We survey basic garbage collection algorithms, and variations such as incremental and generational collection; we then discuss low-level implementation considerations and the relationships between storage management systems, languages, and compilers. Throughout, we attempt to present a uni ed view based on abstract traversal strategies, addressing issues of conservatism, opportunism, and immediacy of reclamation; we also point outavariety of implementation details that are likely to have a significant impact on performance.

We describe a new compiler for Standard ML called TIL, that is based on four technologies: intensional polymorphism, tag-free garbage collection, conventional functional language optimization, and loop optimization. We use intensional polymorphism and tag-free garbage collection to provide specialized representations, even though SML is a polymorphic language. We use conventional functional language optimization to reduce the cost of intensional polymorphism, and loop optimization to generate good code for recursive functions. We present an example of TIL compiling an SML function to machine code, and compare the performance of TIL code against that of a widely used compiler, Standard ML of New Jersey.

Compilers for monomorphic languages, such as C and Pascal, take advantage of types to determine data representations, alignment, calling conventions, and register selection. However, these languages lack important features including polymorphism, abstract datatypes, and garbage collection. In contrast, modern programming languages such as Standard ML (SML), provide all of these features, but existing implementations fail to take full advantage of types. The result is that performance of SML code is quite bad when compared to C. In this thesis, I provide a general framework, called type-directed compilation, that allows compiler writers to take advantage of types at all stages in compilation. In the framework, types are used not only to determine efficient representations and calling conventions, but also to prove the correctness of the compiler. A key property of typedirected compilation is that all but the lowest levels of the compiler use typed intermediate languages. An advantage of this approach is that it provides a means for automatically checking the integrity of the resulting code. An important

Pointer swizzling at page fault time is a novel address translation mechanism that exploits conventional address translation hardware. It can support huge address spaces efficiently without long hardware addresses; such large address spaces are attractive for persistent object stores, distributed shared memories, and shared address space operating systems. This swizzling scheme can be used to provide data compatibility across machines with different word sizes, and even to provide binary code compatibility across machines with different hardware address sizes. Pointers are translated ("swizzled") from a long format to a shorter hardware-supported format at page fault time. No extra hardware is required, and no continual software overhead is incurred by presence checks or indirection of pointers. This pagewise technique exploits temporal and spatial locality in much the same way as a normal virtual memory; this gives it many desirable performance characteristics, especially given the tr...

Dynamic storage allocation is used heavily in many application areas including interpreters, simulators, optimizers, and translators. We describe research that can improve all aspects of the performance of dynamic storage allocation by predicting the lifetimes of short-lived objects when they are allocated. Using five significant, allocation-intensive C programs, we show that a great fraction of all bytes allocated are short-lived (? 90% in all cases). Furthermore, we describe an algorithm for lifetime prediction that accurately predicts the lifetimes of 42--99% of all objects allocated. We describe and simulate a storage allocator that takes advantage of lifetime prediction of short-lived objects and show that it can significantly improve a program's memory overhead and reference locality, and even, at times, improve CPU performance as well.

Heterogeneous Process Migration is a technique whereby an active process is moved from one machine to another. It must then continue normal execution and communication. The source and destination processors can have a different architecture, that is, different instruction sets and data formats. Because of this heterogeneity, the entire process memory image must be translated during the migration. "Tui" is a migration system that is able to translate the memory image of a program (written in ANSI-C) between four common architectures (m68000, SPARC, i486 and PowerPC). This requires detailed knowledge of all data types and variables used with the program. This is not always possible in non-type-safe (but popular) languages such as ANSI-C, Pascal and Fortran. The important features of the Tui algorithm are discussed in great detail. This includes the method by which a program's entire set of data values can be located, and eventually reconstructed on the target processor. Perfo...

The Marmot system is a research platform for studying the implementation of high level programming languages. It currently comprises an optimizing native-code compiler, runtime system, and libraries for a large subset of Java. Marmot integrates well-known representation, optimization, code generation, and runtime techniques with a few Java-specific features to achieve competitive performance. This paper contains a description of the Marmot system design, along with highlights of our experience applying and adapting traditional implementation techniques to Java. A detailed performance evaluation assesses both Marmot's overall performance relative to other Java and C++ implementations and the relative costs of various Java language features in Marmot-compiled code. Our experience with Marmot has demonstrated that well-known compilation techniques can produce very good performance for static Java applications---comparable or superior to other Java systems, and approaching that o...

Abstract The trends in software development are towards larger programs, more complex programs, and more use of programs as "component software. " These trends mean that the features of modern programming languages are becoming more important than ever before. Programming languages need to have features such as strong typing, a module system, polymorphism, automatic storage management, and higher-order functions. In short, modern programming languages are becoming more important than ever before.

By combining existing type systems with standard typebased compilation techniques, we describe how to write strongly typed programs that include a function that acts as a tracing garbage collector for the program. Since the garbage collector is an explicit function, we do not need to provide a trusted garbage collector as a runtime service to manage memory. Since our language is strongly typed, the standard type soundness guarantee "Well typed programs do not go wrong" is extended to include the collector. Our type safety guarantee is non-trivial since not only does it guarantee the type safety of the garbage collector, but it guarantees that the collector preservers the type safety of the program being garbage collected. We describe the technique in detail and report performance measurements for a few microbenchmarks as well as sketch the proofs of type soundness for our system. 1 Introduction We outline an approach, based on ideas from existing type systems, to build a type-preser...

We present a technique for moving objects and threads among heterogeneous computers at the native code level. To enable mobility of threads running native code, we convert thread states among machine-dependent and machine-independent formats. We introduce the concept of bus stops, which are machine-independent representations of program points as represented by program counter values. The concept of bus stops can be used also for other purposes, e.g., to aid inspecting and debugging optimized code, garbage collection etc. We also discuss techniques for thread mobility among processors executing differently optimized codes. We demonstrate the viability of our ideas by providing a prototype implementation of object and thread mobility among heterogeneous computers. The prototype uses the Emerald distributed programming language without modification; we have merely extended the Emerald runtime system and the code generator of the Emerald compiler. Our extensions allow object and thread m...