1//===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements a hash set that can be used to remove duplication of
11// nodes in a graph.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/ADT/FoldingSet.h"
16#include "llvm/ADT/Hashing.h"
17#include "llvm/Support/Allocator.h"
18#include "llvm/Support/ErrorHandling.h"
19#include "llvm/Support/Host.h"
20#include "llvm/Support/MathExtras.h"
21#include <cassert>
22#include <cstring>
23using namespace llvm;
24
25//===----------------------------------------------------------------------===//
26// FoldingSetNodeIDRef Implementation
27
28/// ComputeHash - Compute a strong hash value for this FoldingSetNodeIDRef,
29/// used to lookup the node in the FoldingSetImpl.
30unsigned FoldingSetNodeIDRef::ComputeHash() const {
31  return static_cast<unsigned>(hash_combine_range(Data, Data+Size));
32}
33
34bool FoldingSetNodeIDRef::operator==(FoldingSetNodeIDRef RHS) const {
35  if (Size != RHS.Size) return false;
36  return memcmp(Data, RHS.Data, Size*sizeof(*Data)) == 0;
37}
38
39/// Used to compare the "ordering" of two nodes as defined by the
40/// profiled bits and their ordering defined by memcmp().
41bool FoldingSetNodeIDRef::operator<(FoldingSetNodeIDRef RHS) const {
42  if (Size != RHS.Size)
43    return Size < RHS.Size;
44  return memcmp(Data, RHS.Data, Size*sizeof(*Data)) < 0;
45}
46
47//===----------------------------------------------------------------------===//
48// FoldingSetNodeID Implementation
49
50/// Add* - Add various data types to Bit data.
51///
52void FoldingSetNodeID::AddPointer(const void *Ptr) {
53  // Note: this adds pointers to the hash using sizes and endianness that
54  // depend on the host.  It doesn't matter however, because hashing on
55  // pointer values in inherently unstable.  Nothing  should depend on the
56  // ordering of nodes in the folding set.
57  Bits.append(reinterpret_cast<unsigned *>(&Ptr),
58              reinterpret_cast<unsigned *>(&Ptr+1));
59}
60void FoldingSetNodeID::AddInteger(signed I) {
61  Bits.push_back(I);
62}
63void FoldingSetNodeID::AddInteger(unsigned I) {
64  Bits.push_back(I);
65}
66void FoldingSetNodeID::AddInteger(long I) {
67  AddInteger((unsigned long)I);
68}
69void FoldingSetNodeID::AddInteger(unsigned long I) {
70  if (sizeof(long) == sizeof(int))
71    AddInteger(unsigned(I));
72  else if (sizeof(long) == sizeof(long long)) {
73    AddInteger((unsigned long long)I);
74  } else {
75    llvm_unreachable("unexpected sizeof(long)");
76  }
77}
78void FoldingSetNodeID::AddInteger(long long I) {
79  AddInteger((unsigned long long)I);
80}
81void FoldingSetNodeID::AddInteger(unsigned long long I) {
82  AddInteger(unsigned(I));
83  if ((uint64_t)(unsigned)I != I)
84    Bits.push_back(unsigned(I >> 32));
85}
86
87void FoldingSetNodeID::AddString(StringRef String) {
88  unsigned Size =  String.size();
89  Bits.push_back(Size);
90  if (!Size) return;
91
92  unsigned Units = Size / 4;
93  unsigned Pos = 0;
94  const unsigned *Base = (const unsigned*) String.data();
95
96  // If the string is aligned do a bulk transfer.
97  if (!((intptr_t)Base & 3)) {
98    Bits.append(Base, Base + Units);
99    Pos = (Units + 1) * 4;
100  } else {
101    // Otherwise do it the hard way.
102    // To be compatible with above bulk transfer, we need to take endianness
103    // into account.
104    if (sys::IsBigEndianHost) {
105      for (Pos += 4; Pos <= Size; Pos += 4) {
106        unsigned V = ((unsigned char)String[Pos - 4] << 24) |
107                     ((unsigned char)String[Pos - 3] << 16) |
108                     ((unsigned char)String[Pos - 2] << 8) |
109                      (unsigned char)String[Pos - 1];
110        Bits.push_back(V);
111      }
112    } else {
113      assert(sys::IsLittleEndianHost && "Unexpected host endianness");
114      for (Pos += 4; Pos <= Size; Pos += 4) {
115        unsigned V = ((unsigned char)String[Pos - 1] << 24) |
116                     ((unsigned char)String[Pos - 2] << 16) |
117                     ((unsigned char)String[Pos - 3] << 8) |
118                      (unsigned char)String[Pos - 4];
119        Bits.push_back(V);
120      }
121    }
122  }
123
124  // With the leftover bits.
125  unsigned V = 0;
126  // Pos will have overshot size by 4 - #bytes left over.
127  // No need to take endianness into account here - this is always executed.
128  switch (Pos - Size) {
129  case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru.
130  case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru.
131  case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
132  default: return; // Nothing left.
133  }
134
135  Bits.push_back(V);
136}
137
138// AddNodeID - Adds the Bit data of another ID to *this.
139void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) {
140  Bits.append(ID.Bits.begin(), ID.Bits.end());
141}
142
143/// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used to
144/// lookup the node in the FoldingSetImpl.
145unsigned FoldingSetNodeID::ComputeHash() const {
146  return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash();
147}
148
149/// operator== - Used to compare two nodes to each other.
150///
151bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS) const {
152  return *this == FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
153}
154
155/// operator== - Used to compare two nodes to each other.
156///
157bool FoldingSetNodeID::operator==(FoldingSetNodeIDRef RHS) const {
158  return FoldingSetNodeIDRef(Bits.data(), Bits.size()) == RHS;
159}
160
161/// Used to compare the "ordering" of two nodes as defined by the
162/// profiled bits and their ordering defined by memcmp().
163bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS) const {
164  return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
165}
166
167bool FoldingSetNodeID::operator<(FoldingSetNodeIDRef RHS) const {
168  return FoldingSetNodeIDRef(Bits.data(), Bits.size()) < RHS;
169}
170
171/// Intern - Copy this node's data to a memory region allocated from the
172/// given allocator and return a FoldingSetNodeIDRef describing the
173/// interned data.
174FoldingSetNodeIDRef
175FoldingSetNodeID::Intern(BumpPtrAllocator &Allocator) const {
176  unsigned *New = Allocator.Allocate<unsigned>(Bits.size());
177  std::uninitialized_copy(Bits.begin(), Bits.end(), New);
178  return FoldingSetNodeIDRef(New, Bits.size());
179}
180
181//===----------------------------------------------------------------------===//
182/// Helper functions for FoldingSetImpl.
183
184/// GetNextPtr - In order to save space, each bucket is a
185/// singly-linked-list. In order to make deletion more efficient, we make
186/// the list circular, so we can delete a node without computing its hash.
187/// The problem with this is that the start of the hash buckets are not
188/// Nodes.  If NextInBucketPtr is a bucket pointer, this method returns null:
189/// use GetBucketPtr when this happens.
190static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr) {
191  // The low bit is set if this is the pointer back to the bucket.
192  if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1)
193    return nullptr;
194
195  return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr);
196}
197
198
199/// testing.
200static void **GetBucketPtr(void *NextInBucketPtr) {
201  intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr);
202  assert((Ptr & 1) && "Not a bucket pointer");
203  return reinterpret_cast<void**>(Ptr & ~intptr_t(1));
204}
205
206/// GetBucketFor - Hash the specified node ID and return the hash bucket for
207/// the specified ID.
208static void **GetBucketFor(unsigned Hash, void **Buckets, unsigned NumBuckets) {
209  // NumBuckets is always a power of 2.
210  unsigned BucketNum = Hash & (NumBuckets-1);
211  return Buckets + BucketNum;
212}
213
214/// AllocateBuckets - Allocated initialized bucket memory.
215static void **AllocateBuckets(unsigned NumBuckets) {
216  void **Buckets = static_cast<void**>(calloc(NumBuckets+1, sizeof(void*)));
217  // Set the very last bucket to be a non-null "pointer".
218  Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
219  return Buckets;
220}
221
222//===----------------------------------------------------------------------===//
223// FoldingSetImpl Implementation
224
225FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) {
226  assert(5 < Log2InitSize && Log2InitSize < 32 &&
227         "Initial hash table size out of range");
228  NumBuckets = 1 << Log2InitSize;
229  Buckets = AllocateBuckets(NumBuckets);
230  NumNodes = 0;
231}
232FoldingSetImpl::~FoldingSetImpl() {
233  free(Buckets);
234}
235void FoldingSetImpl::clear() {
236  // Set all but the last bucket to null pointers.
237  memset(Buckets, 0, NumBuckets*sizeof(void*));
238
239  // Set the very last bucket to be a non-null "pointer".
240  Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
241
242  // Reset the node count to zero.
243  NumNodes = 0;
244}
245
246/// GrowHashTable - Double the size of the hash table and rehash everything.
247///
248void FoldingSetImpl::GrowHashTable() {
249  void **OldBuckets = Buckets;
250  unsigned OldNumBuckets = NumBuckets;
251  NumBuckets <<= 1;
252
253  // Clear out new buckets.
254  Buckets = AllocateBuckets(NumBuckets);
255  NumNodes = 0;
256
257  // Walk the old buckets, rehashing nodes into their new place.
258  FoldingSetNodeID TempID;
259  for (unsigned i = 0; i != OldNumBuckets; ++i) {
260    void *Probe = OldBuckets[i];
261    if (!Probe) continue;
262    while (Node *NodeInBucket = GetNextPtr(Probe)) {
263      // Figure out the next link, remove NodeInBucket from the old link.
264      Probe = NodeInBucket->getNextInBucket();
265      NodeInBucket->SetNextInBucket(nullptr);
266
267      // Insert the node into the new bucket, after recomputing the hash.
268      InsertNode(NodeInBucket,
269                 GetBucketFor(ComputeNodeHash(NodeInBucket, TempID),
270                              Buckets, NumBuckets));
271      TempID.clear();
272    }
273  }
274
275  free(OldBuckets);
276}
277
278/// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,
279/// return it.  If not, return the insertion token that will make insertion
280/// faster.
281FoldingSetImpl::Node
282*FoldingSetImpl::FindNodeOrInsertPos(const FoldingSetNodeID &ID,
283                                     void *&InsertPos) {
284  unsigned IDHash = ID.ComputeHash();
285  void **Bucket = GetBucketFor(IDHash, Buckets, NumBuckets);
286  void *Probe = *Bucket;
287
288  InsertPos = nullptr;
289
290  FoldingSetNodeID TempID;
291  while (Node *NodeInBucket = GetNextPtr(Probe)) {
292    if (NodeEquals(NodeInBucket, ID, IDHash, TempID))
293      return NodeInBucket;
294    TempID.clear();
295
296    Probe = NodeInBucket->getNextInBucket();
297  }
298
299  // Didn't find the node, return null with the bucket as the InsertPos.
300  InsertPos = Bucket;
301  return nullptr;
302}
303
304/// InsertNode - Insert the specified node into the folding set, knowing that it
305/// is not already in the map.  InsertPos must be obtained from
306/// FindNodeOrInsertPos.
307void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) {
308  assert(!N->getNextInBucket());
309  // Do we need to grow the hashtable?
310  if (NumNodes+1 > NumBuckets*2) {
311    GrowHashTable();
312    FoldingSetNodeID TempID;
313    InsertPos = GetBucketFor(ComputeNodeHash(N, TempID), Buckets, NumBuckets);
314  }
315
316  ++NumNodes;
317
318  /// The insert position is actually a bucket pointer.
319  void **Bucket = static_cast<void**>(InsertPos);
320
321  void *Next = *Bucket;
322
323  // If this is the first insertion into this bucket, its next pointer will be
324  // null.  Pretend as if it pointed to itself, setting the low bit to indicate
325  // that it is a pointer to the bucket.
326  if (!Next)
327    Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1);
328
329  // Set the node's next pointer, and make the bucket point to the node.
330  N->SetNextInBucket(Next);
331  *Bucket = N;
332}
333
334/// RemoveNode - Remove a node from the folding set, returning true if one was
335/// removed or false if the node was not in the folding set.
336bool FoldingSetImpl::RemoveNode(Node *N) {
337  // Because each bucket is a circular list, we don't need to compute N's hash
338  // to remove it.
339  void *Ptr = N->getNextInBucket();
340  if (!Ptr) return false;  // Not in folding set.
341
342  --NumNodes;
343  N->SetNextInBucket(nullptr);
344
345  // Remember what N originally pointed to, either a bucket or another node.
346  void *NodeNextPtr = Ptr;
347
348  // Chase around the list until we find the node (or bucket) which points to N.
349  while (true) {
350    if (Node *NodeInBucket = GetNextPtr(Ptr)) {
351      // Advance pointer.
352      Ptr = NodeInBucket->getNextInBucket();
353
354      // We found a node that points to N, change it to point to N's next node,
355      // removing N from the list.
356      if (Ptr == N) {
357        NodeInBucket->SetNextInBucket(NodeNextPtr);
358        return true;
359      }
360    } else {
361      void **Bucket = GetBucketPtr(Ptr);
362      Ptr = *Bucket;
363
364      // If we found that the bucket points to N, update the bucket to point to
365      // whatever is next.
366      if (Ptr == N) {
367        *Bucket = NodeNextPtr;
368        return true;
369      }
370    }
371  }
372}
373
374/// GetOrInsertNode - If there is an existing simple Node exactly
375/// equal to the specified node, return it.  Otherwise, insert 'N' and it
376/// instead.
377FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) {
378  FoldingSetNodeID ID;
379  GetNodeProfile(N, ID);
380  void *IP;
381  if (Node *E = FindNodeOrInsertPos(ID, IP))
382    return E;
383  InsertNode(N, IP);
384  return N;
385}
386
387//===----------------------------------------------------------------------===//
388// FoldingSetIteratorImpl Implementation
389
390FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) {
391  // Skip to the first non-null non-self-cycle bucket.
392  while (*Bucket != reinterpret_cast<void*>(-1) &&
393         (!*Bucket || !GetNextPtr(*Bucket)))
394    ++Bucket;
395
396  NodePtr = static_cast<FoldingSetNode*>(*Bucket);
397}
398
399void FoldingSetIteratorImpl::advance() {
400  // If there is another link within this bucket, go to it.
401  void *Probe = NodePtr->getNextInBucket();
402
403  if (FoldingSetNode *NextNodeInBucket = GetNextPtr(Probe))
404    NodePtr = NextNodeInBucket;
405  else {
406    // Otherwise, this is the last link in this bucket.
407    void **Bucket = GetBucketPtr(Probe);
408
409    // Skip to the next non-null non-self-cycle bucket.
410    do {
411      ++Bucket;
412    } while (*Bucket != reinterpret_cast<void*>(-1) &&
413             (!*Bucket || !GetNextPtr(*Bucket)));
414
415    NodePtr = static_cast<FoldingSetNode*>(*Bucket);
416  }
417}
418
419//===----------------------------------------------------------------------===//
420// FoldingSetBucketIteratorImpl Implementation
421
422FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) {
423  Ptr = (!*Bucket || !GetNextPtr(*Bucket)) ? (void*) Bucket : *Bucket;
424}
425