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 
19 namespace 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 ///
35 class 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 
51 public:
PHITransAddr(Value * addr,const DataLayout & DL,AssumptionCache * AC)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 
getAddr()59   Value *getAddr() const { return Addr; }
60 
61   /// NeedsPHITranslationFromBlock - Return true if moving from the specified
62   /// BasicBlock to its predecessors requires PHI translation.
NeedsPHITranslationFromBlock(BasicBlock * BB)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 
102 private:
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.
AddAsInput(Value * V)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