Commit Graph

68 Commits

Author SHA1 Message Date
Nilay Vaish 7f287390d7 [libc++] Add introsort to avoid O(n^2) behavior
This commit adds a benchmark that tests std::sort on an adversarial inputs,
and uses introsort in std::sort to avoid O(n^2) behavior on adversarial
inputs.

Inputs where partitions are unbalanced even after 2 log(n) pivots have
been selected, the algorithm switches to heap sort to avoid the
possibility of spending O(n^2) time on sorting the input.
Benchmark results show that the intro sort implementation does
significantly better.

Benchmarking results before this change. Time represents the sorting
time required per element:

----------------------------------------------------------------------------------------------------------
Benchmark                                                                Time             CPU   Iterations
----------------------------------------------------------------------------------------------------------
BM_Sort_uint32_QuickSortAdversary_1                                   3.75 ns         3.74 ns    187432960
BM_Sort_uint32_QuickSortAdversary_4                                   3.05 ns         3.05 ns    231211008
BM_Sort_uint32_QuickSortAdversary_16                                  2.45 ns         2.45 ns    288096256
BM_Sort_uint32_QuickSortAdversary_64                                  32.8 ns         32.8 ns     21495808
BM_Sort_uint32_QuickSortAdversary_256                                  132 ns          132 ns      5505024
BM_Sort_uint32_QuickSortAdversary_1024                                 498 ns          497 ns      1572864
BM_Sort_uint32_QuickSortAdversary_16384                               3846 ns         3845 ns       262144
BM_Sort_uint32_QuickSortAdversary_262144                             61431 ns        61400 ns       262144
BM_Sort_uint64_QuickSortAdversary_1                                   3.93 ns         3.92 ns    181141504
BM_Sort_uint64_QuickSortAdversary_4                                   3.10 ns         3.09 ns    222560256
BM_Sort_uint64_QuickSortAdversary_16                                  2.50 ns         2.50 ns    283639808
BM_Sort_uint64_QuickSortAdversary_64                                  33.2 ns         33.2 ns     21757952
BM_Sort_uint64_QuickSortAdversary_256                                  132 ns          132 ns      5505024
BM_Sort_uint64_QuickSortAdversary_1024                                 478 ns          477 ns      1572864
BM_Sort_uint64_QuickSortAdversary_16384                               3932 ns         3930 ns       262144
BM_Sort_uint64_QuickSortAdversary_262144                             61646 ns        61615 ns       262144

Benchmarking results after this change:

----------------------------------------------------------------------------------------------------------
Benchmark                                                                Time             CPU   Iterations
----------------------------------------------------------------------------------------------------------
BM_Sort_uint32_QuickSortAdversary_1                                   6.31 ns         6.30 ns    107741184
BM_Sort_uint32_QuickSortAdversary_4                                   4.51 ns         4.50 ns    158859264
BM_Sort_uint32_QuickSortAdversary_16                                  3.00 ns         3.00 ns    223608832
BM_Sort_uint32_QuickSortAdversary_64                                  44.8 ns         44.8 ns     15990784
BM_Sort_uint32_QuickSortAdversary_256                                 69.0 ns         68.9 ns      9961472
BM_Sort_uint32_QuickSortAdversary_1024                                 118 ns          118 ns      6029312
BM_Sort_uint32_QuickSortAdversary_16384                                175 ns          175 ns      4194304
BM_Sort_uint32_QuickSortAdversary_262144                               210 ns          210 ns      3407872
BM_Sort_uint64_QuickSortAdversary_1                                   6.75 ns         6.73 ns    103809024
BM_Sort_uint64_QuickSortAdversary_4                                   4.53 ns         4.53 ns    160432128
BM_Sort_uint64_QuickSortAdversary_16                                  2.98 ns         2.97 ns    234356736
BM_Sort_uint64_QuickSortAdversary_64                                  44.3 ns         44.3 ns     15990784
BM_Sort_uint64_QuickSortAdversary_256                                 69.2 ns         69.2 ns     10223616
BM_Sort_uint64_QuickSortAdversary_1024                                 119 ns          119 ns      6029312
BM_Sort_uint64_QuickSortAdversary_16384                                173 ns          173 ns      4194304
BM_Sort_uint64_QuickSortAdversary_262144                               212 ns          212 ns      3407872

Differential Revision: https://reviews.llvm.org/D113413
2021-11-16 11:38:46 -05:00
Louis Dionne 855a419b92 [libc++] Add missing _LIBCPP_HIDE_FROM_ABI to __rewrap_iter 2021-11-15 10:10:33 -05:00
Louis Dionne f4c1258d56 [libc++] Add an option to disable wide character support in libc++
Some embedded platforms do not wish to support the C library functionality
for handling wchar_t because they have no use for it. It makes sense for
libc++ to work properly on those platforms, so this commit adds a carve-out
of functionality for wchar_t.

Unfortunately, unlike some other carve-outs (e.g. random device), this
patch touches several parts of the library. However, despite the wide
impact of this patch, I still think it is important to support this
configuration since it makes it much simpler to port libc++ to some
embedded platforms.

Differential Revision: https://reviews.llvm.org/D111265
2021-10-12 06:08:23 -04:00
Arthur O'Dwyer 16bf43398a [libc++] Comma-operator-proof a lot of algorithm/container code.
Detected by evil-izing the widely used `MoveOnly` testing type.
I had to patch some tests that were themselves using its comma operator,
but I think that's a worthwhile cost in order to catch more places
in our headers that needed comma-proofing.

The trick here is that even `++ptr, SomeClass()` can find a comma operator
by ADL, if `ptr` is of type `Evil*`. (A comma between two operands
of non-class-or-enum type is always treated as the built-in
comma, without ADL. But if either operand is class-or-enum, then
ADL happens for _both_ operands' types.)

Differential Revision: https://reviews.llvm.org/D109414
2021-09-08 13:34:01 -04:00
Louis Dionne 64184b4af0 [libc++][NFC] Remove useless _LIBCPP_PUSH_MACROS
Only files that actually use min/max are required to do this dance.

Differential Revision: https://reviews.llvm.org/D108778
2021-08-27 12:41:55 -04:00
Arthur O'Dwyer ca7926bd79 [libc++] Eliminate needless `add_lvalue_reference` from <algorithm> helpers. NFCI.
When `_Compare` is a function parameter already (so it's not `void`
and it's not an abominable function type), `add_lvalue_reference_t<_Compare>`
is simply a synonym for `_Compare&`. We don't need to pull in `<type_traits>`
and instantiate a template trait to figure that out.

Differential Revision: https://reviews.llvm.org/D108400
2021-08-22 11:43:12 -04:00
Joe Loser 9807626bc7 [libc++] Include <__iterator/distance.h> instead of <iterator> in a few algorithm headers
A few headers in algorithm include `<iterator>` when
`<__iterator/distance.h>` would suffice. Change them
to just include `<__iterator.distance.h>`.

Differential Revision: https://reviews.llvm.org/D108393
2021-08-20 15:02:33 -04:00
Arthur O'Dwyer f221d905b1 [libc++] IWYU to fix Modules complaints about _LIBCPP_ASSERT. NFCI.
This fixes all places that used _LIBCPP_ASSERT without including <__debug>.

    git grep -l _LIBCPP_ASSERT | xargs git grep -L __debug
2021-08-06 09:20:59 -04:00
Louis Dionne d03aa7d6b6 [libc++] NFCI: Remove __functional/search.h
The __search helper function was once split into __functional for circular
dependency reasons, however this is not an issue anymore now that we have
finer grained headers.
2021-06-29 11:40:47 -04:00
Louis Dionne 7756216547 [libc++] NFCI: Remove code duplication and obsolete declarations in wrap_iter
Differential Revision: https://reviews.llvm.org/D105040
2021-06-29 10:51:07 -04:00
Christopher Di Bella 6adbc83ee9 [libcxx][modularisation] moves <utility> content out of <type_traits>
Moves:

* `std::move`, `std::forward`, `std::declval`, and `std::swap` into
  `__utility/${FUNCTION_NAME}`.
* `std::swap_ranges` and `std::iter_swap` into
  `__algorithm/${FUNCTION_NAME}`

Differential Revision: https://reviews.llvm.org/D103734
2021-06-24 17:57:29 +00:00
Louis Dionne 134723edd5 [libcxx] Move all algorithms into their own headers
This is a fairly mechanical change, it just moves each algorithm into
its own header. This is intended to be a NFC.

This commit re-applies 7ed7d4ccb8, which was reverted in 692d7166f7
because the Modules build got broken. The modules build has now been
fixed, so we're re-committing this.

Differential Revision: https://reviews.llvm.org/D103583

Attribution note
----------------
I'm only committing this. This commit is a mix of D103583, D103330 and
D104171 authored by:

Co-authored-by: Christopher Di Bella <cjdb@google.com>
Co-authored-by: zoecarver <z.zoelec2@gmail.com>
2021-06-19 07:49:06 -04:00
Petr Hosek 692d7166f7 Revert "[libcxx][gardening] Move all algorithms into their own headers."
This reverts commit 7ed7d4ccb8 as it
uncovered a Clang bug PR50592.
2021-06-07 17:15:20 -07:00
zoecarver 7ed7d4ccb8 [libcxx][gardening] Move all algorithms into their own headers.
This is a fairly mechanical change, it just moves each algorithm into its own header. This is a NFC.

Note: during this change, I burned down all the includes, so this follows "include only and exactly what you use."

Differential Revision: https://reviews.llvm.org/D103583
2021-06-04 09:37:12 -07:00
Louis Dionne 05d164b25c Revert "[libc++] NFC: Move unwrap_iter to its own header"
This reverts commit 924ea3bb53 *again*, this time because it broke the
LLDB build with modules. We need to figure out what's up with the libc++
modules build once and for all.

Differential Revision: https://reviews.llvm.org/D103369
2021-06-02 15:58:27 -04:00
Louis Dionne 924ea3bb53 [libc++] NFC: Move unwrap_iter to its own header
This re-applies 9968896cd6, which was reverted in b13edf6e90 because
it broke the build.

Differential Revision: https://reviews.llvm.org/D103369
2021-06-01 21:46:59 -04:00
Mark de Wever b13edf6e90 Revert "[libc++] NFC: Move unwrap_iter to its own header"
This reverts commit 9968896cd6.

This commit seems to cause the build failures of main.
2021-05-29 09:50:26 +02:00
Louis Dionne 9968896cd6 [libc++] NFC: Move unwrap_iter to its own header 2021-05-28 12:42:07 -04:00