Bug Summary

File:lib/Support/FoldingSet.cpp
Warning:line 223, column 23
Array access (from variable 'Buckets') results in a null pointer dereference

Annotated Source Code

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 FoldingSetBase.
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 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}
61void FoldingSetNodeID::AddInteger(signed I) {
62 Bits.push_back(I);
63}
64void FoldingSetNodeID::AddInteger(unsigned I) {
65 Bits.push_back(I);
66}
67void FoldingSetNodeID::AddInteger(long I) {
68 AddInteger((unsigned long)I);
69}
70void 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)")::llvm::llvm_unreachable_internal("unexpected sizeof(long)", "/build/llvm-toolchain-snapshot-6.0~svn318693/lib/Support/FoldingSet.cpp"
, 76)
;
77 }
78}
79void FoldingSetNodeID::AddInteger(long long I) {
80 AddInteger((unsigned long long)I);
81}
82void FoldingSetNodeID::AddInteger(unsigned long long I) {
83 AddInteger(unsigned(I));
84 AddInteger(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 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[[clang::fallthrough]];
131 case 2: V = (V << 8) | (unsigned char)String[Size - 2]; LLVM_FALLTHROUGH[[clang::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.
140void 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.
146unsigned FoldingSetNodeID::ComputeHash() const {
147 return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash();
148}
149
150/// operator== - Used to compare two nodes to each other.
151///
152bool 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///
158bool 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().
164bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS) const {
165 return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
166}
167
168bool 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.
175FoldingSetNodeIDRef
176FoldingSetNodeID::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.
191static 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.
201static void **GetBucketPtr(void *NextInBucketPtr) {
202 intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr);
203 assert((Ptr & 1) && "Not a bucket pointer")(static_cast <bool> ((Ptr & 1) && "Not a bucket pointer"
) ? void (0) : __assert_fail ("(Ptr & 1) && \"Not a bucket pointer\""
, "/build/llvm-toolchain-snapshot-6.0~svn318693/lib/Support/FoldingSet.cpp"
, 203, __extension__ __PRETTY_FUNCTION__))
;
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.
209static 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.
216static void **AllocateBuckets(unsigned NumBuckets) {
217 void **Buckets = static_cast<void**>(calloc(NumBuckets+1, sizeof(void*)));
2
'Buckets' initialized here
218
219 if (Buckets == nullptr)
3
Assuming the condition is true
4
Assuming pointer value is null
5
Taking true branch
220 report_bad_alloc_error("Allocation of Buckets failed.");
221
222 // Set the very last bucket to be a non-null "pointer".
223 Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
6
Array access (from variable 'Buckets') results in a null pointer dereference
224 return Buckets;
225}
226
227//===----------------------------------------------------------------------===//
228// FoldingSetBase Implementation
229
230void FoldingSetBase::anchor() {}
231
232FoldingSetBase::FoldingSetBase(unsigned Log2InitSize) {
233 assert(5 < Log2InitSize && Log2InitSize < 32 &&(static_cast <bool> (5 < Log2InitSize && Log2InitSize
< 32 && "Initial hash table size out of range") ?
void (0) : __assert_fail ("5 < Log2InitSize && Log2InitSize < 32 && \"Initial hash table size out of range\""
, "/build/llvm-toolchain-snapshot-6.0~svn318693/lib/Support/FoldingSet.cpp"
, 234, __extension__ __PRETTY_FUNCTION__))
234 "Initial hash table size out of range")(static_cast <bool> (5 < Log2InitSize && Log2InitSize
< 32 && "Initial hash table size out of range") ?
void (0) : __assert_fail ("5 < Log2InitSize && Log2InitSize < 32 && \"Initial hash table size out of range\""
, "/build/llvm-toolchain-snapshot-6.0~svn318693/lib/Support/FoldingSet.cpp"
, 234, __extension__ __PRETTY_FUNCTION__))
;
235 NumBuckets = 1 << Log2InitSize;
236 Buckets = AllocateBuckets(NumBuckets);
1
Calling 'AllocateBuckets'
237 NumNodes = 0;
238}
239
240FoldingSetBase::FoldingSetBase(FoldingSetBase &&Arg)
241 : Buckets(Arg.Buckets), NumBuckets(Arg.NumBuckets), NumNodes(Arg.NumNodes) {
242 Arg.Buckets = nullptr;
243 Arg.NumBuckets = 0;
244 Arg.NumNodes = 0;
245}
246
247FoldingSetBase &FoldingSetBase::operator=(FoldingSetBase &&RHS) {
248 free(Buckets); // This may be null if the set is in a moved-from state.
249 Buckets = RHS.Buckets;
250 NumBuckets = RHS.NumBuckets;
251 NumNodes = RHS.NumNodes;
252 RHS.Buckets = nullptr;
253 RHS.NumBuckets = 0;
254 RHS.NumNodes = 0;
255 return *this;
256}
257
258FoldingSetBase::~FoldingSetBase() {
259 free(Buckets);
260}
261
262void FoldingSetBase::clear() {
263 // Set all but the last bucket to null pointers.
264 memset(Buckets, 0, NumBuckets*sizeof(void*));
265
266 // Set the very last bucket to be a non-null "pointer".
267 Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
268
269 // Reset the node count to zero.
270 NumNodes = 0;
271}
272
273void FoldingSetBase::GrowBucketCount(unsigned NewBucketCount) {
274 assert((NewBucketCount > NumBuckets) && "Can't shrink a folding set with GrowBucketCount")(static_cast <bool> ((NewBucketCount > NumBuckets) &&
"Can't shrink a folding set with GrowBucketCount") ? void (0
) : __assert_fail ("(NewBucketCount > NumBuckets) && \"Can't shrink a folding set with GrowBucketCount\""
, "/build/llvm-toolchain-snapshot-6.0~svn318693/lib/Support/FoldingSet.cpp"
, 274, __extension__ __PRETTY_FUNCTION__))
;
275 assert(isPowerOf2_32(NewBucketCount) && "Bad bucket count!")(static_cast <bool> (isPowerOf2_32(NewBucketCount) &&
"Bad bucket count!") ? void (0) : __assert_fail ("isPowerOf2_32(NewBucketCount) && \"Bad bucket count!\""
, "/build/llvm-toolchain-snapshot-6.0~svn318693/lib/Support/FoldingSet.cpp"
, 275, __extension__ __PRETTY_FUNCTION__))
;
276 void **OldBuckets = Buckets;
277 unsigned OldNumBuckets = NumBuckets;
278
279 // Clear out new buckets.
280 Buckets = AllocateBuckets(NewBucketCount);
281 // Set NumBuckets only if allocation of new buckets was succesful
282 NumBuckets = NewBucketCount;
283 NumNodes = 0;
284
285 // Walk the old buckets, rehashing nodes into their new place.
286 FoldingSetNodeID TempID;
287 for (unsigned i = 0; i != OldNumBuckets; ++i) {
288 void *Probe = OldBuckets[i];
289 if (!Probe) continue;
290 while (Node *NodeInBucket = GetNextPtr(Probe)) {
291 // Figure out the next link, remove NodeInBucket from the old link.
292 Probe = NodeInBucket->getNextInBucket();
293 NodeInBucket->SetNextInBucket(nullptr);
294
295 // Insert the node into the new bucket, after recomputing the hash.
296 InsertNode(NodeInBucket,
297 GetBucketFor(ComputeNodeHash(NodeInBucket, TempID),
298 Buckets, NumBuckets));
299 TempID.clear();
300 }
301 }
302
303 free(OldBuckets);
304}
305
306/// GrowHashTable - Double the size of the hash table and rehash everything.
307///
308void FoldingSetBase::GrowHashTable() {
309 GrowBucketCount(NumBuckets * 2);
310}
311
312void FoldingSetBase::reserve(unsigned EltCount) {
313 // This will give us somewhere between EltCount / 2 and
314 // EltCount buckets. This puts us in the load factor
315 // range of 1.0 - 2.0.
316 if(EltCount < capacity())
317 return;
318 GrowBucketCount(PowerOf2Floor(EltCount));
319}
320
321/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists,
322/// return it. If not, return the insertion token that will make insertion
323/// faster.
324FoldingSetBase::Node *
325FoldingSetBase::FindNodeOrInsertPos(const FoldingSetNodeID &ID,
326 void *&InsertPos) {
327 unsigned IDHash = ID.ComputeHash();
328 void **Bucket = GetBucketFor(IDHash, Buckets, NumBuckets);
329 void *Probe = *Bucket;
330
331 InsertPos = nullptr;
332
333 FoldingSetNodeID TempID;
334 while (Node *NodeInBucket = GetNextPtr(Probe)) {
335 if (NodeEquals(NodeInBucket, ID, IDHash, TempID))
336 return NodeInBucket;
337 TempID.clear();
338
339 Probe = NodeInBucket->getNextInBucket();
340 }
341
342 // Didn't find the node, return null with the bucket as the InsertPos.
343 InsertPos = Bucket;
344 return nullptr;
345}
346
347/// InsertNode - Insert the specified node into the folding set, knowing that it
348/// is not already in the map. InsertPos must be obtained from
349/// FindNodeOrInsertPos.
350void FoldingSetBase::InsertNode(Node *N, void *InsertPos) {
351 assert(!N->getNextInBucket())(static_cast <bool> (!N->getNextInBucket()) ? void (
0) : __assert_fail ("!N->getNextInBucket()", "/build/llvm-toolchain-snapshot-6.0~svn318693/lib/Support/FoldingSet.cpp"
, 351, __extension__ __PRETTY_FUNCTION__))
;
352 // Do we need to grow the hashtable?
353 if (NumNodes+1 > capacity()) {
354 GrowHashTable();
355 FoldingSetNodeID TempID;
356 InsertPos = GetBucketFor(ComputeNodeHash(N, TempID), Buckets, NumBuckets);
357 }
358
359 ++NumNodes;
360
361 /// The insert position is actually a bucket pointer.
362 void **Bucket = static_cast<void**>(InsertPos);
363
364 void *Next = *Bucket;
365
366 // If this is the first insertion into this bucket, its next pointer will be
367 // null. Pretend as if it pointed to itself, setting the low bit to indicate
368 // that it is a pointer to the bucket.
369 if (!Next)
370 Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1);
371
372 // Set the node's next pointer, and make the bucket point to the node.
373 N->SetNextInBucket(Next);
374 *Bucket = N;
375}
376
377/// RemoveNode - Remove a node from the folding set, returning true if one was
378/// removed or false if the node was not in the folding set.
379bool FoldingSetBase::RemoveNode(Node *N) {
380 // Because each bucket is a circular list, we don't need to compute N's hash
381 // to remove it.
382 void *Ptr = N->getNextInBucket();
383 if (!Ptr) return false; // Not in folding set.
384
385 --NumNodes;
386 N->SetNextInBucket(nullptr);
387
388 // Remember what N originally pointed to, either a bucket or another node.
389 void *NodeNextPtr = Ptr;
390
391 // Chase around the list until we find the node (or bucket) which points to N.
392 while (true) {
393 if (Node *NodeInBucket = GetNextPtr(Ptr)) {
394 // Advance pointer.
395 Ptr = NodeInBucket->getNextInBucket();
396
397 // We found a node that points to N, change it to point to N's next node,
398 // removing N from the list.
399 if (Ptr == N) {
400 NodeInBucket->SetNextInBucket(NodeNextPtr);
401 return true;
402 }
403 } else {
404 void **Bucket = GetBucketPtr(Ptr);
405 Ptr = *Bucket;
406
407 // If we found that the bucket points to N, update the bucket to point to
408 // whatever is next.
409 if (Ptr == N) {
410 *Bucket = NodeNextPtr;
411 return true;
412 }
413 }
414 }
415}
416
417/// GetOrInsertNode - If there is an existing simple Node exactly
418/// equal to the specified node, return it. Otherwise, insert 'N' and it
419/// instead.
420FoldingSetBase::Node *FoldingSetBase::GetOrInsertNode(FoldingSetBase::Node *N) {
421 FoldingSetNodeID ID;
422 GetNodeProfile(N, ID);
423 void *IP;
424 if (Node *E = FindNodeOrInsertPos(ID, IP))
425 return E;
426 InsertNode(N, IP);
427 return N;
428}
429
430//===----------------------------------------------------------------------===//
431// FoldingSetIteratorImpl Implementation
432
433FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) {
434 // Skip to the first non-null non-self-cycle bucket.
435 while (*Bucket != reinterpret_cast<void*>(-1) &&
436 (!*Bucket || !GetNextPtr(*Bucket)))
437 ++Bucket;
438
439 NodePtr = static_cast<FoldingSetNode*>(*Bucket);
440}
441
442void FoldingSetIteratorImpl::advance() {
443 // If there is another link within this bucket, go to it.
444 void *Probe = NodePtr->getNextInBucket();
445
446 if (FoldingSetNode *NextNodeInBucket = GetNextPtr(Probe))
447 NodePtr = NextNodeInBucket;
448 else {
449 // Otherwise, this is the last link in this bucket.
450 void **Bucket = GetBucketPtr(Probe);
451
452 // Skip to the next non-null non-self-cycle bucket.
453 do {
454 ++Bucket;
455 } while (*Bucket != reinterpret_cast<void*>(-1) &&
456 (!*Bucket || !GetNextPtr(*Bucket)));
457
458 NodePtr = static_cast<FoldingSetNode*>(*Bucket);
459 }
460}
461
462//===----------------------------------------------------------------------===//
463// FoldingSetBucketIteratorImpl Implementation
464
465FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) {
466 Ptr = (!*Bucket || !GetNextPtr(*Bucket)) ? (void*) Bucket : *Bucket;
467}