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