Resolves https://github.com/llvm/llvm-project/issues/144477

---------

Co-authored-by: Simon Pilgrim <llvm-dev@redking.me.uk>

Add SDPatternMatch matcher and unit test coverage for `ISD::LOAD`
opcode.
This only matches the loaded value i.e. ResNo 0 and not the output
chain.
e.g.
```
m_Load(m_Value(), m_Value(), m_Value())
```

The first value is the input chain, the second is the base pointer, and
the last value is the offset.

`m_Result<N>` matches a SDValue that is the N-th result of the defining
SDNode. This is useful for creating a more fine-grained matching on
SDNode with multiple results.

-----
Inspired by #145481

Add SDPatternMatch matcher and unit test coverage for ISD::POISON opcode

e.g.
```
m_InsertElt(m_Poison(), m_Value(), m_Zero())
```

This patch transforms:

  X && *X == Y

to:

  X == Y

where X is of std::optional<T>, and Y is of T or similar.

## Purpose

This patch is one in a series of code-mods that annotate LLVM’s public
interface for export. This patch annotates the `llvm/CGData` and
`llvm/CodeGen` libraries. These annotations currently have no meaningful
impact on the LLVM build; however, they are a prerequisite to support an
LLVM Windows DLL (shared library) build.

## Background

This effort is tracked in #109483. Additional context is provided in
[this
discourse](https://discourse.llvm.org/t/psa-annotating-llvm-public-interface/85307),
and documentation for `LLVM_ABI` and related annotations is found in the
LLVM repo
[here](https://github.com/llvm/llvm-project/blob/main/llvm/docs/InterfaceExportAnnotations.rst).

The bulk of these changes were generated automatically using the
[Interface Definition Scanner (IDS)](https://github.com/compnerd/ids)
tool, followed formatting with `git clang-format`.

The following manual adjustments were also applied after running IDS on
Linux:
- Add `LLVM_ABI` to a subset of private class methods and fields that
require export
- Add `LLVM_TEMPLATE_ABI` and `LLVM_EXPORT_TEMPLATE` to exported
instantiated templates defined via X-macro
- Add `LLVM_ABI_FRIEND` to friend member functions declared with
`LLVM_ABI`
- Explicitly make classes non-copyable where needed to due IDS adding
LLVM_ABI at the class level
- Add `#include "llvm/Support/Compiler.h"` to files where it was not
auto-added by IDS due to no pre-existing block of include statements.
- Add `LLVM_ABI` to a small number of symbols that require export but
are not declared in headers

## Validation

Local builds and tests to validate cross-platform compatibility. This
included llvm, clang, and lldb on the following configurations:

- Windows with MSVC
- Windows with Clang
- Linux with GCC
- Linux with Clang
- Darwin with Clang

This continues s-barannikov's work TableGen-erating SDNode descriptions. 
This takes the initial patch from #119709 and moves documentation and the
rest of the AArch64ISD nodes to TableGen. Some issues were found by the
generated SDNode verification added in this patch. These issues have been 
described and fixed in the following PRs:

- #140706 
- #140711 
- #140713 
- #140715

---------

Co-authored-by: Sergei Barannikov <barannikov88@gmail.com>

A few files of llvm dir had duplicate headers included. This patch
removes those redundancies.

---------

Co-authored-by: Akash Agrawal <akashag@qti.qualcomm.com>