282 lines
9.3 KiB
C++
282 lines
9.3 KiB
C++
//===- llvm/ADT/SmallPtrSet.cpp - 'Normally small' pointer set ------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the SmallPtrSet class. See SmallPtrSet.h for an
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// overview of the algorithm.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/DenseMapInfo.h"
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#include "llvm/Support/MathExtras.h"
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#include <algorithm>
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#include <cstdlib>
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using namespace llvm;
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void SmallPtrSetImpl::shrink_and_clear() {
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assert(!isSmall() && "Can't shrink a small set!");
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free(CurArray);
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// Reduce the number of buckets.
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CurArraySize = NumElements > 16 ? 1 << (Log2_32_Ceil(NumElements) + 1) : 32;
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NumElements = NumTombstones = 0;
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// Install the new array. Clear all the buckets to empty.
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CurArray = (const void**)malloc(sizeof(void*) * (CurArraySize+1));
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assert(CurArray && "Failed to allocate memory?");
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memset(CurArray, -1, CurArraySize*sizeof(void*));
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// The end pointer, always valid, is set to a valid element to help the
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// iterator.
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CurArray[CurArraySize] = 0;
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}
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bool SmallPtrSetImpl::insert_imp(const void * Ptr) {
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if (isSmall()) {
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// Check to see if it is already in the set.
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for (const void **APtr = SmallArray, **E = SmallArray+NumElements;
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APtr != E; ++APtr)
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if (*APtr == Ptr)
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return false;
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// Nope, there isn't. If we stay small, just 'pushback' now.
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if (NumElements < CurArraySize-1) {
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SmallArray[NumElements++] = Ptr;
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return true;
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}
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// Otherwise, hit the big set case, which will call grow.
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}
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if (NumElements*4 >= CurArraySize*3) {
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// If more than 3/4 of the array is full, grow.
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Grow(CurArraySize < 64 ? 128 : CurArraySize*2);
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} else if (CurArraySize-(NumElements+NumTombstones) < CurArraySize/8) {
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// If fewer of 1/8 of the array is empty (meaning that many are filled with
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// tombstones), rehash.
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Grow(CurArraySize);
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}
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// Okay, we know we have space. Find a hash bucket.
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const void **Bucket = const_cast<const void**>(FindBucketFor(Ptr));
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if (*Bucket == Ptr) return false; // Already inserted, good.
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// Otherwise, insert it!
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if (*Bucket == getTombstoneMarker())
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--NumTombstones;
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*Bucket = Ptr;
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++NumElements; // Track density.
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return true;
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}
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bool SmallPtrSetImpl::erase_imp(const void * Ptr) {
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if (isSmall()) {
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// Check to see if it is in the set.
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for (const void **APtr = SmallArray, **E = SmallArray+NumElements;
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APtr != E; ++APtr)
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if (*APtr == Ptr) {
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// If it is in the set, replace this element.
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*APtr = E[-1];
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E[-1] = getEmptyMarker();
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--NumElements;
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return true;
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}
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return false;
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}
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// Okay, we know we have space. Find a hash bucket.
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void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
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if (*Bucket != Ptr) return false; // Not in the set?
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// Set this as a tombstone.
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*Bucket = getTombstoneMarker();
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--NumElements;
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++NumTombstones;
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return true;
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}
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const void * const *SmallPtrSetImpl::FindBucketFor(const void *Ptr) const {
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unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1);
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unsigned ArraySize = CurArraySize;
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unsigned ProbeAmt = 1;
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const void *const *Array = CurArray;
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const void *const *Tombstone = 0;
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while (1) {
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// Found Ptr's bucket?
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if (Array[Bucket] == Ptr)
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return Array+Bucket;
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// If we found an empty bucket, the pointer doesn't exist in the set.
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// Return a tombstone if we've seen one so far, or the empty bucket if
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// not.
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if (Array[Bucket] == getEmptyMarker())
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return Tombstone ? Tombstone : Array+Bucket;
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// If this is a tombstone, remember it. If Ptr ends up not in the set, we
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// prefer to return it than something that would require more probing.
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if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
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Tombstone = Array+Bucket; // Remember the first tombstone found.
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// It's a hash collision or a tombstone. Reprobe.
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Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
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}
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}
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/// Grow - Allocate a larger backing store for the buckets and move it over.
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///
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void SmallPtrSetImpl::Grow(unsigned NewSize) {
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// Allocate at twice as many buckets, but at least 128.
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unsigned OldSize = CurArraySize;
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const void **OldBuckets = CurArray;
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bool WasSmall = isSmall();
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// Install the new array. Clear all the buckets to empty.
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CurArray = (const void**)malloc(sizeof(void*) * (NewSize+1));
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assert(CurArray && "Failed to allocate memory?");
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CurArraySize = NewSize;
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memset(CurArray, -1, NewSize*sizeof(void*));
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// The end pointer, always valid, is set to a valid element to help the
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// iterator.
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CurArray[NewSize] = 0;
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// Copy over all the elements.
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if (WasSmall) {
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// Small sets store their elements in order.
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for (const void **BucketPtr = OldBuckets, **E = OldBuckets+NumElements;
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BucketPtr != E; ++BucketPtr) {
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const void *Elt = *BucketPtr;
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*const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
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}
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} else {
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// Copy over all valid entries.
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for (const void **BucketPtr = OldBuckets, **E = OldBuckets+OldSize;
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BucketPtr != E; ++BucketPtr) {
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// Copy over the element if it is valid.
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const void *Elt = *BucketPtr;
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if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
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*const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
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}
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free(OldBuckets);
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NumTombstones = 0;
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}
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}
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SmallPtrSetImpl::SmallPtrSetImpl(const void **SmallStorage,
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const SmallPtrSetImpl& that) {
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SmallArray = SmallStorage;
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// If we're becoming small, prepare to insert into our stack space
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if (that.isSmall()) {
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CurArray = SmallArray;
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// Otherwise, allocate new heap space (unless we were the same size)
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} else {
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CurArray = (const void**)malloc(sizeof(void*) * (that.CurArraySize+1));
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assert(CurArray && "Failed to allocate memory?");
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}
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// Copy over the new array size
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CurArraySize = that.CurArraySize;
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// Copy over the contents from the other set
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memcpy(CurArray, that.CurArray, sizeof(void*)*(CurArraySize+1));
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NumElements = that.NumElements;
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NumTombstones = that.NumTombstones;
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}
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/// CopyFrom - implement operator= from a smallptrset that has the same pointer
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/// type, but may have a different small size.
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void SmallPtrSetImpl::CopyFrom(const SmallPtrSetImpl &RHS) {
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if (isSmall() && RHS.isSmall())
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assert(CurArraySize == RHS.CurArraySize &&
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"Cannot assign sets with different small sizes");
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// If we're becoming small, prepare to insert into our stack space
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if (RHS.isSmall()) {
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if (!isSmall())
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free(CurArray);
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CurArray = SmallArray;
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// Otherwise, allocate new heap space (unless we were the same size)
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} else if (CurArraySize != RHS.CurArraySize) {
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if (isSmall())
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CurArray = (const void**)malloc(sizeof(void*) * (RHS.CurArraySize+1));
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else
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CurArray = (const void**)realloc(CurArray, sizeof(void*)*(RHS.CurArraySize+1));
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assert(CurArray && "Failed to allocate memory?");
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}
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// Copy over the new array size
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CurArraySize = RHS.CurArraySize;
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// Copy over the contents from the other set
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memcpy(CurArray, RHS.CurArray, sizeof(void*)*(CurArraySize+1));
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NumElements = RHS.NumElements;
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NumTombstones = RHS.NumTombstones;
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}
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void SmallPtrSetImpl::swap(SmallPtrSetImpl &RHS) {
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if (this == &RHS) return;
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// We can only avoid copying elements if neither set is small.
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if (!this->isSmall() && !RHS.isSmall()) {
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std::swap(this->CurArray, RHS.CurArray);
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std::swap(this->CurArraySize, RHS.CurArraySize);
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std::swap(this->NumElements, RHS.NumElements);
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std::swap(this->NumTombstones, RHS.NumTombstones);
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return;
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}
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// FIXME: From here on we assume that both sets have the same small size.
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// If only RHS is small, copy the small elements into LHS and move the pointer
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// from LHS to RHS.
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if (!this->isSmall() && RHS.isSmall()) {
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std::copy(RHS.SmallArray, RHS.SmallArray+RHS.CurArraySize,
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this->SmallArray);
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std::swap(this->NumElements, RHS.NumElements);
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std::swap(this->CurArraySize, RHS.CurArraySize);
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RHS.CurArray = this->CurArray;
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RHS.NumTombstones = this->NumTombstones;
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this->CurArray = this->SmallArray;
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this->NumTombstones = 0;
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return;
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}
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// If only LHS is small, copy the small elements into RHS and move the pointer
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// from RHS to LHS.
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if (this->isSmall() && !RHS.isSmall()) {
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std::copy(this->SmallArray, this->SmallArray+this->CurArraySize,
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RHS.SmallArray);
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std::swap(RHS.NumElements, this->NumElements);
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std::swap(RHS.CurArraySize, this->CurArraySize);
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this->CurArray = RHS.CurArray;
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this->NumTombstones = RHS.NumTombstones;
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RHS.CurArray = RHS.SmallArray;
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RHS.NumTombstones = 0;
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return;
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}
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// Both a small, just swap the small elements.
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assert(this->isSmall() && RHS.isSmall());
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assert(this->CurArraySize == RHS.CurArraySize);
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std::swap_ranges(this->SmallArray, this->SmallArray+this->CurArraySize,
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RHS.SmallArray);
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std::swap(this->NumElements, RHS.NumElements);
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}
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SmallPtrSetImpl::~SmallPtrSetImpl() {
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if (!isSmall())
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free(CurArray);
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}
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