To separately compile a program module in traditional statically-typed languages, one has to manually write down an import interface which explicitly specifies all the external symbols referenced in the module. Whenever the definitions of these external symbols are changed, the module has to be recompiled. In this paper, we present an algorithm which can automatically infer the "minimum" import interface for any module in languages based on the Damas-Milner type discipline (e.g., ML). By "minimum", we mean that the interface specifies a set of assumptions (for external symbols) that are just enough to make the module type-check and compile. By compiling each module using its "minimum" import interface, we get a separate compilation method that can achieve the following optimal property: A compilation unit never needs to be recompiled unless its own implementation changes.

This dissertation addresses a number of important issues related to interprocedural optimization. Interprocedural optimization is an integral component in a compilation system for high-performance computing. The importance of interprocedural optimization stems from two sources: it increases the context available to the optimizing compiler, and it enables programmers to use procedure calls without the concern of hurting execution time. While important, interprocedural optimization can introduce some significant compile-time costs. When interprocedural information is used to optimize a procedure, the procedure is then dependent on those interprocedural facts. Thus, even if the procedure is not edited, it may require recompilation due to changes in the interprocedural facts. In addition to these effects on recompilation, interprocedural information can also be expensive to compute. Furthermore, interprocedural optimizations can increase program size which can in turn increase compile tim...

We present a formulation of interconnection models and present the unit and syntactic models --- the primary models used for managing the evolution of large software systems. We discuss various tools that use these models and evaluate how well these models support the management of system evolution. We then introduce the semantic interconnection model. The semantic interconnection model incorporates the advantages of the unit and syntactic interconnection models and provides extremely useful extensions to them. By refining the grain of interconnections to the level of semantics (that is, to the predicates that define aspects of behavior) we provide tools that are better suited to manage the details of evolution in software systems and that provide a better understanding of the implications of changes. We do this by using the semantic interconnection model to formalize the semantics of program construction, the semantics of changes, and the semantics of version equivalence and compatibi...

This paper describes a semantic basis for a compositional approach to the analysis of logic programs. A logic program is viewed as consisting of a set of modules, each module defining a subset of the program's predicates. Analyses are constructed by considering abstract interpretations of a compositional semantics. The abstract meaning of a module corresponds to its analysis and composition of abstract meanings corresponds to composition of analyses. Such an approach is essential for large program development so that altering one module does not require re-analysis of the entire program. A compositional analysis for ground dependencies is included to illustrate the approach. To the best of our knowledge this is the first account of a compositional framework for the analysis of (logic) programs. 1 Introduction It is widely acknowledged that as the size of a program increases, it becomes impractical to maintain it as a single monolithic structure. Instead, the program has to be...

A technique for representing programs abstractly and independently of the eventual target architecture is presented that yields a file representation twice as compact as machine code for a CISC processor. It forms the basis of an implementation, in which the process of code generation is deferred until the time of loading. At that point, native code is created on_the_fly by a code_generating loader. The process of loading with dynamic code_generation is so fast that it requires little more time than the input of equivalent native code from a disk storage medium. This is predominantly due to the compactness of the abstract program representation, which allows to counterbalance the ad...

While efficient new algorithms for interprocedural data-flow analysis have made these techniques practical for use in production compilation systems,a new problem has arisen: collecting and using interprocedural information in a compiler introduces subtle dependence among the proceduresof a program. If the compiler dependson interprocedural information to optimize a given module, a subsequentediting changeto another module in the program may changethe interprocedural information and necessitaterecompilation. To avoid having to recompile every module in a program in responseto a single editing changeto one module, we have developed techniquesto more precisely determine which compilations have actually beeninvalidated by a changeto the program’s source.This paper presents a general recoi-npzlatton test to determine which proceduresmust be compiled in responseto a series of editing changes.Three different implementation strategies, which demonstrate the fundamental tradeoff between the cost of analysis and the precision of the resulting test, are also discussed.

We present a new approach to the control of versions of software and other hierarchically structured entities. Any part of a system, from the smallest component to a complete system, may exist in different versions. The set of all possible versions under the refinement relation forms a partial order (in fact, a lattice). The fact that version V approximates version V in this order means that V is relevant to V in this sense: when constructing version V of a system, we can sometimes use version V of a component if nothing more appropriate is available. More precisely, a particular version of an entire system is formed by combining the most relevant existing versions of the various components of the system. We call this the variant structure principle; it makes precise the idea that components of a given version of the system can be inherited by more refined versions of the system.

This chapter surveys extended transaction models proposed to support long duration, interactive and/or cooperative activities in the context of multi-user software development and CAD/CAM environments. Many of these are variants of the checkout model, which addresses the long duration and interactive nature of the activities supported by environments but still isolates environment users, making it difficult for them to collaborate while their activities are in progress. However, a few cooperative transaction models have been proposed to facilitate collaboration, usually while maintaining some guarantees of consistency.

Compilers and other programming environment tools derive information from the source code of programs; derived information includes compiled code, interprocedural summary information, and call graph views. If the source program changes, the derived information needs to be updated. We present a simple framework for maintaining intermodule dependencies, embodying different tradeoffs in terms of space usage, speed of processing, and selectivity of invalidation, that eases the implementation of incremental update of derived information. Our framework augments a directed acyclic graph representation of dependencies with factoring nodes (to save space) and filtering nodes (to increase selectivity), and it includes an algorithm for efficient invalidation processing. We show how several schemes for selective recompilation, such as smart recompilation, filter sets for interprocedural summary information, and dependencies for whole-program optimization of object-oriented languages, map naturally...

We introduce and compare two models of cooperation among programmers during software maintenance. Enforced cooperation is the normal mode of operation when the sheer size of the software maintenance effort makes laissez-faire management infeasible. Voluntary cooperation is more common when a small group works together to enhance a small system or modify a small portion of a large system. We describe a tool, Infuse, that provides change management in the context of both models of cooperation. We demonstrate how Infuse automates change propagation and enforces negotiation of conflicts for the enforced model, but provides less restrictive aids for maintaining consistency for the voluntary model. _______________ * Supported in part by a grant from the AT&T Foundation, in part by a grant from Siemens Research and Technology Laboratories, and in part by a Faculty Award from Digital Equipment Corporation. 1. Introduction The maintenance and evolution of large systems requires cooperation a...