PHITransAddr.h revision 353358 
1//===- PHITransAddr.h - PHI Translation for Addresses -----------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file declares the PHITransAddr class.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_ANALYSIS_PHITRANSADDR_H
14#define LLVM_ANALYSIS_PHITRANSADDR_H
15
16#include "llvm/ADT/SmallVector.h"
17#include "llvm/IR/Instruction.h"
18
19namespace llvm {
20  class AssumptionCache;
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.
40  const DataLayout &DL;
41
42  /// TLI - The target library info if known, otherwise null.
43  const TargetLibraryInfo *TLI;
44
45  /// A cache of \@llvm.assume calls used by SimplifyInstruction.
46  AssumptionCache *AC;
47
48  /// InstInputs - The inputs for our symbolic address.
49  SmallVector<Instruction*, 4> InstInputs;
50
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;
101
102private:
103  Value *PHITranslateSubExpr(Value *V, BasicBlock *CurBB, BasicBlock *PredBB,
104                             const DominatorTree *DT);
105
106  /// InsertPHITranslatedSubExpr - Insert a computation of the PHI translated
107  /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
108  /// block.  All newly created instructions are added to the NewInsts list.
109  /// This returns null on failure.
110  ///
111  Value *InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
112                                    BasicBlock *PredBB, const DominatorTree &DT,
113                                    SmallVectorImpl<Instruction *> &NewInsts);
114
115  /// AddAsInput - If the specified value is an instruction, add it as an input.
116  Value *AddAsInput(Value *V) {
117    // If V is an instruction, it is now an input.
118    if (Instruction *VI = dyn_cast<Instruction>(V))
119      InstInputs.push_back(VI);
120    return V;
121  }
122};
123
124} // end namespace llvm
125
126#endif
127