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