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/Pass.h" 23 #include "llvm/Support/Casting.h" 24 #include "llvm/Transforms/Utils.h" 25 #include "llvm/Transforms/Utils/PromoteMemToReg.h" 26 #include <vector> 27 28 using namespace llvm; 29 30 #define DEBUG_TYPE "mem2reg" 31 32 STATISTIC(NumPromoted, "Number of alloca's promoted"); 33 34 static bool promoteMemoryToRegister(Function &F, DominatorTree &DT, 35 AssumptionCache &AC) { 36 std::vector<AllocaInst *> Allocas; 37 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 38 bool Changed = false; 39 40 while (true) { 41 Allocas.clear(); 42 43 // Find allocas that are safe to promote, by looking at all instructions in 44 // the entry node 45 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 46 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 47 if (isAllocaPromotable(AI)) 48 Allocas.push_back(AI); 49 50 if (Allocas.empty()) 51 break; 52 53 PromoteMemToReg(Allocas, DT, &AC); 54 NumPromoted += Allocas.size(); 55 Changed = true; 56 } 57 return Changed; 58 } 59 60 PreservedAnalyses PromotePass::run(Function &F, FunctionAnalysisManager &AM) { 61 auto &DT = AM.getResult<DominatorTreeAnalysis>(F); 62 auto &AC = AM.getResult<AssumptionAnalysis>(F); 63 if (!promoteMemoryToRegister(F, DT, AC)) 64 return PreservedAnalyses::all(); 65 66 PreservedAnalyses PA; 67 PA.preserveSet<CFGAnalyses>(); 68 return PA; 69 } 70 71 namespace { 72 73 struct PromoteLegacyPass : public FunctionPass { 74 // Pass identification, replacement for typeid 75 static char ID; 76 77 PromoteLegacyPass() : FunctionPass(ID) { 78 initializePromoteLegacyPassPass(*PassRegistry::getPassRegistry()); 79 } 80 81 // runOnFunction - To run this pass, first we calculate the alloca 82 // instructions that are safe for promotion, then we promote each one. 83 bool runOnFunction(Function &F) override { 84 if (skipFunction(F)) 85 return false; 86 87 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 88 AssumptionCache &AC = 89 getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); 90 return promoteMemoryToRegister(F, DT, AC); 91 } 92 93 void getAnalysisUsage(AnalysisUsage &AU) const override { 94 AU.addRequired<AssumptionCacheTracker>(); 95 AU.addRequired<DominatorTreeWrapperPass>(); 96 AU.setPreservesCFG(); 97 } 98 }; 99 100 } // end anonymous namespace 101 102 char PromoteLegacyPass::ID = 0; 103 104 INITIALIZE_PASS_BEGIN(PromoteLegacyPass, "mem2reg", "Promote Memory to " 105 "Register", 106 false, false) 107 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 108 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 109 INITIALIZE_PASS_END(PromoteLegacyPass, "mem2reg", "Promote Memory to Register", 110 false, false) 111 112 // createPromoteMemoryToRegister - Provide an entry point to create this pass. 113 FunctionPass *llvm::createPromoteMemoryToRegisterPass() { 114 return new PromoteLegacyPass(); 115 } 116