[llvm-commits] CVS: llvm/lib/Support/FoldingSet.cpp

Jim Laskey jlaskey at apple.com
Fri Oct 27 09:16:33 PDT 2006



Changes in directory llvm/lib/Support:

FoldingSet.cpp added (r1.1)
---
Log message:

Breakout folding hash set from SelectionDAGCSEMap.

---
Diffs of the changes:  (+282 -0)

 FoldingSet.cpp |  282 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 282 insertions(+)


Index: llvm/lib/Support/FoldingSet.cpp
diff -c /dev/null llvm/lib/Support/FoldingSet.cpp:1.1
*** /dev/null	Fri Oct 27 11:16:26 2006
--- llvm/lib/Support/FoldingSet.cpp	Fri Oct 27 11:16:16 2006
***************
*** 0 ****
--- 1,282 ----
+ //===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===//
+ //
+ //                     The LLVM Compiler Infrastructure
+ //
+ // This file was developed by James M. Laskey and is distributed under
+ // the University of Illinois Open Source License. See LICENSE.TXT for details.
+ //
+ //===----------------------------------------------------------------------===//
+ //
+ // This file implements a hash set that can be used to remove duplication of
+ // nodes in a graph.  This code was originally created by Chris Lattner for use
+ // with SelectionDAGCSEMap, but was isolated to provide use across the llvm code
+ // set. 
+ //
+ //===----------------------------------------------------------------------===//
+ 
+ #include "llvm/ADT/FoldingSet.h"
+ 
+ #include "llvm/ADT/MathExtras.h"
+ 
+ using namespace llvm;
+ 
+ //===----------------------------------------------------------------------===//
+ // FoldingSetImpl::NodeID Implementation
+ 
+ /// Add* - Add various data types to Bit data.
+ ///
+ void FoldingSetImpl::NodeID::AddPointer(const void *Ptr) {
+   // Note: this adds pointers to the hash using sizes and endianness that
+   // depend on the host.  It doesn't matter however, because hashing on
+   // pointer values in inherently unstable.  Nothing  should depend on the 
+   // ordering of nodes in the folding set.
+   intptr_t PtrI = (intptr_t)Ptr;
+   Bits.push_back(unsigned(PtrI));
+   if (sizeof(intptr_t) > sizeof(unsigned))
+     Bits.push_back(unsigned(uint64_t(PtrI) >> 32));
+ }
+ void FoldingSetImpl::NodeID::AddInteger(signed I) {
+   Bits.push_back(I);
+ }
+ void FoldingSetImpl::NodeID::AddInteger(unsigned I) {
+   Bits.push_back(I);
+ }
+ void FoldingSetImpl::NodeID::AddInteger(uint64_t I) {
+   Bits.push_back(unsigned(I));
+   Bits.push_back(unsigned(I >> 32));
+ }
+ void FoldingSetImpl::NodeID::AddFloat(float F) {
+   Bits.push_back(FloatToBits(F));
+ }
+ void FoldingSetImpl::NodeID::AddDouble(double D) {
+   Bits.push_back(DoubleToBits(D));
+ }
+ void FoldingSetImpl::NodeID::AddString(const std::string &String) {
+   // Note: An assumption is made here that strings are composed of one byte
+   // chars.
+   unsigned Size = String.size();
+   unsigned Units = Size / sizeof(unsigned);
+   const unsigned *Base = (const unsigned *)String.data();
+   Bits.insert(Bits.end(), Base, Base + Units);
+   if (Size & 3) {
+     unsigned V = 0;
+     for (unsigned i = Units * sizeof(unsigned); i < Size; ++i)
+       V = (V << 8) | String[i];
+     Bits.push_back(V);
+   }
+ }
+ 
+ /// ComputeHash - Compute a strong hash value for this NodeID, used to 
+ /// lookup the node in the FoldingSetImpl.
+ unsigned FoldingSetImpl::NodeID::ComputeHash() const {
+   // This is adapted from SuperFastHash by Paul Hsieh.
+   unsigned Hash = Bits.size();
+   for (const unsigned *BP = &Bits[0], *E = BP+Bits.size(); BP != E; ++BP) {
+     unsigned Data = *BP;
+     Hash         += Data & 0xFFFF;
+     unsigned Tmp  = ((Data >> 16) << 11) ^ Hash;
+     Hash          = (Hash << 16) ^ Tmp;
+     Hash         += Hash >> 11;
+   }
+   
+   // Force "avalanching" of final 127 bits.
+   Hash ^= Hash << 3;
+   Hash += Hash >> 5;
+   Hash ^= Hash << 4;
+   Hash += Hash >> 17;
+   Hash ^= Hash << 25;
+   Hash += Hash >> 6;
+   return Hash;
+ }
+ 
+ /// operator== - Used to compare two nodes to each other.
+ ///
+ bool FoldingSetImpl::NodeID::operator==(const FoldingSetImpl::NodeID &RHS)const{
+   if (Bits.size() != RHS.Bits.size()) return false;
+   return memcmp(&Bits[0], &RHS.Bits[0], Bits.size()*sizeof(Bits[0])) == 0;
+ }
+ 
+ 
+ //===----------------------------------------------------------------------===//
+ // FoldingSetImpl Implementation
+ 
+ FoldingSetImpl::FoldingSetImpl() : NumNodes(0) {
+   NumBuckets = 64;
+   Buckets = new void*[NumBuckets];
+   memset(Buckets, 0, NumBuckets*sizeof(void*));
+ }
+ FoldingSetImpl::~FoldingSetImpl() {
+   delete [] Buckets;
+ }
+ 
+ /// GetNextPtr - In order to save space, each bucket is a
+ /// singly-linked-list. In order to make deletion more efficient, we make
+ /// the list circular, so we can delete a node without computing its hash.
+ /// The problem with this is that the start of the hash buckets are not
+ /// Nodes.  If NextInBucketPtr is a bucket pointer, this method returns null
+ /// : use GetBucketPtr when this happens.
+ FoldingSetImpl::Node *FoldingSetImpl::GetNextPtr(void *NextInBucketPtr) {
+   if (NextInBucketPtr >= Buckets && NextInBucketPtr < Buckets+NumBuckets)
+     return 0;
+   return static_cast<Node*>(NextInBucketPtr);
+ }
+ 
+ /// GetNextPtr - This is just like the previous GetNextPtr implementation,
+ /// but allows a bucket array to be specified.
+ FoldingSetImpl::Node *FoldingSetImpl::GetNextPtr(void *NextInBucketPtr,
+                                                  void **Bucks,
+                                                  unsigned NumBuck) {
+   if (NextInBucketPtr >= Bucks && NextInBucketPtr < Bucks+NumBuck)
+     return 0;
+   return static_cast<Node*>(NextInBucketPtr);
+ }
+ 
+ /// GetBucketPtr - Provides a casting of a bucket pointer for isNode
+ /// testing.
+ void **FoldingSetImpl::GetBucketPtr(void *NextInBucketPtr) {
+   return static_cast<void**>(NextInBucketPtr);
+ }
+ 
+ /// GetBucketFor - Hash the specified node ID and return the hash bucket for
+ /// the specified ID.
+ void **FoldingSetImpl::GetBucketFor(const NodeID &ID) const {
+   // NumBuckets is always a power of 2.
+   unsigned BucketNum = ID.ComputeHash() & (NumBuckets-1);
+   return Buckets+BucketNum;
+ }
+ 
+ /// GrowHashTable - Double the size of the hash table and rehash everything.
+ ///
+ void FoldingSetImpl::GrowHashTable() {
+   void **OldBuckets = Buckets;
+   unsigned OldNumBuckets = NumBuckets;
+   NumBuckets <<= 1;
+   
+   // Reset the node count to zero: we're going to reinsert everything.
+   NumNodes = 0;
+   
+   // Clear out new buckets.
+   Buckets = new void*[NumBuckets];
+   memset(Buckets, 0, NumBuckets*sizeof(void*));
+ 
+   // Walk the old buckets, rehashing nodes into their new place.
+   for (unsigned i = 0; i != OldNumBuckets; ++i) {
+     void *Probe = OldBuckets[i];
+     if (!Probe) continue;
+     while (Node *NodeInBucket = GetNextPtr(Probe, OldBuckets, OldNumBuckets)){
+       // Figure out the next link, remove NodeInBucket from the old link.
+       Probe = NodeInBucket->getNextInBucket();
+       NodeInBucket->SetNextInBucket(0);
+ 
+       // Insert the node into the new bucket, after recomputing the hash.
+       NodeID ID;
+       GetNodeProfile(ID, NodeInBucket);
+       InsertNode(NodeInBucket, GetBucketFor(ID));
+     }
+   }
+   
+   delete[] OldBuckets;
+ }
+ 
+ /// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,
+ /// return it.  If not, return the insertion token that will make insertion
+ /// faster.
+ FoldingSetImpl::Node *FoldingSetImpl::FindNodeOrInsertPos(const NodeID &ID,
+                                                           void *&InsertPos) {
+   void **Bucket = GetBucketFor(ID);
+   void *Probe = *Bucket;
+   
+   InsertPos = 0;
+   
+   while (Node *NodeInBucket = GetNextPtr(Probe)) {
+     NodeID OtherID;
+     GetNodeProfile(OtherID, NodeInBucket);
+     if (OtherID == ID)
+       return NodeInBucket;
+ 
+     Probe = NodeInBucket->getNextInBucket();
+   }
+   
+   // Didn't find the node, return null with the bucket as the InsertPos.
+   InsertPos = Bucket;
+   return 0;
+ }
+ 
+ /// InsertNode - Insert the specified node into the folding set, knowing that it
+ /// is not already in the map.  InsertPos must be obtained from 
+ /// FindNodeOrInsertPos.
+ void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) {
+   ++NumNodes;
+   // Do we need to grow the hashtable?
+   if (NumNodes > NumBuckets*2) {
+     GrowHashTable();
+     NodeID ID;
+     GetNodeProfile(ID, N);
+     InsertPos = GetBucketFor(ID);
+   }
+   
+   /// The insert position is actually a bucket pointer.
+   void **Bucket = static_cast<void**>(InsertPos);
+   
+   void *Next = *Bucket;
+   
+   // If this is the first insertion into this bucket, its next pointer will be
+   // null.  Pretend as if it pointed to itself.
+   if (Next == 0)
+     Next = Bucket;
+ 
+   // Set the nodes next pointer, and make the bucket point to the node.
+   N->SetNextInBucket(Next);
+   *Bucket = N;
+ }
+ 
+ /// RemoveNode - Remove a node from the folding set, returning true if one was
+ /// removed or false if the node was not in the folding set.
+ bool FoldingSetImpl::RemoveNode(Node *N) {
+   // Because each bucket is a circular list, we don't need to compute N's hash
+   // to remove it.  Chase around the list until we find the node (or bucket)
+   // which points to N.
+   void *Ptr = N->getNextInBucket();
+   if (Ptr == 0) return false;  // Not in folding set.
+ 
+   --NumNodes;
+ 
+   void *NodeNextPtr = Ptr;
+   N->SetNextInBucket(0);
+   while (true) {
+     if (Node *NodeInBucket = GetNextPtr(Ptr)) {
+       // Advance pointer.
+       Ptr = NodeInBucket->getNextInBucket();
+       
+       // We found a node that points to N, change it to point to N's next node,
+       // removing N from the list.
+       if (Ptr == N) {
+         NodeInBucket->SetNextInBucket(NodeNextPtr);
+         return true;
+       }
+     } else {
+       void **Bucket = GetBucketPtr(Ptr);
+       Ptr = *Bucket;
+       
+       // If we found that the bucket points to N, update the bucket to point to
+       // whatever is next.
+       if (Ptr == N) {
+         *Bucket = NodeNextPtr;
+         return true;
+       }
+     }
+   }
+ }
+ 
+ /// GetOrInsertNode - If there is an existing simple Node exactly
+ /// equal to the specified node, return it.  Otherwise, insert 'N' and it
+ /// instead.
+ FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) {
+   NodeID ID;
+   GetNodeProfile(ID, N);
+   void *IP;
+   if (Node *E = FindNodeOrInsertPos(ID, IP))
+     return E;
+   InsertNode(N, IP);
+   return N;
+ }






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