Summary: The current implementations of __hash_table::find used by std::unordered_set/unordered_map call key_eq on each key that lands in the same bucket as the key you're looking for. However, since equal objects mush hash to the same value, you can short-circuit the possibly expensive call to key_eq by checking the hashes first.
Reviewers: EricWF
Subscribers: kmensah, cfe-commits
Differential Revision: http://reviews.llvm.org/D21510
llvm-svn: 274857
This patch improves the performance of unordered_set's find by 45% when
the value exists within the set. __hash_tables find method
needs to check if it's reached the end of the bucket by constraining the
hash of the current node and checking it against the bucket index. However
constraining the hash is an expensive operations and it can be avoided if the
two unconstrained hashes are equal. This patch applies that optimization.
This patch also adds a top level directory called benchmarks. 'benchmarks/'
is intended to store any/all benchmarks written for the standard library.
Currently nothing is done with files under 'benchmarks/' but I would like
to move towards introducing a formal format and test runner.
llvm-svn: 274423
This patch is the last in a series that replaces recursive meta-programming
in std::tuple with non-recursive implementations.
Previously std::tuple could only be instantiated with 126 elements before
it blew the max template instantiation depth. Now the size of std::tuple is
essentially unbounded (I've tested with over 5000 elements).
One unfortunate side-effect of this change is that tuple_constructible
and similar no longer short circuit after the first failure. Instead they
evaluate the conditions for all elements. This could be potentially breaking.
I plan to look into this further.
llvm-svn: 274331
This patch attempts to improve the QoI of std::tuples tuple_element and
__make_tuple_types helpers. Previously they required O(N) instantiations,
one for every element in the tuple
The new implementations are O(1) after __tuple_indices<Id...> is created.
llvm-svn: 274330
The previous __make_tuple_indices implementation caused O(N) instantiations
and was pretty inefficient. The C++14 __make_integer_sequence implementation
is much better, since it either uses a builtin to generate the sequence or
a very nice Log8(N) implementation provided by richard smith.
This patch moves the __make_integer_sequence implementation into __tuple
and uses it to implement __make_tuple_indices.
Since libc++ can't expose the name 'integer_sequence' in C++11 this patch
also introduces a dummy type '__integer_sequence' which is used when generating
the sequence. One the sequence is generated '__integer_sequence' can be
converted into the required type; either '__tuple_indices' or 'integer_sequence'.
llvm-svn: 274286
* P0163r0: Implemented in r273839.
* LWG 2309: pthread_mutex_lock only returns this error if certain debug flags
were passed during construction. libc++ does not pass these flags. There is
nothing to do.
* LWG 2310: Wording fix. No impact on libc++'s implementation.
* LWG 2312: libc++'s std::tuple implementation already constrains the overloads
based on the number of arguments.
* LWG 2549: libc++'s std::tuple already applied this fix.
* LWG 2674: libc++ already depends on this relaxed wording.
* LWG 2704, 2706, 2707, 2719, 2720, 2721, 2723, 2725, 2728: All of these filesystem were either
submitted by me and fixed before submission, or have already been applied.
llvm-svn: 274214
Since at least the C++11 standard insert iterators are specified
as having ::reference typedef void. Libc++ was not doing that.
This patch corrects the typedef.
This patch changes the std::iterator base class of insert_iterator,
front_insert_iterator and back_insert_iterator. This should not
be an ABI breaking change.
llvm-svn: 274209
The end pointer should point to one past the end of the newly allocated
buffer.
rdar://problem/24265174
Differential Revision: http://reviews.llvm.org/D20334
llvm-svn: 274132
This patch adds the weak_type typedef in shared_ptr. It is available in
C++17 and newer.
This patch also updates the _LIBCPP_STD_VER and TEST_STD_VER macros to
have the value of 16, since 2016 is the current year.
llvm-svn: 273839
Marshall Clow