Abstract: A computer program consisting of a compiler for compiling source code programs into executable code. The compiler is suited to achieving high efficiency on a processor that can process many instructions at once but the instructions have dependency constraints and the processor has no internal mechanism for dealing with these constraints, such as the Itanium class of processors. As each instruction is considered for addition to a group of instructions for a single cycle, dependencies are checked to determine whether the entire group can be scheduled in any possible order. Once all the instructions of the group have been selected, the instructions are then reordered for placement in a reservation table. For implementation in the Itanium class of processors, detailed requirements of the processor are accommodated with a structure that can be adjusted for any processor in the class. The structure can also be adjusted for other classes of processors.

Abstract: Method and apparatus for managing access to registers that are outside a current register stack frame are disclosed. An instruction execution unit in a processor receives an instruction to be executed. A processor includes a register stack, the register stack including a plurality of register stack frames. Each of the register stack frames includes zero or more registers. One of the plurality of register stack frames is a current register stack frame. When execution of the instruction requires writing to a register referenced by the instruction, the instruction execution unit determines whether the register referenced by the instruction is within the current register stack frame. If the instruction execution unit determines that the register is not within the current register stack frame, the instruction execution unit does not execute the instruction and may, for example, generate a fault.

Abstract: Method and apparatus for managing access to registers that are outside a current register stack frame are disclosed. An instruction execution unit in a processor receives an instruction to be executed. A processor includes a register stack, the register stack including a plurality of register stack frames. Each of the register stack frames includes zero or more registers. One of the plurality of register stack frames is a current register stack frame. When execution of the instruction requires writing to a register referenced by the instruction, the instruction execution unit determines whether the register referenced by the instruction is within the current register stack frame. If the instruction execution unit determines that the register is not within the current register stack frame, the instruction execution unit does not execute the instruction and may, for example, generate a fault.

Abstract: Method and apparatus for switching between multiple implementations of a routine. A plurality of implementations of a routine are compiled into respective object code modules. In one embodiment, each implementation of the routine is adapted for a particular hardware configuration. The different object code modules are associated with respective sets of hardware characteristics and with the name of the routine. When the application program and library are loaded into memory of the computer system, a references to the routine are resolved using the sets of hardware characteristics and the hardware configuration of the system.

Abstract: Method and apparatus for verifying at runtime an invariant property of a data structure. In various example embodiments, code that verifies whether a runtime value of the data structure is consistent with the invariant property is automatically generated in response to an annotation of the data structure in the source code. In executing the program, the runtime value of the data structure is compared to the invariant property in the automatically generated code. If the runtime property is inconsistent with the invariant property, the program branches to exception handler code.

Abstract: A method of efficient code generation for modulo scheduled uncounted loops includes: assigning a given stage predicate to each instruction in each stage, including assigning a given stage predicate to each instruction in each speculative stage; and using the stage predicate to conditionally enable or disable the execution of an instruction during the prologue and epilogue execution.

Abstract: Method and apparatus for inserting prefetch instructions in an executable computer program. Profile data are generated for executed load instructions and store instructions. The profile data include instruction addresses, target addresses, data loaded and stored, and execution counts. From the profile data, recurring patterns of instructions resulting in cache-miss conditions are identified. Prefetch instructions are inserted prior to the instructions that result in cache-miss conditions for patterns of instructions recurring more than a selected frequency.

Abstract: A method and an apparatus that enable spare instruction slots within a code module to be utilized opportunistically for insertion of instructions associated with correctness check functions. The apparatus comprises a compiler that generates code and an initial instruction schedule. During generation of the initial instruction schedule, the compiler ignores code sequences associated with correctness check functions. After the initial instruction schedule has been generated, the compiler examines the initial instruction schedule and determines locations of spare instruction slots in the initial instruction schedule that can potentially be utilized for insertion of the code sequences associated with the correctness checks. The code sequences associated with the correctness checks are then inserted into the instruction schedule to the extent that insertion of the code sequences does not lengthen the final instruction schedule. Consequently, no performance penalty is incurred at run time.

Abstract: The present invention provides a method (FIG. 6) and an apparatus that enable spare instruction slots within a code module to be utilized opportunistically for insertion of instructions associated with correctness check functions. During the generation of the initial instruction schedule, the compiler examines the initial instruction schedule and determines locations of spare instruction slots that can potentially be utilized for insertion of the correctness check code sequences. If a sufficient number of spare instruction slots exist to accommodate the correctness check code sequences, the sequences are inserted into the instruction schedule. If an insufficient number of spare instruction slots exist to accommodate a code sequence, the compiler adds additional instruction slots if a sufficient number of additional instruction slots can be added for insertion of the check sequences without exceeding a run-time performance cost tolerance level designated by a user.

Abstract: Method and apparatus for resuming execution of a failed computer program. A program is compiled using two compilers to generate first and second sets of object code. Checkpoints are identified in the program, and checkpoint code is generated for execution at the checkpoints. If execution of the first set of object code fails, checkpoint data is recovered and execution of the program is resumed using either the first or second set of object code. In one embodiment, the first set of object code is re-executed before trying the second set of object code.

Abstract: A method for reducing cache memory misses in a computer that performs context switches between at least a first context and a second context. A First logic identifies a first prefetch region in a first memory element and a second logic identifies critical memory references within the first prefetch region during compilation of a computer program. The critical memory references within the first prefetch region correspond to data in cache memory if a context switch occurs from a process or thread associated with the second context to a process or thread associated with the first context during program execution. Third logic prefetches data associated with the identified critical memory references and stores the prefetched data in cache memory prior to a process or thread associated with the first context being resumed when a switch from the second context to the first context occurs during program execution.

Abstract: The present invention relates to a system and method for reducing the adverse impact of assertion instructions to processor performance so that programmers will be encouraged to include assertion instructions in computer programs. The system of the present invention includes memory and a compiler. The memory stores a first program to be compiled by the compiler. The compiler, in compiling the first program, translates a first function of the first program into a second function of a second program. The first function has assertion instructions that are translated by the compiler into translated assertion instructions, which are included in the second function. In compiling the first program, the compiler enables selective execution, based on a run time input, of a portion of the translated assertion instructions included in the second function.

Abstract: The system of the present invention utilizes memory for storing a computer program and processing circuitry for executing instructions of the computer program. In particular, the computer program includes at least one branch instruction and a set of code that is to be selectively enabled or disabled. The branch instruction includes an address identifier identifying a memory address to which the processing circuitry may branch when executing the branch instruction. The processing circuitry, in executing the computer program, receives run time data indicative of whether the set of code is enabled or disabled, and based on the run time data, the processing circuitry sets a value of a mode indicator. While the program is running, the processing circuitry executes the branch instruction. In executing the branch instruction, the processing circuitry, depending on the value of the mode indicator, branches to the address identified by address identifier or branches to a different address.

Abstract: Method and apparatus for managing access to registers that are outside a current register stack frame are disclosed. An instruction execution unit in a processor receives an instruction to be executed. A processor includes a register stack, the register stack including a plurality of register stack frames. Each of the register stack frames includes zero or more registers. One of the plurality of register stack frames is a current register stack frame. When execution of the instruction requires writing to a register referenced by the instruction, the instruction execution unit determines whether the register referenced by the instruction is within the current register stack frame. If the instruction execution unit determines that the register is not within the current register stack frame, the instruction execution unit does not execute the instruction and may, for example, generate a fault.

Abstract: Method and apparatus for managing access to registers that are outside a current register stack frame are disclosed. An instruction execution unit in a processor receives an instruction to be executed. A processor includes a register stack, the register stack including a plurality of register stack frames. Each of the register stack frames includes zero or more registers. One of the plurality of register stack frames is a current register stack frame. When execution of the instruction requires writing to a register referenced by the instruction, the instruction execution unit determines whether the register referenced by the instruction is within the current register stack frame. If the instruction execution unit determines that the register is not within the current register stack frame, the instruction execution unit does not execute the instruction and may, for example, generate a fault.

Abstract: Compiler-based checkpointing for error recovery. In various embodiments, a compiler is adapted to identify checkpoints in program code. Sets of data objects are associated with the checkpoints, and checkpoint code is generated by the compiler for execution at the checkpoints. The checkpoint code stores state information of the associated data objects for recovery if execution of the program is interrupted.

Abstract: The present invention relates to a system and method for reducing the adverse impact of assertion instructions to processor performance so that programmers will be encouraged to include assertion instructions in computer programs. The system of the present invention includes memory and a compiler. The memory stores a first program to be compiled by the compiler. The compiler, in compiling the first program, translates a first function of the first program into a second function of a second program. The first function has assertion instructions that are translated by the compiler into translated assertion instructions, which are included in the second function. In compiling the first program, the compiler enables selective execution, based on a run time input, of a portion of the translated assertion instructions included in the second function.

Abstract: Method and apparatus for creating alternative versions of code segments and dynamically substituting execution of the alternative code versions. Checkpoints in program code are identified by a compiler, and the checkpoints are used to delineate segments of object code. Two sets of segments of object code are generated, where the first and second sets of object code segments are optimized at different levels. In one embodiment, the first set of segments is optimized at a greater level than the second set of segments. Upon detecting a program error in executing the first set of segments, state information of the program is recovered from a checkpoint, and an object code module is selected from either the first set or second set for execution.

Abstract: A method of efficient code generation for modulo scheduled uncounted loops includes: assigning a given stage predicate to each instruction in each stage, including assigning a given stage predicate to each instruction in each speculative stage; and using the stage predicate to conditionally enable or disable the execution of an instruction during the prologue and epilogue execution.

Abstract: Method and apparatus for managing access to registers that are outside a current register stack frame are disclosed. An instruction execution unit in a processor receives an instruction to be executed. A processor includes a register stack, the register stack including a plurality of register stack frames. Each of the register stack frames includes zero or more registers. One of the plurality of register stack frames is a current register stack frame. When execution of the instruction requires writing to a register referenced by the instruction, the instruction execution unit determines whether the register referenced by the instruction is within the current register stack frame. If the instruction execution unit determines that the register is not within the current register stack frame, the instruction execution unit does not execute the instruction and may, for example, generate a fault.