[llvm] annotate interfaces in llvm/Transforms for DLL export (#143413)

## Purpose

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

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:
- Removed a redundant `operator<<` from Attributor.h. IDS only
auto-annotates the 1st declaration, and the 2nd declaration being
un-annotated resulted in an "inconsistent linkage" error on Windows when
building LLVM as a DLL.
- `#include` the `VirtualFileSystem.h` in PGOInstrumentation.h and
remove the local declaration of the `vfs::FileSystem` class. This is
required because exporting the `PGOInstrumentationUse` constructor
requires the class be fully defined because it is used by an argument.
- 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_TEMPLATE_ABI` and `LLVM_EXPORT_TEMPLATE` to exported
instantiated templates.

## 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

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 3621989..0681ebc 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -41,6 +41,7 @@
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
@@ -1820,10 +1821,11 @@ void llvm::appendLoopsToWorklist(RangeT &&Loops,
   appendReversedLoopsToWorklist(reverse(Loops), Worklist);
 }
 
-template void llvm::appendLoopsToWorklist<ArrayRef<Loop *> &>(
+template LLVM_EXPORT_TEMPLATE void
+llvm::appendLoopsToWorklist<ArrayRef<Loop *> &>(
     ArrayRef<Loop *> &Loops, SmallPriorityWorklist<Loop *, 4> &Worklist);
 
-template void
+template LLVM_EXPORT_TEMPLATE void
 llvm::appendLoopsToWorklist<Loop &>(Loop &L,
                                     SmallPriorityWorklist<Loop *, 4> &Worklist);