed.
In an environment with a virtual machine, e.g., a Java™ virtual machine developed by Sun Microsystems, Inc. of Palo Alto, Calif., it may be desirable to convert optimized code to interpreted code. In order to accurately return optimized code to an interpreted equivalent, valid Java™ virtual machine states are typically needed for all variables. Not all states may be available in the event that code pertaining to some states may have been removed during an optimization process. When such states are unavailable, the conversion to interpreted code generally may not occur at all, or may be inaccurate. Inaccuracy in a conversion may result in substantially incorrect results for the overall-computing environment.
Therefore, what is desired is an efficient method for obtaining debugging information from optimized code. That is, what is needed is a method and an apparatus for enabling states associated with unused values to be efficiently obtained during a debugging, or deoptimizing, process.
SUMMARY OF THE INVENTION
The present invention relates to providing a substantially full set of state information to a debugger, without significantly compromising system performance, in order to debug optimized computer program code. According to one aspect of the present invention, a method for obtaining information associated with program code includes adding a segment of code, which includes a representation that is effectively not used after it is computed, “the debugging code”, to the program code. A “break point” is chosen in proximity to the segment of code, and machine code is generated from the program code. Finally, the method includes replacing the instruction at the break point with a branch instruction that is arranged to cause the debugging code to execute. By executing the debugging code, states that would generally be eliminated in optimized machine code are available to a debugger or deoptimizer, thereby enabling the machine code to be accurately debugged or deoptimized.
In one embodiment, the segment of code is associated with a program loop. In such an embodiment, adding a break point in proximity to the segment of code may include integrating the break point into the program loop. The debugging code may further include code that calls a debugging function arranged to debug the program code.
According to another aspect of the present invention, a computer-implemented method for obtaining information associated with program code may include adding a call to a subrouti
Click, Jr. Clifford N.
Paleczny Michael H.
Vick Christopher A.
Beyer Weaver & Thomas LLP
Morse Gregory
Sun Microsystems Inc
Vo Ted T.
LandOfFree
Method and apparatus for debugging optimized code does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for debugging optimized code, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for debugging optimized code will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3094233