PHITransAddr.h revision 9d2ed8e632b71914b2a668932f4f49b87c3ca0b1 
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/Instruction.h"
18#include "llvm/ADT/SmallVector.h"
19
20namespace llvm {
21  class DominatorTree;
22  class TargetData;
23
24/// PHITransAddr - An address value which tracks and handles phi translation.
25/// As we walk "up" the CFG through predecessors, we need to ensure that the
26/// address we're tracking is kept up to date.  For example, if we're analyzing
27/// an address of "&A[i]" and walk through the definition of 'i' which is a PHI
28/// node, we *must* phi translate i to get "&A[j]" or else we will analyze an
29/// incorrect pointer in the predecessor block.
30///
31/// This is designed to be a relatively small object that lives on the stack and
32/// is copyable.
33///
34class PHITransAddr {
35  /// Addr - The actual address we're analyzing.
36  Value *Addr;
37
38  /// TD - The target data we are playing with if known, otherwise null.
39  const TargetData *TD;
40
41  /// InstInputs - The inputs for our symbolic address.
42  SmallVector<Instruction*, 4> InstInputs;
43public:
44  PHITransAddr(Value *addr, const TargetData *td) : Addr(addr), TD(td) {
45    // If the address is an instruction, the whole thing is considered an input.
46    if (Instruction *I = dyn_cast<Instruction>(Addr))
47      InstInputs.push_back(I);
48  }
49
50  Value *getAddr() const { return Addr; }
51
52  /// NeedsPHITranslationFromBlock - Return true if moving from the specified
53  /// BasicBlock to its predecessors requires PHI translation.
54  bool NeedsPHITranslationFromBlock(BasicBlock *BB) const {
55    // We do need translation if one of our input instructions is defined in
56    // this block.
57    for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
58      if (InstInputs[i]->getParent() == BB)
59        return true;
60    return false;
61  }
62
63  /// IsPotentiallyPHITranslatable - If this needs PHI translation, return true
64  /// if we have some hope of doing it.  This should be used as a filter to
65  /// avoid calling PHITranslateValue in hopeless situations.
66  bool IsPotentiallyPHITranslatable() const;
67
68  /// PHITranslateValue - PHI translate the current address up the CFG from
69  /// CurBB to Pred, updating our state to reflect any needed changes.  If the
70  /// dominator tree DT is non-null, the translated value must dominate
71  /// PredBB.  This returns true on failure and sets Addr to null.
72  bool PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB,
73                         const DominatorTree *DT);
74
75  /// PHITranslateWithInsertion - PHI translate this value into the specified
76  /// predecessor block, inserting a computation of the value if it is
77  /// unavailable.
78  ///
79  /// All newly created instructions are added to the NewInsts list.  This
80  /// returns null on failure.
81  ///
82  Value *PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
83                                   const DominatorTree &DT,
84                                   SmallVectorImpl<Instruction*> &NewInsts);
85
86  void dump() const;
87
88  /// Verify - Check internal consistency of this data structure.  If the
89  /// structure is valid, it returns true.  If invalid, it prints errors and
90  /// returns false.
91  bool Verify() const;
92private:
93  Value *PHITranslateSubExpr(Value *V, BasicBlock *CurBB, BasicBlock *PredBB,
94                             const DominatorTree *DT);
95
96  /// InsertPHITranslatedSubExpr - Insert a computation of the PHI translated
97  /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
98  /// block.  All newly created instructions are added to the NewInsts list.
99  /// This returns null on failure.
100  ///
101  Value *InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
102                                    BasicBlock *PredBB, const DominatorTree &DT,
103                                    SmallVectorImpl<Instruction*> &NewInsts);
104
105  /// AddAsInput - If the specified value is an instruction, add it as an input.
106  Value *AddAsInput(Value *V) {
107    // If V is an instruction, it is now an input.
108    if (Instruction *VI = dyn_cast<Instruction>(V))
109      InstInputs.push_back(VI);
110    return V;
111  }
112
113};
114
115} // end namespace llvm
116
117#endif
118