[libc++] Consistently replace `std::` qualification with `_VSTD::` or nothing. NFCI.

I used a lot of `git grep` to find places where `std::` was being used
outside of comments and assert-messages. T

[libc++] Consistently replace `std::` qualification with `_VSTD::` or nothing. NFCI.

I used a lot of `git grep` to find places where `std::` was being used
outside of comments and assert-messages. There were three outcomes:

- Qualified function calls, e.g. `std::move` becomes `_VSTD::move`.
This is the most common case.

- Typenames that don't need qualification, e.g. `std::allocator` becomes `allocator`.
Leaving these as `_VSTD::allocator` would also be fine, but I decided
that removing the qualification is more consistent with existing practice.

- Names that specifically need un-versioned `std::` qualification,
or that I wasn't sure about. For example, I didn't touch any code in
<atomic>, <math.h>, <new>, or any ext/ or experimental/ headers;
and I didn't touch any instances of `std::type_info`.

In some deduction guides, we were accidentally using `class Alloc = typename std::allocator<T>`,
despite `std::allocator<T>`'s type-ness not being template-dependent.
Because `std::allocator` is a qualified name, this did parse as we intended;
but what we meant was simply `class Alloc = allocator<T>`.

Differential Revision: https://reviews.llvm.org/D92250

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[libc++] Optimize the number of assignments in std::exclusive_scan

Reported in https://twitter.com/blelbach/status/1169807347142676480

Differential Revision: https://reviews.llvm.org/D67273

[libc++] P1645 constexpr for <numeric>

Implements P1645: constexpr for <numeric> algorithms

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D90569

[libc++] Use std::move in numeric algorithms (P0616R0).

This patch updates algorithms in <numeric> to use std::move
based on p0616r0. Moving values instead of copying them
creates huge speed improve

[libc++] Use std::move in numeric algorithms (P0616R0).

This patch updates algorithms in <numeric> to use std::move
based on p0616r0. Moving values instead of copying them
creates huge speed improvements (see the paper for details).

Differential Revision: https://reviews.llvm.org/D61170

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Revert "[libc++] P1645 constexpr for <numeric>"

This reverts commit eb9b063539c34d0d4dd14e8516eeb77bb8b9e4bd.

The commit fails to build on build bots using LLVM 8.

[libc++] P1645 constexpr for <numeric>

Implements P1645: constexpr for <numeric> algorithms

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D90569

[libc++] NFC: Fix confusing indentation in <numeric>

[libc++] Fix typo in std::midpoint

Reviewed By: mclow.lists

Differential Revision: https://reviews.llvm.org/D71525

Optimize std::midpoint for integers

Same idea as the current algorithm, that is, add (half of the difference between a and b) to a.

But we use a different technique for computing the difference: we

Optimize std::midpoint for integers

Same idea as the current algorithm, that is, add (half of the difference between a and b) to a.

But we use a different technique for computing the difference: we compute b - a into a pair of integers that are named "sign_bit" and "diff". We have to use a pair because subtracting two 32-bit integers produces a 33-bit result.

Computing half of that is a simple matter of shifting diff right by 1, and adding sign_bit shifted left by 31. llvm knows how to do that with one instruction: shld.

The only tricky part is that if the difference is odd and negative, then shifting it by one isn't the same as dividing it by two - shifting a negative one produces a negative one, for example. So there's one more adjustment: if the sign bit and the low bit of diff are one, we add one.

For a demonstration of the codegen difference, see https://godbolt.org/z/7ar3K9 , which also has a built-in test.

Differential Revision: https://reviews.llvm.org/D69459

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[pstl][libc++] Provide uglified header names for interface headers

For the few (currently four) headers that make up the PSTL's interface
to other Standard Libraries, provide a stable uglified heade

[pstl][libc++] Provide uglified header names for interface headers

For the few (currently four) headers that make up the PSTL's interface
to other Standard Libraries, provide a stable uglified header file that
can be included by those Standard Libraries.

We can then more easily change the internal organization of the PSTL
without having to change the integration with Standard Libraries.

llvm-svn: 368088

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[libc++] Take 2: Integrate the PSTL into libc++

Summary:
This commit allows specifying LIBCXX_ENABLE_PARALLEL_ALGORITHMS when
configuring libc++ in CMake. When that option is enabled, libc++ will
as

[libc++] Take 2: Integrate the PSTL into libc++

Summary:
This commit allows specifying LIBCXX_ENABLE_PARALLEL_ALGORITHMS when
configuring libc++ in CMake. When that option is enabled, libc++ will
assume that the PSTL can be found somewhere on the CMake module path,
and it will provide the C++17 parallel algorithms based on the PSTL
(that is assumed to be available).

The commit also adds support for running the PSTL tests as part of
the libc++ test suite.

The first attempt to commit this failed because it exposed a bug in the
tests for modules. Now that this has been fixed, it should be safe to
commit this.

Reviewers: EricWF

Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits, mclow.lists, EricWF

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60480

llvm-svn: 367903

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Revert "[libc++] Integrate the PSTL into libc++"

This reverts r366593, which caused unforeseen breakage on the build bots.
I'm reverting until the problems have been figured out and fixed.

llvm-svn

Revert "[libc++] Integrate the PSTL into libc++"

This reverts r366593, which caused unforeseen breakage on the build bots.
I'm reverting until the problems have been figured out and fixed.

llvm-svn: 366603

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[libc++] Integrate the PSTL into libc++

Summary:
This commit allows specifying LIBCXX_ENABLE_PARALLEL_ALGORITHMS when
configuring libc++ in CMake. When that option is enabled, libc++ will
assume tha

[libc++] Integrate the PSTL into libc++

Summary:
This commit allows specifying LIBCXX_ENABLE_PARALLEL_ALGORITHMS when
configuring libc++ in CMake. When that option is enabled, libc++ will
assume that the PSTL can be found somewhere on the CMake module path,
and it will provide the C++17 parallel algorithms based on the PSTL
(that is assumed to be available).

The commit also adds support for running the PSTL tests as part of
the libc++ test suite.

Reviewers: rodgert, EricWF

Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits, mclow.lists, EricWF

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60480

llvm-svn: 366593

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Fix the floating point version of midpoint. It wasn't constexpr, among other things. Add more tests. As a drive-by, the LCD implementation had a class named '__abs' which did a 'absolute value to a c

Fix the floating point version of midpoint. It wasn't constexpr, among other things. Add more tests. As a drive-by, the LCD implementation had a class named '__abs' which did a 'absolute value to a common-type' conversion. Rename that to be '__ct_abs'.

llvm-svn: 363714

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[NFC][libcxx] Remove trailing whitespace

It's incredibly annoying when trying to create diffs

llvm-svn: 361981

Add additional constraints on midpoint(pointer, pointer). Fixes PR#42037.

llvm-svn: 361970

Mark private function __sign as constexpr.

llvm-svn: 360167

Implement midpoint for floating point types. Reviewed as https://reviews.llvm.org/D61014.

llvm-svn: 359184

Add std::midpoint for integral and poiner types. Described in P0811, reviewed as D59099.

llvm-svn: 356162

Update more file headers across all of the LLVM projects in the monorepo
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.

We understand that

Update more file headers across all of the LLVM projects in the monorepo
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351648

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Implement the infrastructure for feature-test macros. Very few actual feature test macros, though. Reviewed as: https://reviews.llvm.org/D51955

llvm-svn: 342073

[NFC][libc++] Consistently use spaces to indent

rdar://problem/19988944

llvm-svn: 338933

Fix incorrect handling of move-only types in transform_reduce iter iter iter init, and add test.

llvm-svn: 321851

Automated trailing whitespace removal by VS Code.

llvm-svn: 321850

Implement inclusive_scan/transform_inclusive_scan for C++17.

llvm-svn: 306083