Abstract: A profiling implementation method for reducing overhead while an application is running with profiling instrumentation inserted but disabled; the method for gathering precise profiling data for a subset of observed values at runtime start; generating an index for each observed value; populating one or more data structures within a hash table with the subset of observed values to count; comparing a corresponding key at the index value of an observed value index; evaluating a value limit of the hash table; incrementing a matched key counter; incrementing an alt-counter; locking the hash table; and updating one or more data structures of the hash table.

Abstract: An approach is provided for optimizing reference counting. Responsive to receiving code representing a program by a just-in-time compiler, one or more processors in computing machinery supporting transactional memory identify regions of the code having respective sets of reference counting operations executed dynamically. Identifying the regions of the code uses an analysis of semantics of the code. The identified regions are enclosed in respective transactions. The code that was to perform atomic operations, including the reference counting operations in the identified regions, is transformed into new code that performs non-atomic operations that are variants of the atomic operations. Fallback code sequences are inserted into the transformed code. In a non-transactional manner and in response to detections of failures in respective transactions, the fallback code sequences execute original code sequences that were in the code prior to the transformation of the code.

Abstract: An approach is provided for optimizing reference counting. Responsive to receiving code representing a program by a just-in-time compiler, one or more processors in computing machinery supporting transactional memory identify regions of the code having respective sets of reference counting operations executed dynamically. Identifying the regions of the code uses an analysis of semantics of the code. The identified regions are enclosed in respective transactions. The code that was to perform atomic operations, including the reference counting operations in the identified regions, is transformed into new code that performs non-atomic operations that are variants of the atomic operations. Fallback code sequences are inserted into the transformed code. In a non-transactional manner and in response to detections of failures in respective transactions, the fallback code sequences execute original code sequences that were in the code prior to the transformation of the code.

Abstract: A profiling implementation method for reducing overhead while an application is running with profiling instrumentation inserted but disabled; the method for gathering precise profiling data for a subset of observed values at runtime start; generating an index for each observed value; populating one or more data structures within a hash table with the subset of observed values to count; comparing a corresponding key at the index value of an observed value index; evaluating a value limit of the hash table; incrementing a matched key counter; incrementing an alt-counter; locking the hash table; and updating one or more data structures of the hash table.

Abstract: A method and system for partial connection of iterations during loop unrolling during compilation of a program by a compiler. Unrolled loop iterations of a loop in the program are selectively connected during loop unrolling during the compilation, including redirecting, to the head of the loop, undesirable edges of a control flow from one iteration to a next iteration of the loop. Merges on a path of hot code are removed to increase a scope for optimization of the program. The head of the loop and a start of a replicated loop body of the loop are equivalent points of the control flow.

Abstract: A profiling implementation method for reducing overhead while an application is running with profiling instrumentation inserted but disabled; the method for gathering precise profiling data for a subset of observed values at runtime start; generating an index for each observed value; populating one or more data structures within a hash table with the subset of observed values to count; comparing a corresponding key at the index value of an observed value index; evaluating a value limit of the hash table; incrementing a matched key counter; incrementing an alt-counter; locking the hash table; and updating one or more data structures of the hash table.

Abstract: A profiling implementation method for reducing overhead while an application is running with profiling instrumentation inserted but disabled; the method for gathering precise profiling data for a subset of observed values at runtime start; generating an index for each observed value; populating one or more data structures within a hash table with the subset of observed values to count; comparing a corresponding key at the index value of an observed value index; evaluating a value limit of the hash table; incrementing a matched key counter; incrementing an alt-counter; locking the hash table; and updating one or more data structures of the hash table.

Abstract: A method and system for enhanced local communing optimization of compilation of a program. Within a first pass of a two pass approach, a determination is made as to where in the program to evaluate volatile expressions that can be commoned. In a second pass of the two pass approach, all remaining expressions that are not volatile expressions are commoned.

Abstract: A method and system for partial connection of iterations during loop unrolling during compilation of a program by a compiler. Unrolled loop iterations of a loop in the program are selectively connected during loop unrolling during the compilation, including redirecting, to the head of the loop, undesirable edges of a control flow from one iteration to a next iteration of the loop. Merges on a path of hot code are removed to increase a scope for optimization of the program. The head of the loop and a start of a replicated loop body of the loop are equivalent points of the control flow.

Abstract: A method and system for partial connection of iterations during loop unrolling during compilation of a program by a compiler. Unrolled loop iterations of a loop in the program are selectively connected, including redirecting, to the head of the loop, undesirable edges of a control flow from one iteration to a next iteration of the loop. Merges on a path of hot code are removed to increase a scope for optimization of the program. The head of the loop and a start of a replicated loop body of the loop are equivalent points of the control flow. A sequence of blocks on the path of hot code, unpolluted by a control flow of a path of cold code, is extended during the compilation. Information computed by an optimizer about the hot code in a first iteration is used to further optimize a second iteration, and the loop is further unrolled.

Abstract: A method for expanding inline function calls in inlining scenarios includes receiving an ordered list of inlining options for a computer program and a relational data structure representing dependencies between the inlining options, wherein each inlining option includes an associated cost value and an associated benefit value. A maximum-benefit inlining plan for a selected inlining option of the ordered list is then determined, wherein the maximum-benefit inlining plan includes a set of inlining options from the ordered list that provide a maximum combined benefit value for a combined cost value that is equal to or less than a maximum cost budget, subject to the following conditions: each inlining option of the set precedes, or is, the selected inlining option in the ordered list, and for each inlining option of the set, the set also includes each inlining option that the respective inlining option is dependent on.

Abstract: Multi-byte compressed string representation embodiments define a String class control field identifying compression as enabled/disabled, and another control field, identifying a decompressed string created when compression enabled. Tests are noped based on null setting of the compression flag. When arguments to a String class constructor are not compressible, a decompressed String is created and stringCompressionFlag initialized. Endian-aware helper methods for reading/writing byte and character values are defined. Enhanced String class constructors, when characters are not compressible, create a decompressed String, and initialize stringCompressionFlag triggering class load assumptions, overwriting all nopable patch points. A String object sign bit is set to one for decompressed strings when compression enabled, and masking/testing this flag bit is noped. Alternative package protected string constructors and operations are provided.

Abstract: A method and system for enhanced local communing optimization of compilation of a program. Within a first pass of a two pass approach, a determination is made as to where in the program to evaluate volatile expressions that can be commoned. In a second pass of the two pass approach, all remaining expressions that are not volatile expressions are commoned.

Abstract: A method and system for enhanced local commoning optimization of compilation of a program. Commoning of volatiles within an extended block for a particular memory model associated with a particular programming language is performed, using a two pass approach. Within a first pass, a determination is made as to where in the program to evaluate volatile expressions that can be commoned. In a second pass, all remaining expressions that are not volatile expressions are commoned.

Abstract: A method and system for enhanced local commoning optimization of compilation of a program. Commoning of volatiles within an extended block for a particular memory model associated with a particular programming language is performed, using a two pass approach. Within a first pass, a determination is made as to where in the program to evaluate volatile expressions that can be commoned. In a second pass, all remaining expressions that are not volatile expressions are commoned.

Abstract: A method and system for partial connection of iterations during loop unrolling during compilation of a program by a compiler. Unrolled loop iterations of a loop in the program are selectively connected, including redirecting, to the head of the loop, undesirable edges of a control flow from one iteration to a next iteration of the loop. Merges on a path of hot code are removed to increase a scope for optimization of the program. The head of the loop and a start of a replicated loop body of the loop are equivalent points of the control flow. A sequence of blocks on the path of hot code, unpolluted by a control flow of a path of cold code, is extended during the compilation. Information computed by an optimizer about the hot code in a first iteration is used to further optimize a second iteration, and the loop is further unrolled.

Abstract: Multi-byte compressed string representation embodiments define a String class control field identifying compression as enabled/disabled, and another control field, identifying a decompressed string created when compression enabled. On pattern matching by a compiler, noping tests based on null setting of stringCompressionFlag and registering a class loading assumption on a nop location. When arguments to a String class constructor are not compressible, a decompressed String is created and stringCompressionFlag initialized. Endian-aware helper methods for reading/writing byte and character values and helper methods for widening, narrowing, truncation, conversion and masking are defined. Enhanced String class constructors, when characters are not compressible, create a decompressed String, and initialize stringCompressionFlag triggering class load assumptions, overwriting all nopable patch points.

Abstract: A method for expanding inline function calls in inlining scenarios includes receiving an ordered list of inlining options for a computer program and a relational data structure representing dependencies between the inlining options, wherein each inlining option includes an associated cost value and an associated benefit value. A maximum-benefit inlining plan for a selected inlining option of the ordered list is then determined, wherein the maximum-benefit inlining plan includes a set of inlining options from the ordered list that provide a maximum combined benefit value for a combined cost value that is equal to or less than a maximum cost budget, subject to the following conditions: each inlining option of the set precedes, or is, the selected inlining option in the ordered list, and for each inlining option of the set, the set also includes each inlining option that the respective inlining option is dependent on.

Abstract: A method for expanding inline function calls in inlining scenarios includes receiving an ordered list of inlining options for a computer program and a relational data structure representing dependencies between the inlining options, wherein each inlining option includes an associated cost value and an associated benefit value. A maximum-benefit inlining plan for a selected inlining option of the ordered list is then determined, wherein the maximum-benefit inlining plan includes a set of inlining options from the ordered list that provide a maximum combined benefit value for a combined cost value that is equal to or less than a maximum cost budget, subject to the following conditions: each inlining option of the set precedes, or is, the selected inlining option in the ordered list, and for each inlining option of the set, the set also includes each inlining option that the respective inlining option is dependent on.