這篇論文展示了一個針對ARM處理器可以獲得確切最差執行時間的工具。 這個工具是一個介於ARM的GCC編譯器和SWEET最差執行時間分析器之間的介面。 SWEET是一個開放原碼的靜態分析器，可獲得程式確切的最差執行時間上限。
在即時系統中，程式的最差執行時間是一個重要的計量，因為工作排程器必須決定分配多少時間給各個程序。 真實的最差執行時間值是有用的，但不幸的是它難以取得。因此靜態程式分析已經成為取得最差執行時間上限的方法，它是透過完整程式中各個獨立片段的保守執行時間近似值來取得最差執行時間上限的方法。 SWEET是靜態分析器的其中一個。
我們的工具工作在ARM-GCC的內部，取出所有SWEET需要的程式特性資訊。 然後這個工具包裝這些資訊成為SWEET的ALF格式。 這個工具已經被測試過且對任何我們已經測試的輸入來源可以正確的運作(包含所有從WCET BENCHMARK SUITE[1] 得到的34個標準檢查程式)

This thesis presents a tool for obtaining worst-case execution time (WCET) guarantees for ARM processors. This tool is an interface between ARM’s GCC compiler and the SWEET WCET analyzer. SWEET is an open-source static analyzer that derives a guaranteed upper bound on the WCET of a program.
The WCET of a program is an important metric in real-time systems. The task scheduler must decide how much time to allot for each process; if the allotted time exceeds the WCET, the process can be guaranteed to always finish in time. Although the WCET value is therefore useful, it is difficult to find. But, for the purpose of guaranteeing that a process finishes on time, an upper bound on the WCET suffices. Static program analysis has been proposed as a method to derive such an upper-bound on the WCET, by means of conservatively approximating the runtime of the individual parts of a complete program. SWEET is one such static analyzer.
Our tool works inside of ARM-GCC, extracting all of the information that SWEET needs about the program’s behavior. Our tool then packages the information into the SWEET’s ALF format. The tool has been tested and works correctly for every input source that we have tested (including all 34 benchmarks from the WCET BENCHMARK SUITE[1]).


This work was funded by Taiwan’s National Science Council, grant NSC 97-2218-E-110-003

摘要…...………….………………………………………………….. i
Abstract.............................................................................................. ii
Index.................................................................................................. iii
SECTION 1 INTRODUCTION………..................................................... 1

SECTION 2 RELATED WORK…........................................................... 6
2.1 STATIC ANALYSIS.................................................................... 6
2.1.1 THE FLOW ANALYSIS PHASE……………........................... 7
2.1.2 THE ARCHITECTURAL MODELING PHASE....................... 10
2.1.3 THE WCET CALCULATION PHASE................................... 12
2.1.4 THE CHOICES MADE BY THE SWEET ANALYZER’S PHASES.............................................................................................. 13
2.2 RELATED WORK IN INTERMEDIATE REPRESENTATIONS......... 15

SECTION 3 IMPLEMENTATION OF OUR CONVERTER............................ 19
3.1 The situation where GIMPLE has all the information needed for the ALF file.................................................................... 20
3.1.1 EXAMPLE............................................................................ 20
3.2 The situation where ALF requires more information than exists in GIMPLE............................................................................ 21
3.3 GCC modifications to produce the missing information that the ALF format requires.......................................................... 26
3.4 Problems that occur in special situations.......................... 28
3.5 Implementation of the GandALF converter...................... 32

SECTION 4 RESULTS.......................................................................... 34
References......................................................................................... 35
APPENDIX.......................................................................................... 38

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