1 //===- llvm/ADT/SmallPtrSet.cpp - 'Normally small' pointer set ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Chris Lattner and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the SmallPtrSet class. See SmallPtrSet.h for an
11 // overview of the algorithm.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/Support/MathExtras.h"
19 bool SmallPtrSetImpl::insert(void *Ptr) {
21 // Check to see if it is already in the set.
22 for (void **APtr = SmallArray, **E = SmallArray+NumElements;
27 // Nope, there isn't. If we stay small, just 'pushback' now.
28 if (NumElements < CurArraySize-1) {
29 SmallArray[NumElements++] = Ptr;
32 // Otherwise, hit the big set case, which will call grow.
35 // If more than 3/4 of the array is full, grow.
36 if (NumElements*4 >= CurArraySize*3 ||
37 CurArraySize-(NumElements+NumTombstones) < CurArraySize/8)
40 // Okay, we know we have space. Find a hash bucket.
41 void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
42 if (*Bucket == Ptr) return false; // Already inserted, good.
44 // Otherwise, insert it!
45 if (*Bucket == getTombstoneMarker())
48 ++NumElements; // Track density.
52 bool SmallPtrSetImpl::erase(void *Ptr) {
54 // Check to see if it is in the set.
55 for (void **APtr = SmallArray, **E = SmallArray+NumElements;
58 // If it is in the set, replace this element.
60 E[-1] = getEmptyMarker();
68 // Okay, we know we have space. Find a hash bucket.
69 void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
70 if (*Bucket != Ptr) return false; // Not in the set?
72 // Set this as a tombstone.
73 *Bucket = getTombstoneMarker();
79 void * const *SmallPtrSetImpl::FindBucketFor(void *Ptr) const {
80 unsigned Bucket = Hash(Ptr);
81 unsigned ArraySize = CurArraySize;
82 unsigned ProbeAmt = 1;
83 void *const *Array = CurArray;
84 void *const *Tombstone = 0;
86 // Found Ptr's bucket?
87 if (Array[Bucket] == Ptr)
90 // If we found an empty bucket, the pointer doesn't exist in the set.
91 // Return a tombstone if we've seen one so far, or the empty bucket if
93 if (Array[Bucket] == getEmptyMarker())
94 return Tombstone ? Tombstone : Array+Bucket;
96 // If this is a tombstone, remember it. If Ptr ends up not in the set, we
97 // prefer to return it than something that would require more probing.
98 if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
99 Tombstone = Array+Bucket; // Remember the first tombstone found.
101 // It's a hash collision or a tombstone. Reprobe.
102 Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
106 /// Grow - Allocate a larger backing store for the buckets and move it over.
108 void SmallPtrSetImpl::Grow() {
109 // Allocate at twice as many buckets, but at least 128.
110 unsigned OldSize = CurArraySize;
111 unsigned NewSize = OldSize < 64 ? 128 : OldSize*2;
113 void **OldBuckets = CurArray;
114 bool WasSmall = isSmall();
116 // Install the new array. Clear all the buckets to empty.
117 CurArray = (void**)malloc(sizeof(void*) * (NewSize+1));
118 assert(CurArray && "Failed to allocate memory?");
119 CurArraySize = NewSize;
120 memset(CurArray, -1, NewSize*sizeof(void*));
122 // The end pointer, always valid, is set to a valid element to help the
124 CurArray[NewSize] = 0;
126 // Copy over all the elements.
128 // Small sets store their elements in order.
129 for (void **BucketPtr = OldBuckets, **E = OldBuckets+NumElements;
130 BucketPtr != E; ++BucketPtr) {
131 void *Elt = *BucketPtr;
132 *const_cast<void**>(FindBucketFor(Elt)) = Elt;
135 // Copy over all valid entries.
136 for (void **BucketPtr = OldBuckets, **E = OldBuckets+OldSize;
137 BucketPtr != E; ++BucketPtr) {
138 // Copy over the element if it is valid.
139 void *Elt = *BucketPtr;
140 if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
141 *const_cast<void**>(FindBucketFor(Elt)) = Elt;
149 SmallPtrSetImpl::SmallPtrSetImpl(const SmallPtrSetImpl& that) {
150 NumElements = that.NumElements;
152 if (that.isSmall()) {
153 CurArraySize = that.CurArraySize;
154 CurArray = &SmallArray[0];
155 // Copy the entire contents of the array, including the -1's and the null
157 memcpy(CurArray, that.CurArray, sizeof(void*)*(CurArraySize+1));
159 CurArraySize = that.NumElements < 64 ? 128 : that.CurArraySize*2;
160 CurArray = (void**)malloc(sizeof(void*) * (CurArraySize+1));
161 assert(CurArray && "Failed to allocate memory?");
162 memset(CurArray, -1, CurArraySize*sizeof(void*));
164 // The end pointer, always valid, is set to a valid element to help the
166 CurArray[CurArraySize] = 0;
168 // Copy over all valid entries.
169 for (void **BucketPtr = that.CurArray, **E = that.CurArray+that.CurArraySize;
170 BucketPtr != E; ++BucketPtr) {
171 // Copy over the element if it is valid.
172 void *Elt = *BucketPtr;
173 if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
174 *const_cast<void**>(FindBucketFor(Elt)) = Elt;
179 /// CopyFrom - implement operator= from a smallptrset that has the same pointer
180 /// type, but may have a different small size.
181 void SmallPtrSetImpl::CopyFrom(const SmallPtrSetImpl &RHS) {
182 if (isSmall() && RHS.isSmall())
183 assert(CurArraySize == RHS.CurArraySize &&
184 "Cannot assign sets with different small sizes");
185 NumElements = RHS.NumElements;
186 NumTombstones = RHS.NumTombstones;
188 // If we're becoming small, prepare to insert into our stack space
190 CurArray = &SmallArray[0];
191 // Otherwise, allocate new heap space (unless we were the same size)
192 else if (CurArraySize != RHS.CurArraySize) {
193 CurArray = (void**)realloc(CurArray, sizeof(void*)*(RHS.CurArraySize+1));
194 assert(CurArray && "Failed to allocate memory?");
197 // Copy over the new array size
198 CurArraySize = RHS.CurArraySize;
200 // Copy over the contents from the other set
201 memcpy(CurArray, RHS.CurArray, sizeof(void*)*(CurArraySize+1));