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      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:
     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 
    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.
    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