Report Number: CSL-TR-79-170
Institution: Stanford University, Computer Systems Laboratory
Title: Interpretive architectures: a theory of ideal language machines
Author: Flynn, Michael J.
Author: Hoevel, Lee
Date: February 1979
Abstract: This paper is a study in ideal computer architectures or program representations. An ideal architecture can be defined with respect to the representation that was used to originally describe a program, i.e. the higher level language. Traditional machine architectures name operations and objects which are presumed to be present in the host machine: a memory space of certain size, ALU operations, etc. An ideal machine framed about a specific higher level language assumes operations present in that language and uses these operations to describe relationships between objects described in the source representation. The notion of ideal is carefully constrained. The object program representation must be easily decompilable, (i.e. the source is readily reconstructable). It is simply assumed that the source itself is a good representation for the original problem, thus any nonassignment operation present in the source program statement will appear as a single instruction (operation) in the ideal representation. All named objects are defined with respect to the natural scope of definition of the source program. For simplicity of discussion, statistical behavior of the program or the language is assumed to be unknown; that is, Huffman codes are not used. From the above, a canonic interpretive form (CIF) or measure of a higher level language program is developed. CIF measures both static space to represent the program and dynamic time measurements of the number of instructions to be interpreted and the number of memory references these instructions will require. The CIF or ideal program representation is then compared using the Whetstone benchmark in its characteristics to several contemporary architectural approaches; IBM 370 Honeywell Level 66, Burroughs S-Language Fortran and DELtran, a quasi-ideal Fortran architecture based on CIF principles.