include/llvm/Analysis/PHITransAddr.h

   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