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/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"
23 using namespace llvm;
24
25 STATISTIC(NumPromoted, "Number of alloca's promoted");
26
27 namespace {
28 struct PromotePass : public FunctionPass {
29 static char ID; // Pass identification, replacement for typeid
PromotePass__anona2cd17a20111::PromotePass30 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
getAnalysisUsage__anona2cd17a20111::PromotePass39 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
50 char PromotePass::ID = 0;
51 INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register",
52 false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)53 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
54 INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register",
55 false, false)
56
57 bool 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 //
createPromoteMemoryToRegisterPass()88 FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
89 return new PromotePass();
90 }
91