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>
22using namespace llvm;
23
24//===----------------------------------------------------------------------===//
25// FoldingSetNodeIDRef Implementation
26
27bool FoldingSetNodeIDRef::operator==(FoldingSetNodeIDRef RHS) const {
28 if (Size != RHS.Size) return false;
29 return memcmp(s1: Data, s2: RHS.Data, n: 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().
34bool FoldingSetNodeIDRef::operator<(FoldingSetNodeIDRef RHS) const {
35 if (Size != RHS.Size)
36 return Size < RHS.Size;
37 return memcmp(s1: Data, s2: RHS.Data, n: Size*sizeof(*Data)) < 0;
38}
39
40//===----------------------------------------------------------------------===//
41// FoldingSetNodeID Implementation
42
43/// Add* - Add various data types to Bit data.
44///
45void FoldingSetNodeID::AddString(StringRef String) {
46 unsigned Size = String.size();
47
48 unsigned NumInserts = 1 + divideCeil(Numerator: Size, Denominator: 4);
49 Bits.reserve(N: Bits.size() + NumInserts);
50
51 Bits.push_back(Elt: 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(in_start: Base, in_end: 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(Elt: 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(Elt: 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(Elt: V);
99}
100
101// AddNodeID - Adds the Bit data of another ID to *this.
102void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) {
103 Bits.append(in_start: ID.Bits.begin(), in_end: ID.Bits.end());
104}
105
106/// operator== - Used to compare two nodes to each other.
107///
108bool 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///
114bool 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().
120bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS) const {
121 return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
122}
123
124bool 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.
131FoldingSetNodeIDRef
132FoldingSetNodeID::Intern(BumpPtrAllocator &Allocator) const {
133 unsigned *New = Allocator.Allocate<unsigned>(Num: Bits.size());
134 llvm::uninitialized_copy(Src: Bits, Dst: 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.
147static 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.
157static 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.
165static 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.
172static void **AllocateBuckets(unsigned NumBuckets) {
173 void **Buckets = static_cast<void**>(safe_calloc(Count: NumBuckets + 1,
174 Sz: 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
183FoldingSetBase::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
191FoldingSetBase::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
198FoldingSetBase &FoldingSetBase::operator=(FoldingSetBase &&RHS) {
199 free(ptr: 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
209FoldingSetBase::~FoldingSetBase() {
210 free(ptr: Buckets);
211}
212
213void FoldingSetBase::clear() {
214 // Set all but the last bucket to null pointers.
215 memset(s: Buckets, c: 0, n: 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
224void 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(NumBuckets: 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(NextInBucketPtr: 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(N: NodeInBucket,
250 InsertPos: GetBucketFor(Hash: Info.ComputeNodeHash(this, NodeInBucket, TempID),
251 Buckets, NumBuckets),
252 Info);
253 TempID.clear();
254 }
255 }
256
257 free(ptr: OldBuckets);
258}
259
260/// GrowHashTable - Double the size of the hash table and rehash everything.
261///
262void FoldingSetBase::GrowHashTable(const FoldingSetInfo &Info) {
263 GrowBucketCount(NewBucketCount: NumBuckets * 2, Info);
264}
265
266void 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(NewBucketCount: llvm::bit_floor(Value: 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.
278FoldingSetBase::Node *FoldingSetBase::FindNodeOrInsertPos(
279 const FoldingSetNodeID &ID, void *&InsertPos, const FoldingSetInfo &Info) {
280 unsigned IDHash = ID.ComputeHash();
281 void **Bucket = GetBucketFor(Hash: IDHash, Buckets, NumBuckets);
282 void *Probe = *Bucket;
283
284 InsertPos = nullptr;
285
286 FoldingSetNodeID TempID;
287 while (Node *NodeInBucket = GetNextPtr(NextInBucketPtr: 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.
303void 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(Hash: 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.
334bool 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(NextInBucketPtr: 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(NextInBucketPtr: 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.
375FoldingSetBase::Node *
376FoldingSetBase::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, InsertPos&: IP, Info))
382 return E;
383 InsertNode(N, InsertPos: IP, Info);
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(NextInBucketPtr: *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(NextInBucketPtr: Probe))
404 NodePtr = NextNodeInBucket;
405 else {
406 // Otherwise, this is the last link in this bucket.
407 void **Bucket = GetBucketPtr(NextInBucketPtr: 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(NextInBucketPtr: *Bucket)));
414
415 NodePtr = static_cast<FoldingSetNode*>(*Bucket);
416 }
417}
418
419//===----------------------------------------------------------------------===//
420// FoldingSetBucketIteratorImpl Implementation
421
422FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) {
423 Ptr = (!*Bucket || !GetNextPtr(NextInBucketPtr: *Bucket)) ? (void*) Bucket : *Bucket;
424}
425