Add a new SmallSet ADT specialized for pointers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33577 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/SmallPtrSet.h

@@ -0,0 +1,165 @@
+//===- llvm/ADT/SmallPtrSet.h - 'Normally small' pointer set ----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Chris Lattner and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the SmallPtrSet class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_SMALLPTRSET_H
+#define LLVM_ADT_SMALLPTRSET_H
+
+#include <cassert>
+#include <cstring>
+
+namespace llvm {
+
+class SmallPtrSetImpl {
+protected:
+  /// CurArray - This is the current set of buckets.  If it points to
+  /// SmallArray, then the set is in 'small mode'.
+  void **CurArray;
+  /// CurArraySize - The allocated size of CurArray, always a power of two.
+  /// Note that CurArray points to an array that has CurArraySize+1 elements in
+  /// it, so that the end iterator actually points to valid memory.
+  unsigned CurArraySize;
+  
+  // If small, this is # elts allocated consequtively
+  unsigned NumElements;
+  void *SmallArray[1];  // Must be last ivar.
+public:
+  SmallPtrSetImpl(unsigned SmallSize) {
+    assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
+           "Initial size must be a power of two!");
+    CurArray = &SmallArray[0];
+    CurArraySize = SmallSize;
+    // The end pointer, always valid, is set to a valid element to help the
+    // iterator.
+    CurArray[SmallSize] = 0;
+    clear();
+  }
+  ~SmallPtrSetImpl() {
+    if (!isSmall())
+      delete[] CurArray;
+  }
+  
+  bool isSmall() const { return CurArray == &SmallArray[0]; }
+
+  static void *getTombstoneMarker() { return reinterpret_cast<void*>(-2); }
+  static void *getEmptyMarker() {
+    // Note that -1 is chosen to make clear() efficiently implementable with
+    // memset and because it's not a valid pointer value.
+    return reinterpret_cast<void*>(-1);
+  }
+  
+  void clear() {
+    // Fill the array with empty markers.
+    memset(CurArray, -1, CurArraySize*sizeof(void*));
+    NumElements = 0;
+  }
+  
+  /// insert - This returns true if the pointer was new to the set, false if it
+  /// was already in the set.
+  bool insert(void *Ptr);
+  
+  bool count(void *Ptr) const {
+    if (isSmall()) {
+      // Linear search for the item.
+      for (void *const *APtr = SmallArray, *const *E = SmallArray+NumElements;
+           APtr != E; ++APtr)
+        if (*APtr == Ptr)
+          return true;
+      return false;
+    }
+    
+    // Big set case.
+    return *FindBucketFor(Ptr) == Ptr;
+  }
+  
+private:
+  unsigned Hash(void *Ptr) const {
+    return ((uintptr_t)Ptr >> 4) & (CurArraySize-1);
+  }
+  void * const *FindBucketFor(void *Ptr) const;
+  
+  /// Grow - Allocate a larger backing store for the buckets and move it over.
+  void Grow();
+};
+
+/// SmallPtrSetIteratorImpl - This is the common base class shared between all
+/// instances of SmallPtrSetIterator.
+class SmallPtrSetIteratorImpl {
+protected:
+  void *const *Bucket;
+public:
+  SmallPtrSetIteratorImpl(void *const *BP) : Bucket(BP) {
+    AdvanceIfNotValid();
+  }
+  
+  bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
+    return Bucket == RHS.Bucket;
+  }
+  bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
+    return Bucket != RHS.Bucket;
+  }
+  
+protected:
+  /// AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket
+  /// that is.   This is guaranteed to stop because the end() bucket is marked
+  /// valid.
+  void AdvanceIfNotValid() {
+    while (*Bucket == SmallPtrSetImpl::getEmptyMarker() ||
+           *Bucket == SmallPtrSetImpl::getTombstoneMarker())
+      ++Bucket;
+  }
+};
+
+/// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
+template<typename PtrTy>
+class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
+public:
+  SmallPtrSetIterator(void *const *BP) : SmallPtrSetIteratorImpl(BP) {}
+
+  // Most methods provided by baseclass.
+  
+  PtrTy operator*() const {
+    return static_cast<PtrTy>(*Bucket);
+  }
+  
+  inline SmallPtrSetIterator& operator++() {          // Preincrement
+    ++Bucket;
+    AdvanceIfNotValid();
+    return *this;
+  }
+  
+  SmallPtrSetIterator operator++(int) {        // Postincrement
+    SmallPtrSetIterator tmp = *this; ++*this; return tmp;
+  }
+};
+
+
+/// SmallPtrSet - This class implements 
+template<class PtrType, unsigned SmallSize>
+class SmallPtrSet : public SmallPtrSetImpl {
+  void *SmallArray[SmallSize];
+public:
+  SmallPtrSet() : SmallPtrSetImpl(SmallSize) {}
+  
+  typedef SmallPtrSetIterator<PtrType> iterator;
+  typedef SmallPtrSetIterator<PtrType> const_iterator;
+  inline iterator begin() const {
+    return iterator(CurArray);
+  }
+  inline iterator end() const {
+    return iterator(CurArray+CurArraySize);
+  }
+};
+
+}
+
+#endif

lib/Support/SmallPtrSet.cpp

@@ -0,0 +1,113 @@
+//===- llvm/ADT/SmallPtrSet.cpp - 'Normally small' pointer set ------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Chris Lattner and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the SmallPtrSet class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/SmallPtrSet.h"
+using namespace llvm;
+
+bool SmallPtrSetImpl::insert(void *Ptr) {
+  if (isSmall()) {
+    // Check to see if it is already in the set.
+    for (void **APtr = SmallArray, **E = SmallArray+NumElements;
+         APtr != E; ++APtr)
+      if (*APtr == Ptr)
+        return false;
+    
+    // Nope, there isn't.  If we stay small, just 'pushback' now.
+    if (NumElements < CurArraySize-1) {
+      SmallArray[NumElements++] = Ptr;
+      return true;
+    }
+    // Otherwise, hit the big set case, which will call grow.
+  }
+  
+  // If more than 3/4 of the array is full, grow.
+  if (NumElements*4 >= CurArraySize*3)
+    Grow();
+  
+  // Okay, we know we have space.  Find a hash bucket.
+  void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
+  if (*Bucket == Ptr) return false; // Already inserted, good.
+  
+  // Otherwise, insert it!
+  *Bucket = Ptr;
+  ++NumElements;  // Track density.
+  return true;
+}
+
+void * const *SmallPtrSetImpl::FindBucketFor(void *Ptr) const {
+  unsigned Bucket = Hash(Ptr);
+  unsigned ArraySize = CurArraySize;
+  unsigned ProbeAmt = 1;
+  void *const *Array = CurArray;
+  void *const *Tombstone = 0;
+  while (1) {
+    // Found Ptr's bucket?
+    if (Array[Bucket] == Ptr)
+      return Array+Bucket;
+    
+    // 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 (Array[Bucket] == getEmptyMarker())
+      return Tombstone ? Tombstone : 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 SmallPtrSetImpl::Grow() {
+  // Allocate at twice as many buckets, but at least 128.
+  unsigned OldSize = CurArraySize;
+  unsigned NewSize = OldSize < 64 ? 128 : OldSize*2;
+  
+  void **OldBuckets = CurArray;
+  bool WasSmall = isSmall();
+  
+  // Install the new array.  Clear all the buckets to empty.
+  CurArray = new void*[NewSize+1];
+  CurArraySize = NewSize;
+  memset(CurArray, -1, NewSize*sizeof(void*));
+  
+  // The end pointer, always valid, is set to a valid element to help the
+  // iterator.
+  CurArray[NewSize] = 0;
+  
+  // Copy over all the elements.
+  if (WasSmall) {
+    // Small sets store their elements in order.
+    for (void **BucketPtr = OldBuckets, **E = OldBuckets+NumElements;
+         BucketPtr != E; ++BucketPtr) {
+      void *Elt = *BucketPtr;
+      *const_cast<void**>(FindBucketFor(Elt)) = Elt;
+    }
+  } else {
+    // Copy over all valid entries.
+    for (void **BucketPtr = OldBuckets, **E = OldBuckets+OldSize;
+         BucketPtr != E; ++BucketPtr) {
+      // Copy over the element if it is valid.
+      void *Elt = *BucketPtr;
+      if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
+        *const_cast<void**>(FindBucketFor(Elt)) = Elt;
+    }
+    
+    delete [] OldBuckets;
+  }
+}