Unisys Corporation

Stephen R Bartels

Craig F Russ

G Lawrence Krablin

Steven Clarke

An intermediate representation of sequences of instructions for a stacked based computer is a code graph using a numbering method on the nodes of the graph, along with a set of relations among the nodes, to determine, in a single pass, the independence of each node or sub-graph represented by the node. The numbering is a post-order that directly, by numerical comparison defines the relevant hierarchical relationships among sub-graphs. The sub-graph of a particular node may have one or more alias nodes that refers to target nodes, a target node being a node representing an argument which is the result of a previous program instruction. For a subgraph to be considered independent, any aliases generated by nodes within the subgraph must themselves be contained in it, and conversely, any aliases in the subgraph must have been generated by nodes also within it.

System and methods for determination of independence of sub-graphs in a graph-based intermediate representation of program instructions

A stack frame associated with a procedure that can alter or affect a shared resource where the procedure is associated with a child stack and is declared by a parent stack is marked isolated. Isolated stack frames are allotted an additional predefined interval of processing time before commands such as terminate and interrupt applied to the child stack are executed. If the command is a terminate command, after the additional allotted time interval has passed, both child and parent stacks are terminated. If the command is an interrupt command, after the additional allotted time interval has passed, the child stack is interrupted. If the command is a resource-terminated command, an operator is permitted to allocate more resource time to the task or may terminate both parent and child stacks. If a parent stack is terminated, all child stacks of the parent are terminated.

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West Chester, PA, United States of America

Stephen R Bartels