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Simplify implementation of the FoldingSet circular list, a necessary step 

to giving it iterators.

llvm-svn: 42586
This commit is contained in:
Chris Lattner 2007-10-03 20:45:43 +00:00
parent c731c97fac
commit 8c41ed61d1
1 changed files with 20 additions and 11 deletions
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31
llvm/lib/Support/FoldingSet.cpp
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@ -139,17 +139,19 @@ bool FoldingSetImpl::NodeID::operator==(const FoldingSetImpl::NodeID &RHS)const{
/// The problem with this is that the start of the hash buckets are not /// The problem with this is that the start of the hash buckets are not
/// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null: /// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null:
/// use GetBucketPtr when this happens. /// use GetBucketPtr when this happens.
static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr, static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr) {
void **Buckets, unsigned NumBuckets) { // The low bit is set if this is the pointer back to the bucket.
if (NextInBucketPtr >= Buckets && NextInBucketPtr < Buckets + NumBuckets) if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1)
return 0; return 0;
return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr); return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr);
} }
/// GetBucketPtr - Provides a casting of a bucket pointer for isNode /// GetBucketPtr - Provides a casting of a bucket pointer for isNode
/// testing. /// testing.
static void **GetBucketPtr(void *NextInBucketPtr) { static void **GetBucketPtr(void *NextInBucketPtr) {
return static_cast<void**>(NextInBucketPtr); intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr);
return reinterpret_cast<void**>(Ptr & ~intptr_t(1));
} }
/// GetBucketFor - Hash the specified node ID and return the hash bucket for /// GetBucketFor - Hash the specified node ID and return the hash bucket for
@ -168,8 +170,11 @@ FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) : NumNodes(0) {
assert(5 < Log2InitSize && Log2InitSize < 32 && assert(5 < Log2InitSize && Log2InitSize < 32 &&
"Initial hash table size out of range"); "Initial hash table size out of range");
NumBuckets = 1 << Log2InitSize; NumBuckets = 1 << Log2InitSize;
Buckets = new void*[NumBuckets]; Buckets = new void*[NumBuckets+1];
memset(Buckets, 0, NumBuckets*sizeof(void*)); memset(Buckets, 0, NumBuckets*sizeof(void*));
// Set the very last bucket to be a non-null "pointer".
Buckets[NumBuckets] = reinterpret_cast<void*>(-2);
} }
FoldingSetImpl::~FoldingSetImpl() { FoldingSetImpl::~FoldingSetImpl() {
delete [] Buckets; delete [] Buckets;
@ -186,14 +191,17 @@ void FoldingSetImpl::GrowHashTable() {
NumNodes = 0; NumNodes = 0;
// Clear out new buckets. // Clear out new buckets.
Buckets = new void*[NumBuckets]; Buckets = new void*[NumBuckets+1];
memset(Buckets, 0, NumBuckets*sizeof(void*)); memset(Buckets, 0, NumBuckets*sizeof(void*));
// Set the very last bucket to be a non-null "pointer".
Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
// Walk the old buckets, rehashing nodes into their new place. // Walk the old buckets, rehashing nodes into their new place.
for (unsigned i = 0; i != OldNumBuckets; ++i) { for (unsigned i = 0; i != OldNumBuckets; ++i) {
void *Probe = OldBuckets[i]; void *Probe = OldBuckets[i];
if (!Probe) continue; if (!Probe) continue;
while (Node *NodeInBucket = GetNextPtr(Probe, OldBuckets, OldNumBuckets)) { while (Node *NodeInBucket = GetNextPtr(Probe)) {
// Figure out the next link, remove NodeInBucket from the old link. // Figure out the next link, remove NodeInBucket from the old link.
Probe = NodeInBucket->getNextInBucket(); Probe = NodeInBucket->getNextInBucket();
NodeInBucket->SetNextInBucket(0); NodeInBucket->SetNextInBucket(0);
@ -218,7 +226,7 @@ FoldingSetImpl::Node *FoldingSetImpl::FindNodeOrInsertPos(const NodeID &ID,
InsertPos = 0; InsertPos = 0;
while (Node *NodeInBucket = GetNextPtr(Probe, Buckets, NumBuckets)) { while (Node *NodeInBucket = GetNextPtr(Probe)) {
NodeID OtherID; NodeID OtherID;
GetNodeProfile(OtherID, NodeInBucket); GetNodeProfile(OtherID, NodeInBucket);
if (OtherID == ID) if (OtherID == ID)
@ -253,9 +261,10 @@ void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) {
void *Next = *Bucket; void *Next = *Bucket;
// If this is the first insertion into this bucket, its next pointer will be // If this is the first insertion into this bucket, its next pointer will be
// null. Pretend as if it pointed to itself. // null. Pretend as if it pointed to itself, setting the low bit to indicate
// that it is a pointer to the bucket.
if (Next == 0) if (Next == 0)
Next = Bucket; Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1);
// Set the node's next pointer, and make the bucket point to the node. // Set the node's next pointer, and make the bucket point to the node.
N->SetNextInBucket(Next); N->SetNextInBucket(Next);
@ -278,7 +287,7 @@ bool FoldingSetImpl::RemoveNode(Node *N) {
// Chase around the list until we find the node (or bucket) which points to N. // Chase around the list until we find the node (or bucket) which points to N.
while (true) { while (true) {
if (Node *NodeInBucket = GetNextPtr(Ptr, Buckets, NumBuckets)) { if (Node *NodeInBucket = GetNextPtr(Ptr)) {
// Advance pointer. // Advance pointer.
Ptr = NodeInBucket->getNextInBucket(); Ptr = NodeInBucket->getNextInBucket();