path: root/include/llvm/Analysis/AliasSetTracker.h

//===- llvm/Analysis/AliasSetTracker.h - Build Alias Sets -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines two classes: AliasSetTracker and AliasSet.  These interface
// are used to classify a collection of pointer references into a maximal number
// of disjoint sets.  Each AliasSet object constructed by the AliasSetTracker
// object refers to memory disjoint from the other sets.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_ALIASSETTRACKER_H
#define LLVM_ANALYSIS_ALIASSETTRACKER_H

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/ilist.h"
#include "llvm/ADT/ilist_node.h"
#include "llvm/Support/ValueHandle.h"
#include <vector>

namespace llvm {

class AliasAnalysis;
class LoadInst;
class StoreInst;
class VAArgInst;
class AliasSetTracker;
class AliasSet;

class AliasSet : public ilist_node<AliasSet> {
  friend class AliasSetTracker;

  class PointerRec {
    Value *Val;  // The pointer this record corresponds to.
    PointerRec **PrevInList, *NextInList;
    AliasSet *AS;
    uint64_t Size;
    const MDNode *TBAAInfo;
  public:
    PointerRec(Value *V)
      : Val(V), PrevInList(0), NextInList(0), AS(0), Size(0),
        TBAAInfo(DenseMapInfo<const MDNode *>::getEmptyKey()) {}

    Value *getValue() const { return Val; }
    
    PointerRec *getNext() const { return NextInList; }
    bool hasAliasSet() const { return AS != 0; }

    PointerRec** setPrevInList(PointerRec **PIL) {
      PrevInList = PIL;
      return &NextInList;
    }

    void updateSizeAndTBAAInfo(uint64_t NewSize, const MDNode *NewTBAAInfo) {
      if (NewSize > Size) Size = NewSize;

      if (TBAAInfo == DenseMapInfo<const MDNode *>::getEmptyKey())
        // We don't have a TBAAInfo yet. Set it to NewTBAAInfo.
        TBAAInfo = NewTBAAInfo;
      else if (TBAAInfo != NewTBAAInfo)
        // NewTBAAInfo conflicts with TBAAInfo.
        TBAAInfo = DenseMapInfo<const MDNode *>::getTombstoneKey();
    }

    uint64_t getSize() const { return Size; }

    /// getTBAAInfo - Return the TBAAInfo, or null if there is no
    /// information or conflicting information.
    const MDNode *getTBAAInfo() const {
      // If we have missing or conflicting TBAAInfo, return null.
      if (TBAAInfo == DenseMapInfo<const MDNode *>::getEmptyKey() ||
          TBAAInfo == DenseMapInfo<const MDNode *>::getTombstoneKey())
        return 0;
      return TBAAInfo;
    }

    AliasSet *getAliasSet(AliasSetTracker &AST) {
      assert(AS && "No AliasSet yet!");
      if (AS->Forward) {
        AliasSet *OldAS = AS;
        AS = OldAS->getForwardedTarget(AST);
        AS->addRef();
        OldAS->dropRef(AST);
      }
      return AS;
    }

    void setAliasSet(AliasSet *as) {
      assert(AS == 0 && "Already have an alias set!");
      AS = as;
    }

    void eraseFromList() {
      if (NextInList) NextInList->PrevInList = PrevInList;
      *PrevInList = NextInList;
      if (AS->PtrListEnd == &NextInList) {
        AS->PtrListEnd = PrevInList;
        assert(*AS->PtrListEnd == 0 && "List not terminated right!");
      }
      delete this;
    }
  };

  PointerRec *PtrList, **PtrListEnd;  // Doubly linked list of nodes.
  AliasSet *Forward;             // Forwarding pointer.

  // All instructions without a specific address in this alias set.
  std::vector<AssertingVH<Instruction> > UnknownInsts;

  // RefCount - Number of nodes pointing to this AliasSet plus the number of
  // AliasSets forwarding to it.
  unsigned RefCount : 28;

  /// AccessType - Keep track of whether this alias set merely refers to the
  /// locations of memory, whether it modifies the memory, or whether it does
  /// both.  The lattice goes from "NoModRef" to either Refs or Mods, then to
  /// ModRef as necessary.
  ///
  enum AccessType {
    NoModRef = 0, Refs = 1,         // Ref = bit 1
    Mods     = 2, ModRef = 3        // Mod = bit 2
  };
  unsigned AccessTy : 2;

  /// AliasType - Keep track the relationships between the pointers in the set.
  /// Lattice goes from MustAlias to MayAlias.
  ///
  enum AliasType {
    MustAlias = 0, MayAlias = 1
  };
  unsigned AliasTy : 1;

  // Volatile - True if this alias set contains volatile loads or stores.
  bool Volatile : 1;

  void addRef() { ++RefCount; }
  void dropRef(AliasSetTracker &AST) {
    assert(RefCount >= 1 && "Invalid reference count detected!");
    if (--RefCount == 0)
      removeFromTracker(AST);
  }

  Instruction *getUnknownInst(unsigned i) const {
    assert(i < UnknownInsts.size());
    return UnknownInsts[i];
  }
  
public:
  /// Accessors...
  bool isRef() const { return AccessTy & Refs; }
  bool isMod() const { return AccessTy & Mods; }
  bool isMustAlias() const { return AliasTy == MustAlias; }
  bool isMayAlias()  const { return AliasTy == MayAlias; }

  // isVolatile - Return true if this alias set contains volatile loads or
  // stores.
  bool isVolatile() const { return Volatile; }

  /// isForwardingAliasSet - Return true if this alias set should be ignored as
  /// part of the AliasSetTracker object.
  bool isForwardingAliasSet() const { return Forward; }

  /// mergeSetIn - Merge the specified alias set into this alias set...
  ///
  void mergeSetIn(AliasSet &AS, AliasSetTracker &AST);

  // Alias Set iteration - Allow access to all of the pointer which are part of
  // this alias set...
  class iterator;
  iterator begin() const { return iterator(PtrList); }
  iterator end()   const { return iterator(); }
  bool empty() const { return PtrList == 0; }

  void print(raw_ostream &OS) const;
  void dump() const;

  /// Define an iterator for alias sets... this is just a forward iterator.
  class iterator : public std::iterator<std::forward_iterator_tag,
                                        PointerRec, ptrdiff_t> {
    PointerRec *CurNode;
  public:
    explicit iterator(PointerRec *CN = 0) : CurNode(CN) {}

    bool operator==(const iterator& x) const {
      return CurNode == x.CurNode;
    }
    bool operator!=(const iterator& x) const { return !operator==(x); }

    const iterator &operator=(const iterator &I) {
      CurNode = I.CurNode;
      return *this;
    }

    value_type &operator*() const {
      assert(CurNode && "Dereferencing AliasSet.end()!");
      return *CurNode;
    }
    value_type *operator->() const { return &operator*(); }

    Value *getPointer() const { return CurNode->getValue(); }
    uint64_t getSize() const { return CurNode->getSize(); }
    const MDNode *getTBAAInfo() const { return CurNode->getTBAAInfo(); }

    iterator& operator++() {                // Preincrement
      assert(CurNode && "Advancing past AliasSet.end()!");
      CurNode = CurNode->getNext();
      return *this;
    }
    iterator operator++(int) { // Postincrement
      iterator tmp = *this; ++*this; return tmp;
    }
  };

private:
  // Can only be created by AliasSetTracker. Also, ilist creates one
  // to serve as a sentinel.
  friend struct ilist_sentinel_traits<AliasSet>;
  AliasSet() : PtrList(0), PtrListEnd(&PtrList), Forward(0), RefCount(0),
               AccessTy(NoModRef), AliasTy(MustAlias), Volatile(false) {
  }

  AliasSet(const AliasSet &AS) LLVM_DELETED_FUNCTION;
  void operator=(const AliasSet