LineageOS/android_external_libcxx
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Don't compute modulus of hash if it is smaller than the bucket count.

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This cleans up a previous optimization attempt in hash, and results in
additional performance improvements over that previous attempt. Additionally
this new optimization does not hinder the power of 2 bucket count optimization.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@275114 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Fiselier
2016-07-11 22:02:02 +00:00
parent 51d7e8e381
commit 576639133a
1 changed files with 4 additions and 5 deletions
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9
include/__hash_table
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@@ -90,7 +90,8 @@ inline _LIBCPP_INLINE_VISIBILITY
size_t size_t
__constrain_hash(size_t __h, size_t __bc) __constrain_hash(size_t __h, size_t __bc)
{ {
return !(__bc & (__bc - 1)) ? __h & (__bc - 1) : __h % __bc; return !(__bc & (__bc - 1)) ? __h & (__bc - 1) :
(__h < __bc ? __h : __h % __bc);
} }
inline _LIBCPP_INLINE_VISIBILITY inline _LIBCPP_INLINE_VISIBILITY
@@ -2201,8 +2202,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::find(const _Key& __k)
if (__nd != nullptr) if (__nd != nullptr)
{ {
for (__nd = __nd->__next_; __nd != nullptr && for (__nd = __nd->__next_; __nd != nullptr &&
(__hash == __nd->__hash_ __constrain_hash(__nd->__hash_, __bc) == __chash;
|| __constrain_hash(__nd->__hash_, __bc) == __chash);
__nd = __nd->__next_) __nd = __nd->__next_)
{ {
if ((__nd->__hash_ == __hash) && key_eq()(__nd->__value_, __k)) if ((__nd->__hash_ == __hash) && key_eq()(__nd->__value_, __k))
@@ -2231,8 +2231,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::find(const _Key& __k) const
if (__nd != nullptr) if (__nd != nullptr)
{ {
for (__nd = __nd->__next_; __nd != nullptr && for (__nd = __nd->__next_; __nd != nullptr &&
(__hash == __nd->__hash_ __constrain_hash(__nd->__hash_, __bc) == __chash;
|| __constrain_hash(__nd->__hash_, __bc) == __chash);
__nd = __nd->__next_) __nd = __nd->__next_)
{ {
if ((__nd->__hash_ == __hash) && key_eq()(__nd->__value_, __k)) if ((__nd->__hash_ == __hash) && key_eq()(__nd->__value_, __k))