We describe the design and implementation of a compiler that automatically translates ordinary programs written in a subset of ML into code that generates native code at run time. Run-time code generation can make use of values and invariants that cannot be exploited at compile time, yielding code that is often superior to statically optimal code. But the cost of optimizing and generating code at run time can be prohibitive. We demonstrate how compile-time specialization can reduce the cost of run-time code generation by an order of magnitude without greatly affecting code quality. Several benchmark programs are examined, which exhibit an average cost of only six cycles per instruction generated at run time. 1 Introduction In this paper, we describe our experience with a prototype system for run-time code generation. Our system, called Fabius, is a compiler that takes ordinary programs written in a subset of ML and automatically compiles them into native code that generates native c...

The views and conclusions contained in this document are those of the authors and should not be interpreted as representing o cial policies, either expressed or implied, of the Advanced Research Projects Agency or the U.S. Government. Any opinions, ndings, and conclusions or recommendations expressed in this material are those of the We study the typing properties of closure conversion for simply-typed and polymorphic-calculi. Unlike most accounts of closure conversion, which only treat the untyped-calculus, we translate well-typed source programs to well-typed target programs. This allows later compiler phases to take advantage of types for representation analysis and tag-free garbage collection, and it facilitates correctness proofs. Our account of closure conversion for the simply-typed language takes advantage of a simple model of objects by mapping closures to existentials. Closure conversion for the polymorphic language requires additional type machinery, namely translucency in the style of Harper and Lillibridge's module calculus, to express the type of a closure.

Today's type-safe low-level languages rely on garbage collection to recycle heap-allocated objects safely. We present LTAL, a safe, low-level, yet simple language that "stands on its own": it guarantees safe execution within a fixed memory space, without relying on external run-time support. We demonstrate the expressiveness of LTAL by giving a type-preserving compiler for the functional core of ML. But this independence comes at a steep price: LTAL's type system imposes a draconian discipline of linearity that ensures that memory can be reused safely, but prohibits any useful kind of sharing. We present the results of experiments with a prototype LTAL system that show just how high the price of linearity can be.

Languages that support abstraction and modular structure, such as Standard ML, Modula, Ada, and (more or less) C++, may have deeply nested dependency hierarchies among source files. In ML the problem is particularly severe because ML's powerful parameterized module (functor) facility entails dependencies among implementation modules, not just among interfaces.

An important function of any register allocator is to target registers so as to eliminate copy instructions. Graph-coloring register allocation is an elegant approach to this problem. If the source and destination of a move instruction do not interfere, then their nodes can be coalesced in the interference graph. Chaitin's coalescing heuristic could make a graph uncolorable (i.e., introduce spills); Briggs et al. demonstrated a conservative coalescing heuristic that preserves colorability. But Briggs's algorithm is too conservative, and leaves too many move instructions in our programs. We show how to interleave coloring reductions with Briggs's coalescing heuristic, leading to an algorithm that is safe but much more aggressive. 1 Introduction Graph coloring is a powerful approach to register allocation and can have a significant impact on the execution of compiled code. A good register allocator does copy propagation, eliminating many move instructions by "coloring" the source tempor...

We give an overview of the Glasgow Haskell compiler, focusing especially on way in which we have been able to exploit the rich theory of functional languages to give very practical improvements in the compiler. The compiler is portable, modular, generates good code, and is freely available. 1 Introduction Computer Science is both a scientific and an engineering discipline. As a scientific discipline, it seeks to establish generic principles and theories that can be used to explain or underpin a variety of particular applications. As an engineering discipline, it constructs substantial artefacts of software and hardware, sees where they fail and where they work, and develops new theory to underpin areas that are inadequately supported. (Milner [1991] eloquently argues for this dual approach in Computer Science. ) Functional programming is a research area that offers an unusually close interplay between these two aspects (Peyton Jones [1992b]). Theory often has immediate practical appl...

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This white paper describes Scout, a new operating system being designed for systems connected to the National Information Infrastructure (NII). Scout provides a communication-oriented software architecture for building operating system code that is specialized for the different systems that we expect to be available on the NII. It includes an explicit path abstraction that both facilitates effective resource management and permits optimizations of the critical path that I/O data follows. These path-enabled optimizations, along with the application of advanced compiler techniques, result in a system that has both predictable and scalable performance. June 17, 1994 Department of Computer Science The University of Arizona Tucson, AZ 1 Introduction As the National Information Infrastructure (NII) evolves, and digital computer networks become ubiquitous, communication will play an increasingly important role in computer systems. In fact, a recent report on the NII rejects the term "compu...

This paper presents the design and implementation of a "quasi real-time" garbage collector for Concurrent Caml Light, an implementation of ML with threads. This two-generation system combines a fast, asynchronous copying collector on the young generation with a nondisruptive concurrent marking collector on the old generation. This design crucially relies on the ML compiletime distinction between mutable and immutable objects. 1 Introduction This paper presents the design and implementation of a garbage collector for Concurrent Caml Light, an implementation of the ML language that provides multiple threads of control executing concurrently in a shared address space. Garbage collection --- the automatic reclamation of unused memory space --- is one of the most problematic components of run-time systems for multi-threaded languages. The naive "stop-the-world" approach, where all threads synchronously stop executing the user's program to perform garbage collection, is clearly inadequate,...

Implementing new operating systems is tedious, costly, and often impractical except for large projects. The Flux OSKit addresses this problem in a novel way by providing clean, well-documented OS components designed to be reused in a wide variety of other environments, rather than defining a new OS structure. The OSKit uses unconventional techniques to maximize its usefulness, such as intentionally exposing implementation details and platform-specific facilities. Further, the OSKit demonstrates a technique that allows unmodified code from existing mature operating systems to be incorporated quickly and updated regularly, by wrapping it with a small amount of carefully designed “glue” code to isolate its dependencies and export well-defined interfaces. The OSKit uses this technique to incorporate over 230,000 lines of stable code including device drivers, file systems, and network protocols. Our experience demonstrates that this approach to component software structure and reuse has a surprisingly large impact in the OS implementation domain. Four real-world examples show how the OSKit is catalyzing research and development in operating systems and programming languages. 1