• ETRI Journal
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• 제37권5호
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• pp.1001-1011
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• 2015

Since just-in-time (JIT) has considerable overhead to detect hot spots and compile them at runtime, using sophisticated optimization techniques for embedded devices means that any resulting performance improvements will be limited. In this paper, we introduce a novel static Dalvik bytecode optimization framework, as a complementary compilation of the Dalvik virtual machine, to improve the performance of Android applications. Our system generates optimized Dalvik bytecodes by using Low Level Virtual Machine (LLVM). A major obstacle in using LLVM for optimizing Dalvik bytecodes is determining how to handle the high-level language features of the Dalvik bytecode in LLVM IR and how to optimize LLVM IR conforming to the language information of the Dalvik bytecode. To this end, we annotate the high-level language features of Dalvik bytecode to LLVM IR and successfully optimize Dalvik bytecodes through instruction selection processes. Our experimental results show that our system with JIT improves the performance of Android applications by up to 6.08 times, and surpasses JIT by up to 4.34 times.

• IEIE Transactions on Smart Processing and Computing
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• 제4권3호
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• pp.169-172
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• 2015

Dalvik is a virtual machine (VM) that is designed to run Java-based Android applications. A trace-based just-in-time (JIT) compilation technique is currently employed to improve performance of the Dalvik VM. However, due to runtime compilation overhead, the trace-based JIT compiler provides only a few simple optimizations. Moreover, because each trace contains only a few instructions, the trace-based JIT compiler inherently exploits fewer optimization and parallelization opportunities than a method-based JIT compiler that compiles method-by-method. So we propose a new method-based JIT compiler, named DEX2C, in order to improve performance by finding more opportunities for both optimization and parallelization in Android applications. We employ C code as an intermediate product in order to find more optimization opportunities by using the GNU C Compiler (GCC), and we will detect parallelism by using the Intel C/C++ parallel compiler and the AESOP compiler in our future work. In this paper, we introduce our DEX2C compiler, which dynamically translates Dalvik bytecodes (DEX) into C code with method granularity. We also describe a new method-based JIT interface in the Dalvik VM for the DEX2C compiler. Our experiment results show that our compiler and its interface achieve significant performance improvement by up to 15.2 times and 3.7 times on average, in Element Benchmark, and up to 2.8 times for FFT in Smartbench.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제2권4호
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• pp.177-180
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• 2013

소프트웨어 버스마크는 프로그램을 인식하는데 사용될 수 있는 고유한 특징을 의미한다. 소프트웨어 버스마크는 단순한 프로그램 변환에 의해서 삭제되지 않기 때문에 코드 도용을 탐지하는데 사용된다. 본 논문에서는 안드로이드 앱에 대한 API k-gram 기반의 버스마크 기법을 제안한다. 안드로이드 SDK는 프로그래머가 쉽게 앱을 개발할 수 있도록 다양한 라이브러리를 제공한다. 그리고 안드로이드 SDK를 사용하기 위해서는 반드시 API 메소드 호출을 이용해야만 한다. API 메소드 호출 명령어는 다른 명령어로 바꾸거나 삭제하기 어렵기 때문에 애플리케이션의 고유한 특징으로서 사용될 수 있다. 본 논문에서 제안하는 버스마크의 효용성을 보여주기 위해서 기존의 버스마크 기법과 비교하였고 오픈소스 앱을 대상으로 평가하였다. 실험으로부터 API k-gram 버스마크가 기존 버스마크보다 신뢰도와 강인도가 높은 것을 확인하였다.