1 //===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This pass is a simple pass wrapper around the PromoteMemToReg function call 11 // exposed by the Utils library. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #define DEBUG_TYPE "mem2reg" 16 #include "llvm/Transforms/Scalar.h" 17 #include "llvm/ADT/Statistic.h" 18 #include "llvm/Analysis/Dominators.h" 19 #include "llvm/IR/DataLayout.h" 20 #include "llvm/IR/Function.h" 21 #include "llvm/IR/Instructions.h" 22 #include "llvm/Transforms/Utils/PromoteMemToReg.h" 23 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h" 24 using namespace llvm; 25 26 STATISTIC(NumPromoted, "Number of alloca's promoted"); 27 28 namespace { 29 struct PromotePass : public FunctionPass { 30 static char ID; // Pass identification, replacement for typeid 31 32 PromotePass() : FunctionPass(ID) { 33 initializePromotePassPass(*PassRegistry::getPassRegistry()); 34 } 35 36 // runOnFunction - To run this pass, first we calculate the alloca 37 // instructions that are safe for promotion, then we promote each one. 38 // 39 virtual bool runOnFunction(Function &F); 40 41 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 42 AU.addRequired<DominatorTree>(); 43 AU.setPreservesCFG(); 44 // This is a cluster of orthogonal Transforms 45 AU.addPreserved<UnifyFunctionExitNodes>(); 46 AU.addPreservedID(LowerSwitchID); 47 AU.addPreservedID(LowerInvokePassID); 48 } 49 }; 50 } // end of anonymous namespace 51 52 char PromotePass::ID = 0; 53 INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register", 54 false, false) 55 INITIALIZE_PASS_DEPENDENCY(DominatorTree) 56 INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register", 57 false, false) 58 59 bool PromotePass::runOnFunction(Function &F) { 60 std::vector<AllocaInst*> Allocas; 61 62 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 63 64 bool Changed = false; 65 66 DominatorTree &DT = getAnalysis<DominatorTree>(); 67 const DataLayout *DL = getAnalysisIfAvailable<DataLayout>(); 68 69 while (1) { 70 Allocas.clear(); 71 72 // Find allocas that are safe to promote, by looking at all instructions in 73 // the entry node 74 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 75 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 76 if (isAllocaPromotable(AI, DL)) 77 Allocas.push_back(AI); 78 79 if (Allocas.empty()) break; 80 81 PromoteMemToReg(Allocas, DT, DL); 82 NumPromoted += Allocas.size(); 83 Changed = true; 84 } 85 86 return Changed; 87 } 88 89 // createPromoteMemoryToRegister - Provide an entry point to create this pass. 90 // 91 FunctionPass *llvm::createPromoteMemoryToRegisterPass() { 92 return new PromotePass(); 93 } 94
