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"
18 bool SmallPtrSetImpl::insert(void *Ptr) {
20 // Check to see if it is already in the set.
21 for (void **APtr = SmallArray, **E = SmallArray+NumElements;
26 // Nope, there isn't. If we stay small, just 'pushback' now.
27 if (NumElements < CurArraySize-1) {
28 SmallArray[NumElements++] = Ptr;
31 // Otherwise, hit the big set case, which will call grow.
34 // If more than 3/4 of the array is full, grow.
35 if (NumElements*4 >= CurArraySize*3)
38 // Okay, we know we have space. Find a hash bucket.
39 void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
40 if (*Bucket == Ptr) return false; // Already inserted, good.
42 // Otherwise, insert it!
44 ++NumElements; // Track density.
48 bool SmallPtrSetImpl::erase(void *Ptr) {
50 // Check to see if it is in the set.
51 for (void **APtr = SmallArray, **E = SmallArray+NumElements;
54 // If it is in the set, move everything over, replacing this element.
55 memmove(APtr, APtr+1, sizeof(void*)*(E-APtr-1));
56 // Clear the end element.
57 E[-1] = getEmptyMarker();
65 // Okay, we know we have space. Find a hash bucket.
66 void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
67 if (*Bucket != Ptr) return false; // Not in the set?
69 // Set this as a tombstone.
70 *Bucket = getTombstoneMarker();
75 void * const *SmallPtrSetImpl::FindBucketFor(void *Ptr) const {
76 unsigned Bucket = Hash(Ptr);
77 unsigned ArraySize = CurArraySize;
78 unsigned ProbeAmt = 1;
79 void *const *Array = CurArray;
80 void *const *Tombstone = 0;
82 // Found Ptr's bucket?
83 if (Array[Bucket] == Ptr)
86 // If we found an empty bucket, the pointer doesn't exist in the set.
87 // Return a tombstone if we've seen one so far, or the empty bucket if
89 if (Array[Bucket] == getEmptyMarker())
90 return Tombstone ? Tombstone : Array+Bucket;
92 // If this is a tombstone, remember it. If Ptr ends up not in the set, we
93 // prefer to return it than something that would require more probing.
94 if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
95 Tombstone = Array+Bucket; // Remember the first tombstone found.
97 // It's a hash collision or a tombstone. Reprobe.
98 Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
102 /// Grow - Allocate a larger backing store for the buckets and move it over.
104 void SmallPtrSetImpl::Grow() {
105 // Allocate at twice as many buckets, but at least 128.
106 unsigned OldSize = CurArraySize;
107 unsigned NewSize = OldSize < 64 ? 128 : OldSize*2;
109 void **OldBuckets = CurArray;
110 bool WasSmall = isSmall();
112 // Install the new array. Clear all the buckets to empty.
113 CurArray = new void*[NewSize+1];
114 CurArraySize = NewSize;
115 memset(CurArray, -1, NewSize*sizeof(void*));
117 // The end pointer, always valid, is set to a valid element to help the
119 CurArray[NewSize] = 0;
121 // Copy over all the elements.
123 // Small sets store their elements in order.
124 for (void **BucketPtr = OldBuckets, **E = OldBuckets+NumElements;
125 BucketPtr != E; ++BucketPtr) {
126 void *Elt = *BucketPtr;
127 *const_cast<void**>(FindBucketFor(Elt)) = Elt;
130 // Copy over all valid entries.
131 for (void **BucketPtr = OldBuckets, **E = OldBuckets+OldSize;
132 BucketPtr != E; ++BucketPtr) {
133 // Copy over the element if it is valid.
134 void *Elt = *BucketPtr;
135 if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
136 *const_cast<void**>(FindBucketFor(Elt)) = Elt;
139 delete [] OldBuckets;