LLVM 源码分析(五)BasicBlockPass
2013-04-01 16:02
483 查看
BasicBlockPass 主要增加
doInitaliztion(Function &) ;doFinalization(Function &);runOnBasicBlock();
注意参数为Funtion & 和FunctionPass 的Module 引用有区别
其实都和前面相似 BasicBlockPass 比FunctionPass粒度更小
使用方式如下
namespace{ struct Hello1 : public BasicBlockPass { static char ID; // Pass identification, replacement for typeid Hello1() : BasicBlockPass(ID) {} virtual bool runOnBasicBlock(BasicBlock &BB) { errs() << "Hello1: "; errs().write_escaped(BB.getName()) << '\n'; return false; } bool doInitialization(Function &F){ // By default, don't do anything. errs()<<"BB doInitialization test"; return false; } }; } char Hello1::ID = 0; static RegisterPass<Hello1> Z("hello1", "Hello World Pass");
下面是一段著名的dead code 删除代码
//===- DCE.cpp - Code to perform dead code elimination --------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements dead inst elimination and dead code elimination. // // Dead Inst Elimination performs a single pass over the function removing // instructions that are obviously dead. Dead Code Elimination is similar, but // it rechecks instructions that were used by removed instructions to see if // they are newly dead. // //===----------------------------------------------------------------------===// #define DEBUG_TYPE "dce" #include "llvm/Transforms/Scalar.h" #include "llvm/Transforms/Utils/Local.h" #include "llvm/Instruction.h" #include "llvm/Pass.h" #include "llvm/Support/InstIterator.h" #include "llvm/Target/TargetLibraryInfo.h" #include "llvm/ADT/Statistic.h" using namespace llvm; STATISTIC(DIEEliminated, "Number of insts removed by DIE pass"); STATISTIC(DCEEliminated, "Number of insts removed"); namespace { //===--------------------------------------------------------------------===// // DeadInstElimination pass implementation // struct DeadInstElimination : public BasicBlockPass { static char ID; // Pass identification, replacement for typeid DeadInstElimination() : BasicBlockPass(ID) { initializeDeadInstEliminationPass(*PassRegistry::getPassRegistry()); } virtual bool runOnBasicBlock(BasicBlock &BB) { TargetLibraryInfo *TLI = getAnalysisIfAvailable<TargetLibraryInfo>(); bool Changed = false; for (BasicBlock::iterator DI = BB.begin(); DI != BB.end(); ) { Instruction *Inst = DI++; if (isInstructionTriviallyDead(Inst, TLI)) { Inst->eraseFromParent(); Changed = true; ++DIEEliminated; } } return Changed; } virtual void getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesCFG(); } }; } char DeadInstElimination::ID = 0; INITIALIZE_PASS(DeadInstElimination, "die", "Dead Instruction Elimination", false, false) Pass *llvm::createDeadInstEliminationPass() { return new DeadInstElimination(); }
相关文章推荐
- LLVM 源码分析 (一) pass 类
- LLVM每日谈之十二 LLVM的源码分析之Pass相关
- LLVM每日谈之十二 LLVM的源码分析之Pass相关
- LLVM 源码分析(三)ImmutablePass
- LLVM 源码分析(四)FunctionPass
- leveldb源码分析--SSTable之block
- iOS Block源码分析系列(二)————局部变量的截获以及__block的作用和理解
- 【tensorflow学习】BasicLSTMCell 源码分析
- iOS Block源码分析系列(一)————2分钟明白Block究竟是什么?
- Linux内核源码分析--内核启动之(6)Image内核启动(do_basic_setup函数)(Linux-3.0 ARMv7)
- Spark 源码分析 – BlockManagerMaster&Slave
- Hadoop处理跨block行源码分析记录
- LLVM 源码分析 (二)ModulePass 类
- golang 移动应用例子 example/basic 源码框架分析
- Go Mobile 例子 basic 源码分析
- [转]HBase BlockCache机制讲解&源码分析
- Spark源码分析 – BlockManager
- Fabric源码分析之invoke执行流程及block生成分析
- block实现源码分析1-黑幕背后的__block修饰符
- dbcp BasicDataSource 连接池获取连接过程源码分析