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Add support for removing elements out of StringMap.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34185 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2007-02-11 20:58:00 +00:00
parent ec68fd4391
commit 44dcd01cb3
2 changed files with 94 additions and 12 deletions
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63
lib/Support/StringMap.cpp
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@@ -21,6 +21,7 @@ StringMapImpl::StringMapImpl(unsigned InitSize, unsigned itemSize) {
NumBuckets = InitSize ? InitSize : 512;
ItemSize = itemSize;
NumItems = 0;
NumTombstones = 0;
TheTable = new ItemBucket[NumBuckets+1]();
memset(TheTable, 0, NumBuckets*sizeof(ItemBucket));
@@ -57,20 +58,32 @@ unsigned StringMapImpl::LookupBucketFor(const char *NameStart,
unsigned BucketNo = FullHashValue & (HTSize-1);
unsigned ProbeAmt = 1;
int FirstTombstone = -1;
while (1) {
ItemBucket &Bucket = TheTable[BucketNo];
StringMapEntryBase *BucketItem = Bucket.Item;
// If we found an empty bucket, this key isn't in the table yet, return it.
if (BucketItem == 0) {
// If we found a tombstone, we want to reuse the tombstone instead of an
// empty bucket. This reduces probing.
if (FirstTombstone != -1) {
TheTable[FirstTombstone].FullHashValue = FullHashValue;
return FirstTombstone;
}
Bucket.FullHashValue = FullHashValue;
return BucketNo;
}
// If the full hash value matches, check deeply for a match. The common
// case here is that we are only looking at the buckets (for item info
// being non-null and for the full hash value) not at the items. This
// is important for cache locality.
if (Bucket.FullHashValue == FullHashValue) {
if (BucketItem == getTombstoneVal()) {
// Skip over tombstones. However, remember the first one we see.
if (FirstTombstone == -1) FirstTombstone = BucketNo;
} else if (Bucket.FullHashValue == FullHashValue) {
// If the full hash value matches, check deeply for a match. The common
// case here is that we are only looking at the buckets (for item info
// being non-null and for the full hash value) not at the items. This
// is important for cache locality.
// Do the comparison like this because NameStart isn't necessarily
// null-terminated!
char *ItemStr = (char*)BucketItem+ItemSize;
@@ -108,11 +121,14 @@ int StringMapImpl::FindKey(const char *KeyStart, const char *KeyEnd) const {
if (BucketItem == 0)
return -1;
// If the full hash value matches, check deeply for a match. The common
// case here is that we are only looking at the buckets (for item info
// being non-null and for the full hash value) not at the items. This
// is important for cache locality.
if (Bucket.FullHashValue == FullHashValue) {
if (BucketItem == getTombstoneVal()) {
// Ignore tombstones.
} else if (Bucket.FullHashValue == FullHashValue) {
// If the full hash value matches, check deeply for a match. The common
// case here is that we are only looking at the buckets (for item info
// being non-null and for the full hash value) not at the items. This
// is important for cache locality.
// Do the comparison like this because NameStart isn't necessarily
// null-terminated!
char *ItemStr = (char*)BucketItem+ItemSize;
@@ -133,6 +149,30 @@ int StringMapImpl::FindKey(const char *KeyStart, const char *KeyEnd) const {
}
}
/// RemoveKey - Remove the specified StringMapEntry from the table, but do not
/// delete it. This aborts if the value isn't in the table.
void StringMapImpl::RemoveKey(StringMapEntryBase *V) {
const char *VStr = (char*)V + ItemSize;
StringMapEntryBase *V2 = RemoveKey(VStr, VStr+V->getKeyLength());
V2 = V2;
assert(V == V2 && "Didn't find key?");
}
/// RemoveKey - Remove the StringMapEntry for the specified key from the
/// table, returning it. If the key is not in the table, this returns null.
StringMapEntryBase *StringMapImpl::RemoveKey(const char *KeyStart,
const char *KeyEnd) {
int Bucket = FindKey(KeyStart, KeyEnd);
if (Bucket == -1) return 0;
StringMapEntryBase *Result = TheTable[Bucket].Item;
TheTable[Bucket].Item = getTombstoneVal();
--NumItems;
++NumTombstones;
return Result;
}
/// RehashTable - Grow the table, redistributing values into the buckets with
/// the appropriate mod-of-hashtable-size.
@@ -147,7 +187,7 @@ void StringMapImpl::RehashTable() {
// Rehash all the items into their new buckets. Luckily :) we already have
// the hash values available, so we don't have to rehash any strings.
for (ItemBucket *IB = TheTable, *E = TheTable+NumBuckets; IB != E; ++IB) {
if (IB->Item) {
if (IB->Item && IB->Item != getTombstoneVal()) {
// Fast case, bucket available.
unsigned FullHash = IB->FullHashValue;
unsigned NewBucket = FullHash & (NewSize-1);
@@ -157,6 +197,7 @@ void StringMapImpl::RehashTable() {
continue;
}
// Otherwise probe for a spot.
unsigned ProbeSize = 1;
do {
NewBucket = (NewBucket + ProbeSize++) & (NewSize-1);