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/ADT/Statistic.h" 18#include "llvm/Analysis/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" 23using namespace llvm; 24 25STATISTIC(NumPromoted, "Number of alloca's promoted"); 26 27namespace { 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 50char PromotePass::ID = 0; 51INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register", 52 false, false) 53INITIALIZE_PASS_DEPENDENCY(DominatorTree) 54INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register", 55 false, false) 56 57bool 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// 88FunctionPass *llvm::createPromoteMemoryToRegisterPass() { 89 return new PromotePass(); 90} 91