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 #include "llvm/Transforms/Scalar.h" 16 #include "llvm/ADT/Statistic.h" 17 #include "llvm/IR/Dominators.h" 18 #include "llvm/IR/Function.h" 19 #include "llvm/IR/Instructions.h" 20 #include "llvm/Transforms/Utils/PromoteMemToReg.h" 21 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h" 22 using namespace llvm; 23 24 #define DEBUG_TYPE "mem2reg" 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 PromotePass() : FunctionPass(ID) { 32 initializePromotePassPass(*PassRegistry::getPassRegistry()); 33 } 34 35 // runOnFunction - To run this pass, first we calculate the alloca 36 // instructions that are safe for promotion, then we promote each one. 37 // 38 bool runOnFunction(Function &F) override; 39 40 void getAnalysisUsage(AnalysisUsage &AU) const override { 41 AU.addRequired<DominatorTreeWrapperPass>(); 42 AU.setPreservesCFG(); 43 // This is a cluster of orthogonal Transforms 44 AU.addPreserved<UnifyFunctionExitNodes>(); 45 AU.addPreservedID(LowerSwitchID); 46 AU.addPreservedID(LowerInvokePassID); 47 } 48 }; 49 } // end of anonymous namespace 50 51 char PromotePass::ID = 0; 52 INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register", 53 false, false) 54 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 55 INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register", 56 false, false) 57 58 bool PromotePass::runOnFunction(Function &F) { 59 std::vector<AllocaInst*> Allocas; 60 61 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 62 63 bool Changed = false; 64 65 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 66 67 while (1) { 68 Allocas.clear(); 69 70 // Find allocas that are safe to promote, by looking at all instructions in 71 // the entry node 72 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 73 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 74 if (isAllocaPromotable(AI)) 75 Allocas.push_back(AI); 76 77 if (Allocas.empty()) break; 78 79 PromoteMemToReg(Allocas, DT); 80 NumPromoted += Allocas.size(); 81 Changed = true; 82 } 83 84 return Changed; 85 } 86 87 // createPromoteMemoryToRegister - Provide an entry point to create this pass. 88 // 89 FunctionPass *llvm::createPromoteMemoryToRegisterPass() { 90 return new PromotePass(); 91 } 92
