International Business Machines Corporation

Mark Novick

William Jon Schmidt

Vita Bortnikov

Bilha Mendelson

Inbal Shavit-Lottem

Robert Ralph Roediger

An apparatus and method reorder portions of a computer program in a way that achieves both enhanced performance and maintainability of the computer program. A global call graph is initially constructed that includes profile data. From the information in the global call graph, an intramodular call graph is generated for each module. Reordering techniques are used to reorder the procedures in each module according to the profile data in each intramodular call graph. An intermodular call graph is generated from the information in the global call graph. Reordering techniques are used to reorder the modules in the computer program. By reordering procedures within modules, then reordering the modules, enhanced performance is achieved without reordering procedures across module boundaries. Respecting module boundaries enhances the maintainability of the computer program by allowing a module to be replaced without adversely affecting the other modules while still providing many of the advantages of global procedure reordering.

Method and apparatus for modular reordering of portions of a computer

An apparatus and several methods provide for a more optimized computer program that will have a faster execution time than was possible using the prior art reordering technique that adds to a trace until it finds no more predecessors or successors to add. The apparatus and methods disclosed herein use a variety of methods to reorder the program portions in a more intelligent manner that will improve its run-time performance. Each of these methods involves constructing traces in the control flow graph of the computer program. In a first embodiment, a basic block is only added to a trace if it is not negligible within predetermined limits. This negligibility test results in traces that are not extended for infrequently executed basic blocks. In a second embodiment, a basic block is only added to a trace if it is a perfect partner with the last basic block added to the trace. The concept of a 'perfect partner' helps to match basic blocks together in a trace that have the greatest affinity for each other. In a third embodiment, a basic block is only added to a trace if it satisfies 'should follow' flags and predetermined negligibility criteria. The 'should follow' flags and negligibility criteria provide a complex criteria for adding basic blocks to a trace, criteria that create more efficient code in some specific circumstances.

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Jerusalem, Israel

Mark Novick