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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
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@@ -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;