Changes

[libc] add back math.h #include utils/FPUtil/ManipulationFunctions.h

This partially reverts cee1e7d14f4628d6174b33640d502bff3b54ae45:
  [libc][NFC][Obvious] Remove few unnecessary #include directives in tests.

That commit causes a test failure in our configuration:
[ RUN      ] ILogbTest.SpecialNumbers_ilogb
third_party/llvm/llvm-project/libc/test/src/math/ILogbTest.h:28: FAILURE
      Expected: FP_ILOGBNAN
      Which is: 2147483647
To be equal to: func(__llvm_libc::fputil::FPBits<T>::buildNaN(1))
      Which is: -2147483648

[X86] Add X86ISD::SUBV_BROADCAST_LOAD and begin removing X86ISD::SUBV_BROADCAST (PR38969)

Subvector broadcasts are only load instructions, yet X86ISD::SUBV_BROADCAST treats them more generally, requiring a lot of fallback tablegen patterns.

This initial patch replaces constant vector lowering inside lowerBuildVectorAsBroadcast with direct X86ISD::SUBV_BROADCAST_LOAD loads which helps us merge a number of equivalent loads/broadcasts.

As well as general plumbing/analysis additions for SUBV_BROADCAST_LOAD, I needed to wrap SelectionDAG::makeEquivalentMemoryOrdering so it can handle result chains from non generic LoadSDNode nodes.

Later patches will continue to replace X86ISD::SUBV_BROADCAST usage.

Differential Revision: https://reviews.llvm.org/D92645

Make LLVM build in C++20 mode

Part of the <=> changes in C++20 make certain patterns of writing equality
operators ambiguous with themselves (sorry!).
This patch goes through and adjusts all the comparison operators such that
they should work in both C++17 and C++20 modes. It also makes two other small
C++20-specific changes (adding a constructor to a type that cases to be an
aggregate, and adding casts from u8 literals which no longer have type
const char*).

There were four categories of errors that this review fixes.
Here are canonical examples of them, ordered from most to least common:

// 1) Missing const
namespace missing_const {
    struct A {
    #ifndef FIXED
        bool operator==(A const&);
    #else
        bool operator==(A const&) const;
    #endif
    };

    bool a = A{} == A{}; // error
}

// 2) Type mismatch on CRTP
namespace crtp_mismatch {
    template <typename Derived>
    struct Base {
    #ifndef FIXED
        bool operator==(Derived const&) const;
    #else
        // in one case changed to taking Base const&
        friend bool operator==(Derived const&, Derived const&);
    #endif
    };

    struct D : Base<D> { };

    bool b = D{} == D{}; // error
}

// 3) iterator/const_iterator with only mixed comparison
namespace iter_const_iter {
    template <bool Const>
    struct iterator {
        using const_iterator = iterator<true>;

        iterator();

        template <bool B, std::enable_if_t<(Const && !B), int> = 0>
        iterator(iterator<B> const&);

    #ifndef FIXED
        bool operator==(const_iterator const&) const;
    #else
        friend bool operator==(iterator const&, iterator const&);
    #endif
    };

    bool c = iterator<false>{} == iterator<false>{} // error
          || iterator<false>{} == iterator<true>{}
          || iterator<true>{} == iterator<false>{}
          || iterator<true>{} == iterator<true>{};
}

// 4) Same-type comparison but only have mixed-type operator
namespace ambiguous_choice {
    enum Color { Red };

    struct C {
        C();
        C(Color);
        operator Color() const;
        bool operator==(Color) const;
        friend bool operator==(C, C);
    };

    bool c = C{} == C{}; // error
    bool d = C{} == Red;
}

Differential revision: https://reviews.llvm.org/D78938

[lldb] Add std::array to the supported template list of the CxxModuleHandler

Identical to the other patches that add STL containers to the supported
templated list.

fix a -Wunused-variable warning in release build

[X86] Remove extract_subvector(subv_broadcast_load()) fold.

This was needed in an earlier version of D92645, but isn't now - and I've just noticed that it was potentially flawed depending on the relevant widths of the broadcasted and extracted subvectors.

[NFC] Reduce include files dependency and AA header cleanup (part 2).

Continuing work started in https://reviews.llvm.org/D92489:

Removed a bunch of includes from "AliasAnalysis.h" and "LoopPassManager.h".

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D92852

[SVE][CodeGen] Add bfloat16 support to scalable masked gather

Reviewed By: david-arm

Differential Revision: https://reviews.llvm.org/D93307

[mlir] partially update LLVM dialect documentation

Rewrite the parts of the documentation that became stale: context/module
handling and type system. Expand the type system description.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D93315

[mlir] Move LLVM Dialect Op documentation to ODS

This was long overdue. The initial documentation for the LLVM dialect was
introduced before ODS had support for long descriptions. This is now possible,
so the documentation is moved to ODS, which can serve as a single source of
truth. The high-level description of the dialect structure is updated to
reflect that.

Depends On: D93315

Reviewed By: rriddle, mehdi_amini

Differential Revision: https://reviews.llvm.org/D93425

[libcxx] Remove ifdefs in the message to static_assert. NFC.

Differential Revision: https://reviews.llvm.org/D93283

[AArch64] Renamed sve-masked-scatter-legalise.ll. NFC.

[clangd] Add llvm:: qualifier to work around GCC bug. NFC

Some old GCC versions seem to miss the default template parameter when
using the clang/Basic/LLVM.h forward declarations of SmallVector.

See D92788

[DebugInfo] Fix MSVC build by adding back necessary reverse_iterator != operator

Put back the std::reverse_iterator<DWARFDie::iterator> != operator that was removed in D78938 to fix VS2019 builds