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Sync the __builtin_expects for our 3 quadratically probed hash table implementations.

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This assumes that
  a) finding the bucket containing the value is LIKELY
  b) finding an empty bucket is LIKELY
  c) growing the table is UNLIKELY

I also switched the a) and b) cases for SmallPtrSet as we seem to use
the set mostly more for insertion than for checking existence.

In a simple benchmark consisting of 2^21 insertions of 2^20 unique
pointers into a DenseMap or SmallPtrSet a few percent speedup on average,
but nothing statistically significant.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230232 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2015-02-23 16:41:36 +00:00
parent 01312dd0b4
commit 42f72e2c16
3 changed files with 18 additions and 15 deletions
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9
include/llvm/ADT/DenseMap.h
View File

@ -442,11 +442,12 @@ private:
// causing infinite loops in lookup.
unsigned NewNumEntries = getNumEntries() + 1;
unsigned NumBuckets = getNumBuckets();
if (NewNumEntries*4 >= NumBuckets*3) {
if (LLVM_UNLIKELY(NewNumEntries * 4 >= NumBuckets * 3)) {
this->grow(NumBuckets * 2);
LookupBucketFor(Key, TheBucket);
NumBuckets = getNumBuckets();
} else if (NumBuckets-(NewNumEntries+getNumTombstones()) <= NumBuckets/8) {
} else if (LLVM_UNLIKELY(NumBuckets-(NewNumEntries+getNumTombstones()) <=
NumBuckets/8)) {
this->grow(NumBuckets);
LookupBucketFor(Key, TheBucket);
}
@ -492,14 +493,14 @@ private:
while (1) {
const BucketT *ThisBucket = BucketsPtr + BucketNo;
// Found Val's bucket? If so, return it.
if (KeyInfoT::isEqual(Val, ThisBucket->getFirst())) {
if (LLVM_LIKELY(KeyInfoT::isEqual(Val, ThisBucket->getFirst()))) {
FoundBucket = ThisBucket;
return true;
}
// If we found an empty bucket, the key doesn't exist in the set.
// Insert it and return the default value.
if (KeyInfoT::isEqual(ThisBucket->getFirst(), EmptyKey)) {
if (LLVM_LIKELY(KeyInfoT::isEqual(ThisBucket->getFirst(), EmptyKey))) {
// If we've already seen a tombstone while probing, fill it in instead
// of the empty bucket we eventually probed to.
FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;

19
lib/Support/SmallPtrSet.cpp
View File

@ -50,11 +50,12 @@ SmallPtrSetImplBase::insert_imp(const void *Ptr) {
}
// Otherwise, hit the big set case, which will call grow.
}
if (NumElements*4 >= CurArraySize*3) {
if (LLVM_UNLIKELY(NumElements * 4 >= CurArraySize * 3)) {
// If more than 3/4 of the array is full, grow.
Grow(CurArraySize < 64 ? 128 : CurArraySize*2);
} else if (CurArraySize-(NumElements+NumTombstones) < CurArraySize/8) {
} else if (LLVM_UNLIKELY(CurArraySize - (NumElements + NumTombstones) <
CurArraySize / 8)) {
// If fewer of 1/8 of the array is empty (meaning that many are filled with
// tombstones), rehash.
Grow(CurArraySize);
@ -107,16 +108,16 @@ const void * const *SmallPtrSetImplBase::FindBucketFor(const void *Ptr) const {
const void *const *Array = CurArray;
const void *const *Tombstone = nullptr;
while (1) {
// Found Ptr's bucket?
if (Array[Bucket] == Ptr)
return Array+Bucket;
// If we found an empty bucket, the pointer doesn't exist in the set.
// Return a tombstone if we've seen one so far, or the empty bucket if
// not.
if (Array[Bucket] == getEmptyMarker())
if (LLVM_LIKELY(Array[Bucket] == getEmptyMarker()))
return Tombstone ? Tombstone : Array+Bucket;
// Found Ptr's bucket?
if (LLVM_LIKELY(Array[Bucket] == Ptr))
return Array+Bucket;
// If this is a tombstone, remember it. If Ptr ends up not in the set, we
// prefer to return it than something that would require more probing.
if (Array[Bucket] == getTombstoneMarker() && !Tombstone)

5
lib/Support/StringMap.cpp
View File

@ -188,9 +188,10 @@ unsigned StringMapImpl::RehashTable(unsigned BucketNo) {
// If the hash table is now more than 3/4 full, or if fewer than 1/8 of
// the buckets are empty (meaning that many are filled with tombstones),
// grow/rehash the table.
if (NumItems*4 > NumBuckets*3) {
if (LLVM_UNLIKELY(NumItems * 4 > NumBuckets * 3)) {
NewSize = NumBuckets*2;
} else if (NumBuckets-(NumItems+NumTombstones) <= NumBuckets/8) {
} else if (LLVM_UNLIKELY(NumBuckets - (NumItems + NumTombstones) <=
NumBuckets / 8)) {
NewSize = NumBuckets;
} else {
return BucketNo;