Commit Graph

98 Commits

Author SHA1 Message Date
Joe Loser d2baefae68
[libc++] Replace _LIBCPP_HAS_NO_CONCEPTS with _LIBCPP_STD_VER > 17. NFCI.
All supported compilers that support C++20 now support concepts. So, remove
`_LIB_LIBCPP_HAS_NO_CONCEPTS` in favor of `_LIBCPP_STD_VER > 17`. Similarly in
the tests, remove `// UNSUPPORTED: libcpp-no-concepts`.

Differential Revision: https://reviews.llvm.org/D121528
2022-03-13 12:32:06 -04:00
Louis Dionne a54d028895 Revert "[libc++] Remove extension to support allocator<const T>"
This reverts commit 276ca873. That commit has quite a history at this
point. It was first landed in dbc647643577, which broke std::shared_ptr<T const>
and was reverted in 9138666f5. It was then re-applied in 276ca873, with
the std::shared_ptr issue fixed, but it caused widespread breakage at
Google (which suggests it would cause similar breakage in the wild too),
so now I'm reverting again.

Instead, I will add a escape hatch that vendors can turn on to enable
the extension and perform a phased transition over one or two releases
like we sometimes do when things become non-trivial.
2022-03-09 17:04:18 -05:00
Louis Dionne 276ca87382 [libc++] Remove extension to support allocator<const T>
This extension is a portability trap for users, since no other standard
library supports it. Furthermore, the Standard explicitly allows
implementations to reject std::allocator<cv T>, so allowing it is
really going against the current.

This was discovered in D120684: this extension required `const_cast`ing
in `__construct_range_forward`, a fishy bit of code that can be removed
if we don't support the extension anymore.

This is a re-application of dbc647643577, which was reverted in 9138666f5
because it broke std::shared_ptr<T const>. Tests have now been added and
we've made sure that std::shared_ptr<T const> wouldn't be broken in this
version.

Differential Revision: https://reviews.llvm.org/D120996
2022-03-08 15:05:12 -05:00
Louis Dionne 9138666f54 Revert "[libc++] Remove extension to support allocator<const T>"
This reverts commit bed3240bf7.

I will need to add more tests for std::shared_ptr<T const> before
re-landing this.
2022-03-07 17:35:12 -05:00
Louis Dionne bed3240bf7 [libc++] Remove extension to support allocator<const T>
This extension is a portability trap for users, since no other standard
library supports it. Furthermore, the Standard explicitly allows
implementations to reject std::allocator<cv T>, so allowing it is
really going against the current.

This was discovered in D120684: this extension required `const_cast`ing
in `__construct_range_forward`, a fishy bit of code that can be removed
if we don't support the extension anymore.

Differential Revision: https://reviews.llvm.org/D120996
2022-03-07 15:36:03 -05:00
Arthur O'Dwyer 1c6e752cfc [libc++] Better handling for zero-sized types.
Zero-sized types are a GCC extension, also supported by Clang.
In theory it's already invalid to `delete` a void pointer or a
pointer-to-incomplete, so we shouldn't need any special code
to catch those cases; but in practice Clang accepts both
constructs with just a warning, and GCC even accepts `sizeof(void)`
with just a warning! So we must keep the static_asserts.
The hard errors are tested in `unique_ptr_dltr_dflt/*.compile.fail.cpp`.

In ranges::begin/end, check `sizeof >= 0` instead of `sizeof != 0`,
so as to permit zero-sized types while still disallowing incomplete
types.

Fixes #54100.

Differential Revision: https://reviews.llvm.org/D120633
2022-03-07 11:50:00 -05:00
Nikolas Klauser 52915d78f4 [libc++] Granularize <utility> includes
Reviewed By: ldionne, #libc

Spies: EricWF, libcxx-commits, arphaman

Differential Revision: https://reviews.llvm.org/D120466
2022-03-05 19:31:46 +01:00
Arthur O'Dwyer f86c2b6f1f [libc++] Add `explicit` to a bunch of internal detail ctors.
Notably the following ctors remain non-explicit because they
are used as implicit conversions in too many places:
* __debug_less(_Compare&)
* __map_iterator(_TreeIterator)
* __map_const_iterator(_TreeIterator)
* __hash_map_iterator(_HashIterator)
* __hash_map_const_iterator(_HashIterator)

Differential Revision: https://reviews.llvm.org/D119894
2022-03-01 14:37:06 -05:00
Louis Dionne 368faacac7 [libc++] Revert "Protect users from relying on detail headers" & related changes
This commit reverts 5aaefa51 (and also partly 7f285f48e7 and b6d75682f9,
which were related to the original commit). As landed, 5aaefa51 had
unintended consequences on some downstream bots and didn't have proper
coverage upstream due to a few subtle things. Implementing this is
something we should do in libc++, however we'll first need to address
a few issues listed in https://reviews.llvm.org/D106124#3349710.

Differential Revision: https://reviews.llvm.org/D120683
2022-03-01 08:20:24 -05:00
Christopher Di Bella 5aaefa510e [libcxx][modules] protects users from relying on detail headers
libc++ has started splicing standard library headers into much more
fine-grained content for maintainability. It's very likely that outdated
and naive tooling (some of which is outside of LLVM's scope) will
suggest users include things such as <__ranges/access.h> instead of
<ranges>, and Hyrum's law suggests that users will eventually begin to
rely on this without the help of tooling. As such, this commit
intends to protect users from themselves, by making it a hard error for
anyone outside of the standard library to include libc++ detail headers.

Differential Revision: https://reviews.llvm.org/D106124
2022-02-26 09:00:25 +00:00
Nikolas Klauser f755806813 Remove __uncvref; use __uncvref_t instead
Reviewed By: Quuxplusone, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D119958
2022-02-17 22:54:31 +01:00
Nikolas Klauser 318507edee [libc++] Remove a few unneeded _LIBCPP_CXX03_LANG ifdefs
Reviewed By: Quuxplusone, ldionne, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D119896
2022-02-17 00:14:42 +01:00
Louis Dionne f87aa19be6 [libc++] Move everything related solely to _LIBCPP_ASSERT to its own file
This is the first step towards disentangling the debug mode and assertions
in libc++. This patch doesn't make any functional change: it simply moves
_LIBCPP_ASSERT-related stuff to its own file so as to make it clear that
libc++ assertions and the debug mode are different things. Future patches
will make it possible to enable assertions without enabling the debug
mode.

Differential Revision: https://reviews.llvm.org/D119769
2022-02-16 12:49:50 -05:00
Arthur O'Dwyer 53406fb691 [libc++] Guard much of std::ranges under _LIBCPP_HAS_NO_INCOMPLETE_RANGES.
The logic here is that we are disabling *only* things in `std::ranges::`.
Everything in `std::` is permitted, including `default_sentinel`, `contiguous_iterator`,
`common_iterator`, `projected`, `swappable`, and so on. Then, we include
anything from `std::ranges::` that is required in order to make those things
work: `ranges::swap`, `ranges::swap_ranges`, `input_range`, `ranges::begin`,
`ranges::iter_move`, and so on. But then that's all. Everything else (including
notably all of the "views" and the `std::views` namespace itself) is still
locked up behind `_LIBCPP_HAS_NO_INCOMPLETE_RANGES`.

Differential Revision: https://reviews.llvm.org/D118736
2022-02-15 10:38:21 -05:00
Nikolas Klauser 169a66eac8 [libc++] Remove __functional_base
Reviewed By: ldionne, Quuxplusone, #libc

Spies: Mordante, mgorny, libcxx-commits, arichardson, llvm-commits, arphaman

Differential Revision: https://reviews.llvm.org/D119439
2022-02-11 19:16:01 +01:00
Nikolas Klauser c77de9490e [libc++][NFC] Reformat and modernize compressed_pair.h
Reviewed By: Quuxplusone, ldionne, Mordante, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D119335
2022-02-10 13:41:14 +01:00
Louis Dionne 157bbe6aea [libc++] Remove the ability to use the std::nullptr_t emulation in C++03 mode
Back in https://reviews.llvm.org/D109459, we stopped using the C++03
emulation for std::nullptr_t by default, which was an ABI break. We
still left a knob for users to turn it back on if they were broken by
the change, with a note that we would remove that knob after one release.

The time has now come to remove the knob and clean up the std::nullptr_t
emulation.

Differential Revision: https://reviews.llvm.org/D114786
2022-02-07 17:51:05 -05:00
Arthur O'Dwyer ea2206d70d [libc++] Replace includes of <utility> with specific detail headers
Basically a rebase of D104980; most of that patch had already happened
via gradual drive-by changes, but this finishes it up.
Don't touch the inclusions from `<__functional_base>`, `<__hash_table>`,
or `<__locale>`; those could be removed if we propagated the
inclusions up to the includers of those files, but there are lots
of those includers.

`<algorithm>`, `<functional>`, and `<memory>` already include `<utility>`
at the top level. `<iterator>` did not, so I've added it there.

Differential Revision: https://reviews.llvm.org/D119020
2022-02-04 17:08:32 -05:00
Arthur O'Dwyer fa6b9e4010 [libc++] Normalize all our '#pragma GCC system_header', and regression-test.
Now we'll notice if a header forgets to include this magic phrase.

Differential Revision: https://reviews.llvm.org/D118800
2022-02-04 12:27:19 -05:00
Arthur O'Dwyer 2eb2ff2a02 [libc++] Merge _LIBCPP_HAS_NO_RANGES into _LIBCPP_HAS_NO_CONCEPTS. NFC.
The macro that opts out of `std::ranges::` functionality is called
`_LIBCPP_HAS_NO_INCOMPLETE_RANGES`, and is unrelated to this macro
which is specifically about _compiler_ support for the _syntax_.

The only non-mechanical diff here is in `<__config>`.

Differential Revision: https://reviews.llvm.org/D118507
2022-01-31 12:10:22 -05:00
Arthur O'Dwyer 63a991d035 [libc++] Eliminate the `__function_like` helper.
As prefigured in the comments on D115315.
This gives us one unified style for all niebloids,
and also simplifies the modulemap.

Differential Revision: https://reviews.llvm.org/D116570
2022-01-20 14:40:16 -05:00
Arthur O'Dwyer cba72e4ce2 [libc++] Normalize some whitespace in preparation for D116570. NFC. 2022-01-15 12:20:33 -05:00
Konstantin Varlamov b9bc3c107c [libc++][ranges] Implement `construct_at` and `destroy{,_at}`.
Differential Revision: https://reviews.llvm.org/D116078
2022-01-12 16:01:04 -08:00
Konstantin Varlamov 8d23b7420c [libc++][ranges] Implement `uninitialized_copy{,_n}` and `uninitialized_move{,_n}`.
Also implement `in_out_result` which is a prerequisite.

Differential Revision: https://reviews.llvm.org/D116023
2022-01-10 22:49:50 -08:00
Arthur O'Dwyer 4d81a46f7f [libc++] Alphabetize header #includes. NFCI.
The NFC part of D116809. We still want to enforce this in CI,
but the mechanism for that is still to-be-determined.

Differential Revision: https://reviews.llvm.org/D116809
2022-01-10 16:30:38 -05:00
Nico Weber 085f078307 Revert "Revert D109159 "[amdgpu] Enable selection of `s_cselect_b64`.""
This reverts commit 859ebca744.
The change contained many unrelated changes and e.g. restored
unit test failes for the old lld port.
2022-01-05 13:10:25 -05:00
David Salinas 859ebca744 Revert D109159 "[amdgpu] Enable selection of `s_cselect_b64`."
This reverts commit 640beb38e7.

That commit caused performance degradtion in Quicksilver test QS:sGPU and a functional test failure in (rocPRIM rocprim.device_segmented_radix_sort).
Reverting until we have a better solution to s_cselect_b64 codegen cleanup

Change-Id: Ibf8e397df94001f248fba609f072088a46abae08

Reviewed By: kzhuravl

Differential Revision: https://reviews.llvm.org/D115960

Change-Id: Id169459ce4dfffa857d5645a0af50b0063ce1105
2022-01-05 17:57:32 +00:00
Konstantin Varlamov 754ea6fd4d [libc++][ranges] Implement `uninitialized_value_construct{,_n}` and `uninitialized_fill{,_n}`.
Also:
- refactor out `__voidify`;
- use the `destroy` algorithm internally;
- refactor out helper classes used in tests for `uninitialized_*`
  algorithms.

Differential Revision: https://reviews.llvm.org/D115626
2021-12-20 00:24:27 -08:00
Konstantin Varlamov 3f630cff65 [libc++][ranges] Implement ranges::uninitialized_default_construct{,_n}.
Defined in [`specialized.algorithms`](wg21.link/specialized.algorithms).

Also:
- refactor the existing non-range implementation so that most of it
  can be shared between the range-based and non-range-based algorithms;
- remove an existing test for the non-range version of
  `uninitialized_default_construct{,_n}` that likely triggered undefined
  behavior (it read the values of built-ins after default-initializing
  them, essentially reading uninitialized memory).

Reviewed By: #libc, Quuxplusone, ldionne

Differential Revision: https://reviews.llvm.org/D115315
2021-12-14 14:11:46 -08:00
Nikolas Klauser a376a3f354 [libc++] Make __compressed_pair fully constexpr
Make `__compressed_pair` fully constexpr

Reviewed By: ldionne, #libc, nilayvaish

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D115687
2021-12-14 15:39:46 +01:00
Nikolas Klauser 4955095fe6 [libc++] Remove _LIBCPP_DEFAULT
clang has `= default` as an extension in c++03, so just use it.

Reviewed By: ldionne, Quuxplusone, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D115275
2021-12-07 22:18:38 +01:00
Konstantin Varlamov 2d9efcfeec [libc++][ranges] Implement [special.mem.concepts].
Implement the exposition-only concepts specified in
`[special.mem.concepts]`. These are all thin wrappers over other
concepts.

Reviewed By: #libc, Quuxplusone, ldionne

Differential Revision: https://reviews.llvm.org/D114761
2021-12-02 17:58:04 -08:00
Konstantin Varlamov 7da4ee6f23 [libcxx][NFC] Make sequence containers slightly more SFINAE-friendly during CTAD.
Disable the constructors taking `(size_type, const value_type&,
allocator_type)` if `allocator_type` is not a valid allocator.
Otherwise, these constructors are considered when resolving e.g.
`(int*, int*, NotAnAllocator())`, leading to a hard error during
instantiation. A hard error makes the Standard's requirement to not
consider deduction guides of the form `(Iterator, Iterator,
BadAllocator)` during overload resolution essentially non-functional.

The previous approach was to SFINAE away `allocator_traits`. This patch
SFINAEs away the specific constructors instead, for consistency with
`basic_string` -- see [LWG3076](wg21.link/lwg3076) which describes
a very similar problem for strings (note, however, that unlike LWG3076,
no valid constructor call is affected by the bad instantiation).

Differential Revision: https://reviews.llvm.org/D114311
2021-12-01 11:56:51 -08:00
Johan Berg 68e2231f87 [libc++] Value-initialize unique_ptr's deleter_type
According to the C++ standard, the stored pointer and the stored deleter
should be value-initialized.

Differential Revision: https://reviews.llvm.org/D113612
2021-11-24 17:31:34 -05:00
Louis Dionne 92832e4889 [libc++] Enable <atomic> when threads are disabled
std::atomic is, for the most part, just a thin veneer on top of compiler
builtins. Hence, it should be available even when threads are not available
on the system, and in fact there has been requests for such support.

This patch:
- Moves __libcpp_thread_poll_with_backoff to its own header so it can
  be used in <atomic> when threads are disabled.
- Adds a dummy backoff policy for atomic polling that doesn't know about
  threads.
- Adjusts the <atomic> feature-test macros so they are provided even when
  threads are disabled.
- Runs the <atomic> tests when threads are disabled.

rdar://77873569

Differential Revision: https://reviews.llvm.org/D114109
2021-11-17 23:02:58 -05:00
Nikolas Klauser b57c22ade8 [libc++] Implement P2186R2 (Remove Garbage Collection)
Reviewed By: Quuxplusone, #libc, ldionne

Differential Revision: https://reviews.llvm.org/D112869
2021-11-11 19:03:00 +01:00
Konstantin Varlamov 68072a7166 [libc++] P0433R2: test that deduction guides are properly SFINAEd away.
Deduction guides for containers should not participate in overload
resolution when called with certain incorrect types (e.g. when called
with a template argument in place of an `InputIterator` that doesn't
qualify as an input iterator). Similarly, class template argument
deduction should not select `unique_ptr` constructors that take a
a pointer.

The tests try out every possible incorrect parameter (but never more
than one incorrect parameter in the same invocation).

Also add deduction guides to the synopsis for associative and unordered
containers (this was accidentally omitted from [D112510](https://reviews.llvm.org/D112510)).

Differential Revision: https://reviews.llvm.org/D112904
2021-11-09 09:32:24 -08:00
Louis Dionne b2d25ef2d1 [libc++] Implement shared_ptr methods inline in the class
This patch refactors the shared_ptr methods from being defined out-of-line
to being defined inline in the class, like what we do for all new code in
the library. The benefits of doing that are that code is not as scattered
around and is hence easier to understand, and it avoids a ton of duplication
due to SFINAE checks. Defining the method where it is declared also removes
the possibility for mismatched attributes.

As a fly-by change, this also:

- Adds a few _LIBCPP_HIDE_FROM_ABI attributes
- Uses __enable_if_t instead of enable_if as a function argument, to match
  the style that we use everywhere else.

Differential Revision: https://reviews.llvm.org/D112478
2021-10-26 13:11:10 -04:00
Konstantin Varlamov 065ac30026 [libc++] LWG3001: add `remove_extent_t` to `weak_ptr::element_type`.
Also fix a few places in the `shared_ptr` implementation where
`element_type` was passed to the `__is_compatible` helper. This could
result in `remove_extent` being applied twice to the pointer's template
type (first by the definition of `element_type` and then by the helper),
potentially leading to somewhat less readable error messages for some
incorrect code.

Differential Revision: https://reviews.llvm.org/D112092
2021-10-25 11:15:54 -04:00
Mikhail Maltsev be10b1f1cc [libcxx] Make allocator<T>:allocate throw bad_array_new_length
Currently the member functions std::allocator<T>::allocate,
std::experimental::pmr::polymorphic_allocator::allocate and
std::resource_adaptor<T>::do_allocate throw an exception of type
std::length_error when the requested size exceeds the maximum size.

According to the C++ standard ([allocator.members]/4,
[mem.poly.allocator.mem]/1), std::allocator<T>::allocate and
std::pmr::polymorphic_allocator::allocate must throw a
std::bad_array_new_length exception in this case.

The patch fixes the issue with std::allocator<T>::allocate and changes
the type the exception thrown by
std::experimental::pmr::resource_adaptor<T>::do_allocate to
std::bad_array_new_length as well for consistency.

The patch resolves LWG 3237, LWG 3038 and LWG 3190.

Reviewed By: ldionne, #libc, Quuxplusone

Differential Revision: https://reviews.llvm.org/D110846
2021-10-18 19:12:42 +01:00
Louis Dionne 83bc88174e [libc++][NFC] Fix include guard for some detail header 2021-10-04 13:36:08 -04:00
Louis Dionne cb793e1a36 [libc++][NFCI] Remove uses of _LIBCPP_INLINE_VAR
All supported compilers provide support for inline variables in C++17 now.
Also, as a fly-by fix, replace some uses of _LIBCPP_CONSTEXPR by just
constexpr.

The only exception in this patch is `std::ignore`, which is provided
prior to C++17. Since it is defined in an anonymous namespace, it always
has internal linkage anyway, so using an inline variable there doesn't
provide any benefit. Instead, `inline` was removed entirely on `std::ignore`.

Differential Revision: https://reviews.llvm.org/D110243
2021-09-22 16:03:00 -04:00
Joe Loser 400b33e18d
[libc++] Disallow volatile types in std::allocator
LWG 2447 is marked as `Complete`, but there is no `static_assert` to
reject volatile types in `std::allocator`. See the discussion at
https://reviews.llvm.org/D108856.

Add `static_assert` in `std::allocator` to disallow volatile types. Since this
is an implementation choice, mark the binding test as `libc++` only.

Remove tests that use containers backed by `std::allocator` that test
the container when used with a volatile type.

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D109056
2021-09-22 11:47:38 -04:00
Louis Dionne b4e88d4db1 [libc++][NFC] Rename _EnableIf to __enable_if_t for consistency
In other places in the code, we use lowercase spelling for things that
are not available in prior standards.

Differential Revision: https://reviews.llvm.org/D109435
2021-09-08 15:20:58 -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 4e0ea2cf2e [libc++] Use enable_if_t instead of _EnableIf
I just ran into a compiler error involving __bind_back and some overloads
that were being disabled with _EnableIf. I noticed that the error message
was quite bad and did not mention the reason for the overload being
excluded. Specifically, the error looked like this:

     candidate template ignored: substitution failure [with _Args =
     <ContiguousView>]: no member named '_EnableIfImpl' in 'std::_MetaBase<false>'

Instead, when using enable_if or enable_if_t, the compiler is clever and
can produce better diagnostics, like so:

     candidate template ignored: requirement 'is_invocable_v<
          std::__bind_back_op<1, std::integer_sequence<unsigned long, 0>>,
          std::ranges::views::__transform::__fn &, std::tuple<PlusOne> &,
          ContiguousView>' was not satisfied [with _Args = <ContiguousView>]

Basically, it tries to do a poor man's implementation of concepts, which
is already a lot better than simply complaining about substitution failure.

Hence, this commit uses enable_if_t instead of _EnableIf whenever
possible. That is both more straightforward than using the internal
helper, and also leads to better error messages in those cases.

I understand the motivation for _EnableIf's implementation was to improve
compile-time performance, however I believe striving to improve error
messages is even more important for our QOI, hence this patch. Furthermore,
it is unclear that _EnableIf actually improved compile-time performance
in any noticeable way (see discussion in the review for details).

Differential Revision: https://reviews.llvm.org/D108216
2021-09-08 09:09:28 -04:00
Arthur O'Dwyer dadbe88a13 [libc++] Fix std::to_address(array).
There were basically two bugs here:

When C++20 `to_address` is called on `int arr[10]`, then `const _Ptr&` becomes
a reference to a const array, and then we dispatch to `__to_address<const int(&)[10]>`,
which, oops, gives us a `const int*` result instead of an `int*` result.
Solution: We need to provide the two standard-specified overloads of
`std::to_address` in exactly the same way that we provide two overloads
of `__to_address`.

When `__to_address` is called on a pointer type, `__to_address(const _Ptr&)`
is disabled so we successfully avoid trying to instantiate pointer_traits of
that pointer type. But when it's called on an array type, it's not disabled
for array types, so we go ahead and instantiate pointer_traits<int[10]>,
which goes boom. Solution: We need to disable `__to_address(const _Ptr&)`
for both pointer and array types. Also disable it for function types,
so that they get the nice error message; and put a test on it.

Differential Revision: https://reviews.llvm.org/D109331
2021-09-07 13:56:25 -04:00
Louis Dionne 3557c7c122 [libc++] Remove workarounds for [[nodebug]] not working properly on typedefs in older Clangs
Clang used to support [[nodebug]] everywhere except on typedefs. Since
we don't support such old Clangs anymore, we can get rid of _LIBCPP_NODEBUG_TYPE
in favour of always using _LIBCPP_NODEBUG.

Differential Revision: https://reviews.llvm.org/D108996
2021-09-01 10:51:09 -04:00
Arthur O'Dwyer c5e7981aec [libc++] Add missing space in (__map_value_compare&__y) etc. NFCI. 2021-08-31 14:30:20 -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