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308 lines
10 KiB
C++
308 lines
10 KiB
C++
//===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by James M. Laskey and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements a hash set that can be used to remove duplication of
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// nodes in a graph. This code was originally created by Chris Lattner for use
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// with SelectionDAGCSEMap, but was isolated to provide use across the llvm code
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// set.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/FoldingSet.h"
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#include "llvm/Support/MathExtras.h"
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#include <cassert>
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// FoldingSetImpl::NodeID Implementation
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/// Add* - Add various data types to Bit data.
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///
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void FoldingSetImpl::NodeID::AddPointer(const void *Ptr) {
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// Note: this adds pointers to the hash using sizes and endianness that
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// depend on the host. It doesn't matter however, because hashing on
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// pointer values in inherently unstable. Nothing should depend on the
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// ordering of nodes in the folding set.
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intptr_t PtrI = (intptr_t)Ptr;
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Bits.push_back(unsigned(PtrI));
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if (sizeof(intptr_t) > sizeof(unsigned))
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Bits.push_back(unsigned(uint64_t(PtrI) >> 32));
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}
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void FoldingSetImpl::NodeID::AddInteger(signed I) {
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Bits.push_back(I);
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}
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void FoldingSetImpl::NodeID::AddInteger(unsigned I) {
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Bits.push_back(I);
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}
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void FoldingSetImpl::NodeID::AddInteger(uint64_t I) {
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Bits.push_back(unsigned(I));
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// If the integer is small, encode it just as 32-bits.
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if ((uint64_t)(int)I != I)
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Bits.push_back(unsigned(I >> 32));
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}
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void FoldingSetImpl::NodeID::AddFloat(float F) {
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Bits.push_back(FloatToBits(F));
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}
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void FoldingSetImpl::NodeID::AddDouble(double D) {
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AddInteger(DoubleToBits(D));
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}
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void FoldingSetImpl::NodeID::AddString(const std::string &String) {
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unsigned Size = String.size();
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Bits.push_back(Size);
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if (!Size) return;
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unsigned Units = Size / 4;
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unsigned Pos = 0;
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const unsigned *Base = (const unsigned *)String.data();
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// If the string is aligned do a bulk transfer.
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if (!((intptr_t)Base & 3)) {
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Bits.append(Base, Base + Units);
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Pos = (Units + 1) * 4;
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} else {
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// Otherwise do it the hard way.
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for ( Pos += 4; Pos <= Size; Pos += 4) {
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unsigned V = ((unsigned char)String[Pos - 4] << 24) |
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((unsigned char)String[Pos - 3] << 16) |
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((unsigned char)String[Pos - 2] << 8) |
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(unsigned char)String[Pos - 1];
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Bits.push_back(V);
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}
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}
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// With the leftover bits.
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unsigned V = 0;
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// Pos will have overshot size by 4 - #bytes left over.
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switch (Pos - Size) {
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case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru.
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case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru.
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case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
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default: return; // Nothing left.
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}
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Bits.push_back(V);
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}
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/// ComputeHash - Compute a strong hash value for this NodeID, used to
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/// lookup the node in the FoldingSetImpl.
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unsigned FoldingSetImpl::NodeID::ComputeHash() const {
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// This is adapted from SuperFastHash by Paul Hsieh.
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unsigned Hash = Bits.size();
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for (const unsigned *BP = &Bits[0], *E = BP+Bits.size(); BP != E; ++BP) {
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unsigned Data = *BP;
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Hash += Data & 0xFFFF;
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unsigned Tmp = ((Data >> 16) << 11) ^ Hash;
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Hash = (Hash << 16) ^ Tmp;
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Hash += Hash >> 11;
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}
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// Force "avalanching" of final 127 bits.
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Hash ^= Hash << 3;
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Hash += Hash >> 5;
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Hash ^= Hash << 4;
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Hash += Hash >> 17;
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Hash ^= Hash << 25;
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Hash += Hash >> 6;
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return Hash;
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}
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/// operator== - Used to compare two nodes to each other.
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///
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bool FoldingSetImpl::NodeID::operator==(const FoldingSetImpl::NodeID &RHS)const{
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if (Bits.size() != RHS.Bits.size()) return false;
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return memcmp(&Bits[0], &RHS.Bits[0], Bits.size()*sizeof(Bits[0])) == 0;
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}
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//===----------------------------------------------------------------------===//
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/// Helper functions for FoldingSetImpl.
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/// GetNextPtr - In order to save space, each bucket is a
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/// singly-linked-list. In order to make deletion more efficient, we make
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/// the list circular, so we can delete a node without computing its hash.
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/// The problem with this is that the start of the hash buckets are not
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/// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null:
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/// use GetBucketPtr when this happens.
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static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr,
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void **Buckets, unsigned NumBuckets) {
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if (NextInBucketPtr >= Buckets && NextInBucketPtr < Buckets + NumBuckets)
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return 0;
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return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr);
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}
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/// GetBucketPtr - Provides a casting of a bucket pointer for isNode
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/// testing.
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static void **GetBucketPtr(void *NextInBucketPtr) {
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return static_cast<void**>(NextInBucketPtr);
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}
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/// GetBucketFor - Hash the specified node ID and return the hash bucket for
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/// the specified ID.
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static void **GetBucketFor(const FoldingSetImpl::NodeID &ID,
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void **Buckets, unsigned NumBuckets) {
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// NumBuckets is always a power of 2.
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unsigned BucketNum = ID.ComputeHash() & (NumBuckets-1);
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return Buckets + BucketNum;
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}
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//===----------------------------------------------------------------------===//
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// FoldingSetImpl Implementation
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FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) : NumNodes(0) {
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assert(5 < Log2InitSize && Log2InitSize < 32 &&
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"Initial hash table size out of range");
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NumBuckets = 1 << Log2InitSize;
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Buckets = new void*[NumBuckets];
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memset(Buckets, 0, NumBuckets*sizeof(void*));
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}
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FoldingSetImpl::~FoldingSetImpl() {
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delete [] Buckets;
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}
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/// GrowHashTable - Double the size of the hash table and rehash everything.
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///
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void FoldingSetImpl::GrowHashTable() {
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void **OldBuckets = Buckets;
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unsigned OldNumBuckets = NumBuckets;
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NumBuckets <<= 1;
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// Reset the node count to zero: we're going to reinsert everything.
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NumNodes = 0;
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// Clear out new buckets.
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Buckets = new void*[NumBuckets];
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memset(Buckets, 0, NumBuckets*sizeof(void*));
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// Walk the old buckets, rehashing nodes into their new place.
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for (unsigned i = 0; i != OldNumBuckets; ++i) {
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void *Probe = OldBuckets[i];
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if (!Probe) continue;
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while (Node *NodeInBucket = GetNextPtr(Probe, OldBuckets, OldNumBuckets)) {
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// Figure out the next link, remove NodeInBucket from the old link.
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Probe = NodeInBucket->getNextInBucket();
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NodeInBucket->SetNextInBucket(0);
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// Insert the node into the new bucket, after recomputing the hash.
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NodeID ID;
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GetNodeProfile(ID, NodeInBucket);
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InsertNode(NodeInBucket, GetBucketFor(ID, Buckets, NumBuckets));
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}
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}
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delete[] OldBuckets;
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}
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/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists,
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/// return it. If not, return the insertion token that will make insertion
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/// faster.
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FoldingSetImpl::Node *FoldingSetImpl::FindNodeOrInsertPos(const NodeID &ID,
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void *&InsertPos) {
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void **Bucket = GetBucketFor(ID, Buckets, NumBuckets);
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void *Probe = *Bucket;
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InsertPos = 0;
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while (Node *NodeInBucket = GetNextPtr(Probe, Buckets, NumBuckets)) {
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NodeID OtherID;
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GetNodeProfile(OtherID, NodeInBucket);
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if (OtherID == ID)
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return NodeInBucket;
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Probe = NodeInBucket->getNextInBucket();
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}
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// Didn't find the node, return null with the bucket as the InsertPos.
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InsertPos = Bucket;
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return 0;
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}
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/// InsertNode - Insert the specified node into the folding set, knowing that it
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/// is not already in the map. InsertPos must be obtained from
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/// FindNodeOrInsertPos.
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void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) {
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assert(N->getNextInBucket() == 0);
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// Do we need to grow the hashtable?
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if (NumNodes+1 > NumBuckets*2) {
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GrowHashTable();
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NodeID ID;
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GetNodeProfile(ID, N);
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InsertPos = GetBucketFor(ID, Buckets, NumBuckets);
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}
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++NumNodes;
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/// The insert position is actually a bucket pointer.
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void **Bucket = static_cast<void**>(InsertPos);
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void *Next = *Bucket;
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// If this is the first insertion into this bucket, its next pointer will be
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// null. Pretend as if it pointed to itself.
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if (Next == 0)
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Next = Bucket;
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// Set the node's next pointer, and make the bucket point to the node.
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N->SetNextInBucket(Next);
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*Bucket = N;
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}
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/// RemoveNode - Remove a node from the folding set, returning true if one was
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/// removed or false if the node was not in the folding set.
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bool FoldingSetImpl::RemoveNode(Node *N) {
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// Because each bucket is a circular list, we don't need to compute N's hash
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// to remove it.
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void *Ptr = N->getNextInBucket();
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if (Ptr == 0) return false; // Not in folding set.
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--NumNodes;
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N->SetNextInBucket(0);
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// Remember what N originally pointed to, either a bucket or another node.
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void *NodeNextPtr = Ptr;
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// Chase around the list until we find the node (or bucket) which points to N.
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while (true) {
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if (Node *NodeInBucket = GetNextPtr(Ptr, Buckets, NumBuckets)) {
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// Advance pointer.
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Ptr = NodeInBucket->getNextInBucket();
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// We found a node that points to N, change it to point to N's next node,
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// removing N from the list.
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if (Ptr == N) {
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NodeInBucket->SetNextInBucket(NodeNextPtr);
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return true;
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}
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} else {
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void **Bucket = GetBucketPtr(Ptr);
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Ptr = *Bucket;
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// If we found that the bucket points to N, update the bucket to point to
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// whatever is next.
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if (Ptr == N) {
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*Bucket = NodeNextPtr;
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return true;
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}
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}
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}
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}
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/// GetOrInsertNode - If there is an existing simple Node exactly
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/// equal to the specified node, return it. Otherwise, insert 'N' and it
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/// instead.
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FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) {
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NodeID ID;
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GetNodeProfile(ID, N);
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void *IP;
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if (Node *E = FindNodeOrInsertPos(ID, IP))
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return E;
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InsertNode(N, IP);
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return N;
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}
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