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DSNode.h

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00001 //===- DSNode.h - Node definition for datastructure graphs ------*- C++ -*-===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // Data structure graph nodes and some implementation of DSNodeHandle.
00011 //
00012 //===----------------------------------------------------------------------===//
00013 
00014 #ifndef LLVM_ANALYSIS_DSNODE_H
00015 #define LLVM_ANALYSIS_DSNODE_H
00016 
00017 #include "llvm/Analysis/DataStructure/DSSupport.h"
00018 
00019 namespace llvm {
00020 
00021 template<typename BaseType>
00022 class DSNodeIterator;          // Data structure graph traversal iterator
00023 class TargetData;
00024 
00025 //===----------------------------------------------------------------------===//
00026 /// DSNode - Data structure node class
00027 ///
00028 /// This class represents an untyped memory object of Size bytes.  It keeps
00029 /// track of any pointers that have been stored into the object as well as the
00030 /// different types represented in this object.
00031 ///
00032 class DSNode {
00033   /// NumReferrers - The number of DSNodeHandles pointing to this node... if
00034   /// this is a forwarding node, then this is the number of node handles which
00035   /// are still forwarding over us.
00036   ///
00037   unsigned NumReferrers;
00038 
00039   /// ForwardNH - This NodeHandle contain the node (and offset into the node)
00040   /// that this node really is.  When nodes get folded together, the node to be
00041   /// eliminated has these fields filled in, otherwise ForwardNH.getNode() is
00042   /// null.
00043   ///
00044   DSNodeHandle ForwardNH;
00045 
00046   /// Next, Prev - These instance variables are used to keep the node on a
00047   /// doubly-linked ilist in the DSGraph.
00048   ///
00049   DSNode *Next, *Prev;
00050   friend struct ilist_traits<DSNode>;
00051 
00052   /// Size - The current size of the node.  This should be equal to the size of
00053   /// the current type record.
00054   ///
00055   unsigned Size;
00056 
00057   /// ParentGraph - The graph this node is currently embedded into.
00058   ///
00059   DSGraph *ParentGraph;
00060 
00061   /// Ty - Keep track of the current outer most type of this object, in addition
00062   /// to whether or not it has been indexed like an array or not.  If the
00063   /// isArray bit is set, the node cannot grow.
00064   ///
00065   const Type *Ty;                 // The type itself...
00066 
00067   /// Links - Contains one entry for every sizeof(void*) bytes in this memory
00068   /// object.  Note that if the node is not a multiple of size(void*) bytes
00069   /// large, that there is an extra entry for the "remainder" of the node as
00070   /// well.  For this reason, nodes of 1 byte in size do have one link.
00071   ///
00072   std::vector<DSNodeHandle> Links;
00073 
00074   /// Globals - The list of global values that are merged into this node.
00075   ///
00076   std::vector<GlobalValue*> Globals;
00077 
00078   void operator=(const DSNode &); // DO NOT IMPLEMENT
00079   DSNode(const DSNode &);         // DO NOT IMPLEMENT
00080 public:
00081   enum NodeTy {
00082     ShadowNode  = 0,        // Nothing is known about this node...
00083     AllocaNode  = 1 << 0,   // This node was allocated with alloca
00084     HeapNode    = 1 << 1,   // This node was allocated with malloc
00085     GlobalNode  = 1 << 2,   // This node was allocated by a global var decl
00086     UnknownNode = 1 << 3,   // This node points to unknown allocated memory 
00087     Incomplete  = 1 << 4,   // This node may not be complete
00088 
00089     Modified    = 1 << 5,   // This node is modified in this context
00090     Read        = 1 << 6,   // This node is read in this context
00091 
00092     Array       = 1 << 7,   // This node is treated like an array
00093     //#ifndef NDEBUG
00094     DEAD        = 1 << 8,   // This node is dead and should not be pointed to
00095     //#endif
00096 
00097     Composition = AllocaNode | HeapNode | GlobalNode | UnknownNode,
00098   };
00099   
00100   /// NodeType - A union of the above bits.  "Shadow" nodes do not add any flags
00101   /// to the nodes in the data structure graph, so it is possible to have nodes
00102   /// with a value of 0 for their NodeType.
00103   ///
00104 private:
00105   unsigned short NodeType;
00106 public:
00107   
00108   /// DSNode ctor - Create a node of the specified type, inserting it into the
00109   /// specified graph.
00110   ///
00111   DSNode(const Type *T, DSGraph *G);
00112 
00113   /// DSNode "copy ctor" - Copy the specified node, inserting it into the
00114   /// specified graph.  If NullLinks is true, then null out all of the links,
00115   /// but keep the same number of them.  This can be used for efficiency if the
00116   /// links are just going to be clobbered anyway.
00117   ///
00118   DSNode(const DSNode &, DSGraph *G, bool NullLinks = false);
00119 
00120   ~DSNode() {
00121     dropAllReferences();
00122     assert(hasNoReferrers() && "Referrers to dead node exist!");
00123   }
00124 
00125   // Iterator for graph interface... Defined in DSGraphTraits.h
00126   typedef DSNodeIterator<DSNode> iterator;
00127   typedef DSNodeIterator<const DSNode> const_iterator;
00128   inline iterator begin();
00129   inline iterator end();
00130   inline const_iterator begin() const;
00131   inline const_iterator end() const;
00132 
00133   //===--------------------------------------------------
00134   // Accessors
00135 
00136   /// getSize - Return the maximum number of bytes occupied by this object...
00137   ///
00138   unsigned getSize() const { return Size; }
00139 
00140   /// getType - Return the node type of this object...
00141   ///
00142   const Type *getType() const { return Ty; }
00143 
00144   bool isArray() const { return NodeType & Array; }
00145 
00146   /// hasNoReferrers - Return true if nothing is pointing to this node at all.
00147   ///
00148   bool hasNoReferrers() const { return getNumReferrers() == 0; }
00149 
00150   /// getNumReferrers - This method returns the number of referrers to the
00151   /// current node.  Note that if this node is a forwarding node, this will
00152   /// return the number of nodes forwarding over the node!
00153   unsigned getNumReferrers() const { return NumReferrers; }
00154 
00155   DSGraph *getParentGraph() const { return ParentGraph; }
00156   void setParentGraph(DSGraph *G) { ParentGraph = G; }
00157 
00158 
00159   /// getTargetData - Get the target data object used to construct this node.
00160   ///
00161   const TargetData &getTargetData() const;
00162 
00163   /// getForwardNode - This method returns the node that this node is forwarded
00164   /// to, if any.
00165   ///
00166   DSNode *getForwardNode() const { return ForwardNH.getNode(); }
00167 
00168   /// isForwarding - Return true if this node is forwarding to another.
00169   ///
00170   bool isForwarding() const { return !ForwardNH.isNull(); }
00171 
00172   /// stopForwarding - When the last reference to this forwarding node has been
00173   /// dropped, delete the node.
00174   ///
00175   void stopForwarding() {
00176     assert(isForwarding() &&
00177            "Node isn't forwarding, cannot stopForwarding()!");
00178     ForwardNH.setTo(0, 0);
00179     assert(ParentGraph == 0 &&
00180            "Forwarding nodes must have been removed from graph!");
00181     delete this;
00182   }
00183 
00184   /// hasLink - Return true if this memory object has a link in slot #LinkNo
00185   ///
00186   bool hasLink(unsigned Offset) const {
00187     assert((Offset & ((1 << DS::PointerShift)-1)) == 0 &&
00188            "Pointer offset not aligned correctly!");
00189     unsigned Index = Offset >> DS::PointerShift;
00190     assert(Index < Links.size() && "Link index is out of range!");
00191     return Links[Index].getNode();
00192   }
00193 
00194   /// getLink - Return the link at the specified offset.
00195   ///
00196   DSNodeHandle &getLink(unsigned Offset) {
00197     assert((Offset & ((1 << DS::PointerShift)-1)) == 0 &&
00198            "Pointer offset not aligned correctly!");
00199     unsigned Index = Offset >> DS::PointerShift;
00200     assert(Index < Links.size() && "Link index is out of range!");
00201     return Links[Index];
00202   }
00203   const DSNodeHandle &getLink(unsigned Offset) const {
00204     assert((Offset & ((1 << DS::PointerShift)-1)) == 0 &&
00205            "Pointer offset not aligned correctly!");
00206     unsigned Index = Offset >> DS::PointerShift;
00207     assert(Index < Links.size() && "Link index is out of range!");
00208     return Links[Index];
00209   }
00210 
00211   /// getNumLinks - Return the number of links in a node...
00212   ///
00213   unsigned getNumLinks() const { return Links.size(); }
00214 
00215   /// mergeTypeInfo - This method merges the specified type into the current
00216   /// node at the specified offset.  This may update the current node's type
00217   /// record if this gives more information to the node, it may do nothing to
00218   /// the node if this information is already known, or it may merge the node
00219   /// completely (and return true) if the information is incompatible with what
00220   /// is already known.
00221   ///
00222   /// This method returns true if the node is completely folded, otherwise
00223   /// false.
00224   ///
00225   bool mergeTypeInfo(const Type *Ty, unsigned Offset,
00226                      bool FoldIfIncompatible = true);
00227 
00228   /// foldNodeCompletely - If we determine that this node has some funny
00229   /// behavior happening to it that we cannot represent, we fold it down to a
00230   /// single, completely pessimistic, node.  This node is represented as a
00231   /// single byte with a single TypeEntry of "void" with isArray = true.
00232   ///
00233   void foldNodeCompletely();
00234 
00235   /// isNodeCompletelyFolded - Return true if this node has been completely
00236   /// folded down to something that can never be expanded, effectively losing
00237   /// all of the field sensitivity that may be present in the node.
00238   ///
00239   bool isNodeCompletelyFolded() const;
00240 
00241   /// setLink - Set the link at the specified offset to the specified
00242   /// NodeHandle, replacing what was there.  It is uncommon to use this method,
00243   /// instead one of the higher level methods should be used, below.
00244   ///
00245   void setLink(unsigned Offset, const DSNodeHandle &NH) {
00246     assert((Offset & ((1 << DS::PointerShift)-1)) == 0 &&
00247            "Pointer offset not aligned correctly!");
00248     unsigned Index = Offset >> DS::PointerShift;
00249     assert(Index < Links.size() && "Link index is out of range!");
00250     Links[Index] = NH;
00251   }
00252 
00253   /// getPointerSize - Return the size of a pointer for the current target.
00254   ///
00255   unsigned getPointerSize() const { return DS::PointerSize; }
00256 
00257   /// addEdgeTo - Add an edge from the current node to the specified node.  This
00258   /// can cause merging of nodes in the graph.
00259   ///
00260   void addEdgeTo(unsigned Offset, const DSNodeHandle &NH);
00261 
00262   /// mergeWith - Merge this node and the specified node, moving all links to
00263   /// and from the argument node into the current node, deleting the node
00264   /// argument.  Offset indicates what offset the specified node is to be merged
00265   /// into the current node.
00266   ///
00267   /// The specified node may be a null pointer (in which case, nothing happens).
00268   ///
00269   void mergeWith(const DSNodeHandle &NH, unsigned Offset);
00270 
00271   /// addGlobal - Add an entry for a global value to the Globals list.  This
00272   /// also marks the node with the 'G' flag if it does not already have it.
00273   ///
00274   void addGlobal(GlobalValue *GV);
00275   void mergeGlobals(const std::vector<GlobalValue*> &RHS);
00276   const std::vector<GlobalValue*> &getGlobals() const { return Globals; }
00277 
00278   typedef std::vector<GlobalValue*>::const_iterator global_iterator;
00279   global_iterator global_begin() const { return Globals.begin(); }
00280   global_iterator global_end() const { return Globals.end(); }
00281 
00282 
00283   /// maskNodeTypes - Apply a mask to the node types bitfield.
00284   ///
00285   void maskNodeTypes(unsigned Mask) {
00286     NodeType &= Mask;
00287   }
00288 
00289   void mergeNodeFlags(unsigned RHS) {
00290     NodeType |= RHS;
00291   }
00292 
00293   /// getNodeFlags - Return all of the flags set on the node.  If the DEAD flag
00294   /// is set, hide it from the caller.
00295   ///
00296   unsigned getNodeFlags() const { return NodeType & ~DEAD; }
00297 
00298   bool isAllocaNode()  const { return NodeType & AllocaNode; }
00299   bool isHeapNode()    const { return NodeType & HeapNode; }
00300   bool isGlobalNode()  const { return NodeType & GlobalNode; }
00301   bool isUnknownNode() const { return NodeType & UnknownNode; }
00302 
00303   bool isModified() const   { return NodeType & Modified; }
00304   bool isRead() const       { return NodeType & Read; }
00305 
00306   bool isIncomplete() const { return NodeType & Incomplete; }
00307   bool isComplete() const   { return !isIncomplete(); }
00308   bool isDeadNode() const   { return NodeType & DEAD; }
00309 
00310   DSNode *setAllocaNodeMarker()  { NodeType |= AllocaNode;  return this; }
00311   DSNode *setHeapNodeMarker()    { NodeType |= HeapNode;    return this; }
00312   DSNode *setGlobalNodeMarker()  { NodeType |= GlobalNode;  return this; }
00313   DSNode *setUnknownNodeMarker() { NodeType |= UnknownNode; return this; }
00314 
00315   DSNode *setIncompleteMarker() { NodeType |= Incomplete; return this; }
00316   DSNode *setModifiedMarker()   { NodeType |= Modified;   return this; }
00317   DSNode *setReadMarker()       { NodeType |= Read;       return this; }
00318   DSNode *setArrayMarker()      { NodeType |= Array; return this; }
00319 
00320   void makeNodeDead() {
00321     Globals.clear();
00322     assert(hasNoReferrers() && "Dead node shouldn't have refs!");
00323     NodeType = DEAD;
00324   }
00325 
00326   /// forwardNode - Mark this node as being obsolete, and all references to it
00327   /// should be forwarded to the specified node and offset.
00328   ///
00329   void forwardNode(DSNode *To, unsigned Offset);
00330 
00331   void print(std::ostream &O, const DSGraph *G) const;
00332   void dump() const;
00333 
00334   void assertOK() const;
00335 
00336   void dropAllReferences() {
00337     Links.clear();
00338     if (isForwarding())
00339       ForwardNH.setTo(0, 0);
00340   }
00341 
00342   /// remapLinks - Change all of the Links in the current node according to the
00343   /// specified mapping.
00344   ///
00345   void remapLinks(hash_map<const DSNode*, DSNodeHandle> &OldNodeMap);
00346 
00347   /// markReachableNodes - This method recursively traverses the specified
00348   /// DSNodes, marking any nodes which are reachable.  All reachable nodes it
00349   /// adds to the set, which allows it to only traverse visited nodes once.
00350   ///
00351   void markReachableNodes(hash_set<DSNode*> &ReachableNodes);
00352 
00353 private:
00354   friend class DSNodeHandle;
00355 
00356   // static mergeNodes - Helper for mergeWith()
00357   static void MergeNodes(DSNodeHandle& CurNodeH, DSNodeHandle& NH);
00358 };
00359 
00360 //===----------------------------------------------------------------------===//
00361 // Define the ilist_traits specialization for the DSGraph ilist.
00362 //
00363 template<>
00364 struct ilist_traits<DSNode> {
00365   static DSNode *getPrev(const DSNode *N) { return N->Prev; }
00366   static DSNode *getNext(const DSNode *N) { return N->Next; }
00367 
00368   static void setPrev(DSNode *N, DSNode *Prev) { N->Prev = Prev; }
00369   static void setNext(DSNode *N, DSNode *Next) { N->Next = Next; }
00370 
00371   static DSNode *createNode() { return new DSNode(0,0); }
00372   //static DSNode *createNode(const DSNode &V) { return new DSNode(V); }
00373 
00374 
00375   void addNodeToList(DSNode *NTy) {}
00376   void removeNodeFromList(DSNode *NTy) {}
00377   void transferNodesFromList(iplist<DSNode, ilist_traits> &L2,
00378                              ilist_iterator<DSNode> first,
00379                              ilist_iterator<DSNode> last) {}
00380 };
00381 
00382 template<>
00383 struct ilist_traits<const DSNode> : public ilist_traits<DSNode> {};
00384 
00385 //===----------------------------------------------------------------------===//
00386 // Define inline DSNodeHandle functions that depend on the definition of DSNode
00387 //
00388 inline DSNode *DSNodeHandle::getNode() const {
00389   // Disabling this assertion because it is failing on a "magic" struct
00390   // in named (from bind).  The fourth field is an array of length 0,
00391   // presumably used to create struct instances of different sizes.
00392   assert((!N ||
00393           N->isNodeCompletelyFolded() ||
00394           (N->Size == 0 && Offset == 0) ||
00395           (int(Offset) >= 0 && Offset < N->Size) ||
00396           (int(Offset) < 0 && -int(Offset) < int(N->Size)) ||
00397           N->isForwarding()) && "Node handle offset out of range!");
00398   if (N == 0 || !N->isForwarding())
00399     return N;
00400 
00401   return HandleForwarding();
00402 }
00403 
00404 inline void DSNodeHandle::setTo(DSNode *n, unsigned NewOffset) const {
00405   assert(!n || !n->isForwarding() && "Cannot set node to a forwarded node!");
00406   if (N) getNode()->NumReferrers--;
00407   N = n;
00408   Offset = NewOffset;
00409   if (N) {
00410     N->NumReferrers++;
00411     if (Offset >= N->Size) {
00412       assert((Offset == 0 || N->Size == 1) &&
00413              "Pointer to non-collapsed node with invalid offset!");
00414       Offset = 0;
00415     }
00416   }
00417   assert(!N || ((N->NodeType & DSNode::DEAD) == 0));
00418   assert((!N || Offset < N->Size || (N->Size == 0 && Offset == 0) ||
00419           N->isForwarding()) && "Node handle offset out of range!");
00420 }
00421 
00422 inline bool DSNodeHandle::hasLink(unsigned Num) const {
00423   assert(N && "DSNodeHandle does not point to a node yet!");
00424   return getNode()->hasLink(Num+Offset);
00425 }
00426 
00427 
00428 /// getLink - Treat this current node pointer as a pointer to a structure of
00429 /// some sort.  This method will return the pointer a mem[this+Num]
00430 ///
00431 inline const DSNodeHandle &DSNodeHandle::getLink(unsigned Off) const {
00432   assert(N && "DSNodeHandle does not point to a node yet!");
00433   return getNode()->getLink(Offset+Off);
00434 }
00435 inline DSNodeHandle &DSNodeHandle::getLink(unsigned Off) {
00436   assert(N && "DSNodeHandle does not point to a node yet!");
00437   return getNode()->getLink(Off+Offset);
00438 }
00439 
00440 inline void DSNodeHandle::setLink(unsigned Off, const DSNodeHandle &NH) {
00441   assert(N && "DSNodeHandle does not point to a node yet!");
00442   getNode()->setLink(Off+Offset, NH);
00443 }
00444 
00445 /// addEdgeTo - Add an edge from the current node to the specified node.  This
00446 /// can cause merging of nodes in the graph.
00447 ///
00448 inline void DSNodeHandle::addEdgeTo(unsigned Off, const DSNodeHandle &Node) {
00449   assert(N && "DSNodeHandle does not point to a node yet!");
00450   getNode()->addEdgeTo(Off+Offset, Node);
00451 }
00452 
00453 /// mergeWith - Merge the logical node pointed to by 'this' with the node
00454 /// pointed to by 'N'.
00455 ///
00456 inline void DSNodeHandle::mergeWith(const DSNodeHandle &Node) const {
00457   if (!isNull())
00458     getNode()->mergeWith(Node, Offset);
00459   else {   // No node to merge with, so just point to Node
00460     Offset = 0;
00461     DSNode *NN = Node.getNode();
00462     setTo(NN, Node.getOffset());
00463   }
00464 }
00465 
00466 } // End llvm namespace
00467 
00468 #endif