PHITransAddr.h revision 288943 
1//===- PHITransAddr.h - PHI Translation for Addresses -----------*- C++ -*-===//
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 file declares the PHITransAddr class.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ANALYSIS_PHITRANSADDR_H
15#define LLVM_ANALYSIS_PHITRANSADDR_H
16
17#include "llvm/ADT/SmallVector.h"
18#include "llvm/IR/Instruction.h"
19
20namespace llvm {
21  class AssumptionCache;
22  class DominatorTree;
23  class DataLayout;
24  class TargetLibraryInfo;
25
26/// PHITransAddr - An address value which tracks and handles phi translation.
27/// As we walk "up" the CFG through predecessors, we need to ensure that the
28/// address we're tracking is kept up to date.  For example, if we're analyzing
29/// an address of "&A[i]" and walk through the definition of 'i' which is a PHI
30/// node, we *must* phi translate i to get "&A[j]" or else we will analyze an
31/// incorrect pointer in the predecessor block.
32///
33/// This is designed to be a relatively small object that lives on the stack and
34/// is copyable.
35///
36class PHITransAddr {
37  /// Addr - The actual address we're analyzing.
38  Value *Addr;
39
40  /// The DataLayout we are playing with.
41  const DataLayout &DL;
42
43  /// TLI - The target library info if known, otherwise null.
44  const TargetLibraryInfo *TLI;
45
46  /// A cache of @llvm.assume calls used by SimplifyInstruction.
47  AssumptionCache *AC;
48
49  /// InstInputs - The inputs for our symbolic address.
50  SmallVector<Instruction*, 4> InstInputs;
51public:
52  PHITransAddr(Value *addr, const DataLayout &DL, AssumptionCache *AC)
53      : Addr(addr), DL(DL), TLI(nullptr), AC(AC) {
54    // If the address is an instruction, the whole thing is considered an input.
55    if (Instruction *I = dyn_cast<Instruction>(Addr))
56      InstInputs.push_back(I);
57  }
58
59  Value *getAddr() const { return Addr; }
60
61  /// NeedsPHITranslationFromBlock - Return true if moving from the specified
62  /// BasicBlock to its predecessors requires PHI translation.
63  bool NeedsPHITranslationFromBlock(BasicBlock *BB) const {
64    // We do need translation if one of our input instructions is defined in
65    // this block.
66    for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
67      if (InstInputs[i]->getParent() == BB)
68        return true;
69    return false;
70  }
71
72  /// IsPotentiallyPHITranslatable - If this needs PHI translation, return true
73  /// if we have some hope of doing it.  This should be used as a filter to
74  /// avoid calling PHITranslateValue in hopeless situations.
75  bool IsPotentiallyPHITranslatable() const;
76
77  /// PHITranslateValue - PHI translate the current address up the CFG from
78  /// CurBB to Pred, updating our state to reflect any needed changes.  If
79  /// 'MustDominate' is true, the translated value must dominate
80  /// PredBB.  This returns true on failure and sets Addr to null.
81  bool PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB,
82                         const DominatorTree *DT, bool MustDominate);
83
84  /// PHITranslateWithInsertion - PHI translate this value into the specified
85  /// predecessor block, inserting a computation of the value if it is
86  /// unavailable.
87  ///
88  /// All newly created instructions are added to the NewInsts list.  This
89  /// returns null on failure.
90  ///
91  Value *PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
92                                   const DominatorTree &DT,
93                                   SmallVectorImpl<Instruction*> &NewInsts);
94
95  void dump() const;
96
97  /// Verify - Check internal consistency of this data structure.  If the
98  /// structure is valid, it returns true.  If invalid, it prints errors and
99  /// returns false.
100  bool Verify() const;
101private:
102  Value *PHITranslateSubExpr(Value *V, BasicBlock *CurBB, BasicBlock *PredBB,
103                             const DominatorTree *DT);
104
105  /// InsertPHITranslatedSubExpr - Insert a computation of the PHI translated
106  /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
107  /// block.  All newly created instructions are added to the NewInsts list.
108  /// This returns null on failure.
109  ///
110  Value *InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
111                                    BasicBlock *PredBB, const DominatorTree &DT,
112                                    SmallVectorImpl<Instruction*> &NewInsts);
113
114  /// AddAsInput - If the specified value is an instruction, add it as an input.
115  Value *AddAsInput(Value *V) {
116    // If V is an instruction, it is now an input.
117    if (Instruction *VI = dyn_cast<Instruction>(V))
118      InstInputs.push_back(VI);
119    return V;
120  }
121
122};
123
124} // end namespace llvm
125
126#endif
127