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...

This paper describes the structure of the compiler, summarizes the experience gained in adapting it for various CISC and RISC processors, and presents some empirical performance data. It also sheds light on the task of grafting an operating environment onto a variety of existing operating systems

. A machine_independent abstract program representation is presented that is 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. Separate compilation of program modules with type_safe interfaces, and dynamic loading (with code generation) on a per_module basis are both supported. To users of the implemented system, working with modules in the abstract representation is as convenient as working with native object_files, although it leads to several new capabilities. The combination of portability with practicality denotes a step toward a software component industry. 1. Introduction The rapid evolution of hardware technology is constantly influencing software development, for better as well as for worse. On the downside, faster hardware can conceal the complexity and cost of badly_designed programs; Reiser [Rei89] is not far off the mark in observing that s...

Abstract: As older mainframe architectures become obsolete, the corresponding legacy software is increasingly executed via platform emulators running on top of more modern commodity hardware. These emulators are virtual machines that often include a combination of interpreters and just-in-time compilers. Implementing interpreters and compilers for each combination of emulated and target platform independently of each other is a redundant and error-prone task. We describe an alternative approach that automatically synthesizes specialized virtual-machine interpreters and just-in-time compilers, which then execute on top of an existing software portability platform such as Java. The result is a considerably reduced implementation effort. 1

Optimizing compilers tend to be much larger and much slower than their straightforward counterparts. Their designers usually do not follow Oberon's maxim of making things "as simple as possible", but are inclined to completely disregard cost (in terms of compiler size, compilation speed, and maintainability) in favor of code_quality benefits that often turn out to be relatively marginal. Trying to make an optimizing compiler as simple as possible and yet as powerful as necessary requires, before all else, a measurement standard, by which both simplicity and power can be judged. For a compiler that is written in the language it compiles, two such standards are easily found by considering first the time required for self_compilation, and then the size of the resulting object program. With the help of these benchmarks, one may pit simplicity against power, requiring that every new capability added to the compiler "pays its own way" by creating more benefit than cost on account of at leas...

Wux is a port of Unix tools to the Microsoft Windows environment. It is based on a library providing a Unixcompatible set of system calls on top of Windows. Unix-derived tools run in parallel, communicating using the Unix pipe abstraction. All processes are run within an application template that gives them basic Windows compatibility such as input and output windows and an icon. The performance of the system is comparable to that of Unix ports to the PC architecture. 1 Motivation The Unix operating system offers a wide variety of tools that can be used as building blocks or autonomous units for application development. Although these and similar tools can be ported to other environments [KP76, Gor93], their usability is often impaired by the lack of the glue elements available under Unix: multitasking and interprocess communication using pipes. Specifically, tool ports to the widely used MS-DOS system have to rely on serialised process execution and pipes implemented using inefficie...

Over the past decade, since Java was first introduced and integrated into the Netscape web browser, several intermediate representations have been developed that might be potentially used for mobile code applications. This paper examines the requirements for a mobile code representation, presents several examples of stack-based, tree-oriented, and proof-annotating mobile code representations, and evaluates each of these representations according to the requirements. Povzetek: Članek podaja pregled mobilnih kod. 1