Specifying and enforcing high-level semantic obligation policies

Obligation policies specify management actions that must be performed when a particular kind of event occurs and certain conditions are satisfied. Large scale distributed systems often produce event streams containing large volumes of low-level events. In many cases, these streams also contain multimedia data (consisting of text, audio or video). Hence, a key challenge is to allow policy writers to specify obligation policies based on high-level events, that may be derived after performing appropriate processing on raw, low-level events. In this paper, we propose a semantic obligation policy specification language called Eagle, which is based on patterns of high-level events, represented as RDF graph patterns. Our policy enforcement architecture uses a compiler that builds a workflow for producing a stream of events, which match the high-level event pattern specified in a policy. This workflow consists of a number of event sources and event processing components, which are described semantically. We present the policy language and enforcement architecture in this paper.     

Direct microprogrammed execution of the intermediate text from a high-level language compiler

Microprogramming commonly executed operations can improve the computational speed of data processing systems. This paper describes how microprogramming may be used to execute directly the intermediate text generated by a high-level language compiler after syntactic and semantic analysis of the input source program.Direct microprogrammed execution of common forms of intermediate text—i.e. quadruples, triples, and duos—has been simulated. A comparison is made, in terms of storage requirements and execution time, of this direct microprogrammed system with the present methods which result in machine language representation and execution of the intermediate text. Direct generation of a microprogram from the high-level language statements is also examined.Timing assumptions for comparative purposes have been based on the IBM 360 MOD 50 system. Simulation and timing estimates for the microprograms have been carried out on a microprogram directed simulator which closely represents the architectural organization of the MOD 50.     

Security types preserving compilation

Starting from the seminal work of Volpano and Smith, there has been growing evidence that type systems may be used to enforce confidentiality of programs through non-interference. However, most type systems operate on high-level languages and calculi, and “low-level languages have not received much attention in studies of secure information flow” (Sabelfeld and Myers, [Language-based information-flow security. IEEE Journal on Selected Areas in Communications 2003; 21:5–19]). Therefore, we introduce an information flow type system for a low-level language featuring jumps and calls, and show that the type system enforces termination-insensitive non-interference.Furthermore, information flow type systems for low-level languages should appropriately relate to their counterparts for high-level languages. Therefore, we introduce a compiler from a high-level imperative programming language to our low-level language, and show that the compiler preserves information flow types.     

GCC后端中四路双精度短向量寄存器的实现

设计和实现一个新的产品化的编译器通常需要几年时间。基于已有的编译器进行修改和扩展,是研发面向新体系结构的编译器的主要途径。GNU编译器集合(GCC)支持多种高级语言和多种目标处理器平台、文档及源代码开放等。基于GCC的Sparc后端,实现了支持四路双精度SIMD指令的四路双精度短向量寄存器的描述。在此过程中,定义了新的目标机,扩充了一类向量模式,定义了一类新的寄存器约束,实现了四路双精度寄存器的描述,定义了四路双精度SIMD指令的机器描述。对于面向此类SIMD指令的内嵌函数,GCC编译器能够正确使用该类向量寄存器来生成对应的SIMD指令。     

Code compaction for parallel architectures

There are two principal methods used to exploit the parallelism available on a parallel machine: the program to be executed can be optimized by hand, or the program can be automatically converted to parallel machine code by a compiler. The first method usually derives parallelism at the procedure level; a parallel program is written in a high-level language and typically has various modules executing in parallel. By contrast, the compiler methodically transforms the program into parallel code using various transformations, such as code movement. The automatic conversion of a program to parallel code is called compaction or parallelization. This paper describes the evolution of a new compaction program and presents a new algorithm for determining legal code movements. A simulator of the target architecture was used to estimate the execution times of a sample suite of programs before and after compaction. The results verify that substantial advantages arise from applying this compaction technique.     

Eclipse Support for Using Eli and Teaching Programming Languages

This demonstration will show Eclipse plugins developed at Macquarie and Colorado to support the Eli Language Processor Generation system and to enhance teaching of programming language concepts and implementation techniques. The plugins support exploration of programming language semantics, integrated development in the Eli system, and high-level observations of compiler execution.     

8088 development system programmed in C

An 8088 development system is described which combines the advantages of a personal computer (IBM PC), with high-level language support in the form of a c compiler, and a rack-based system. A suite of programs has been developed to enable the c compiler output to be converted into a form suitable for execution on the rack-based target as either ROM- or RAM-resident applications.     

ILX: Extending the .NET Common IL for Functional Language Interoperability

This paper describes several extensions to the .NET Common Intermediary Language (CIL), each of which is designed to enable easier implementation of typed high-level programming languages on the .NET platform, and to promote closer integration and interoperability between these languages. In particular we aim for easier interoperability between components whose interfaces are expressed using function types, discriminated unions and parametric polymorphism, regardless of the languages in which these components are implemented. We show that it is possible to add these constructs to an existing, “real world” intermediary language and that this allows corresponding subsets of constructs to be compiled uniformly, which in turn will allow programmers to use these constructs seamlessly between different languages. In this paper we discuss the motivations for our extensions, which are together called Extended IL (ILX), and describe them via examples. In this setting, many of the traditional responsibilities of the backend of a compiler must be moved to ILX and the execution environment, in particular those related to representation choices and low-level optimizations. We have modified a Haskell compiler to generate this language, and have implemented an assembler that translates the extensions to regular or polymorphic CIL code.I am very grateful to Nick Benton, Cedric Fournet, Andrew Kennedy, Andy Gordon, Simon Peyton Jones, Claudio Russo, Reuben Thomas, Andrew Tolmach and the anonymous referees for their help and advice with this work.     

P3 L: A structured high-level parallel language,and its structured support

The paper presents a parallel programming methodology that ensures easy programming, efficiency and portability of programs to different machines belonging to the class of the general-purpose, distributed-memory, MIMD architectures. The methodology is based on the definition of a new, high-level, explicitly parallel language, called P³ L, and of a set of static tools that automatically adapt the program features for each target architecture. P³ L does not require programmers to specify process activations, the actual parallelism degree, scheduling, or interprocess communications, i.e. all those features that need to be adjusted to harness each specific target machine. Parallelism is, on the other hand, expressed in a structured and qualitative way, by hierarchical composition of a restricted set of language constructs, corresponding to those forms of parallelism that are frequently encountered in parallel applications, and that can be efficiently implemented. The efficient portability of P³ L applications is guaranteed by the compiler along with the novel structure of the support. The compiler automatically adapts the program features for each specific architecture, using the costs (in terms of performance) of the low-level mechanisms exported by the architecture itself. In our methodology, these costs, along with other features of the architecture, are viewed through an abstract machine, whose interface is used by the compiler to produce the final object code.     

Optimizing Java bytecodes

We have developed a research compiler for Java class files. The compiler, which we call Briki, is designed to test new compilation techniques. We focus on optimizations which are only possible or much easier to perform on a high-level intermediate representation. We have designed such a representation, JavaIR, and have written a front-end which recovers the high-level structure from the information from the class file. Some of the high-level optimizations can be performed by the Java compiler which produces the class file. There is, however, a set of machine-dependent optimizations which have to be customized for the specific architecture and so can only be performed when the machine code is generated from the bytecodes, e.g. in a just-in-time (JIT) compiler. We choose memory hierarchy optimizations as an example of machine-dependent techniques. We show that there is an intersection of the set of machine-dependent optimizations and the set of high-level optimizations. One such example is array remapping, which requires multi-dimensional array references which are not present in the bytecodes and at the same time requires information about memory organization and the mapping of bytecodes to machine instructions. We develop a set of optimizations for accessing array elements and object fields and show their impact on a set of benchmarks which we run on two machines with a JIT compiler. The execution times are reduced by as much as 50% and we argue that the improvement could be even higher with a more mature JIT technology. © 1997 John Wiley & Sons, Ltd.