llvm-6502/lib/Support/SmallPtrSet.cpp
2007-02-07 01:11:25 +00:00

146 lines
4.6 KiB
C++

//===- 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. See SmallPtrSet.h for an
// overview of the algorithm.
//
//===----------------------------------------------------------------------===//
#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 ||
CurArraySize-(NumElements+NumTombstones) < CurArraySize/8)
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!
if (*Bucket == getTombstoneMarker())
--NumTombstones;
*Bucket = Ptr;
++NumElements; // Track density.
return true;
}
bool SmallPtrSetImpl::erase(void *Ptr) {
if (isSmall()) {
// Check to see if it is in the set.
for (void **APtr = SmallArray, **E = SmallArray+NumElements;
APtr != E; ++APtr)
if (*APtr == Ptr) {
// If it is in the set, move everything over, replacing this element.
memmove(APtr, APtr+1, sizeof(void*)*(E-APtr-1));
// Clear the end element.
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;
}
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;
}
}