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/DataLayout.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/Instructions.h"
22 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
23 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
24 using namespace llvm;
25
26 STATISTIC(NumPromoted, "Number of alloca's promoted");
27
28 namespace {
29 struct PromotePass : public FunctionPass {
30 static char ID; // Pass identification, replacement for typeid
31
PromotePass__anonc15990690111::PromotePass32 PromotePass() : FunctionPass(ID) {
33 initializePromotePassPass(*PassRegistry::getPassRegistry());
34 }
35
36 // runOnFunction - To run this pass, first we calculate the alloca
37 // instructions that are safe for promotion, then we promote each one.
38 //
39 virtual bool runOnFunction(Function &F);
40
getAnalysisUsage__anonc15990690111::PromotePass41 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
42 AU.addRequired<DominatorTree>();
43 AU.setPreservesCFG();
44 // This is a cluster of orthogonal Transforms
45 AU.addPreserved<UnifyFunctionExitNodes>();
46 AU.addPreservedID(LowerSwitchID);
47 AU.addPreservedID(LowerInvokePassID);
48 }
49 };
50 } // end of anonymous namespace
51
52 char PromotePass::ID = 0;
53 INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register",
54 false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)55 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
56 INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register",
57 false, false)
58
59 bool PromotePass::runOnFunction(Function &F) {
60 std::vector<AllocaInst*> Allocas;
61
62 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
63
64 bool Changed = false;
65
66 DominatorTree &DT = getAnalysis<DominatorTree>();
67 const DataLayout *DL = getAnalysisIfAvailable<DataLayout>();
68
69 while (1) {
70 Allocas.clear();
71
72 // Find allocas that are safe to promote, by looking at all instructions in
73 // the entry node
74 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
75 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
76 if (isAllocaPromotable(AI, DL))
77 Allocas.push_back(AI);
78
79 if (Allocas.empty()) break;
80
81 PromoteMemToReg(Allocas, DT, DL);
82 NumPromoted += Allocas.size();
83 Changed = true;
84 }
85
86 return Changed;
87 }
88
89 // createPromoteMemoryToRegister - Provide an entry point to create this pass.
90 //
createPromoteMemoryToRegisterPass()91 FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
92 return new PromotePass();
93 }
94