## Purpose

This patch is one in a series of code-mods that annotate LLVM’s public
interface for export. This patch annotates the `llvm/Target` library.
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).

A sub-set 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 bulk of this change is manual additions of `LLVM_ABI` to
`LLVMInitializeX` functions defined in .cpp files under llvm/lib/Target.
Adding `LLVM_ABI` to the function implementation is required here
because they do not `#include "llvm/Support/TargetSelect.h"`, which
contains the declarations for this functions and was already updated
with `LLVM_ABI` in a previous patch. I considered patching these files
with `#include "llvm/Support/TargetSelect.h"` instead, but since
TargetSelect.h is a large file with a bunch of preprocessor x-macro
stuff in it I was concerned it would unnecessarily impact compile times.

In addition, a number of unit tests under llvm/unittests/Target required
additional dependencies to make them build correctly against the LLVM
DLL on Windows using MSVC.

## 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

As noticed in https://github.com/llvm/llvm-project/pull/140471, the
SystemZ target currently implements disassembly of PC-relative target
addresses differently from other back-ends. This patch brings SystemZ in
line with other targets.

Specifically, this patch changes the relevant MCInst instructions to
carry a PC-relative displacement instead of an absolute target address
in their immediate fields. When printing the instruction, this
displacement will either be shown as is (e.g. for llvm-mc), or else
translated into an absolute address at print time (e.g. for
llvm-objdump).

The existing llvm-mc based tests using PC-relative operands no longer
work and have to be rewritten, but printing displacements makes those
tests easier to maintain anyway.

Identified with misc-include-cleaner.

Some fixes for style issues pointed out by clang-tidy:

- Upper case/lower case fixes
- No else after return
- Removed unused #include's
- Added NOLINTNEXTLINE() for the LLVM* functions

All changes are NFC.

Prepare for removing the MemOpsEmitted workaround for symbolic
displacements by letting TableGen know about the offsets of the
displacement sub-operands within the instruction.

There are alternative ways to do this that were tried and rejected:

- Creating encoders and decoders for each possible displacement offset.
  This is too repetitive.

- Use VarLenCodeEmitter [1]. The resulting diff is quite large.

Instead, use the named sub-operand support introduced by commit
a538d1f13a13 ("[TableGen][CodeEmitterGen] Allow local names for
sub-operands in a operand list.").

Describe instruction encodings in terms of sub-operands instead of
operands (e.g. B, D, L vs BDL) - this also better matches the pictures
from the Principles of Operation. Decompose operands into sub-operands
using the new (bdaddr12only $B1, $D1):$BD1 syntax. Replace the
encoders and the decoders of the operands with these of the
sub-operands.

Since DecodeADDR64BitRegisterClass() is now used for bases and indices,
change it to return NoRegister when decoding 0. This also changes the
disassembly of some instructions, e.g., br %r0 becomes br 0. Since this
better captures the instruction semantics, namely, that the value of
%r0 is not used, keep this change and update the tests.

[1] https://m680x0.github.io/blog/2022/02/varlen-encoder.html

Reviewed By: uweigand

Differential Revision: https://reviews.llvm.org/D155194

/data/llvm-project/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp:209:21: error: unused function 'decodeU6ImmOperand' [-Werror,-Wunused-function]
static DecodeStatus decodeU6ImmOperand(MCInst &Inst, uint64_t Imm,
                    ^
1 error generated.

MCSymbolizer::tryAddingSymbolicOperand() overloaded the Size parameter
to specify either the instruction size or the operand size depending on
the architecture. However, for proper symbolic disassembly on X86, we
need to know both sizes, as an instruction can have two operands, and
the instruction size cannot be reliably calculated based on the operand
offset and its size. Hence, split Size into OpSize and InstSize.

For X86, the new interface allows to fix a couple of issues:
  * Correctly adjust the value of PC-relative operands.
  * Set operand size to zero when the operand is specified implicitly.

Differential Revision: https://reviews.llvm.org/D126101

The name `MCFixedLenDisassembler.h` is out of date after D120958.

Rename it as `MCDecoderOps.h` to reflect the change.

Reviewed By: myhsu

Differential Revision: https://reviews.llvm.org/D124987

All LLVM backends use MCDisassembler as a base class for their
instruction decoders. Use "const MCDisassembler *" for the decoder
instead of "const void *". Remove unnecessary static casts.

Reviewed By: skan

Differential Revision: https://reviews.llvm.org/D122245

This moves the registry higher in the LLVM library dependency stack.
Every client of the target registry needs to link against MC anyway to
actually use the target, so we might as well move this out of Support.

This allows us to ensure that Support doesn't have includes from MC/*.

Differential Revision: https://reviews.llvm.org/D111454