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 
20 namespace 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 ///
34 class 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;
43 public:
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;
92 private:
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