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 INITIALIZE_PASS(PromotePass, "mem2reg", "Promote Memory to Register",
55 bool PromotePass::runOnFunction(Function &F) {
56 std::vector<AllocaInst*> Allocas;
58 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
62 DominatorTree &DT = getAnalysis<DominatorTree>();
63 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
68 // Find allocas that are safe to promote, by looking at all instructions in
70 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
71 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
72 if (isAllocaPromotable(AI))
73 Allocas.push_back(AI);
75 if (Allocas.empty()) break;
77 PromoteMemToReg(Allocas, DT, DF);
78 NumPromoted += Allocas.size();
85 // createPromoteMemoryToRegister - Provide an entry point to create this pass.
87 FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
88 return new PromotePass();