/3rd_party/llvm/lib/Transforms/Utils/Mem2Reg.cpp

 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/Function.h"
20#include "llvm/IR/Instructions.h"
21#include "llvm/Transforms/Utils/PromoteMemToReg.h"
22#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
23using namespace llvm;
24
25STATISTIC(NumPromoted, "Number of alloca's promoted");
26
27namespace {
28  struct PromotePass : public FunctionPass {
29    static char ID; // Pass identification, replacement for typeid
30    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
39    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
50char PromotePass::ID = 0;
51INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register",
52                false, false)
53INITIALIZE_PASS_DEPENDENCY(DominatorTree)
54INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register",
55                false, false)
56
57bool 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//
88FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
89  return new PromotePass();
90}