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/Analysis/AssumptionCache.h" 18 #include "llvm/IR/Dominators.h" 19 #include "llvm/IR/Function.h" 20 #include "llvm/IR/Instructions.h" 21 #include "llvm/Transforms/Utils/PromoteMemToReg.h" 22 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h" 23 using namespace llvm; 24 25 #define DEBUG_TYPE "mem2reg" 26 27 STATISTIC(NumPromoted, "Number of alloca's promoted"); 28 29 namespace { 30 struct PromotePass : public FunctionPass { 31 static char ID; // Pass identification, replacement for typeid 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 bool runOnFunction(Function &F) override; 40 41 void getAnalysisUsage(AnalysisUsage &AU) const override { 42 AU.addRequired<AssumptionCacheTracker>(); 43 AU.addRequired<DominatorTreeWrapperPass>(); 44 AU.setPreservesCFG(); 45 // This is a cluster of orthogonal Transforms 46 AU.addPreserved<UnifyFunctionExitNodes>(); 47 AU.addPreservedID(LowerSwitchID); 48 AU.addPreservedID(LowerInvokePassID); 49 } 50 }; 51 } // end of anonymous namespace 52 53 char PromotePass::ID = 0; 54 INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register", 55 false, false) 56 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 57 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 58 INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register", 59 false, false) 60 61 bool PromotePass::runOnFunction(Function &F) { 62 std::vector<AllocaInst*> Allocas; 63 64 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 65 66 bool Changed = false; 67 68 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 69 AssumptionCache &AC = 70 getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); 71 72 while (1) { 73 Allocas.clear(); 74 75 // Find allocas that are safe to promote, by looking at all instructions in 76 // the entry node 77 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 78 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 79 if (isAllocaPromotable(AI)) 80 Allocas.push_back(AI); 81 82 if (Allocas.empty()) break; 83 84 PromoteMemToReg(Allocas, DT, nullptr, &AC); 85 NumPromoted += Allocas.size(); 86 Changed = true; 87 } 88 89 return Changed; 90 } 91 92 // createPromoteMemoryToRegister - Provide an entry point to create this pass. 93 // 94 FunctionPass *llvm::createPromoteMemoryToRegisterPass() { 95 return new PromotePass(); 96 } 97
