1 //===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This pass is a simple pass wrapper around the PromoteMemToReg function call 10 // exposed by the Utils library. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Transforms/Utils/Mem2Reg.h" 15 #include "llvm/ADT/Statistic.h" 16 #include "llvm/Analysis/AssumptionCache.h" 17 #include "llvm/IR/BasicBlock.h" 18 #include "llvm/IR/Dominators.h" 19 #include "llvm/IR/Function.h" 20 #include "llvm/IR/Instructions.h" 21 #include "llvm/IR/PassManager.h" 22 #include "llvm/InitializePasses.h" 23 #include "llvm/Pass.h" 24 #include "llvm/Support/Casting.h" 25 #include "llvm/Transforms/Utils.h" 26 #include "llvm/Transforms/Utils/PromoteMemToReg.h" 27 #include <vector> 28 29 using namespace llvm; 30 31 #define DEBUG_TYPE "mem2reg" 32 33 STATISTIC(NumPromoted, "Number of alloca's promoted"); 34 35 static bool promoteMemoryToRegister(Function &F, DominatorTree &DT, 36 AssumptionCache &AC) { 37 std::vector<AllocaInst *> Allocas; 38 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 39 bool Changed = false; 40 41 while (true) { 42 Allocas.clear(); 43 44 // Find allocas that are safe to promote, by looking at all instructions in 45 // the entry node 46 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 47 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 48 if (isAllocaPromotable(AI)) 49 Allocas.push_back(AI); 50 51 if (Allocas.empty()) 52 break; 53 54 PromoteMemToReg(Allocas, DT, &AC); 55 NumPromoted += Allocas.size(); 56 Changed = true; 57 } 58 return Changed; 59 } 60 61 PreservedAnalyses PromotePass::run(Function &F, FunctionAnalysisManager &AM) { 62 auto &DT = AM.getResult<DominatorTreeAnalysis>(F); 63 auto &AC = AM.getResult<AssumptionAnalysis>(F); 64 if (!promoteMemoryToRegister(F, DT, AC)) 65 return PreservedAnalyses::all(); 66 67 PreservedAnalyses PA; 68 PA.preserveSet<CFGAnalyses>(); 69 return PA; 70 } 71 72 namespace { 73 74 struct PromoteLegacyPass : public FunctionPass { 75 // Pass identification, replacement for typeid 76 static char ID; 77 78 PromoteLegacyPass() : FunctionPass(ID) { 79 initializePromoteLegacyPassPass(*PassRegistry::getPassRegistry()); 80 } 81 82 // runOnFunction - To run this pass, first we calculate the alloca 83 // instructions that are safe for promotion, then we promote each one. 84 bool runOnFunction(Function &F) override { 85 if (skipFunction(F)) 86 return false; 87 88 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 89 AssumptionCache &AC = 90 getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); 91 return promoteMemoryToRegister(F, DT, AC); 92 } 93 94 void getAnalysisUsage(AnalysisUsage &AU) const override { 95 AU.addRequired<AssumptionCacheTracker>(); 96 AU.addRequired<DominatorTreeWrapperPass>(); 97 AU.setPreservesCFG(); 98 } 99 }; 100 101 } // end anonymous namespace 102 103 char PromoteLegacyPass::ID = 0; 104 105 INITIALIZE_PASS_BEGIN(PromoteLegacyPass, "mem2reg", "Promote Memory to " 106 "Register", 107 false, false) 108 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 109 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 110 INITIALIZE_PASS_END(PromoteLegacyPass, "mem2reg", "Promote Memory to Register", 111 false, false) 112 113 // createPromoteMemoryToRegister - Provide an entry point to create this pass. 114 FunctionPass *llvm::createPromoteMemoryToRegisterPass() { 115 return new PromoteLegacyPass(); 116 } 117