llvm-6502/include/llvm/ADT/FoldingSet.h
Chris Lattner 32f3bd43db clean up comment
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33566 91177308-0d34-0410-b5e6-96231b3b80d8
2007-01-27 01:14:20 +00:00

259 lines
8.9 KiB
C++

//===-- llvm/ADT/FoldingSet.h - 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 defines 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.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_FOLDINGSET_H
#define LLVM_ADT_FOLDINGSET_H
#include "llvm/Support/DataTypes.h"
#include "llvm/ADT/SmallVector.h"
#include <string>
namespace llvm {
/// This folding set used for two purposes:
/// 1. Given information about a node we want to create, look up the unique
/// instance of the node in the set. If the node already exists, return
/// it, otherwise return the bucket it should be inserted into.
/// 2. Given a node that has already been created, remove it from the set.
///
/// This class is implemented as a single-link chained hash table, where the
/// "buckets" are actually the nodes themselves (the next pointer is in the
/// node). The last node points back to the bucket to simplified node removal.
///
/// Any node that is to be included in the folding set must be a subclass of
/// FoldingSetNode. The node class must also define a Profile method used to
/// establish the unique bits of data for the node. The Profile method is
/// passed a FoldingSetNodeID object which is used to gather the bits. Just
/// call one of the Add* functions defined in the FoldingSetImpl::NodeID class.
/// NOTE: That the folding set does not own the nodes and it is the
/// responsibility of the user to dispose of the nodes.
///
/// Eg.
/// class MyNode : public FoldingSetNode {
/// private:
/// std::string Name;
/// unsigned Value;
/// public:
/// MyNode(const char *N, unsigned V) : Name(N), Value(V) {}
/// ...
/// void Profile(FoldingSetNodeID &ID) {
/// ID.AddString(Name);
/// ID.AddInteger(Value);
/// }
/// ...
/// };
///
/// To define the folding set itself use the FoldingSet template;
///
/// Eg.
/// FoldingSet<MyNode> MyFoldingSet;
///
/// Four public methods are available to manipulate the folding set;
///
/// 1) If you have an existing node that you want add to the set but unsure
/// that the node might already exist then call;
///
/// MyNode *M = MyFoldingSet.GetOrInsertNode(N);
///
/// If The result is equal to the input then the node has been inserted.
/// Otherwise, the result is the node existing in the folding set, and the
/// input can be discarded (use the result instead.)
///
/// 2) If you are ready to construct a node but want to check if it already
/// exists, then call FindNodeOrInsertPos with a FoldingSetNodeID of the bits to
/// check;
///
/// FoldingSetNodeID ID;
/// ID.AddString(Name);
/// ID.AddInteger(Value);
/// void *InsertPoint;
///
/// MyNode *M = MyFoldingSet.FindNodeOrInsertPos(ID, InsertPoint);
///
/// If found then M with be non-NULL, else InsertPoint will point to where it
/// should be inserted using InsertNode.
///
/// 3) If you get a NULL result from FindNodeOrInsertPos then you can as a new
/// node with FindNodeOrInsertPos;
///
/// InsertNode(N, InsertPoint);
///
/// 4) Finally, if you want to remove a node from the folding set call;
///
/// bool WasRemoved = RemoveNode(N);
///
/// The result indicates whether the node existed in the folding set.
//===----------------------------------------------------------------------===//
/// FoldingSetImpl - Implements the folding set functionality. The main
/// structure is an array of buckets. Each bucket is indexed by the hash of
/// the nodes it contains. The bucket itself points to the nodes contained
/// in the bucket via a singly linked list. The last node in the list points
/// back to the bucket to facilitate node removal.
///
class FoldingSetImpl {
private:
/// Buckets - Array of bucket chains.
///
void **Buckets;
/// NumBuckets - Length of the Buckets array. Always a power of 2.
///
unsigned NumBuckets;
/// NumNodes - Number of nodes in the folding set. Growth occurs when NumNodes
/// is greater than twice the number of buckets.
unsigned NumNodes;
public:
FoldingSetImpl(unsigned Log2InitSize = 6);
virtual ~FoldingSetImpl();
// Forward declaration.
class Node;
//===--------------------------------------------------------------------===//
/// NodeID - This class is used to gather all the unique data bits of a
/// node. When all the bits are gathered this class is used to produce a
/// hash value for the node.
///
class NodeID {
/// Bits - Vector of all the data bits that make the node unique.
/// Use a SmallVector to avoid a heap allocation in the common case.
SmallVector<unsigned, 32> Bits;
public:
NodeID() {}
/// getRawData - Return the ith entry in the Bits data.
///
unsigned getRawData(unsigned i) const {
return Bits[i];
}
/// Add* - Add various data types to Bit data.
///
void AddPointer(const void *Ptr);
void AddInteger(signed I);
void AddInteger(unsigned I);
void AddInteger(uint64_t I);
void AddFloat(float F);
void AddDouble(double D);
void AddString(const std::string &String);
/// ComputeHash - Compute a strong hash value for this NodeID, used to
/// lookup the node in the FoldingSetImpl.
unsigned ComputeHash() const;
/// operator== - Used to compare two nodes to each other.
///
bool operator==(const NodeID &RHS) const;
};
//===--------------------------------------------------------------------===//
/// Node - This class is used to maintain the singly linked bucket list in
/// a folding set.
///
class Node {
private:
// NextInFoldingSetBucket - next link in the bucket list.
void *NextInFoldingSetBucket;
public:
Node() : NextInFoldingSetBucket(0) {}
// Accessors
void *getNextInBucket() const { return NextInFoldingSetBucket; }
void SetNextInBucket(void *N) { NextInFoldingSetBucket = 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 RemoveNode(Node *N);
/// GetOrInsertNode - If there is an existing simple Node exactly
/// equal to the specified node, return it. Otherwise, insert 'N' and return
/// it instead.
Node *GetOrInsertNode(Node *N);
/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists,
/// return it. If not, return the insertion token that will make insertion
/// faster.
Node *FindNodeOrInsertPos(const NodeID &ID, void *&InsertPos);
/// InsertNode - Insert the specified node into the folding set, knowing that
/// it is not already in the folding set. InsertPos must be obtained from
/// FindNodeOrInsertPos.
void InsertNode(Node *N, void *InsertPos);
private:
/// GrowHashTable - Double the size of the hash table and rehash everything.
///
void GrowHashTable();
protected:
/// GetNodeProfile - Instantiations of the FoldingSet template implement
/// this function to gather data bits for the given node.
virtual void GetNodeProfile(NodeID &ID, Node *N) const = 0;
};
// Convenience types to hide the implementation of the folding set.
typedef FoldingSetImpl::Node FoldingSetNode;
typedef FoldingSetImpl::NodeID FoldingSetNodeID;
//===----------------------------------------------------------------------===//
/// FoldingSet - This template class is used to instantiate a specialized
/// implementation of the folding set to the node class T. T must be a
/// subclass of FoldingSetNode and implement a Profile function.
///
template<class T> class FoldingSet : public FoldingSetImpl {
private:
/// GetNodeProfile - Each instantiatation of the FoldingSet needs to provide a
/// way to convert nodes into a unique specifier.
virtual void GetNodeProfile(NodeID &ID, Node *N) const {
T *TN = static_cast<T *>(N);
TN->Profile(ID);
}
public:
FoldingSet(unsigned Log2InitSize = 6)
: FoldingSetImpl(Log2InitSize)
{}
/// GetOrInsertNode - If there is an existing simple Node exactly
/// equal to the specified node, return it. Otherwise, insert 'N' and
/// return it instead.
T *GetOrInsertNode(Node *N) {
return static_cast<T *>(FoldingSetImpl::GetOrInsertNode(N));
}
/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists,
/// return it. If not, return the insertion token that will make insertion
/// faster.
T *FindNodeOrInsertPos(const FoldingSetNodeID &ID, void *&InsertPos) {
return static_cast<T *>(FoldingSetImpl::FindNodeOrInsertPos(ID, InsertPos));
}
};
} // End of namespace llvm.
#endif