R-Code a Very Capable Virtual Computer

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R-Code a Very Capable Virtual Computer

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Title: R-Code a Very Capable Virtual Computer
Author: Walton, Robert L.
Citation: Walton, Robert Lee. 1995. R-Code a Very Capable Virtual Computer. Harvard Computer Science Group Technical Report TR-37-95.
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Abstract: This thesis investigates the design of a machine independent virtual computer, the R-CODE computer, for use as a target by high level language compilers. Unlike previous machine independent targets, R-CODE provides higher level capabilities, such as a garbage collecting memory manager, tagged data, type maps, array descriptors, register dataflow semantics, and a shared object memory. Emphasis is on trying to find universal versions of these high level features to promote interoperability of future programming languages and to suggest a migration path for future hardware. The memory manager design combines both automatic garbage detection and an explicit "manual" delete operation. It permits objects to be copied at any time, to compact memory or expand objects. It traps obsolete addresses and instantly forwards copied objects using a software cache of an object map. It uses an optimized write-barrier, and is better suited for real-time than a standard copying collector. R-CODE investigates the design of type maps that extend the virtual function tables of C++ and similar tables of HASKELL, EIFFEL, and SATHER 0.6. R-CODE proposes to include numeric types and sizes in type maps, and to inline information from type maps by using dynamic case statements, which switch on a type map identifier. When confronted with a type map not seen before, a dynamic case statement compiles a new case of itself to handle the new type. R-CODE also investigates using IEEE and making array descriptors R-CODE uses a new "register dataflow" execution flow model to better watch the coming generation of superscalar processors. Functional dataflow is used for operations on register values, and memory operations are treated as unordered I/O. Barriers are introduced to sequence groups of unordered memory operations. A detailed semantic execution flow model is presented. R-CODE includes a shared object memory design to support multi-threaded programming within a building where network shared object memory reads and writes take several thousand instruction-execution-times to complete. The design runs on existing symmetric processors, but requires special caches to run on future within-building systems.
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Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:26506458
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