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

1 files changed, 113 insertions, 0 deletions

diff --git a/lib/Support/SmallPtrSet.cpp b/lib/Support/SmallPtrSet.cpp
new file mode 100644
index 0000000..0e6d334
--- /dev/null
+++ b/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;
+  }
+}