Hewlett-packard Company

Veritas Operating Corporation

Symantec Operating Corporation

Incert Software Corporation

Andrew E Ayers

Anant Agarwal

Richard Schooler

Christopher D Metcalf

Jiyang Liu

Emmett Witchel

Chun C Gong

Robert Gottlieb

Vineet Soni

A computer method for issuing an early warning includes determining, using change and test coverage and control flow and data flow analyses of a program, locations in the program at which to insert early warning (EW) code to monitor for an event. The program is instrumented with EW code which monitors for the event, by inserting EW code at the determined locations. Upon detecting the event, EW code performs an early action warning, or issues an early action. Early warnings are issued when an EW-instrumented block is reached. Issuance of an early warning action can be conditional upon execution of the program in a particular environment, such as a production environment. Issuance of an EW can also be conditional upon executing an untested block of code that was recently modified.

Early warning mechanism for enhancing enterprise availability

A program execution data trace is created by instrumenting a program to record value sets during execution and an instruction trace. By simulating instructions either backward or forward from a first instruction associated with a recorded value set to a second instruction according to the instruction trace, a value set is determined for the second instruction. Backward and forward simulation can be combined to complement each other. For backward simulation, a table of simulation instructions is preferably maintained, which associates program instructions encountered in the instruction trace with simulation instructions which reverse the operation of the associated program instructions. Preferably, one or more probes is inserted into the program to save values of particular variables whose value may be difficult to determine. Preferably, the instruction trace is displayed alongside and correlated with the data trace.

Method for simulating back program execution from a traceback sequence

A method for determining changed code in a second program binary relative to a first or baseline program binary, where the second program is a different version of the first program, includes translating, responsive to symbol tables and/or control flow representations, machine addresses of both program binaries to symbols. The first and second program binaries are disassembled using the translated symbols. Differences between the two resulting disassemblies are determined, and a list of the differences is created. Differences between the program binaries can be determined by textually comparing the disassemblies, or alternatively, by determining the differences between the control flow representations of the programs. The list of differences can be presented to a user, or alternatively, can be passed to another process for further processing, such as test coverage analysis, code change analysis, or failure analysis, among other analyses.

Method for determining the degree to which changed code has been exercised

A program execution data trace is created by instrumenting a program to record value sets during execution and an instruction trace. By simulating instructions either backward or forward from a first instruction associated with a recorded value set to a second instruction according to the instruction trace, a value set is determined for the second instruction. Backward and forward simulation can be combined to complement each other. For backward simulation, a table of simulation instructions is preferably maintained, which associates program instructions encountered in the instruction trace with simulation instructions which reverse the operation of the of the associated program instructions. Preferably, one or more probes is inserted into the program to save values of particular variables whose value may be difficult to determine. Preferably, the instruction trace is displayed alongside and correlated with the data trace. In one embodiment, the instruction trace is displayed and a value set is determined for an instruction upon a request by the user indicating the instruction for which the value set is desired.

A method for determining changed code in a second program binary relative to a first or baseline program binary, where the second program is a different version of the first program, includes translating, responsive to symbol tables and/or control flow representations, machine addresses of both program binaries to symbols. The first and second program binaries are disassembled using the translated symbols. Differences between the two resulting disassemblies are determined, and a list of the differences is created. Differences between the program binaries can be determined by textually comparing the disassemblies, or alternatively, by determining the differences between the control flow representations of the programs. The list of differences can be presented to a user, or alternatively, can be passed to another process for further processing, such as test coverage analysis, code change analysis, or failure analysis, among other analyses. Analyzing changed code coverage includes marking code in the second program which is changed or different from the first program. The second program is then executed in a test environment, and code which is executed is marked as having been executed. Next, the second program is executed in a non-test environment, such as a production environment, and code which is executed in this second environment is marked accordingly. Finally, from the variously marked code, a list of changed code which have not executed in the test environment but have executed in the non-test environment is provided.

A computer method for issuing an early warning includes determining, using change and test coverage and control flow and data flow analyses of a program, locations in the program at which to insert early warning (EW) code to monitor for an event. The program is instrumented with EW code which monitors for the event, by inserting EW code at the determined locations. Upon detecting the event, EW code performs an early action warning, or issues an early action. Early warnings are issued when an EW-instrumented block is reached. Issuance of an early warning action can be conditional upon execution of the program in a particular environment, such as a production environment. Issuance of an EW can also be conditional upon executing an untested block of code that was recently modified. The issuing of an early warning can include sending an email, writing into a log file, sending a message to a console, where the message causes the change of a human-perceptible characteristic, placing the program into a wait state, halting the program, sending an alarm to an operator, or triggering a failover. In some embodiments, EW code can be deactivated upon certain conditions. Issuance of an early warning can also occur upon an event such as the execution of a user-inserted assert or warning statement, or before a file is opened, wherein the EW issues if a null pointer about to be passed to a system function. In some embodiments, an EW will issue if the value of an argument to some function exceeds a predetermined range. In various embodiments, the EW code is placed in a loop, and issues an EW if the loop is executed more than a predetermined number of times, or the EW code issues an EW upon the execution of user-marked code, or the EW code issues an EW when the time duration between execution of two points in the program exceeds a predetermined value, or upon the detection of an untested configuration.

A method of back-tracing execution of a computer program, where the computer program comprises a plurality of blocks, comprises instrumenting an original version of the program by adding instrumentation code to some or all of the blocks to form an instrumented program. Instrumentation can be added at the binary or source level, or at link time. The instrumentation code records execution sequence information upon execution of the corresponding instrumented block to create a trace record of the executed program. The execution sequence information for each block comprises a block identifier which identifies the corresponding block. A detailed back-trace is generated, after the program has executed, by replacing each recorded block identifier with program counters associated with each instruction in the corresponding block. The application may comprise several programs or subprograms, in which case separate regions of memory can be maintained. Each region is associated with a program or subprogram or a set of programs or subprograms and stores therein part of the trace record corresponding to the associated set of programs or subprograms. The trace records themselves may be of different types. After execution, the trace record is presented to a user, in the form of assembly code, or more preferably, in the form of source level code. In an alternative embodiment, a summary of the trace record recorded during execution of an instrumented program is presented to a user. Various types of traces can be produced, including a last instruction trace and a first instruction trace.

Method for back tracing program execution

A compile method employs loop fusion to improve execution of a first loop and a second loop in a code sequence. A compile method initially peels one or more loop iterations from one of the loops to cause each of the loops to exhibit an equal number of loop iterations. Thereafter, an attempt is made to fuse the first and second loops, upon a condition that the resulting fused loop produces a same computational result as would be produced if the first loop and second loop were not fused. If the condition is not met, a loop reversal is performed on one of the loops and a fusing action is again attempted; if the attempted fusing action of the loops does not fulfill the condition, a loop reversal is performed on the other loop and a fusing action is again attempted. The combined loop peeling/loop reversal actions provide a higher probability of an ability to fuse the loops than otherwise.

Compiler for performing a loop fusion, dependent upon loop peeling

A compiler method analyzes a program listing to identify a first set of subroutines therein, each of which accepts a variable number of arguments, converting the first set of subroutines into further sets of subroutines which accept fixed numbers of arguments. The method includes the steps of: locating subroutines in the program listing which accept a variable number of arguments and identifying which thereof comprise a first set of subroutines that can be altered to a form which accepts a fixed number of arguments; for each subroutine identified as part of the first set, determining call sites which pass arguments to each subroutine and determining a number and kind of said arguments to be passed therefrom; partitioning call sites to each subroutine of the first set into one or more groups, each group comprising call sites which pass an identical number and kind of arguments to an associated subroutine of said first set; duplicating each subroutine of said first set into plural second sets of N corresponding subroutines, wherein N is equal to the number of groups associated with the subroutine of the first set, and revising each one of said N corresponding subroutines to receive a number of fixed arguments to be passed by call sites partitioned into an associated group; and substituting in the program listing the N corresponding subroutines and revising call sites in each group to refer to an associated one of said N corresponding subroutines.

Method for conversion of a variable argument routine to a fixed argument

The procedure of the invention eliminates redundant conditional branch statements (CBSs) from a program, wherein the program includes (i) plural blocks of program statements, (ii) a definition statement (DEF) for each variable in the program that assigns a value to each variable, (iii) a defining point (DEFP) which is a first point in the program that a value is calculated, and (iv) plural CBSs. Each CBS transfers control to one of two target blocks of program statements, dependent upon an operation code and controlling variable that form a part of the test associated with the CBS. The procedure associates all DEFs which define a same value, with a DEFP for the same value and determines (i) a controlling variable upon which a test CBS is dependent, (ii) a DEF of the controlling variable of the test CBS and (iii) a DEFP for the DEF of the controlling variable. If a value first calculated at the DEFP found in (iii) is utilized by a CBS, the procedure finds which arm of the CBS reaches the test CBS; and then revises a block of program statements that include the test CBS, to eliminate at least a test required by the test CBS, and replace the conditional branch with an unconditional branch.

Method and apparatus for elimination of redundant branch instructions

A compiler method converts an indirect call to a callee routine in a caller routine program listing, to an in-line listing of, or a direct call to, the callee routine in the caller routine. An indirect call is a call to a callee routine wherein the callee routine is not absolutely identified until run time of the program listing. The method includes the steps of: comparing plural prospective callee routines in the program listing with characteristics of an indirect caller site in the caller routine and eliminating prospective callee routines which evidence other than a match with those characteristics; employing call statistics associated with remaining prospective callee routines (and the caller routine) to eliminate further ones of the prospective callee routines to arrive at a set of one or more chosen prospective callee routines. The method concludes by in-lining at the indirect caller site at least one of the set of chosen prospective callee routines. As an alternative, a direct call can be inserted. At run time, the program listing is executed and, in the process of execution, the callee routine is absolutely identified. If the identified callee routine has already been in-lined (or there is a direct call present), it is executed and the program continues. If the identified callee routine is not present in the caller's code listing, via either an in-line listing or a direct call, an indirect call is executed to the identified callee routine.

Growing community of inventors

Amherst, NH, United States of America

Andrew E Ayers