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