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SmallPtrSet: Reuse DenseMapInfo's pointer hash function instead of inventing a bad one ourselves.

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DenseMap's hash function uses slightly more entropy and reduces hash collisions
significantly.  I also experimented with Hashing.h, but it didn't gave a lot of
improvement while being much more expensive to compute.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154996 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2012-04-18 10:37:32 +00:00
parent 9a1484165c
commit 4bb87cbac5
2 changed files with 2 additions and 4 deletions
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3
include/llvm/ADT/SmallPtrSet.h
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@@ -126,9 +126,6 @@ protected:
private: private:
bool isSmall() const { return CurArray == SmallArray; } bool isSmall() const { return CurArray == SmallArray; }
unsigned Hash(const void *Ptr) const {
return static_cast<unsigned>(((uintptr_t)Ptr >> 4) & (CurArraySize-1));
}
const void * const *FindBucketFor(const void *Ptr) const; const void * const *FindBucketFor(const void *Ptr) const;
void shrink_and_clear(); void shrink_and_clear();

3
lib/Support/SmallPtrSet.cpp
View File

@@ -13,6 +13,7 @@
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/Support/MathExtras.h" #include "llvm/Support/MathExtras.h"
#include <algorithm> #include <algorithm>
#include <cstdlib> #include <cstdlib>
@@ -102,7 +103,7 @@ bool SmallPtrSetImpl::erase_imp(const void * Ptr) {
} }
const void * const *SmallPtrSetImpl::FindBucketFor(const void *Ptr) const { const void * const *SmallPtrSetImpl::FindBucketFor(const void *Ptr) const {
unsigned Bucket = Hash(Ptr); unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1);
unsigned ArraySize = CurArraySize; unsigned ArraySize = CurArraySize;
unsigned ProbeAmt = 1; unsigned ProbeAmt = 1;
const void *const *Array = CurArray; const void *const *Array = CurArray;