mirror of
https://github.com/RPCSX/llvm.git
synced 2024-12-05 02:16:46 +00:00
6316fbcb04
- Yay for '-'s and simplifications! - I kept StringMap::GetOrCreateValue for compatibility purposes, this can eventually go away. Likewise the StringMapEntry Create functions still follow the old style. - NIFC. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76888 91177308-0d34-0410-b5e6-96231b3b80d8
229 lines
8.0 KiB
C++
229 lines
8.0 KiB
C++
//===--- StringMap.cpp - String Hash table map implementation -------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the StringMap class.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/ADT/StringMap.h"
|
|
#include <cassert>
|
|
using namespace llvm;
|
|
|
|
StringMapImpl::StringMapImpl(unsigned InitSize, unsigned itemSize) {
|
|
ItemSize = itemSize;
|
|
|
|
// If a size is specified, initialize the table with that many buckets.
|
|
if (InitSize) {
|
|
init(InitSize);
|
|
return;
|
|
}
|
|
|
|
// Otherwise, initialize it with zero buckets to avoid the allocation.
|
|
TheTable = 0;
|
|
NumBuckets = 0;
|
|
NumItems = 0;
|
|
NumTombstones = 0;
|
|
}
|
|
|
|
void StringMapImpl::init(unsigned InitSize) {
|
|
assert((InitSize & (InitSize-1)) == 0 &&
|
|
"Init Size must be a power of 2 or zero!");
|
|
NumBuckets = InitSize ? InitSize : 16;
|
|
NumItems = 0;
|
|
NumTombstones = 0;
|
|
|
|
TheTable = (ItemBucket*)calloc(NumBuckets+1, sizeof(ItemBucket));
|
|
|
|
// Allocate one extra bucket, set it to look filled so the iterators stop at
|
|
// end.
|
|
TheTable[NumBuckets].Item = (StringMapEntryBase*)2;
|
|
}
|
|
|
|
|
|
/// HashString - Compute a hash code for the specified string.
|
|
///
|
|
static unsigned HashString(const char *Start, const char *End) {
|
|
// Bernstein hash function.
|
|
unsigned int Result = 0;
|
|
// TODO: investigate whether a modified bernstein hash function performs
|
|
// better: http://eternallyconfuzzled.com/tuts/algorithms/jsw_tut_hashing.aspx
|
|
// X*33+c -> X*33^c
|
|
while (Start != End)
|
|
Result = Result * 33 + *Start++;
|
|
Result = Result + (Result >> 5);
|
|
return Result;
|
|
}
|
|
|
|
/// LookupBucketFor - Look up the bucket that the specified string should end
|
|
/// up in. If it already exists as a key in the map, the Item pointer for the
|
|
/// specified bucket will be non-null. Otherwise, it will be null. In either
|
|
/// case, the FullHashValue field of the bucket will be set to the hash value
|
|
/// of the string.
|
|
unsigned StringMapImpl::LookupBucketFor(const StringRef &Name) {
|
|
unsigned HTSize = NumBuckets;
|
|
if (HTSize == 0) { // Hash table unallocated so far?
|
|
init(16);
|
|
HTSize = NumBuckets;
|
|
}
|
|
unsigned FullHashValue = HashString(Name.begin(), Name.end());
|
|
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 (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 Name isn't necessarily
|
|
// null-terminated!
|
|
char *ItemStr = (char*)BucketItem+ItemSize;
|
|
if (Name == StringRef(ItemStr, BucketItem->getKeyLength())) {
|
|
// We found a match!
|
|
return BucketNo;
|
|
}
|
|
}
|
|
|
|
// Okay, we didn't find the item. Probe to the next bucket.
|
|
BucketNo = (BucketNo+ProbeAmt) & (HTSize-1);
|
|
|
|
// Use quadratic probing, it has fewer clumping artifacts than linear
|
|
// probing and has good cache behavior in the common case.
|
|
++ProbeAmt;
|
|
}
|
|
}
|
|
|
|
|
|
/// FindKey - Look up the bucket that contains the specified key. If it exists
|
|
/// in the map, return the bucket number of the key. Otherwise return -1.
|
|
/// This does not modify the map.
|
|
int StringMapImpl::FindKey(const StringRef &Key) const {
|
|
unsigned HTSize = NumBuckets;
|
|
if (HTSize == 0) return -1; // Really empty table?
|
|
unsigned FullHashValue = HashString(Key.begin(), Key.end());
|
|
unsigned BucketNo = FullHashValue & (HTSize-1);
|
|
|
|
unsigned ProbeAmt = 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.
|
|
if (BucketItem == 0)
|
|
return -1;
|
|
|
|
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;
|
|
if (Key == StringRef(ItemStr, BucketItem->getKeyLength())) {
|
|
// We found a match!
|
|
return BucketNo;
|
|
}
|
|
}
|
|
|
|
// Okay, we didn't find the item. Probe to the next bucket.
|
|
BucketNo = (BucketNo+ProbeAmt) & (HTSize-1);
|
|
|
|
// Use quadratic probing, it has fewer clumping artifacts than linear
|
|
// probing and has good cache behavior in the common case.
|
|
++ProbeAmt;
|
|
}
|
|
}
|
|
|
|
/// 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(StringRef(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 StringRef &Key) {
|
|
int Bucket = FindKey(Key);
|
|
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.
|
|
void StringMapImpl::RehashTable() {
|
|
unsigned NewSize = NumBuckets*2;
|
|
// Allocate one extra bucket which will always be non-empty. This allows the
|
|
// iterators to stop at end.
|
|
ItemBucket *NewTableArray =(ItemBucket*)calloc(NewSize+1, sizeof(ItemBucket));
|
|
NewTableArray[NewSize].Item = (StringMapEntryBase*)2;
|
|
|
|
// 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 && IB->Item != getTombstoneVal()) {
|
|
// Fast case, bucket available.
|
|
unsigned FullHash = IB->FullHashValue;
|
|
unsigned NewBucket = FullHash & (NewSize-1);
|
|
if (NewTableArray[NewBucket].Item == 0) {
|
|
NewTableArray[FullHash & (NewSize-1)].Item = IB->Item;
|
|
NewTableArray[FullHash & (NewSize-1)].FullHashValue = FullHash;
|
|
continue;
|
|
}
|
|
|
|
// Otherwise probe for a spot.
|
|
unsigned ProbeSize = 1;
|
|
do {
|
|
NewBucket = (NewBucket + ProbeSize++) & (NewSize-1);
|
|
} while (NewTableArray[NewBucket].Item);
|
|
|
|
// Finally found a slot. Fill it in.
|
|
NewTableArray[NewBucket].Item = IB->Item;
|
|
NewTableArray[NewBucket].FullHashValue = FullHash;
|
|
}
|
|
}
|
|
|
|
free(TheTable);
|
|
|
|
TheTable = NewTableArray;
|
|
NumBuckets = NewSize;
|
|
}
|