Client ahead‐of‐time compiler for embedded Java platforms

Many embedded Java platforms execute two types of Java classes: those installed statically on the client device and those downloaded dynamically from service providers at run time. For achieving higher performance, the static Java classes can be compiled into machine code by ahead‐of‐time compiler (AOTC) in the server, and the translated machine code can be installed on the client device. Unfortunately, AOTC cannot be applicable to the dynamically downloaded classes. This paper proposes client‐AOTC (c‐AOTC), which performs AOTC on the client device using the just‐in‐time compiler (JITC) module installed on the device, obviating the JITC overhead and complementing the server‐AOTC. The machine code of a method translated by JITC is cached on a persistent memory of the device, and when the method is invoked again in a later run of the program, the machine code is loaded and executed directly without any translation overhead. A major issue in c‐AOTC is relocation because some of the address constants embedded in the cached machine code are not correct when the machine code is loaded and used in a different run; those addresses should be corrected before they are used. Constant pool resolution and inlining complicate the relocation problem, and we propose our solutions. The persistent memory overhead for saving the relocation information is also an issue, and we propose a technique to encode the relocation information and compress the machine code efficiently. We developed a c‐AOTC on Sun's CDC VM reference implementation, and our evaluation results indicate that c‐AOTC can improve the performance significantly, as much as an average of 12% for EEMBC and 4% for SpecJVM98, with a persistent memory overhead of 1% on average. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

Research on Decompiling Technology

Decompiling,as a means of analysing and understanding software,has great practical value.This paper presents a kind of ecompiling method offered by the anthors,in which the techniques of library-function pattern recognition,intermediate language, symbolic execution, rule-based data type recovery,program transformation,and knowl edge engineering are separately applied to different phases of decompiling.Then it is discussed that the techniques of developing expert systems are adopted to build a decompiling system shell independent of the knowledge of language and program running environment.The shell will become a real decompiler,as long as the new knowledge of application environment is interactively acquired.     

一种简单高级语言编译器的设计

在编译原理和虚拟机技术的基础上,采用一种高级语言设计了一个简单的编译器。通过词法分析、语法分析和中间代码、虚拟机等进程,将源程序编译成目标程序,实现了复杂编译器的简单设计。     

面向对象软件反编译中类的识别方法研究

在反编译面向对象软件的过程中,反编译工具必须能够揭示出该软件的体系结构,因此反编译器必须能够识别出软件中的类和类中所包含的方法和属性以及类之间的关系.通过对编译器产生的面向对象软件汇编码进行细致深入的分析,归纳出了类函数的特征码,由此给出了一种能够对软件所包含类中类成员函数进行识别和归类的方法,其中运用了程序切片模拟执行算法等技术并据此开发了一个实验系统,此系统显示方法平均能识别出一个类中约80%的类函数.     

多媒体处理器的SIMD代码生成

通用处理器的SIMD（Single Instruction Multiple Data）多媒体扩展，为提高多媒体应用的性能提供了新的体系结构支持。但目前编译技术对这类指令不能提供很好的支持。本文提出了一个新的SIMD指令生成算法，基于把编译器前端的程序分析和编译器后端的机器信息相结合的思想，采用扩展的treeparsing技术，有效识别程序中的并行操作以生成SIMD指令。基于SUIF（Stanford University Intermediate Format）编译器框架的实验表明，针对一组多媒体kernel，本文提出的算法可平均减少其非SIMD代码47％的cycles。     

基于结构分析的高级语言控制结构恢复方法

为正确获得嵌入式可执行程序和汇编代码的高级语言控制结构,弥补现有高级程序控制结构恢复算法在处理非结构化区域的不足,将编译领域经典的控制流分析方法——结构分析算法引入到嵌入式汇编代码高级程序控制结构恢复研究中;针对嵌入式可执行程序的特点,对结构分析算法加以改进;利用结构分析算法的结果构造程序的控制树,生成高级语言代码。与开源反编译器DCC的对比实验结果表明,改进的结构分析算法在高级程序结构恢复问题上是可行有效的。     

Towards a verified compiler prototype for the synchronous language SIGNAL

SIGNAL belongs to the synchronous languages family which are widely used in the design of safety-critical real-time systems such as avionics, space systems, and nuclear power plants. This paper reports a compiler prototype for SIGNAL. Compared with the existing SIGNAL compiler, we propose a new intermediate representation (named S-CGA, a variant of clocked guarded actions), to integrate more synchronous programs into our compiler prototype in the future. The front-end of the compiler, i.e., the translation from SIGNAL to S-CGA, is presented. As well, the proof of semantics preservation is mechanized in the theorem prover Coq. Moreover, we present the back-end of the compiler, including sequential code generation and multithreaded code generation with time-predictable properties. With the rising importance of multi-core processors in safetycritical embedded systems or cyber-physical systems (CPS), there is a growing need for model-driven generation of multithreaded code and thus mapping on multi-core. We propose a time-predictable multi-core architecture model in architecture analysis and design language (AADL), and map the multi-threaded code to this model.     

Efficient Java exception handling in just‐in‐time compilation

Java uses exceptions to provide elegant error handling capabilities during program execution. However, the presence of exception handlers complicates the job of the just‐in‐time (JIT) compiler, while exceptions are rarely used in most programs. This paper describes two techniques for reducing such complications. First, we delay the translation of an exception handler until the exception really occurs. This on‐demand translation of exception handlers allows more optimizations when translating the main flow, without being hindered by constraints caused by the exception flows. Secondly, for those exceptions that are actually thrown during program execution we insert exception‐type check code and a direct branch to the translated exception handlers. This exception handler prediction is motivated by an observation that frequently thrown exceptions are likely to be handled by the same exception handlers, so this will eliminate the exception processing overhead of the Java virtual machine. Our experiments indicate that the code quality of the main flow is no longer affected by the presence of exception handlers. Also, frequently thrown exceptions can be efficiently handled by the exception handler prediction. Copyright © 2004 John Wiley & Sons, Ltd.     

The Back-End of a Two-Layer Model for a Federated National Datastore for Academic Research VOs that Integrates EGEE Data Management

This paper proposes an architecture for the back-end of a federated national datastore for use by academic research communities, developed by the e-INIS (Irish National e-InfraStructure) project, and describes in detail one member of the federation, the regional datastore at Trinity College Dublin. It builds upon existing infrastructure and services, including Grid-Ireland, the National Grid Initiative and EGEE, Europe’s leading Grid infrastructure. It assumes users are in distinct research communities and that their data access patterns can be described via two properties, denoted as mutability and frequency-of-access. The architecture is for a back-end—individual academic communities are best qualified to define their own front-end services and user interfaces. The proposal is designed to facilitate front-end development by placing minimal restrictions on how the front-end is implemented and on the internal community security policies. The proposal also seeks to ensure that the communities are insulated from the back-end and from each other in order to ensure quality of service and to decouple their front-end implementation from site-specific back-end implementations.     

基于TRANSPUTER多机系统的研究与设计

并行知识库机是利用多机系统的并行性提高知识库系统理效率的专用机，我们研制的并行知识库机由前后端机组成。其中，前端机是一台４８６微机，而后端机是基于ＴＲＡＮＳＰＵＴＥＲ的多机系统，本文重点研究后端机的拓扑结构，与ＰＣ机的接口和存储器的设计等问题。     

一种基于智能终端的人体心电信号监护系统设计

设计了一种基于智能终端的人体心电信号监测的系统,通过该系统可以实时连续地检测到被监护者的心电信号。该系统主要包括前端心电信号采集模块和后端心电信号无线发送模块。其中前端采集模块对心电信号进行了预处理;后端心电信号发送模块采用蓝牙无线通信方式,从而实现心电数据短距离无线传输且方便与PDA或Android智能手机等手持终端通信,保证了对被监护者的连续实时监测。     

CScout: A refactoring browser for C

Despite its maturity and popularity, the C programming language still lacks tool support for reliably performing even simple refactoring, browsing, or analysis operations. This is primarily due to identifier scope complications introduced by the C preprocessor. The CScout refactoring browser analyses complete program families by tagging the original identifiers with their precise location and classifying them into equivalence classes orthogonal to the C language’s namespace and scope extents. A web-based user interface provides programmers with an intuitive source code analysis and navigation front-end, while an sql-based back-end allows more complex source code analysis and manipulation. CScout has been successfully applied to many medium and large-sized proprietary and open-source projects identifying thousands of modest refactoring opportunities.     

反编译中IA-64指令语义抽象技术的研究

反编译技术可以将二进制可执行程序转换为等价的高级语言形式代码,它是软件逆向工程研究的一个重要方向。对机器指令进行语义抽象以产生中间代码表示是反编译程序的一个关键环节。介绍了在反编译过程中通过语义描述由IA-64汇编代码生成更高级的中间表示的实现技术。将语义描述技术与IA-64体系结构的EPIC特性结合起来,有效地解决了EPIC机器指令的语义抽象问题。     

Valgrind: A Program Supervision Framework

Valgrind is a programmable framework for creating program supervision tools such as bug detectors and profilers. It executes supervised programs using dynamic binary translation, giving it total control over their every part without requiring source code, and without the need for recompilation or relinking prior to execution.New supervision tools can be easily created by writing skins that plug into Valgrind's core. As an example, we describe one skin that performs Purify-style memory checks for C and C++ programs.     

CoSy C语言编译器安全性研究

为验证CoSy编译器的安全性,并确定不安全因素大致出现的位置,提出一种通过控制流图的同构对比判定CoSy编译器是否安全的方法。该方法生成源程序的控制流图以及CoSy中级中间表示的控制流图后,生成由CoSy编译器产生的目标汇编码的控制流图,根据控制流图同构算法,判断控制流图是否同构,由此确定CoSy编译器的不安全因素发生在编译器的前端还是后端。实验结果表明,该方法能有效验证编译器的安全性。     

Accurately Selecting Block Size at Runtime in Pipelined Parallel Programs

Loops that contain cross-processor data dependencies, known as DOACROSS loops, are often found in scientific programs. Efficiently parallelizing such loops is important yet nontrivial. One useful parallelization technique for DOACROSS loops is pipelining, where each processor (node) performs its computation in blocks; after each, it sends data to the next node in the pipeline. The amount of computation before sending a message is called the block size; its choice, although difficult to make statically, is important for efficient execution. This paper describes a flexible runtime approach to choosing the block size. Rather than rely on static estimation of workload, our system takes measurements during the first two iterations of a program and then uses the results to build an execution model and choose an appropriate block size which, unlike a static choice, may be nonuniform. To increase accuracy of the chosen block size, our execution model takes intra- and inter-node performance into account. It is important to note that our system finds an effective block size automatically, without experimentation that is necessary when using a statically chosen block size. Performance on a network of workstations shows that programs that use our runtime analysis outperform those that use static block sizes by as much as 18% when the workload is unbalanced. When the workload is balanced, competitive performance is achieved as long as the initial overhead is sufficiently amortized.     

软件维护与逆向工程评述

本介绍并分析了近几年在软件维护与逆向开程领域中的一些研究工作。这些工作涉及软件维护模型，程序观察，程序数据库，超本，程序高层抽象和反编译等内容。