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。     

基于GCC的高性能DSP Matrix向量指令集扩展

自动向量化技术是编译器提高程序并行性的优化方法。随着支持SIMD结构处理器的计算平台的广泛应用,自动向量化技术也成为编译器技术研究的热点。GCC编译器是一种开源、跨平台的编译器。本文基于GCC内部自动向量化算法,结合Matrix芯片的体系结构和指令集特点,完成了Matrix向量指令集在GCC后端扩展,实现了基本的自动向量化支持。测试结果表明,扩展后的编译器能够支持Matrix向量指令集,进行基本的自动向量化,同时支持以内建函数方式开发基于Matrix的并行程序。     

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。     

典型编译器自动向量化效果评估与分析

SIMD(Single-Instruction-Multiple-Data)体系结构在现代处理器体系结构中扮演重要的角色。多种国产高性能通用处理器也大都实现了SIMD结构。SIMD体系结构提供了短向量数据并行处理能力,编译器自动向量化是应用程序获得性能提升的主要手段之一。使用成熟的支持SIMD的商用处理器平台评估典型编译器自动向量化的效果,对于处理器体系结构的设计以及编译器的分析和设计非常有益。采用SPECCPU2006和SPECOMPM2001基准测试程序,评估了典型编译器(包括Intel编译器、PGI编译器和GCC编译器)的自动向量化的效果。并且以产品级的开源编译器GCC为目标,用手工编写的程序片段(主要是多种类型的循环结构)评估了当前GCC编译器自动向量化的效果,并深入分析了GCC编译器中现有的自动向量化的能力和局限。此项工作为进一步研发高效的编译器自动向量化提供了有价值的参考。     

基于数据对齐属性指导的GCC自动向量化优化

主流通用处理器都已经实现了多核并行以及处理器核内的SIMD并行。虽然GCC编译器实现了面向SIMD并行的自动向量化,但是编译器针对OpenMP并行程序的自动向量化效果仍很不理想。针对多线程并行的OpenMP程序,基于GCC的OpenMP编译实现,扩展了数据对齐属性指导语句,使编译器在自动向量化时能够进行更准确的数据对齐与否的判断,优化了GCC编译器的自动向量化。     

基于LLVM架构的NiosⅡ后端快速移植

编译器后端移植是目前嵌入式系统研究的重要领域,如何快速实现编译器后端移植仍然是嵌入式系统研究的热点。采用新的编译器架构LLVM,移植NiosⅡ处理器来分析LLVM快速后端移植架构。使用LLVM后端移植架构的TableGen描述NiosⅡ体系结构例如指令、寄存器等,使用完备LLVM C++函数库实现复杂或特殊的操作。TableGen与C++函数库互相配合,最终实现LLVM架构对NiosⅡ后端的支持。实验结果表明与GCC编译器后端移植方法相比,基于LLVM架构的编译器后端移植方法的工作量减少了64.2%～83.9%,大大节省后端移植时间。     

二维SIMD结构的低功耗调度

针对二维SIMD结构,提出一种可以动态关闭空转部件且结合编译器、指令集和体系结构支持的低功耗调度算法,其中包括编译器优化二维SIMD指令,功耗指令发出部件开关信号,系统接收信号并执行。采用对不同功能单元分别调度的方式和部件局部化的方法。在模拟器上的实验结果表明该方法可以节省整个系统约15％的能量消耗。     

面向RISC-V处理器的GCC移植与优化

嵌入式RISC-V处理器交叉开发生成高质量目标代码的关键是GCC的移植与优化.分析GCC的基本结构和RISC-V体系结构的数据与指令特点,建立GCC后端移植机制,采用机器描述方法,生成32位riscv-none-embed-gcc编译器,实现RISC-V处理器的GCC移植,设计强度削弱的窥孔优化方法解决中间代码生成过程中CPU计算代价高的问题.验证与测试结果表明编译器编译正确并具有通用功能,优化后编译生成的目标代码体积减少约11％,提高了目标代码质量,节省了嵌入式处微理器的存储空间.     

面向VLIW DSP结构的编译器的设计与实现

VLIW编译器实现指令并行性挖掘、相关性检查、指令调度等职能,对VLIW处理器的性能影响较大.本文基于一款VLIW DSP芯片,利用可重定位编译器IMPACT的前端和代码生成器模板,设计和实现了高性能的VLIW编译器.利用伪数据类型和Intrinsic函数结合,在编译器中构建了对SIMD功能的支持.实验结果显示,对比基于GCC版本的编译器,该编译器生成的指令数平均下降42%,并行包数下降30%.     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate