. We introduce MetaML, a practically-motivated, staticallytyped multi-stage programming language. MetaML is a "real" language. We have built an implementation and used it to solve multi-stage problems. MetaML allows the programmer to construct, combine, and execute code fragments in a type-safe manner. Code fragments can contain free variables, but they obey the static-scoping principle. MetaML performs typechecking for all stages once and for all before the execution of the first stage. Certain anomalies with our first MetaML implementation led us to formalize an illustrative subset of the MetaML implementation. We present both a big-step semantics and type system for this subset, and prove the type system's soundness with respect to a big-step semantics. From a software engineering point of view, this means that generators written in the MetaML subset never generate unsafe programs. A type system and semantics for full MetaML is still ongoing work. We argue that multi-...

ing with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works, requires prior specific permission and/or a fee. Permissions may be requested from Publications Dept, ACM Inc., 1515 Broadway, New York, NY 10036 USA, fax +1 (212) 869-0481, or permissions@acm.org. 2 \Delta Compose project subsequent reads and writes to that file [Pu et al. 1995]. To take advantage of such opportunities, a partial evaluator must: ---Treat the C programming language, since operating systems are typically written in C. ---Exploit specialization opportunities, such as those due to generality and modularity. ---Exploit run-time invariants, like those found in file reads and writes. ---Handle large applications, because certain operating systems contain up to a million lines of code. ---Ensure predictability, by informing the user how the code will be transformed during specialization. Tempo addresses each of the...

The Java language provides a promising solution to the design of safe programs, with an application spectrum ranging from Web services to operating system components. The well-known tradeoff of Java's portability is the inefficiency of its basic execution model, which relies on the interpretation of an object-based virtual machine. Many solutions have been proposed to overcome this problem, such as just-in-time (JIT) and offline bytecode compilers. However, most compilers trade efficiency for either portability or the ability to dynamically load bytecode. In this paper, we present an approach which reconciles portability and efficiency, and preserves the ability to dynamically load bytecode. We have designed and implemented an efficient environment for the execution of Java programs, named Harissa. Harissa permits the mixing of compiled and interpreted methods. Harissa's compiler translates Java bytecode to C, incorporating aggressive optimizations such as virtualmethod call optimizati...

Specializing programs with respect to run-time values has been shown to drastically improve code performance on realistic programs ranging from operating systems to graphics. Recently, various approaches to specializing code at run-time have been proposed. However, these approaches still suffer from shortcomings that limit their applicability: they are manual, too expensive, or require programs to be written in a dedicated language. We solve these problems by introducing new techniques to implement run-time specialization. The key to our approach is the use of code templates. Templates are automatically generated from ordinary programs and are optimized before run time, allowing high-quality code to be quickly generated at run time. Experimental results obtained on scientific and graphics code indicate that our approach is highly effective. Little run-time overhead is introduced, since code generation primarily consists of copying instructions. Run-time specialized programs run up to 1...

Designing and implementing generic software components is encouraged by languages such as object-oriented ones and commonly advocated in most application areas. Generic software components have many advantages among which the most important is reusability. However, it comes at a price: genericity often incurs a loss of efficiency. This paper presents an approach aimed at reconciling genericity and efficiency. To do so, we introduce declarations to the Java language to enable a programmer to specify how generic programs should be specialized for a particular usage pattern. Our approach has been implemented as a compiler from our extended language into standard Java. 1 Introduction The object-oriented paradigm has well-recognized advantages for application design, and more specifically for program structure. It makes it possible to decompose an application in terms of well-defined, generic components, closely corresponding to the structure of the modeled problem. This structuring leads...

Specialization has been recognized as a powerful technique for optimizing operating systems. However, specialization has not been broadly applied beyond the research community because current techniques, based on manual specialization, are time-consuming and error-prone. The goal of the work described in this paper is to help operating system tuners perform specialization more easily. We have built a specialization toolkit that assists the major tasks of specializing operating systems. We demonstrate the effectiveness of the toolkit by applying it to three diverse operating system components. We show that using tools to assist specialization enables significant performance optimizations without errorprone manual modifications. Our experience with the toolkit suggests new ways of designing systems that combine high performance and clean structure. 1

A certifying compiler takes a source language program and produces object code, as well as a "certificate" that can be used to verify that the object code satisfies desirable properties, such as type safety and memory safety. Certifying compilation helps to increase both compiler robustness and program safety. Compiler robustness is improved since some compiler errors can be caught by checking the object code against the certificate immediately after compilation. Program safety is improved because the object code and certificate alone are sufficient to establish safety: even if the object code and certificate are produced on an unknown machine by an unknown compiler and sent over an untrusted network, safe execution is guaranteed as long as the code and certificate pass the verifier. Existing work in certifying compilation has addressed statically generated code. In this paper, we extend this to code generated at run time. Our goal is to combine certifying compilation with run-time code generation to produce programs that are both verifiably safe and extremely fast. To achieve this goal, we present two new languages with explicit run-time code generation constructs: Cyclone, a type safe dialect of C, and TAL/T, a type safe assembly language. We have designed and implemented a system that translates a safe C program into Cyclone, which is then compiled to TAL/T, and finally assembled into executable object code. This paper focuses on our overall approach and the front end of our system; details about TAL/T will appear in a subsequent paper.

The object-oriented style of programming facilitates program adaptation and enhances program genericness, but at the expense of efficiency. We demonstrate experimentally that state-of-the-art Java compilation technology fails to compensate for the use of object-oriented abstractions to implement generic programs, and that program specialization can be used to eliminate these overheads. We present an automatic program specializer for Java, and demonstrate experimentally that significant speedups in program execution time can be obtained through automatic specialization. Although automatic program specialization could be seen as overlapping with existing optimizing compiler technology, we show that specialization and compiler optimization are in fact complementary. 1 Introduction Object-oriented languages encourage a style of programming that facilitates program adaptation. Encapsulation enhances code resilience to program modifications and increases the possibilities for di...

Tempo is a specializer for the C language that automatically customizes a program with respect to the values of con guration parameters. It oers specialization at both compile time and run time, and both program and data specialization. To control the specialization process, Tempo provides the program developer with a declarative language to describe specialization opportunities for a given program.

In order to exploit specialization opportunities that exist in programs written by researchers outside of the programming language community, a partial evaluator needs to effectively treat existing realistic applications. Our empirical studies have demonstrated real-sized applications extensively use non-liftable values such as pointers and data structures. Therefore, it is essential that the binding-time analysis accurately treats nonliftable values. To achieve this accuracy, we introduce the notion of use sensitivity, and present a use-sensitive binding-time analysis for C programs which is obtained by a forward analysis followed by a backward analysis. This analysis has been implemented and integrated into our partial evaluator for C, called Tempo. To validate the effectiveness of our analysis and demonstrate that use sensitivity is critical to obtain highly-specialized programs, we have conducted experimental studies on various components of existing operating systems code. Our res...