1 //===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass is a simple pass wrapper around the PromoteMemToReg function call
11 // exposed by the Utils library.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "mem2reg"
16 #include "llvm/Transforms/Scalar.h"
17 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
18 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
19 #include "llvm/Analysis/Dominators.h"
20 #include "llvm/Instructions.h"
21 #include "llvm/Function.h"
22 #include "llvm/ADT/Statistic.h"
25 STATISTIC(NumPromoted, "Number of alloca's promoted");
28 struct PromotePass : public FunctionPass {
29 static char ID; // Pass identification, replacement for typeid
30 PromotePass() : FunctionPass(ID) {}
32 // runOnFunction - To run this pass, first we calculate the alloca
33 // instructions that are safe for promotion, then we promote each one.
35 virtual bool runOnFunction(Function &F);
37 // getAnalysisUsage - We need dominance frontiers
39 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
40 AU.addRequired<DominatorTree>();
41 AU.addRequired<DominanceFrontier>();
43 // This is a cluster of orthogonal Transforms
44 AU.addPreserved<UnifyFunctionExitNodes>();
45 AU.addPreservedID(LowerSwitchID);
46 AU.addPreservedID(LowerInvokePassID);
49 } // end of anonymous namespace
51 char PromotePass::ID = 0;
52 static RegisterPass<PromotePass> X("mem2reg", "Promote Memory to Register");
54 bool PromotePass::runOnFunction(Function &F) {
55 std::vector<AllocaInst*> Allocas;
57 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
61 DominatorTree &DT = getAnalysis<DominatorTree>();
62 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
67 // Find allocas that are safe to promote, by looking at all instructions in
69 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
70 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
71 if (isAllocaPromotable(AI))
72 Allocas.push_back(AI);
74 if (Allocas.empty()) break;
76 PromoteMemToReg(Allocas, DT, DF);
77 NumPromoted += Allocas.size();
84 // createPromoteMemoryToRegister - Provide an entry point to create this pass.
86 FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
87 return new PromotePass();