PHITransAddr.h revision 34f849098bfb8850fa34fbd115ba9b2e55c85a32 
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 the reflect any needed changes.  This
70  /// returns true on failure and sets Addr to null.
71  bool PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB);
72
73  /// PHITranslateWithInsertion - PHI translate this value into the specified
74  /// predecessor block, inserting a computation of the value if it is
75  /// unavailable.
76  ///
77  /// All newly created instructions are added to the NewInsts list.  This
78  /// returns null on failure.
79  ///
80  Value *PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
81                                   const DominatorTree &DT,
82                                   SmallVectorImpl<Instruction*> &NewInsts);
83private:
84  Value *PHITranslateSubExpr(Value *V, BasicBlock *CurBB, BasicBlock *PredBB);
85
86
87  /// GetAvailablePHITranslatedSubExpr - Return the value computed by
88  /// PHITranslateSubExpr if it dominates PredBB, otherwise return null.
89  Value *GetAvailablePHITranslatedSubExpr(Value *V,
90                                          BasicBlock *CurBB, BasicBlock *PredBB,
91                                          const DominatorTree &DT) const;
92
93  /// InsertPHITranslatedSubExpr - Insert a computation of the PHI translated
94  /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
95  /// block.  All newly created instructions are added to the NewInsts list.
96  /// This returns null on failure.
97  ///
98  Value *InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
99                                    BasicBlock *PredBB, const DominatorTree &DT,
100                                    SmallVectorImpl<Instruction*> &NewInsts);
101};
102
103} // end namespace llvm
104
105#endif
106