Method of procedure control descriptor-based code specialization for context sensitive memory disambiguation

A computer program product comprising:

• a computer usable medium having computer usable program code for specializing code, the computer program product including:
• computer usable program code for identifying at least one code region having a code specialization opportunity, wherein a code specialization opportunity occurs when the at least one code region contains corresponding candidate code that can be disambiguated during compile time;
• computer usable program code for performing an alias analysis to select at least one procedure, wherein the at least one procedure contains the candidate code;
• computer usable program code for associating at least one procedure control descriptor with corresponding ones of the at least one code regions, wherein a corresponding procedure control descriptor has a corresponding flag parameter of a corresponding flag, wherein the corresponding flag parameter identifies that a corresponding code region contains corresponding candidate code;
• and
• computer usable program code for performing specialization, at compile time, of selected ones of the at least one code regions having the code specialization opportunity.

A computer program product comprising:

• a computer usable medium having computer usable program code for specializing code, the computer program product including:
• computer usable program code for gathering intra-procedural information during a forward pass compilation of the code;
• computer usable program code for traversing a call graph of the code in reverse depth-first order;
• computer usable program code for, for each procedure of code, creating a corresponding procedure control descriptor for the corresponding candidate procedure, wherein at least one candidate procedure is a part of at least one code region;
• computer usable program code for performing an intra-procedural alias analysis for all pointer variables referenced in the corresponding candidate procedure;
• computer usable program code for collecting alias relationships for each at least one candidate procedure;
• computer usable program code for analyzing the alias relationships for arguments of pointer types, wherein analyzing is performed at the end of the forward pass compilation when all nodes in the call graph have been traversed;
• computer usable program code for refining corresponding aliases for all pointer variables for the code;
• computer usable program code for computing the alias relationships for arguments of pointer type at all call sites for all procedures, wherein, for each procedure, all predecessor edges of a corresponding procedure node are traversed;
• computer usable program code for constructing a corresponding bit vector to describe the alias relationships for each corresponding call edge of the call graph, if the corresponding call edge is from a defined procedure;
• computer usable program code for examining sets of formal parameters in the corresponding procedure control descriptor;
• computer usable program code for, for each set of formal parameters in the corresponding procedure control descriptor, computing the alias relationships for the arguments, and recording a corresponding bit value in the corresponding bit vector;
• computer usable program code for, responsive to all the arguments in a given set being determined as not aliasing each other, recording a first bit value for the given set, otherwise, recording a second bit value in the given set;
• computer usable program code for, responsive to the corresponding bit vectors for at least two of the predecessor edges from the defined procedures being different, and responsive to an existence of a predecessor edge from an undefined procedure, cloning each corresponding procedure to form a corresponding cloned procedure;
• computer usable program code for replacing a corresponding call site by calling the corresponding cloned procedure, copying the corresponding procedure control descriptor from the corresponding cloned procedure, and updating the call graph by moving all call edges from the defined procedure as predecessors of the corresponding cloned procedure;
• computer usable program code for, responsive to alias bit vectors for at least two predecessor edges from the defined procedure being different, and responsive to at least two predecessor edges of the corresponding procedure all being from defined procedures, selecting a corresponding procedure as a candidate procedure for interface change and code versioning;
• computer usable program code for modifying the code during a backward pass by traversing the call graph in a depth-first order and, for each defined procedure, modifying all the call sites with new interfaces using a procedure interface descriptor;
• computer usable program code for modifying a corresponding call interface for the at least one candidate procedure by, responsive to the at least one candidate procedure being a candidate for interface change and code versioning, creating a new formal parameter;
• computer usable program code for creating an extra formal parameter for at least one candidate procedure, wherein a corresponding symbol identifying the new formal parameter is created;
• computer usable program code for building a corresponding procedure interface descriptor for the at least one candidate procedure;
• computer usable program code for recording an interface change in the corresponding procedure interface descriptor, wherein a corresponding entry in the corresponding procedure interface descriptor is added for the new formal parameter, wherein the corresponding entry contains the corresponding symbol and a type of the formal parameter;
• computer usable program code for modifying the corresponding call interface with the new formal parameter;
• computer usable program code for updating the corresponding procedure control descriptor with the corresponding symbol;
• computer usable program code for, for each set of formal parameters in the corresponding procedure control descriptor, responsive to alias bit vectors for at least two predecessor edges from the defined procedure being different, updating an attribute field with the corresponding symbol of the new formal parameter;
• computer usable program code for, for each set of formal parameters in the corresponding procedure control descriptor, responsive to all alias bit vectors of the defined procedure being the same, indicating uniform alias relationships for the set of the formal parameters and propagating the uniform alias relationships to the at least one candidate procedure;
• computer usable program code for versioning the at least one code region using a corresponding procedure control descriptor condition based on the corresponding procedure control descriptor;
• computer usable program code for creating, for each corresponding procedure control descriptor condition, at least one new corresponding symbol having more precise aliasing information;
• and
• computer usable program code for replacing the corresponding symbols with the at least one new corresponding symbol.

A computer implemented method for specializing code, the method comprising:

• identifying at least one code region having a code specialization opportunity, wherein a code specialization opportunity occurs when the at least one code region contains corresponding candidate code that can be disambiguated during compile time;
• performing an alias analysis to select at least one procedure, wherein the at least one procedure contains the candidate code;
• associating at least one procedure control descriptor with corresponding ones of the at least one code regions, wherein a corresponding procedure control descriptor has a corresponding flag parameter of a corresponding flag, wherein the corresponding flag parameter identifies that a corresponding code region contains corresponding candidate code;
• performing specialization, at compile time, of selected ones of the at least one code regions having the code specialization opportunity, wherein specialized code regions are formed;
• and
• storing at least the specialized code regions in a memory.

A data processing system comprising:

• a bus;
• at least one processor coupled to the bus;
• a computer usable medium coupled to the bus, wherein the computer usable medium contains a set of instructions for specializing code, wherein the at least one processor is adapted to carry out the set of instructions to:
• identify at least one code region having a code specialization opportunity, wherein a code specialization opportunity occurs when the at least one code region contains corresponding candidate code that can be disambiguated during compile time;
• perform an alias analysis to select at least one procedure, wherein the at least one procedure contains the candidate code;
• associate at least one procedure control descriptor with corresponding ones of the at least one code regions, wherein a corresponding procedure control descriptor has a corresponding flag parameter of a corresponding flag, wherein the corresponding flag parameter identifies that a corresponding code region contains corresponding candidate code;
• and
• perform specialization, at compile time, of selected ones of the at least one code regions having the code specialization opportunity.