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>
23 using 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 FoldingSetBase.
ComputeHash() const30 unsigned FoldingSetNodeIDRef::ComputeHash() const {
31 return static_cast<unsigned>(hash_combine_range(Data, Data+Size));
32 }
33
operator ==(FoldingSetNodeIDRef RHS) const34 bool 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().
operator <(FoldingSetNodeIDRef RHS) const41 bool 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 ///
AddPointer(const void * Ptr)52 void 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 is inherently unstable. Nothing should depend on the
56 // ordering of nodes in the folding set.
57 static_assert(sizeof(uintptr_t) <= sizeof(unsigned long long),
58 "unexpected pointer size");
59 AddInteger(reinterpret_cast<uintptr_t>(Ptr));
60 }
AddInteger(signed I)61 void FoldingSetNodeID::AddInteger(signed I) {
62 Bits.push_back(I);
63 }
AddInteger(unsigned I)64 void FoldingSetNodeID::AddInteger(unsigned I) {
65 Bits.push_back(I);
66 }
AddInteger(long I)67 void FoldingSetNodeID::AddInteger(long I) {
68 AddInteger((unsigned long)I);
69 }
AddInteger(unsigned long I)70 void FoldingSetNodeID::AddInteger(unsigned long I) {
71 if (sizeof(long) == sizeof(int))
72 AddInteger(unsigned(I));
73 else if (sizeof(long) == sizeof(long long)) {
74 AddInteger((unsigned long long)I);
75 } else {
76 llvm_unreachable("unexpected sizeof(long)");
77 }
78 }
AddInteger(long long I)79 void FoldingSetNodeID::AddInteger(long long I) {
80 AddInteger((unsigned long long)I);
81 }
AddInteger(unsigned long long I)82 void FoldingSetNodeID::AddInteger(unsigned long long I) {
83 AddInteger(unsigned(I));
84 AddInteger(unsigned(I >> 32));
85 }
86
AddString(StringRef String)87 void 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 static_assert(sys::IsBigEndianHost || sys::IsLittleEndianHost,
105 "Unexpected host endianness");
106 if (sys::IsBigEndianHost) {
107 for (Pos += 4; Pos <= Size; Pos += 4) {
108 unsigned V = ((unsigned char)String[Pos - 4] << 24) |
109 ((unsigned char)String[Pos - 3] << 16) |
110 ((unsigned char)String[Pos - 2] << 8) |
111 (unsigned char)String[Pos - 1];
112 Bits.push_back(V);
113 }
114 } else { // Little-endian host
115 for (Pos += 4; Pos <= Size; Pos += 4) {
116 unsigned V = ((unsigned char)String[Pos - 1] << 24) |
117 ((unsigned char)String[Pos - 2] << 16) |
118 ((unsigned char)String[Pos - 3] << 8) |
119 (unsigned char)String[Pos - 4];
120 Bits.push_back(V);
121 }
122 }
123 }
124
125 // With the leftover bits.
126 unsigned V = 0;
127 // Pos will have overshot size by 4 - #bytes left over.
128 // No need to take endianness into account here - this is always executed.
129 switch (Pos - Size) {
130 case 1: V = (V << 8) | (unsigned char)String[Size - 3]; LLVM_FALLTHROUGH;
131 case 2: V = (V << 8) | (unsigned char)String[Size - 2]; LLVM_FALLTHROUGH;
132 case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
133 default: return; // Nothing left.
134 }
135
136 Bits.push_back(V);
137 }
138
139 // AddNodeID - Adds the Bit data of another ID to *this.
AddNodeID(const FoldingSetNodeID & ID)140 void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) {
141 Bits.append(ID.Bits.begin(), ID.Bits.end());
142 }
143
144 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used to
145 /// lookup the node in the FoldingSetBase.
ComputeHash() const146 unsigned FoldingSetNodeID::ComputeHash() const {
147 return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash();
148 }
149
150 /// operator== - Used to compare two nodes to each other.
151 ///
operator ==(const FoldingSetNodeID & RHS) const152 bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS) const {
153 return *this == FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
154 }
155
156 /// operator== - Used to compare two nodes to each other.
157 ///
operator ==(FoldingSetNodeIDRef RHS) const158 bool FoldingSetNodeID::operator==(FoldingSetNodeIDRef RHS) const {
159 return FoldingSetNodeIDRef(Bits.data(), Bits.size()) == RHS;
160 }
161
162 /// Used to compare the "ordering" of two nodes as defined by the
163 /// profiled bits and their ordering defined by memcmp().
operator <(const FoldingSetNodeID & RHS) const164 bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS) const {
165 return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
166 }
167
operator <(FoldingSetNodeIDRef RHS) const168 bool FoldingSetNodeID::operator<(FoldingSetNodeIDRef RHS) const {
169 return FoldingSetNodeIDRef(Bits.data(), Bits.size()) < RHS;
170 }
171
172 /// Intern - Copy this node's data to a memory region allocated from the
173 /// given allocator and return a FoldingSetNodeIDRef describing the
174 /// interned data.
175 FoldingSetNodeIDRef
Intern(BumpPtrAllocator & Allocator) const176 FoldingSetNodeID::Intern(BumpPtrAllocator &Allocator) const {
177 unsigned *New = Allocator.Allocate<unsigned>(Bits.size());
178 std::uninitialized_copy(Bits.begin(), Bits.end(), New);
179 return FoldingSetNodeIDRef(New, Bits.size());
180 }
181
182 //===----------------------------------------------------------------------===//
183 /// Helper functions for FoldingSetBase.
184
185 /// GetNextPtr - In order to save space, each bucket is a
186 /// singly-linked-list. In order to make deletion more efficient, we make
187 /// the list circular, so we can delete a node without computing its hash.
188 /// The problem with this is that the start of the hash buckets are not
189 /// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null:
190 /// use GetBucketPtr when this happens.
GetNextPtr(void * NextInBucketPtr)191 static FoldingSetBase::Node *GetNextPtr(void *NextInBucketPtr) {
192 // The low bit is set if this is the pointer back to the bucket.
193 if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1)
194 return nullptr;
195
196 return static_cast<FoldingSetBase::Node*>(NextInBucketPtr);
197 }
198
199
200 /// testing.
GetBucketPtr(void * NextInBucketPtr)201 static void **GetBucketPtr(void *NextInBucketPtr) {
202 intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr);
203 assert((Ptr & 1) && "Not a bucket pointer");
204 return reinterpret_cast<void**>(Ptr & ~intptr_t(1));
205 }
206
207 /// GetBucketFor - Hash the specified node ID and return the hash bucket for
208 /// the specified ID.
GetBucketFor(unsigned Hash,void ** Buckets,unsigned NumBuckets)209 static void **GetBucketFor(unsigned Hash, void **Buckets, unsigned NumBuckets) {
210 // NumBuckets is always a power of 2.
211 unsigned BucketNum = Hash & (NumBuckets-1);
212 return Buckets + BucketNum;
213 }
214
215 /// AllocateBuckets - Allocated initialized bucket memory.
AllocateBuckets(unsigned NumBuckets)216 static void **AllocateBuckets(unsigned NumBuckets) {
217 void **Buckets = static_cast<void**>(safe_calloc(NumBuckets + 1,
218 sizeof(void*)));
219 // Set the very last bucket to be a non-null "pointer".
220 Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
221 return Buckets;
222 }
223
224 //===----------------------------------------------------------------------===//
225 // FoldingSetBase Implementation
226
anchor()227 void FoldingSetBase::anchor() {}
228
FoldingSetBase(unsigned Log2InitSize)229 FoldingSetBase::FoldingSetBase(unsigned Log2InitSize) {
230 assert(5 < Log2InitSize && Log2InitSize < 32 &&
231 "Initial hash table size out of range");
232 NumBuckets = 1 << Log2InitSize;
233 Buckets = AllocateBuckets(NumBuckets);
234 NumNodes = 0;
235 }
236
FoldingSetBase(FoldingSetBase && Arg)237 FoldingSetBase::FoldingSetBase(FoldingSetBase &&Arg)
238 : Buckets(Arg.Buckets), NumBuckets(Arg.NumBuckets), NumNodes(Arg.NumNodes) {
239 Arg.Buckets = nullptr;
240 Arg.NumBuckets = 0;
241 Arg.NumNodes = 0;
242 }
243
operator =(FoldingSetBase && RHS)244 FoldingSetBase &FoldingSetBase::operator=(FoldingSetBase &&RHS) {
245 free(Buckets); // This may be null if the set is in a moved-from state.
246 Buckets = RHS.Buckets;
247 NumBuckets = RHS.NumBuckets;
248 NumNodes = RHS.NumNodes;
249 RHS.Buckets = nullptr;
250 RHS.NumBuckets = 0;
251 RHS.NumNodes = 0;
252 return *this;
253 }
254
~FoldingSetBase()255 FoldingSetBase::~FoldingSetBase() {
256 free(Buckets);
257 }
258
clear()259 void FoldingSetBase::clear() {
260 // Set all but the last bucket to null pointers.
261 memset(Buckets, 0, NumBuckets*sizeof(void*));
262
263 // Set the very last bucket to be a non-null "pointer".
264 Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
265
266 // Reset the node count to zero.
267 NumNodes = 0;
268 }
269
GrowBucketCount(unsigned NewBucketCount)270 void FoldingSetBase::GrowBucketCount(unsigned NewBucketCount) {
271 assert((NewBucketCount > NumBuckets) && "Can't shrink a folding set with GrowBucketCount");
272 assert(isPowerOf2_32(NewBucketCount) && "Bad bucket count!");
273 void **OldBuckets = Buckets;
274 unsigned OldNumBuckets = NumBuckets;
275
276 // Clear out new buckets.
277 Buckets = AllocateBuckets(NewBucketCount);
278 // Set NumBuckets only if allocation of new buckets was successful.
279 NumBuckets = NewBucketCount;
280 NumNodes = 0;
281
282 // Walk the old buckets, rehashing nodes into their new place.
283 FoldingSetNodeID TempID;
284 for (unsigned i = 0; i != OldNumBuckets; ++i) {
285 void *Probe = OldBuckets[i];
286 if (!Probe) continue;
287 while (Node *NodeInBucket = GetNextPtr(Probe)) {
288 // Figure out the next link, remove NodeInBucket from the old link.
289 Probe = NodeInBucket->getNextInBucket();
290 NodeInBucket->SetNextInBucket(nullptr);
291
292 // Insert the node into the new bucket, after recomputing the hash.
293 InsertNode(NodeInBucket,
294 GetBucketFor(ComputeNodeHash(NodeInBucket, TempID),
295 Buckets, NumBuckets));
296 TempID.clear();
297 }
298 }
299
300 free(OldBuckets);
301 }
302
303 /// GrowHashTable - Double the size of the hash table and rehash everything.
304 ///
GrowHashTable()305 void FoldingSetBase::GrowHashTable() {
306 GrowBucketCount(NumBuckets * 2);
307 }
308
reserve(unsigned EltCount)309 void FoldingSetBase::reserve(unsigned EltCount) {
310 // This will give us somewhere between EltCount / 2 and
311 // EltCount buckets. This puts us in the load factor
312 // range of 1.0 - 2.0.
313 if(EltCount < capacity())
314 return;
315 GrowBucketCount(PowerOf2Floor(EltCount));
316 }
317
318 /// FindNodeOrInsertPos - Look up the node specified by ID. If it exists,
319 /// return it. If not, return the insertion token that will make insertion
320 /// faster.
321 FoldingSetBase::Node *
FindNodeOrInsertPos(const FoldingSetNodeID & ID,void * & InsertPos)322 FoldingSetBase::FindNodeOrInsertPos(const FoldingSetNodeID &ID,
323 void *&InsertPos) {
324 unsigned IDHash = ID.ComputeHash();
325 void **Bucket = GetBucketFor(IDHash, Buckets, NumBuckets);
326 void *Probe = *Bucket;
327
328 InsertPos = nullptr;
329
330 FoldingSetNodeID TempID;
331 while (Node *NodeInBucket = GetNextPtr(Probe)) {
332 if (NodeEquals(NodeInBucket, ID, IDHash, TempID))
333 return NodeInBucket;
334 TempID.clear();
335
336 Probe = NodeInBucket->getNextInBucket();
337 }
338
339 // Didn't find the node, return null with the bucket as the InsertPos.
340 InsertPos = Bucket;
341 return nullptr;
342 }
343
344 /// InsertNode - Insert the specified node into the folding set, knowing that it
345 /// is not already in the map. InsertPos must be obtained from
346 /// FindNodeOrInsertPos.
InsertNode(Node * N,void * InsertPos)347 void FoldingSetBase::InsertNode(Node *N, void *InsertPos) {
348 assert(!N->getNextInBucket());
349 // Do we need to grow the hashtable?
350 if (NumNodes+1 > capacity()) {
351 GrowHashTable();
352 FoldingSetNodeID TempID;
353 InsertPos = GetBucketFor(ComputeNodeHash(N, TempID), Buckets, NumBuckets);
354 }
355
356 ++NumNodes;
357
358 /// The insert position is actually a bucket pointer.
359 void **Bucket = static_cast<void**>(InsertPos);
360
361 void *Next = *Bucket;
362
363 // If this is the first insertion into this bucket, its next pointer will be
364 // null. Pretend as if it pointed to itself, setting the low bit to indicate
365 // that it is a pointer to the bucket.
366 if (!Next)
367 Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1);
368
369 // Set the node's next pointer, and make the bucket point to the node.
370 N->SetNextInBucket(Next);
371 *Bucket = N;
372 }
373
374 /// RemoveNode - Remove a node from the folding set, returning true if one was
375 /// removed or false if the node was not in the folding set.
RemoveNode(Node * N)376 bool FoldingSetBase::RemoveNode(Node *N) {
377 // Because each bucket is a circular list, we don't need to compute N's hash
378 // to remove it.
379 void *Ptr = N->getNextInBucket();
380 if (!Ptr) return false; // Not in folding set.
381
382 --NumNodes;
383 N->SetNextInBucket(nullptr);
384
385 // Remember what N originally pointed to, either a bucket or another node.
386 void *NodeNextPtr = Ptr;
387
388 // Chase around the list until we find the node (or bucket) which points to N.
389 while (true) {
390 if (Node *NodeInBucket = GetNextPtr(Ptr)) {
391 // Advance pointer.
392 Ptr = NodeInBucket->getNextInBucket();
393
394 // We found a node that points to N, change it to point to N's next node,
395 // removing N from the list.
396 if (Ptr == N) {
397 NodeInBucket->SetNextInBucket(NodeNextPtr);
398 return true;
399 }
400 } else {
401 void **Bucket = GetBucketPtr(Ptr);
402 Ptr = *Bucket;
403
404 // If we found that the bucket points to N, update the bucket to point to
405 // whatever is next.
406 if (Ptr == N) {
407 *Bucket = NodeNextPtr;
408 return true;
409 }
410 }
411 }
412 }
413
414 /// GetOrInsertNode - If there is an existing simple Node exactly
415 /// equal to the specified node, return it. Otherwise, insert 'N' and it
416 /// instead.
GetOrInsertNode(FoldingSetBase::Node * N)417 FoldingSetBase::Node *FoldingSetBase::GetOrInsertNode(FoldingSetBase::Node *N) {
418 FoldingSetNodeID ID;
419 GetNodeProfile(N, ID);
420 void *IP;
421 if (Node *E = FindNodeOrInsertPos(ID, IP))
422 return E;
423 InsertNode(N, IP);
424 return N;
425 }
426
427 //===----------------------------------------------------------------------===//
428 // FoldingSetIteratorImpl Implementation
429
FoldingSetIteratorImpl(void ** Bucket)430 FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) {
431 // Skip to the first non-null non-self-cycle bucket.
432 while (*Bucket != reinterpret_cast<void*>(-1) &&
433 (!*Bucket || !GetNextPtr(*Bucket)))
434 ++Bucket;
435
436 NodePtr = static_cast<FoldingSetNode*>(*Bucket);
437 }
438
advance()439 void FoldingSetIteratorImpl::advance() {
440 // If there is another link within this bucket, go to it.
441 void *Probe = NodePtr->getNextInBucket();
442
443 if (FoldingSetNode *NextNodeInBucket = GetNextPtr(Probe))
444 NodePtr = NextNodeInBucket;
445 else {
446 // Otherwise, this is the last link in this bucket.
447 void **Bucket = GetBucketPtr(Probe);
448
449 // Skip to the next non-null non-self-cycle bucket.
450 do {
451 ++Bucket;
452 } while (*Bucket != reinterpret_cast<void*>(-1) &&
453 (!*Bucket || !GetNextPtr(*Bucket)));
454
455 NodePtr = static_cast<FoldingSetNode*>(*Bucket);
456 }
457 }
458
459 //===----------------------------------------------------------------------===//
460 // FoldingSetBucketIteratorImpl Implementation
461
FoldingSetBucketIteratorImpl(void ** Bucket)462 FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) {
463 Ptr = (!*Bucket || !GetNextPtr(*Bucket)) ? (void*) Bucket : *Bucket;
464 }
465