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[libc++] Optimize __hash_table::find for integral types #156660

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[libc++] Optimize __hash_table::find for integral types #156660

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19 changes: 15 additions & 4 deletions libcxx/include/__hash_table
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
#include <__type_traits/invoke.h>
#include <__type_traits/is_const.h>
#include <__type_traits/is_constructible.h>
#include <__type_traits/is_integral.h>
#include <__type_traits/is_nothrow_assignable.h>
#include <__type_traits/is_nothrow_constructible.h>
#include <__type_traits/is_reference.h>
Expand Down Expand Up @@ -1833,11 +1834,16 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::find(const _Key& __k) {
size_t __hash = hash_function()(__k);
size_t __chash = std::__constrain_hash(__hash, __bc);
__next_pointer __nd = __bucket_list_[__chash];

constexpr bool __has_cheap_comparator = is_integral<key_type>::value;

if (__nd != nullptr) {
for (__nd = __nd->__next_;
__nd != nullptr && (__nd->__hash() == __hash || std::__constrain_hash(__nd->__hash(), __bc) == __chash);
__nd != nullptr &&
((__has_cheap_comparator ? key_eq()(__nd->__upcast()->__get_value(), __k) : __hash == __nd->__hash()) ||
std::__constrain_hash(__nd->__hash(), __bc) == __chash);
__nd = __nd->__next_) {
if ((__nd->__hash() == __hash) && key_eq()(__nd->__upcast()->__get_value(), __k))
if ((__has_cheap_comparator || __nd->__hash() == __hash) && key_eq()(__nd->__upcast()->__get_value(), __k))
return iterator(__nd);
}
}
Expand All @@ -1854,11 +1860,16 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::find(const _Key& __k) const {
size_t __hash = hash_function()(__k);
size_t __chash = std::__constrain_hash(__hash, __bc);
__next_pointer __nd = __bucket_list_[__chash];

constexpr bool __has_cheap_comparator = is_integral<key_type>::value;

if (__nd != nullptr) {
for (__nd = __nd->__next_;
__nd != nullptr && (__hash == __nd->__hash() || std::__constrain_hash(__nd->__hash(), __bc) == __chash);
__nd != nullptr &&
((__has_cheap_comparator ? key_eq()(__nd->__upcast()->__get_value(), __k) : __hash == __nd->__hash()) ||
std::__constrain_hash(__nd->__hash(), __bc) == __chash);
__nd = __nd->__next_) {
if ((__nd->__hash() == __hash) && key_eq()(__nd->__upcast()->__get_value(), __k))
if ((__has_cheap_comparator || __nd->__hash() == __hash) && key_eq()(__nd->__upcast()->__get_value(), __k))
return const_iterator(__nd);
}
}
Expand Down
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