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Mem2Reg.cpp
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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"
19 #include "llvm/IR/Function.h"
20 #include "llvm/IR/Instructions.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
30  PromotePass() : FunctionPass(ID) {
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 {
41  AU.setPreservesCFG();
42  // This is a cluster of orthogonal Transforms
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)
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 //
89  return new PromotePass();
90 }
AnalysisUsage & addPreserved()
static PassRegistry * getPassRegistry()
An abstraction for memory operations.
Definition: Memory.h:45
Promote Memory to false
Definition: Mem2Reg.cpp:54
STATISTIC(NumPromoted,"Number of alloca's promoted")
void PromoteMemToReg(ArrayRef< AllocaInst * > Allocas, DominatorTree &DT, AliasSetTracker *AST=0)
Promote the specified list of alloca instructions into scalar registers, inserting PHI nodes as appro...
F(f)
char & LowerSwitchID
bool isAllocaPromotable(const AllocaInst *AI)
Return true if this alloca is legal for promotion.
void initializePromotePassPass(PassRegistry &)
iterator begin()
Definition: BasicBlock.h:193
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:167
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:172
ID
LLVM Calling Convention Representation.
Definition: CallingConv.h:26
AnalysisUsage & addPreservedID(const void *ID)
LLVM Basic Block Representation.
Definition: BasicBlock.h:72
char & LowerInvokePassID
iterator end()
Definition: BasicBlock.h:195
Promote Memory to Register
Definition: Mem2Reg.cpp:54
void setPreservesCFG()
Definition: Pass.cpp:249
mem2reg
Definition: Mem2Reg.cpp:54
#define I(x, y, z)
Definition: MD5.cpp:54
INITIALIZE_PASS_BEGIN(PromotePass,"mem2reg","Promote Memory to Register", false, false) INITIALIZE_PASS_END(PromotePass
FunctionPass * createPromoteMemoryToRegisterPass()
Definition: Mem2Reg.cpp:88