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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33973 91177308-0d34-0410-b5e6-96231b3b80d8
146 lines
4.6 KiB
C++
146 lines
4.6 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 was developed by Chris Lattner and is distributed under
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// the University of Illinois Open Source 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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using namespace llvm;
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bool SmallPtrSetImpl::insert(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 (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 more than 3/4 of the array is full, grow.
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if (NumElements*4 >= CurArraySize*3 ||
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CurArraySize-(NumElements+NumTombstones) < CurArraySize/8)
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Grow();
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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; // 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(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 (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, move everything over, replacing this element.
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memmove(APtr, APtr+1, sizeof(void*)*(E-APtr-1));
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// Clear the end element.
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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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void * const *SmallPtrSetImpl::FindBucketFor(void *Ptr) const {
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unsigned Bucket = Hash(Ptr);
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unsigned ArraySize = CurArraySize;
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unsigned ProbeAmt = 1;
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void *const *Array = CurArray;
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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() {
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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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unsigned NewSize = OldSize < 64 ? 128 : OldSize*2;
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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 = new void*[NewSize+1];
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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 (void **BucketPtr = OldBuckets, **E = OldBuckets+NumElements;
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BucketPtr != E; ++BucketPtr) {
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void *Elt = *BucketPtr;
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*const_cast<void**>(FindBucketFor(Elt)) = Elt;
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}
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} else {
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// Copy over all valid entries.
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for (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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void *Elt = *BucketPtr;
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if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
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*const_cast<void**>(FindBucketFor(Elt)) = Elt;
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}
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delete [] OldBuckets;
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}
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}
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