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

//===- llvm/Analysis/AliasSetTracker.h - Build Alias Sets -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and 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/Support/CallSite.h"
#include "llvm/ADT/iterator"
#include "llvm/ADT/hash_map"
#include "llvm/ADT/ilist"

namespace llvm {

class AliasAnalysis;
class LoadInst;
class StoreInst;
class FreeInst;
class AliasSetTracker;
class AliasSet;

class AliasSet {
  friend class AliasSetTracker;

  class PointerRec;
  typedef std::pair<Value* const, PointerRec> HashNodePair;

  class PointerRec {
    HashNodePair **PrevInList, *NextInList;
    AliasSet *AS;
    unsigned Size;
  public:
    PointerRec() : PrevInList(0), NextInList(0), AS(0), Size(0) {}

    HashNodePair *getNext() const { return NextInList; }
    bool hasAliasSet() const { return AS != 0; }

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

    void updateSize(unsigned NewSize) {
      if (NewSize > Size) Size = NewSize;
    }

    unsigned getSize() const { return Size; }

    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 removeFromList() {
      if (NextInList) NextInList->second.PrevInList = PrevInList;
      *PrevInList = NextInList;
      if (AS->PtrListEnd == &NextInList) {
        AS->PtrListEnd = PrevInList;
        assert(*AS->PtrListEnd == 0 && "List not terminated right!");
      }
    }
  };

  HashNodePair *PtrList, **PtrListEnd;  // Doubly linked list of nodes
  AliasSet *Forward;             // Forwarding pointer
  AliasSet *Next, *Prev;         // Doubly linked list of AliasSets

  std::vector<CallSite> CallSites; // All calls & invokes in this node

  // 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;

  friend struct ilist_traits<AliasSet>;
  AliasSet *getPrev() const { return Prev; }
  AliasSet *getNext() const { return Next; }
  void setPrev(AliasSet *P) { Prev = P; }
  void setNext(AliasSet *N) { Next = N; }

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

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(std::ostream &OS) const;
  void dump() const;

  /// Define an iterator for alias sets... this is just a forward iterator.
  class iterator : public forward_iterator<HashNodePair, ptrdiff_t> {
    HashNodePair *CurNode;
  public:
    iterator(HashNodePair *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->first; }
    unsigned getSize() const { return CurNode->second.getSize(); }

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

private:
  // Can only be created by AliasSetTracker
  AliasSet() : PtrList(0), PtrListEnd(&PtrList), Forward(0), RefCount(0),
               AccessTy(NoModRef), AliasTy(MustAlias), Volatile(false) {
  }

  AliasSet(const AliasSet &AS) {
    assert(0 && "Copy ctor called!?!?!");
    abort();
  }

  HashNodePair *getSomePointer() const {
    return PtrList;
  }

  /// getForwardedTarget - Return the real alias set this represents.  If this
  /// has been merged with another set and is forwarding, return the ultimate
  /// destination set.  This also implements the union-find collapsing as well.
  AliasSet *getForwardedTarget(AliasSetTracker &AST) {
    if (!Forward) return this;

    AliasSet *Dest = Forward->getForwardedTarget(AST);
    if (Dest != Forward) {
      Dest->addRef();
      Forward->dropRef(AST);
      Forward = Dest;
    }
    return Dest;
  }

  void removeFromTracker(AliasSetTracker &AST);

  void addPointer(AliasSetTracker &AST, HashNodePair &Entry, unsigned Size,
                  bool KnownMustAlias = false);
  void addCallSite(CallSite CS, AliasAnalysis &AA);
  void removeCallSite(CallSite CS) {
    for (unsigned i = 0, e = CallSites.size(); i !=