[llvm-commits] [llvm] r42586 - /llvm/trunk/lib/Support/FoldingSet.cpp
Chris Lattner
sabre at nondot.org
Wed Oct 3 13:45:43 PDT 2007
Author: lattner
Date: Wed Oct 3 15:45:43 2007
New Revision: 42586
URL: http://llvm.org/viewvc/llvm-project?rev=42586&view=rev
Log:
Simplify implementation of the FoldingSet circular list, a necessary step
to giving it iterators.
Modified:
llvm/trunk/lib/Support/FoldingSet.cpp
Modified: llvm/trunk/lib/Support/FoldingSet.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/FoldingSet.cpp?rev=42586&r1=42585&r2=42586&view=diff
==============================================================================
--- llvm/trunk/lib/Support/FoldingSet.cpp (original)
+++ llvm/trunk/lib/Support/FoldingSet.cpp Wed Oct 3 15:45:43 2007
@@ -139,17 +139,19 @@
/// 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:
/// use GetBucketPtr when this happens.
-static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr,
- void **Buckets, unsigned NumBuckets) {
- if (NextInBucketPtr >= Buckets && NextInBucketPtr < Buckets + NumBuckets)
+static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr) {
+ // The low bit is set if this is the pointer back to the bucket.
+ if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1)
return 0;
+
return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr);
}
/// GetBucketPtr - Provides a casting of a bucket pointer for isNode
/// testing.
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
@@ -168,8 +170,11 @@
assert(5 < Log2InitSize && Log2InitSize < 32 &&
"Initial hash table size out of range");
NumBuckets = 1 << Log2InitSize;
- Buckets = new void*[NumBuckets];
+ Buckets = new void*[NumBuckets+1];
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() {
delete [] Buckets;
@@ -186,14 +191,17 @@
NumNodes = 0;
// Clear out new buckets.
- Buckets = new void*[NumBuckets];
+ Buckets = new void*[NumBuckets+1];
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.
for (unsigned i = 0; i != OldNumBuckets; ++i) {
void *Probe = OldBuckets[i];
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.
Probe = NodeInBucket->getNextInBucket();
NodeInBucket->SetNextInBucket(0);
@@ -218,7 +226,7 @@
InsertPos = 0;
- while (Node *NodeInBucket = GetNextPtr(Probe, Buckets, NumBuckets)) {
+ while (Node *NodeInBucket = GetNextPtr(Probe)) {
NodeID OtherID;
GetNodeProfile(OtherID, NodeInBucket);
if (OtherID == ID)
@@ -253,9 +261,10 @@
void *Next = *Bucket;
// 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)
- 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.
N->SetNextInBucket(Next);
@@ -278,7 +287,7 @@
// Chase around the list until we find the node (or bucket) which points to N.
while (true) {
- if (Node *NodeInBucket = GetNextPtr(Ptr, Buckets, NumBuckets)) {
+ if (Node *NodeInBucket = GetNextPtr(Ptr)) {
// Advance pointer.
Ptr = NodeInBucket->getNextInBucket();
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