Abstract: A method determines if a revised fragment of a program provides an identical answer as does an original fragment of the program, wherein a fragment is one operator and one or more operands that are subject to processing by the operator. The method comprises the steps of: executing both an original fragment of the program and one or more revised fragment(s) which correspond to the original fragment, using first equvalent variables and determining if both fragments produce equivalent results; executing both the revised fragment(s) and the original fragment of the program using additional variables to determine if both fragments produce equivalent results under all test conditions; if the results are not equivalent, making a notation of that fact for later examination; and if the fragments are equivalent, repeating the aforementioned test steps until all revised code fragments have been tested.

Abstract: A process for transforming source code into efficient shared library executable code in which global offset table address values are computed only when needed by a function. A condition register and current global offset table address register are added to the code by the compiler. The condition register controls recalculation of the global offset table address. The current global offset table register is saved and the condition register is invalidated by the calling function prior to branching to the new function. The new function calculates the global offset address value only if it is needed. The intermediate code generated by the compiler includes specific routines to process local function calls, function calls by pointer, and external function calls. The system efficiency is improved whenever the actual global offset table access is infrequent compared to function calls across module boundaries.

Abstract: A method and apparatus allows a compiler to optimize code in the presence of exception handlers. According to a first embodiment, arcs are added to a control flow graph, prior to performing global optimizations, to account for exception handling code. According to the second embodiment, information relating to control flow to exception handlers is provided in pseudo-references in the code, which allows the compiler to determine how to appropriately optimize the code.

Abstract: A system and method for resolving external references in single address space operating systems using client context based external reference resolution. The source code of a shared library module is analyzed during compilation and external references (exported variables and functions) identified. The compiler adds code to resolve the external reference based on a Global Offset Table (GOT) for each client instance of that library. The client instance maintains a global context area address register (GCR) that is combined with a library module offset value to define a real address in the single address space. Only the offset resolution code is fixed by the loader at load-time. The remaining module code is unchanged by the loader. The loader constructs a global context area for each client process as it is loaded and loads the address of that area into the Global Context Register for that process.

Abstract: A method and apparatus for coloring an interference graph yields a higher number of colored nodes by taking into consideration the colors of neighbors of a node's uncolored constrained neighbors. By assigning a color to a node that is also the color of a neighbor of an uncolored constrained neighbor, one color constraint is removed, increasing the probability of coloring the uncolored constrained neighbor. If more than one of the neighbors of the uncolored constrained neighbors are colored, one of the colors may be selected over the others using an appropriate heuristic.