xref: /freebsd/contrib/llvm-project/llvm/lib/Support/FoldingSet.cpp (revision f126890ac5386406dadf7c4cfa9566cbb56537c5)
1 //===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements a hash set that can be used to remove duplication of
10 // nodes in a graph.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ADT/FoldingSet.h"
15 #include "llvm/ADT/StringRef.h"
16 #include "llvm/Support/Allocator.h"
17 #include "llvm/Support/ErrorHandling.h"
18 #include "llvm/Support/MathExtras.h"
19 #include "llvm/Support/SwapByteOrder.h"
20 #include <cassert>
21 #include <cstring>
22 using namespace llvm;
23 
24 //===----------------------------------------------------------------------===//
25 // FoldingSetNodeIDRef Implementation
26 
27 bool FoldingSetNodeIDRef::operator==(FoldingSetNodeIDRef RHS) const {
28   if (Size != RHS.Size) return false;
29   return memcmp(Data, RHS.Data, Size*sizeof(*Data)) == 0;
30 }
31 
32 /// Used to compare the "ordering" of two nodes as defined by the
33 /// profiled bits and their ordering defined by memcmp().
34 bool FoldingSetNodeIDRef::operator<(FoldingSetNodeIDRef RHS) const {
35   if (Size != RHS.Size)
36     return Size < RHS.Size;
37   return memcmp(Data, RHS.Data, Size*sizeof(*Data)) < 0;
38 }
39 
40 //===----------------------------------------------------------------------===//
41 // FoldingSetNodeID Implementation
42 
43 /// Add* - Add various data types to Bit data.
44 ///
45 void FoldingSetNodeID::AddString(StringRef String) {
46   unsigned Size =  String.size();
47 
48   unsigned NumInserts = 1 + divideCeil(Size, 4);
49   Bits.reserve(Bits.size() + NumInserts);
50 
51   Bits.push_back(Size);
52   if (!Size) return;
53 
54   unsigned Units = Size / 4;
55   unsigned Pos = 0;
56   const unsigned *Base = (const unsigned*) String.data();
57 
58   // If the string is aligned do a bulk transfer.
59   if (!((intptr_t)Base & 3)) {
60     Bits.append(Base, Base + Units);
61     Pos = (Units + 1) * 4;
62   } else {
63     // Otherwise do it the hard way.
64     // To be compatible with above bulk transfer, we need to take endianness
65     // into account.
66     static_assert(sys::IsBigEndianHost || sys::IsLittleEndianHost,
67                   "Unexpected host endianness");
68     if (sys::IsBigEndianHost) {
69       for (Pos += 4; Pos <= Size; Pos += 4) {
70         unsigned V = ((unsigned char)String[Pos - 4] << 24) |
71                      ((unsigned char)String[Pos - 3] << 16) |
72                      ((unsigned char)String[Pos - 2] << 8) |
73                       (unsigned char)String[Pos - 1];
74         Bits.push_back(V);
75       }
76     } else {  // Little-endian host
77       for (Pos += 4; Pos <= Size; Pos += 4) {
78         unsigned V = ((unsigned char)String[Pos - 1] << 24) |
79                      ((unsigned char)String[Pos - 2] << 16) |
80                      ((unsigned char)String[Pos - 3] << 8) |
81                       (unsigned char)String[Pos - 4];
82         Bits.push_back(V);
83       }
84     }
85   }
86 
87   // With the leftover bits.
88   unsigned V = 0;
89   // Pos will have overshot size by 4 - #bytes left over.
90   // No need to take endianness into account here - this is always executed.
91   switch (Pos - Size) {
92   case 1: V = (V << 8) | (unsigned char)String[Size - 3]; [[fallthrough]];
93   case 2: V = (V << 8) | (unsigned char)String[Size - 2]; [[fallthrough]];
94   case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
95   default: return; // Nothing left.
96   }
97 
98   Bits.push_back(V);
99 }
100 
101 // AddNodeID - Adds the Bit data of another ID to *this.
102 void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) {
103   Bits.append(ID.Bits.begin(), ID.Bits.end());
104 }
105 
106 /// operator== - Used to compare two nodes to each other.
107 ///
108 bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS) const {
109   return *this == FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
110 }
111 
112 /// operator== - Used to compare two nodes to each other.
113 ///
114 bool FoldingSetNodeID::operator==(FoldingSetNodeIDRef RHS) const {
115   return FoldingSetNodeIDRef(Bits.data(), Bits.size()) == RHS;
116 }
117 
118 /// Used to compare the "ordering" of two nodes as defined by the
119 /// profiled bits and their ordering defined by memcmp().
120 bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS) const {
121   return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
122 }
123 
124 bool FoldingSetNodeID::operator<(FoldingSetNodeIDRef RHS) const {
125   return FoldingSetNodeIDRef(Bits.data(), Bits.size()) < RHS;
126 }
127 
128 /// Intern - Copy this node's data to a memory region allocated from the
129 /// given allocator and return a FoldingSetNodeIDRef describing the
130 /// interned data.
131 FoldingSetNodeIDRef
132 FoldingSetNodeID::Intern(BumpPtrAllocator &Allocator) const {
133   unsigned *New = Allocator.Allocate<unsigned>(Bits.size());
134   std::uninitialized_copy(Bits.begin(), Bits.end(), New);
135   return FoldingSetNodeIDRef(New, Bits.size());
136 }
137 
138 //===----------------------------------------------------------------------===//
139 /// Helper functions for FoldingSetBase.
140 
141 /// GetNextPtr - In order to save space, each bucket is a
142 /// singly-linked-list. In order to make deletion more efficient, we make
143 /// the list circular, so we can delete a node without computing its hash.
144 /// The problem with this is that the start of the hash buckets are not
145 /// Nodes.  If NextInBucketPtr is a bucket pointer, this method returns null:
146 /// use GetBucketPtr when this happens.
147 static FoldingSetBase::Node *GetNextPtr(void *NextInBucketPtr) {
148   // The low bit is set if this is the pointer back to the bucket.
149   if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1)
150     return nullptr;
151 
152   return static_cast<FoldingSetBase::Node*>(NextInBucketPtr);
153 }
154 
155 
156 /// testing.
157 static void **GetBucketPtr(void *NextInBucketPtr) {
158   intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr);
159   assert((Ptr & 1) && "Not a bucket pointer");
160   return reinterpret_cast<void**>(Ptr & ~intptr_t(1));
161 }
162 
163 /// GetBucketFor - Hash the specified node ID and return the hash bucket for
164 /// the specified ID.
165 static void **GetBucketFor(unsigned Hash, void **Buckets, unsigned NumBuckets) {
166   // NumBuckets is always a power of 2.
167   unsigned BucketNum = Hash & (NumBuckets-1);
168   return Buckets + BucketNum;
169 }
170 
171 /// AllocateBuckets - Allocated initialized bucket memory.
172 static void **AllocateBuckets(unsigned NumBuckets) {
173   void **Buckets = static_cast<void**>(safe_calloc(NumBuckets + 1,
174                                                    sizeof(void*)));
175   // Set the very last bucket to be a non-null "pointer".
176   Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
177   return Buckets;
178 }
179 
180 //===----------------------------------------------------------------------===//
181 // FoldingSetBase Implementation
182 
183 FoldingSetBase::FoldingSetBase(unsigned Log2InitSize) {
184   assert(5 < Log2InitSize && Log2InitSize < 32 &&
185          "Initial hash table size out of range");
186   NumBuckets = 1 << Log2InitSize;
187   Buckets = AllocateBuckets(NumBuckets);
188   NumNodes = 0;
189 }
190 
191 FoldingSetBase::FoldingSetBase(FoldingSetBase &&Arg)
192     : Buckets(Arg.Buckets), NumBuckets(Arg.NumBuckets), NumNodes(Arg.NumNodes) {
193   Arg.Buckets = nullptr;
194   Arg.NumBuckets = 0;
195   Arg.NumNodes = 0;
196 }
197 
198 FoldingSetBase &FoldingSetBase::operator=(FoldingSetBase &&RHS) {
199   free(Buckets); // This may be null if the set is in a moved-from state.
200   Buckets = RHS.Buckets;
201   NumBuckets = RHS.NumBuckets;
202   NumNodes = RHS.NumNodes;
203   RHS.Buckets = nullptr;
204   RHS.NumBuckets = 0;
205   RHS.NumNodes = 0;
206   return *this;
207 }
208 
209 FoldingSetBase::~FoldingSetBase() {
210   free(Buckets);
211 }
212 
213 void FoldingSetBase::clear() {
214   // Set all but the last bucket to null pointers.
215   memset(Buckets, 0, NumBuckets*sizeof(void*));
216 
217   // Set the very last bucket to be a non-null "pointer".
218   Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
219 
220   // Reset the node count to zero.
221   NumNodes = 0;
222 }
223 
224 void FoldingSetBase::GrowBucketCount(unsigned NewBucketCount,
225                                      const FoldingSetInfo &Info) {
226   assert((NewBucketCount > NumBuckets) &&
227          "Can't shrink a folding set with GrowBucketCount");
228   assert(isPowerOf2_32(NewBucketCount) && "Bad bucket count!");
229   void **OldBuckets = Buckets;
230   unsigned OldNumBuckets = NumBuckets;
231 
232   // Clear out new buckets.
233   Buckets = AllocateBuckets(NewBucketCount);
234   // Set NumBuckets only if allocation of new buckets was successful.
235   NumBuckets = NewBucketCount;
236   NumNodes = 0;
237 
238   // Walk the old buckets, rehashing nodes into their new place.
239   FoldingSetNodeID TempID;
240   for (unsigned i = 0; i != OldNumBuckets; ++i) {
241     void *Probe = OldBuckets[i];
242     if (!Probe) continue;
243     while (Node *NodeInBucket = GetNextPtr(Probe)) {
244       // Figure out the next link, remove NodeInBucket from the old link.
245       Probe = NodeInBucket->getNextInBucket();
246       NodeInBucket->SetNextInBucket(nullptr);
247 
248       // Insert the node into the new bucket, after recomputing the hash.
249       InsertNode(NodeInBucket,
250                  GetBucketFor(Info.ComputeNodeHash(this, NodeInBucket, TempID),
251                               Buckets, NumBuckets),
252                  Info);
253       TempID.clear();
254     }
255   }
256 
257   free(OldBuckets);
258 }
259 
260 /// GrowHashTable - Double the size of the hash table and rehash everything.
261 ///
262 void FoldingSetBase::GrowHashTable(const FoldingSetInfo &Info) {
263   GrowBucketCount(NumBuckets * 2, Info);
264 }
265 
266 void FoldingSetBase::reserve(unsigned EltCount, const FoldingSetInfo &Info) {
267   // This will give us somewhere between EltCount / 2 and
268   // EltCount buckets.  This puts us in the load factor
269   // range of 1.0 - 2.0.
270   if(EltCount < capacity())
271     return;
272   GrowBucketCount(llvm::bit_floor(EltCount), Info);
273 }
274 
275 /// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,
276 /// return it.  If not, return the insertion token that will make insertion
277 /// faster.
278 FoldingSetBase::Node *FoldingSetBase::FindNodeOrInsertPos(
279     const FoldingSetNodeID &ID, void *&InsertPos, const FoldingSetInfo &Info) {
280   unsigned IDHash = ID.ComputeHash();
281   void **Bucket = GetBucketFor(IDHash, Buckets, NumBuckets);
282   void *Probe = *Bucket;
283 
284   InsertPos = nullptr;
285 
286   FoldingSetNodeID TempID;
287   while (Node *NodeInBucket = GetNextPtr(Probe)) {
288     if (Info.NodeEquals(this, NodeInBucket, ID, IDHash, TempID))
289       return NodeInBucket;
290     TempID.clear();
291 
292     Probe = NodeInBucket->getNextInBucket();
293   }
294 
295   // Didn't find the node, return null with the bucket as the InsertPos.
296   InsertPos = Bucket;
297   return nullptr;
298 }
299 
300 /// InsertNode - Insert the specified node into the folding set, knowing that it
301 /// is not already in the map.  InsertPos must be obtained from
302 /// FindNodeOrInsertPos.
303 void FoldingSetBase::InsertNode(Node *N, void *InsertPos,
304                                 const FoldingSetInfo &Info) {
305   assert(!N->getNextInBucket());
306   // Do we need to grow the hashtable?
307   if (NumNodes+1 > capacity()) {
308     GrowHashTable(Info);
309     FoldingSetNodeID TempID;
310     InsertPos = GetBucketFor(Info.ComputeNodeHash(this, N, TempID), Buckets,
311                              NumBuckets);
312   }
313 
314   ++NumNodes;
315 
316   /// The insert position is actually a bucket pointer.
317   void **Bucket = static_cast<void**>(InsertPos);
318 
319   void *Next = *Bucket;
320 
321   // If this is the first insertion into this bucket, its next pointer will be
322   // null.  Pretend as if it pointed to itself, setting the low bit to indicate
323   // that it is a pointer to the bucket.
324   if (!Next)
325     Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1);
326 
327   // Set the node's next pointer, and make the bucket point to the node.
328   N->SetNextInBucket(Next);
329   *Bucket = N;
330 }
331 
332 /// RemoveNode - Remove a node from the folding set, returning true if one was
333 /// removed or false if the node was not in the folding set.
334 bool FoldingSetBase::RemoveNode(Node *N) {
335   // Because each bucket is a circular list, we don't need to compute N's hash
336   // to remove it.
337   void *Ptr = N->getNextInBucket();
338   if (!Ptr) return false;  // Not in folding set.
339 
340   --NumNodes;
341   N->SetNextInBucket(nullptr);
342 
343   // Remember what N originally pointed to, either a bucket or another node.
344   void *NodeNextPtr = Ptr;
345 
346   // Chase around the list until we find the node (or bucket) which points to N.
347   while (true) {
348     if (Node *NodeInBucket = GetNextPtr(Ptr)) {
349       // Advance pointer.
350       Ptr = NodeInBucket->getNextInBucket();
351 
352       // We found a node that points to N, change it to point to N's next node,
353       // removing N from the list.
354       if (Ptr == N) {
355         NodeInBucket->SetNextInBucket(NodeNextPtr);
356         return true;
357       }
358     } else {
359       void **Bucket = GetBucketPtr(Ptr);
360       Ptr = *Bucket;
361 
362       // If we found that the bucket points to N, update the bucket to point to
363       // whatever is next.
364       if (Ptr == N) {
365         *Bucket = NodeNextPtr;
366         return true;
367       }
368     }
369   }
370 }
371 
372 /// GetOrInsertNode - If there is an existing simple Node exactly
373 /// equal to the specified node, return it.  Otherwise, insert 'N' and it
374 /// instead.
375 FoldingSetBase::Node *
376 FoldingSetBase::GetOrInsertNode(FoldingSetBase::Node *N,
377                                 const FoldingSetInfo &Info) {
378   FoldingSetNodeID ID;
379   Info.GetNodeProfile(this, N, ID);
380   void *IP;
381   if (Node *E = FindNodeOrInsertPos(ID, IP, Info))
382     return E;
383   InsertNode(N, IP, Info);
384   return N;
385 }
386 
387 //===----------------------------------------------------------------------===//
388 // FoldingSetIteratorImpl Implementation
389 
390 FoldingSetIteratorImpl::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 
399 void 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 
422 FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) {
423   Ptr = (!*Bucket || !GetNextPtr(*Bucket)) ? (void*) Bucket : *Bucket;
424 }
425