北京顺义去哪找做网站的,设计赚钱的平台有哪些,亳州市建设局网站,潜江市住房城乡建设厅网站参考#xff1a;南京大学《软件分析》课程2
1、控制流分析
控制流分析实际上指的是构建控制流图#xff08;Control Flow Graph#xff0c;CFG#xff09;CFG是静态分析的基础数据结构CFG的节点可以是单个指令、基本块#xff08;Basic Block#xff0c;BB#xff09;…参考南京大学《软件分析》课程2
1、控制流分析
控制流分析实际上指的是构建控制流图Control Flow GraphCFGCFG是静态分析的基础数据结构CFG的节点可以是单个指令、基本块Basic BlockBB
2、构建基本块Basic BlockBB
1基本块的概念 Basic blocks (BB) are maximal sequences of consecutive three-address instructions with the properties that It can be entered only at the beginning, i.e., the first instruction in the blockIt can be exited only at the end, i.e., the last instruction in the block 解释 基本块是具有以下属性的连续3AC指令的最大序列 只有一个入口仅在开头进入即块的第一条指令。只有一个出口仅在结尾退出即块的最后一条指令。 2构建基本块 INPUT: A sequence of three-address instructions of P OUTPUT: A list of basic blocks of P METHOD: (1) Determine the leaders in P • The first instruction in P is a leader • Any target instruction of a conditional or unconditional jump is a leader • Any instruction that immediately follows a conditional or unconditional jump is a leader (2) Build BBs for P • A BB consists of a leader and all its subsequent instructions until the next leader 解释 输入程序的3AC指令序列 输出程序的基本块序列 方法 1确定每个基本块的第一条指令leader • 程序的第一条指令作为leader • 有条件或无条件跳转的目标指令作为leader • 紧接着有条件或无条件跳转指令的下一条指令作为leader 2构建基本块 • BB由一个leader及其所有后续指令组成直到下一个leader 例子
3、构建控制流图Control Flow Graph CFG • The nodes of CFG are basic blocks goto (i) Control Flow Graph (CFG) • There is an edge from block A to block B if and only if There is a conditional or unconditional jump from the end of A to the beginning of BB immediately follows A in the original order of instructions and A does not end in an unconditional jump • It is normal to replace the jumps to instruction labels by jumps to basic blocks • Usually we add two nodes, Entry and Exit. They do not correspond to executable IRAn edge from Entry to the BB containing the first instruction of IRAn edge to Exit from any BB containing an instruction that could be the last instruction of IR 解释 • 控制流图的节点是基本块 • 基本块之间的边 有条件或无条件跳转的基本块之间存在一条跳转边按照指令的原始顺序基本块之间存在一条顺序边但无条件跳转的基本块不存在顺序边 • 将跳转到指令替换成跳转到基本块 • 添加entry和exit CFG和IR通常不对应Entry到BB的边包括IR的第一条指令BB到Exit的边可能是多条包括IR的最后一条指令
