PHITransAddr.h revision 341825 
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;
51
52public:
53  PHITransAddr(Value *addr, const DataLayout &DL, AssumptionCache *AC)
54      : Addr(addr), DL(DL), TLI(nullptr), AC(AC) {
55    // If the address is an instruction, the whole thing is considered an input.
56    if (Instruction *I = dyn_cast<Instruction>(Addr))
57      InstInputs.push_back(I);
58  }
59
60  Value *getAddr() const { return Addr; }
61
62  /// NeedsPHITranslationFromBlock - Return true if moving from the specified
63  /// BasicBlock to its predecessors requires PHI translation.
64  bool NeedsPHITranslationFromBlock(BasicBlock *BB) const {
65    // We do need translation if one of our input instructions is defined in
66    // this block.
67    for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
68      if (InstInputs[i]->getParent() == BB)
69        return true;
70    return false;
71  }
72
73  /// IsPotentiallyPHITranslatable - If this needs PHI translation, return true
74  /// if we have some hope of doing it.  This should be used as a filter to
75  /// avoid calling PHITranslateValue in hopeless situations.
76  bool IsPotentiallyPHITranslatable() const;
77
78  /// PHITranslateValue - PHI translate the current address up the CFG from
79  /// CurBB to Pred, updating our state to reflect any needed changes.  If
80  /// 'MustDominate' is true, the translated value must dominate
81  /// PredBB.  This returns true on failure and sets Addr to null.
82  bool PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB,
83                         const DominatorTree *DT, bool MustDominate);
84
85  /// PHITranslateWithInsertion - PHI translate this value into the specified
86  /// predecessor block, inserting a computation of the value if it is
87  /// unavailable.
88  ///
89  /// All newly created instructions are added to the NewInsts list.  This
90  /// returns null on failure.
91  ///
92  Value *PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
93                                   const DominatorTree &DT,
94                                   SmallVectorImpl<Instruction *> &NewInsts);
95
96  void dump() const;
97
98  /// Verify - Check internal consistency of this data structure.  If the
99  /// structure is valid, it returns true.  If invalid, it prints errors and
100  /// returns false.
101  bool Verify() const;
102
103private:
104  Value *PHITranslateSubExpr(Value *V, BasicBlock *CurBB, BasicBlock *PredBB,
105                             const DominatorTree *DT);
106
107  /// InsertPHITranslatedSubExpr - Insert a computation of the PHI translated
108  /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
109  /// block.  All newly created instructions are added to the NewInsts list.
110  /// This returns null on failure.
111  ///
112  Value *InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
113                                    BasicBlock *PredBB, const DominatorTree &DT,
114                                    SmallVectorImpl<Instruction *> &NewInsts);
115
116  /// AddAsInput - If the specified value is an instruction, add it as an input.
117  Value *AddAsInput(Value *V) {
118    // If V is an instruction, it is now an input.
119    if (Instruction *VI = dyn_cast<Instruction>(V))
120      InstInputs.push_back(VI);
121    return V;
122  }
123};
124
125} // end namespace llvm
126
127#endif
128